Locomotor and heart rate responses of floaters during small-sided games in elite soccer players: effect of pitch size and inclusion of goal keepers

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Lacome M., Simpson B.M, Cholley Y., Buchheit M. Locomotor and heart rate responses of floaters during small-sided games in elite soccer players: effect of pitch size and inclusion of goal keepers. IJSPP, In press

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Figure 1_All stats_Joker

Figure 1: Standardised differences between floaters and regular players SWC: smallest worthwhile change; *: possibly; **: likely; ***: most likely; ****: almost certainly difference.

Abstract

Purpose: To (1) compare the locomotor and heart rate responses between floaters and regular players during both small and large small sided games (SSGs) and (2) examine whether the type of game (i.e., game simulation vs possession game) affects the magnitude of the difference between floaters and regular players.

Methods: Data were collected in 41 players belonging to an elite French football team during three consecutive seasons (2014-2017). 5-Hz GPS were used to collect all training data, with the Athletic Data Innovation analyser (v5.4.1.514, Sydney, Australia) used to derive total distance (m), high-speed distance (> 14.4 km.h-1, m) and external mechanical load (MechL, a.u). All SSGs included exclusively one floater, and were divided into two main categories, according to the participation of goal-keepers (GK) (game simulation, GS) or not (possession games, PO) and then further divided into small and large (>100 m2/player) SSGs based on the area per player ratio.

Results: Locomotor activity and mechanical load performed were likely-to-most likely lower (moderate to large magnitude) in floaters compared with regular players, while differences in HR responses were unclear to possibly higher (small) in floaters. The magnitude of the difference in locomotor activity and MechL between floaters and regular players was substantially greater during GS compared with PO.

Conclusions: Compared with regular players, floaters present decreased external load (both locomotor and MechL) despite unclear to possibly slightly higher HR responses during SSGs. Moreover, the responses of floaters compared with regular players are not consistent across different sizes of SSGs, with greater differences during GS than PO.

Keywords: Small-sided games, soccer, floaters, locomotor activity, mechanical load.

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Neuromuscular responses to conditioned soccer sessions assessed via GPS-embedded accelerometers: insights into tactical periodization

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Buchheit M, Lacome M, Cholley Y & Simpson B.M. Neuromuscular responses to conditioned soccer sessions assessed via GPS-embedded accelerometers: insights into tactical periodization. IJSPP, In press.

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Abstract

Purpose. To 1) examine the reliability of field-based running-specific measures of neuromuscular function assessed via GPS-embedded accelerometers and 2) examine their responses to three typical conditioned sessions (i.e., Strength, Endurance and Speed) in elite soccer players.

 Methods. Before and immediately after each session, vertical jump (CMJ) and adductors squeeze strength (Groin) performances were recorded. Players also performed a 4-min run at 12 km/h followed by 4 ~60-m runs (run =12 s, r =33 s). GPS (15-Hz) and accelerometer (100 Hz) data collected during the four runs + the recovery periods excluding the last recovery period were used to derive vertical stiffness (K), peak loading force (peak force over all the foot-strikes, Fpeak) and propulsion efficiency (i.e., ratio between velocity and force loads, Vl/Fl).

Results. Typical errors were small (CMJ, Groin, K and Vl/Fl) and moderate (Fpeak), with moderate (Fpeak), high (K and Vl/Fl) and very high ICC (CMJ and Groin). After all sessions, there were small decreases in Groin and increases in K, while changes in F were all unclear. In contrast, the CMJ and Vl/Fl ratio responses were session-dependent: small increase in CMJ after Speed and Endurance, but unclear changes after Strength; the Vl/Fl ratio increased largely after Strength, while there was a small and a moderate decrease after the Endurance and Speed, respectively.

 Conclusions. Running-specific measures of neuromuscular function assessed in the field via GPS-embedded accelerometers show acceptable levels of reliability. While the three sessions examined may be associated with limited neuromuscular fatigue, changes in neuromuscular performance and propulsion-efficiency are likely session objective-dependent.

Keywords: specificity; running mechanisms; fatigue; horizontal force application; association football.

Figure 1Figure 1. Changes in counter movement jump (CMJ) and groin squeeze (Groin) performance, vertical stiffness (K), peak loading force (Fpeak) and velocity load/force load ratio (Vl/Fl) following the three conditioned sessions. *: possible, **: likely, ***: very likely and ****: almost certain change/difference in the change.

Monitoring player fitness, fatigue status and running performance during an in-season training camp in elite Gaelic football

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Malone S., B. Hughes, M. Roe, K. Collins, M. Buchheit. Monitoring player fitness, fatigue status and running performance during an in-season training camp in elite Gaelic football. Science and Medicine in Football, In press, 2017.

Full paper here

ABSTRACT

We examined selected perceptual and physiological measures to monitor fitness, fatigue and running performance during a one week in-season training camp in elite Gaelic football. Twenty-two elite Gaelic football players were monitored for training load (session RPE x duration), perceived ratings of wellness (fatigue, sleep quality, soreness); heart rate variability (HRV;LnSD1), heart rate recovery (HRR), exercise heart rate (HRex), lower limb muscular power (CMJ) and global positioning system (GPS) variables. The Yo-Yo intermittent recovery test level 1 (Yo-YoIR1) was assessed pre-and post the training camp. GPS units were used to monitor players throughout the camp period, with specific small sided games (SSG) used as a measure of running performance. There were significant day-to-day variations in training load measures (Coefficent of variation, CV: 51%; p ≤ 0.001), HRex decreased (-12.2%), HRR increased (+3.3%) CMJ decreased (-8.1%) and pre-training LnSD1 (+14.1%) increased during the camp period. Yo-YoIR1 performance (+19.7%), total distance (TD) (+9.4%), high speed distance (HSD) (+12.1%) and sprint distance (SPD) (+5.8%) within SSG improved as the camp progressed. ∆ HRex and ∆ HRR were correlated with ∆ Yo-YoIR1 (r = 0.64; – 0.55), ∆HSD (r = 0.44; −0.58), ∆ SPD (r = 0.58; −0.52). ∆ LnSD1 was correlated with ∆Yo-YoIR1(r = 0.48; 90%CI: 0.33 to 0.59) and ∆ TD (r = 0.71) There were large correlations between ∆ wellness and ∆ Yo-YoIR1 (r = 0.71), ∆ TD (r = 0.68) and ∆ SPD (r = 0.68). Increases in training load were observed during the training camp. Daily variations in training load measures across the camp period were shown to systematically impact player’s physiological, performance and wellness measures.

Keywords: GPS, HR, Team-sports, Monitoring, Training Load

Fig1

Figure 1 –  Daily changes in (A) total distance (m) – double bars indicate completion of two sessions on the given day, (B) training load (sRPE; AU) – double bars indicate completion of two sessions on the given day, (C) sub-maximal exercise heart rate (HRex) and Heart rate recovery (HRR), (D) natural logarithm of standard deviation of instantaneous beat-to-beat R–R interval variability, measured from Poincaré plots prior to the completion of training (LnSD1). All data presented as mean ± SD.

 

Small-Sided Games in elite soccer: Does one size fits all?

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Lacome M., B.M. Simpson, Y. Cholley, P. Lambert, and M Buchheit. Small-Sided Games in elite soccer: Does one size fits all? IJSPP, In press 2017.

Full Text here

Abstract

Purpose: To compare the peak intensity of typical Small Sided Games (SSGs) with those of official matches in terms of running demands and mechanical work over different rolling average durations and playing positions.

Method: Data were collected in 21 players (25±5 y, 181±7 cm, 77±7 kg) belonging to an elite French football team. SSG data were collected over two seasons during typical training sessions (249 files, 12±4 per player) and official matches (n=12). Players’ locomotor activity was recorded using 15-Hz GPS. Total distance (TD, m), high-speed distance (HS, distance above 14.4 km.h-1, m) and mechanical work (MechW, a.u) were analysed during different rolling average periods (1 to 15 min). The SSGs examined were 4v4+Goal Keepers (GKs), 6v6+GKs, 8v8+GKs and 10v10+GKs.

Results: Peak TD and HS during 4v4, 6v6 and 8v8 were likely-to-most likely largely lower than during matches (ES: -0.59,±0.38 to -7.36,±1.20). MechW during 4v4 was likely-to-most likely higher than during matches (1-4-min; 0.61±,0.77 to 2.30±,0.64). Relative to their match demands, central defenders (CD) performed more HS than other positions (0.63±,0.81 to 1.61±,0.52) during 6v6. Similarly, central midfielders (CM) performed less MechW than the other positions during 6v6 (0.68,±0.72 to 1.34,±0.99) and 8v8 (0.73,±0.50 to 1.39,±0.32).

Conclusion: Peak locomotor intensity can be modulated during SSGs of various formats and durations to either over- or underload match demands, with 4v4 placing the greatest and the least emphasis on MechW and HS, respectively. Additionally, CD and CM tend to be the most and least overloaded during SSGs, respectively.

Key words: Small sided games, soccer, peak intensity, match demands, periodisation,

 

SSG_Figure2 (600)2

Peak locomotor intensity during the different small-sided games compared with match demands as a function of each rolling average period for all players pooled together (grey zones stand for match average ± standard deviations). Confidence intervals for mean values are not provided for clarity.

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Houston, we still have a problem

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M. Buchheit. Houston, we still have a problem. IJSPP, In press 2017.

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Apollo 13 was launched at 1313 Houston time on Saturday, April 11, 1970. Following months of meticulous preparation, highly-skilled and experienced commandant J.A. Lovell and his crew were on their way for the third lunar landing in the history of humanity. Apollo 13 was looking like it would be the smoothest flight ever.1 When the astronauts finished their TV broadcast, wishing us earthlings a good evening, they didn’t imagine that an oxygen tank would explode a few moments later, rendering them close to spending the rest of their lives in rotation around the planet. While the crew eventually reached Earth safely, I wished to use this well-known incident to discuss further the link, or lack thereof, between sport sciences research and current field practices.2,3 My feeling is that failure to rethink the overall research/publishing process will keep us on orbit ad aeternum. That is, the sport sciences as a field will remain only at the periphery of elite sport practice.

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Sport sciences in orbit. The somewhat extreme point I want to make is that there is a feeling that the academic culture and its publishing requirements have created a bit of an Apollo 13-like orbiting world (e.g., journals and conferences) that is mostly disconnected from the reality of elite performance.2,3 For example, how many coaches read publications or attend to sport sciences conferences?4 These guys are competition beasts, so if they could find any winning advantage, why wouldn’t they read or attend these? The reality is that what matters the most for coaches and players is the outcome, which is unfortunately rarely straightforward with the sport sciences. As one example, the first thing that Steve Redgrave (5 times Rowing Olympian) asked Steve Ingham (Lead Physiologist, English Institute of Sport) was if he was going to win more medals with his scientific support.5 Likewise, the first time I offered some amino acids to Zlatan Ibrahimović (top Swedish soccer player), he asked me straight up: “are these going to make me score more goals?” Adding to the problem, support staff in elite clubs often have high egos and as recently tweeted by R. Verheijen (Dutch football coach), they often can’t distinguish between experience (which they have) and knowledge (which they don’t always have). Such workers often don’t want to hear about the evidenced-based approach that we endlessly try to promote6 and devalue the importance of sharing data.7 Personal development courses and research & development departments are perceived as a waste of time and money, or as trivial undertakings that sport scientists pursue to promote themselves. To justify such an aggressive attitude against sport sciences, they often cite poorly designed, poorly interpreted and misleading studies, which is, in effect an argument that we have to accept.

Poor research discredits our profession. Life has told me that people rarely change. However, I believe that sport science can (and should). Today, we, sports scientists, are rarely asked to land on the moon. In fact, the majority of us spend our time and energy building the spaceship. We often don’t realize that keeping our feet on earth is the only way we can make an impact.3 When we meet other sport scientists either at conferences or otherwise, we talk about papers, PhD defenses and complain about idiot reviewers that we just wrestled with. We rarely chat about winning trophies or servicing athletes. The reality we have to accept however is that most of our studies can’t help coaches or practitioners, and in fact some of our investigations are so illogical that they directly discredit our profession and keep us 36 000 km in the sky. Which conditioning coach working in a club is naïve enough to believe that muscle metabolite contents could predict match running performance, knowing the importance of contextual variables (scoreline, team formation, position-specific demands8)? Which physiotherapist could be bothered enough to look at the recovery kinetic of fatigue markers following a treadmill run, from which all field-specific muscle damaging actions have been removed? British Journal of Sports Medicine surveys often blame practitioners for not following certain interventions believed to be optimal, when in reality, personnel in the field are often implementing things that are more advanced than what the academic ‘experts’ are trying to advise. Additionally, poor use of statistics in research often leads to the wrong conclusions,9,10 which creates confusion in clubs where such benefits might be expected for individual athletes. Poor research and translation keeps us in orbit.

Houston1

The research doesn’t always apply.11 There are many situations where (often successful) practitioners and athletes don’t apply what the sport sciences might suggest. Does it mean that these people are all wrong? Shall we systematically blame all practices that are not “Evidenced-Based”? With the huge quantity of research produced nowadays, it is easy to find contradictory studies. The findings from one day are often refuted the next. So what is “the evidence” in the end? Meta-analyses are likely a part of the answer, but the quality of the studies included and the profile of the populations involved can always be discussed. Shouldn’t we be more pragmatic and reconsider the importance of “best practice” instead?11 Here are some examples of clear disconnects between current practices and scientific evidence:

  • There is almost no evidence that massage provides any sort of physiological recovery benefit.12 Fact: every single athlete in the world loves to be massaged after competition/heavy training.
  • Beta-alanine and beetroot juice have both been shown to have clear ergogenic effects on some aspects of performance.13 Fact: the majority of athletes can’t be bothered using them for their constraining ingestion protocols (2-3 doses/day for 4-10 weeks for beta-alanine13) and awful tastes, respectively.
  • Load monitoring has been shown to be key to understanding training and lowers injury risk. 14 Fact: many of the most successful coaches, teams and athletes in the world win major championships and keep athletes healthy without use of a single load monitoring system.
  • The importance of sleep for recovery and performance is clearly established.15 Fact: teams often train in the morning the day following an away game, which comprises sleep, mainly for social (time with family in the afternoon) and business (sponsors operations) aspects. And they still win trophies.
  • Training at the same time of the day as matches may help body clock adjustments and subsequence performance.16 Fact: Most teams train in the morning for the reasons mentioned above.
  • The optimal quantity of the various macronutrients to be ingested for athletes has been described for decades.17 Fact: most elite athletes have actual nutrition practices that are substantially different to what is prescribed,18,19 and they still win trophies.

We don’t have the right answers. Here is a discussion I had with a colleague a couple of years ago while observing their cold water immersion protocol after an away match:

  • MB: Hey buddy, what’s the temperature of the cold bath?
  • Physio: (looking busy) 9 °C
  • MB: Wow! how long do the players immerse themselves?
  • Physio: 2 minutes!
  • MB: hum…, thanks. 2 minutes only? Are you aware of the literature20 suggesting that it might be best if we can get them to stay for 10-15 min, with the temperature at 11-15°C instead?
  • Physio: (rolling his eyes over and looking bothered) THANK YOU. With 2 bath containers and the bus leaving in 35 min, how do you want me to deal with each of the 10 players? They’ve got press interviews and selfies with the fans on their plate before we take off… what temperature do you suggest for 2 min then? And while you’re thinking of that, pass me my tape, I need to pack!
  • MB: …. (In fact, as far as I know, none of the ˜300 studies on cold water immersion has addressed this specific question yet … he just sent me back to orbit!)

This discussion, together with the above-mentioned examples when research doesn’t apply show that often, instead of a “what is best”-type of answer, practitioners need a “what is the least worst option in our context”-type of answer. Do we really need to know the effect of total sleep deprivation on performance? We rather need to know if there is a difference between sleeping 8, 6 or only 4 hours but with a catch-up nap in the afternoon. Do we really need to know the effect of a 6-week hypoxic training intervention using repeated all-out cycling efforts 3 times/week, while in most soccer clubs conditioning is systematically done with the ball on the pitch? We are likely more interested in the optimal exercise formats that should be used in the specific context of congested training and match situations. We rather need to know what is the minimum volume of high-intensity sessions necessary to keep substitute players fit. In fact, it is very likely that an academic would shot himself a bullet in the foot (or send himself to orbit) if he decides by himself the topic of a research question, simply because things are way more complex than he may think.

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How do we bring Sport Sciences back to earth? One solution might be for us to start where the questions actually arise (i.e., in clubs or federations) and then develop the structures required to conduct applied research, through research & development departments.21-23 Such sport scientists, who attempt to apply a degree of scientific rigor in a world of beliefs,3 are more than capable of creating relevant knowledge and best practice guidance within only a few weeks (Figure 1). This model contrasts with academic research that takes years to reach publication, before remaining inaccessible to the majority of coaches, athletes and practitioners (e.g., paper format,4 cost of journal subscription24). However, this type of in-house research can’t be the only research model for at least two reasons. First, club scientists don’t always have the opportunity (population, materials, skills, funding) to investigate the questions they are asking (e.g., should players sleep for 6 or 4 + 2 h following games?). Second, the knowledge that club scientists produce, if any, remains generally inside the clubs. While this is sometimes intentional (trying to keep a competitive advantage over the opposition), often club scientists have neither the need nor the skills and time to publish papers. For club practitioners, their mission is to improve club practices. A better use of their time is to multiply in-house data analyses/research projects than writing papers. Additionally, given the heavy requirements of peer-reviewed research (ethical approval, need for balanced study designs, control of external variables, large sample sizes, submission processes and reviewing battles), only the tip of the iceberg work ends up being published. In order for the rest of the iceberg to be disseminated outside of the club in the name of science, an option might be to offer shorter submission formats that are more accessible for busy club scientists, i.e., extended abstracts with figures, which is more or less what most people only have time to read anyway. Case studies, which reflect more the type of data and interest of club practitioners, should also be promoted. Editors should also encourage authors to adjust their data for confounding variables when possible, which can help to account for the noise related to real-life data collection. For larger-scale projects, clubs must strengthen their links with universities so that their data can be analyzed appropriately, and full papers can be written by academics with the time, experience and club level understanding. Similarly, experiments that can’t be conducted at the club level can be continued and refined in the laboratory environment. Only the latter conducted ‘academic’ studies may find their relevance in the real world of applied sport. Nevertheless, even with such a club-university partnership, it may not be as smooth as it looks. The ‘most rejected paper’,25 which was only published because we paid for it (7 rejections, despite the elite population, the robust study design, the data analysis and variables measured including hemoglobin mass and performance) illustrates the failure of the overall publishing process26 and the difficulties of publishing 100% club-driven research. It is also worth noting that by the time a ‘club paper’ is published, the coaching staff have likely already been replaced, a fact that may limit return on investment.

Fig 1

Figure 1. Possible research processes both in Universities/Laboratories and Clubs/Federations. In addition to its likely increased relevance, the ‘delivery time’ is much faster for club/federation- vs. university-driven research. See a Club/Uni collabortion example (among others thankfully) that fits the model

Conclusion. To conclude, if we as sport scientists want to have a word to say about the game that matters, we need to work towards keeping our feet on the earth and produce BETTER research; research tailored toward practitioner needs rather than aimed at being published per se. For such research to find its audience, we probably need to rethink the overall publishing process, starting with promotion of relevant submission types (e.g., short paper format types, short reports, as provided by IJSPP), improving the review process (faster turnaround, reviewers identified to increase accountability and in turn, review quality), and media types (e.g., free downloads, simplified versions published into coaching journals, book chapters, infographics, dissemination via social media).24 Once these first steps are achieved, and only after, club sport scientists may then be in better position to personally transfer research findings to staff and/or educate athletes.3 When it comes to guiding practitioners and athletes, instead of using an evidence-based approach, we’d rather promote an “evidence-lead” or “informed practice” approach; one that appreciates context over simple scientific conclusions.11

Acknowledgements. Sincere thanks to Paul Laursen and David Pyne for their insightful comments on drafts of the present manuscript.

 References

  1. Lovell, J.A., Houston, we’ve had a problem. Apollo expeditions to the moon. Https://history.Nasa.Gov/sp-350/ch-13-1.Html. 1975.
  2. Burke, E.R., Bridging the gap in sports science. Athletic Purchasing and Facilities, 1980;4(11):24-15.
  3. Buchheit, M., Chasing the 0.2. Int J Sports Physiol Perform, 2016;11(4):417-418.
  4. Reade, I., R. W., and N. Hall, Knowledge transfer: How do high performance coaches access the knowledge of sport scientists? Int J Sport Sci Coach, 2008;3(3):319-334.
  5. Ingham, S.A., How to support a champion: The art of applying science to the elite athlete, ed. Simply Said. 2016.
  6. Sackett, D.L., Protection for human subjects in medical research. JAMA, 2000;283(18):2388-9; author reply 2389-90.
  7. Rolls, A., No more poker face, it is time to finally lay our cards on the table. Bjsm blog, http://blogs.Bmj.Com/bjsm/2017/03/06/no-poker-face-time-finally-lay-cards-table/. 2017.
  8. Carling, C., Interpreting physical performance in professional soccer match-play: Should we be more pragmatic in our approach? Sports Med, 2013;43(8):655-63.
  9. Buchheit, M., The numbers will love you back in return-i promise. Int J Sports Physiol Perform, 2016;11(4):551-4.
  10. Buchheit, M., Does beetroot juice really improve sprint and high-intensity running performance? – probably not as much as it seems: How (poor) stats can help to tell a nice story. Https://martin-buchheit.Net/2017/01/04/does-beetroot-juice-really-improve-sprint-and-high-intensity-running-performance-probably-not-as-much-as-it-seems-how-stats-can-help-to-tell-a-nice-story/. 2017.
  11. Burgess, D.J., The research doesn’t always apply: Practical solutions to evidence-based training-load monitoring in elite team sports. Int J Sports Physiol Perform, 2017;12(Suppl 2):S2136-s2141.
  12. Poppendieck, W., et al., Massage and performance recovery: A meta-analytical review. Sports Med, 2016;46(2):183-204.
  13. Burke, L.M., Practical issues in evidence-based use of performance supplements: Supplement interactions, repeated use and individual responses. Sports Med, 2017;47(Suppl 1):79-100.
  14. Blanch, P. and T.J. Gabbett, Has the athlete trained enough to return to play safely? The acute:Chronic workload ratio permits clinicians to quantify a player’s risk of subsequent injury. Br J Sports Med, 2016;50(8):471-5.
  15. Fullagar, H.H., et al., Sleep and recovery in team sport: Current sleep-related issues facing professional team-sport athletes. Int J Sports Physiol Perform, 2015;10(8):950-7.
  16. Chtourou, H. and N. Souissi, The effect of training at a specific time of day: A review. J Strength Cond Res, 2012;26(7):1984-2005.
  17. Burke, L.M., The complete guide to food for sports performance: Peak nutrition for your sport. 1996: Allen & Unwin; Second edition edition.
  18. Bilsborough, J.C., et al., Changes in anthropometry, upper-body strength, and nutrient intake in professional australian football players during a season. Int J Sports Physiol Perform, 2016;11(3):290-300.
  19. Burke, L.M., et al., Guidelines for daily carbohydrate intake: Do athletes achieve them? Sports Med, 2001;31(4):267-99.
  20. Machado, A.F., et al., Can water temperature and immersion time influence the effect of cold water immersion on muscle soreness? A systematic review and meta-analysis. Sports Med, 2016;46(4):503-14.
  21. Coutts, A.J., Working fast and working slow: The benefits of embedding research in high performance sport. Int J Sports Physiol Perform, 2016;11(1):1-2.
  22. McCall, A., et al., Can off-field ‘brains’ provide a competitive advantage in professional football? Br J Sports Med, 2016;50(12):710-2.
  23. Eisenmann, J.C., Translational gap between laboratory and playing field: New era to solve old problems in sports science. Translational Journal of the American College of Sports Medicine, 2017;2(8):37-43.
  24. Barton, C., The current sports medicine journal model is outdated and ineffective. Aspetar – Sports Medicine Journal, 2017;7:58-63.
  25. Buchheit, M., et al., Adding heat to the live-high train-low altitude model: A practical insight from professional football. Br J Sports Med, 2013;47 Suppl 1:i59-69.
  26. Buchheit, M., The most rejected paper -heat + altitude, accepted- illustrates the failure of the publication process https://martin-buchheit.Net/2013/09/13/adding-heat-to-the-live-high-train-low-altitude-model-a-practical-insight-from-professional-football/. 2013.

 

Want to see my report, coach?

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In this new paper I merged and developed a bit further the 2 IJSPP papers on 1) the stats that changed my life and 2) some personal thoughts on chasing the 0.2 (i., making an impact) in an elite setting.

aspetar-201702

The value and importance of sport science varies greatly between elite clubs and federations. Among the different components of effective sport science support, the three most important elements are likely the following:

  1. Appropriate understanding and analysis of the data; i.e. using the most important and useful metrics only and using magnitude-based inferences as statistics. In fact, traditional null hypothesis significance testing (P values) is neither appropriate to answer the types of questions that arise from the field (i.e. assess magnitude of effects and examine small sample sizes) nor to assess changes in individual performances.
  2. Attractive and informative reports via improved data presentation/ visualisation (‘simple but powerful’).
  3. Appropriate communication skills and personality traits that help to deliver data and reports to coaches and athletes. Developing such an individual profile requires time, effort and most importantly, humility

Does beetroot juice really improve sprint and high-intensity running performance? – probably not as much as it seems: how (poor) stats can help to tell a nice story

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beetrootfoot

 A few tweets, re-tweets and emails from colleagues have caught my attention within the last 24 hrs, all pointing toward a new study showing improvements in sprinting and high-intensity intermittent running performance after dietary nitrate supplementation (beetroot shots) (1). In the 36 team-sports players (training 5-10h a week) who volunteered for the study, significant “improvements” in 5- (2.3%), 10- (1.6%) and 20-m (1.2%) sprint times and a 3.9% “increase” in high-intensity intermittent performance were reported, after no longer than 5 days of supplementation! (1)

nosprint

To all practitioners who may read both the article (1) and the present blog post, the topic is obviously highly relevant; we are all looking for various ways to improve our players’ running performance – even better if these improvements can be gained legally (no doping) and without (physical) efforts. If you can convince yourself to commit to drink daily an awful 70-ml beetroot shot for 5 days before an important competition, then you may have found a really cool and lazy way to get faster and fitter!!

However, before I began to tell (again) every player at the club (who would systematically pass on beetroot because of its taste) to finally commit themselves to drink this stuff, because it really works, I wished to make sure it would be worth the effort, both for them and me. After a deeper read of the paper, a closer look at the study design, the data analysis and the stat approach, I realized that in fact, beetroot supplementation, within the context of the present study, may not be as promising as it could be understood while only reading the title of the paper. This for at least two important reasons: 1) the somewhat limited magnitude of the “changes”, although significant and 2) the questionable study design/data analysis that doesn’t allow individual responses to be clearly accounted for and analyzed.

  1. The magnitude of the “improvement” may not be large enough to be meaningful. When considering the magnitude of the smallest worthwhile changes for different sprint distances (SWC, i.e., the minimum improvement likely to have an impact on the field, such as that required to be 20 cm ahead of an opponent to win a ball) (2), the changes reported in the present study are in fact either smaller (5 m: study 2.3% vs SWC ̴ 4%, 10 m: study 1.6% vs SWC ̴2%) or just similar to (20 m: study 1.2% vs SWC ̴1%) (2). Even for 20-m time, which magnitudes equals the SWC, chances for the “improvement” to be substantial may be no more than 50% at the individual level (when considering a typical error of the measurement (TE) of the same magnitude than the SWC – while in fact the TE may actually be twice as large as the SWC for such a distance (2), decreasing further the likelihood of a substantial change) (2). The same reasoning applies to the “increase” in Yo-YoIR1 performance (+3.9%), which SWC is generally twice larger (̴ +8% (3), +7% as 0.2xSD in the present study). In conclusion, the comparison of the reported changes, although significant, to their specific SWC directly questions the practical impact and in turn, the usefullness of beetroot supplementation in the context of the present study. These data illustrate once again that the use of null hypothesis significance testing (NHST) is clearly limited to assess the actual performance benefit of a supplement or an intervention (4, see the blog on the topic) – in the present case the significant P value likely results from the large sample size (n=36) – different conclusions (and probably less misleading in the present case) would be drawn with lower samples (i.e., n<15).
  1. The data analysis doesn’t allow individual responses to be clearly accounted for/analyzed. In fact, the authors simply chose to compare the sprints/YoYoIR1 performances following beetroot supplementation to these following the placebo drink (Post beetroot – Post placebo, via paired-samples t-tests)!? While it is not clear why such a limited approach was chosen, the proper way to analyze these data would be to look first at within-group changes, and more importantly, to compare these within-group changes (i.e., between-group differences in the changes – typical crossover design, as ‘post beetroot – pre beetroot’ compared with ‘post placebo – pre placebo’). This latter approach is way more powerful and allows the understanding of i) the effect of each treatment per se (within-group effect, in relation to the SWC), ii) the variability of the response within each treatment (SD of the change, which has important implications when using supplementation with athletes – some will respond, some not !! – and how many and by which magnitude?), iii) compare the efficacy of the treatments (differences in the magnitude of the changes) and even more importantly, iiii) compare the magnitude of the individual responses between each treatment (i.e., which treatment shows the greater variability in response). Unfortunately, all these relevant information for practitioners are missing in the manuscript.

That being said, I am happy to keep beetroot shots on the supplement table for the moment (for players that can cope with the taste… at least it hasn’t been shown to be detrimental). I may, however, not use the present study to advertise the benefit of beetroot to the players – if we want to keep our legitimacy and maintain the trust that the players put on us, I believe it is important to come to them with the right message – and in that case, applying some appropriate stats surely helps!

References

  1. Thompson C, Vanhatalo A, Jell H, Fulford J, Carter c, Nyman L, Bailey SJ and Jones AM. Dietary nitrate supplementation improves sprint and high-intensity intermittent running performance. Nitric Oxide 61 (2016) 55-61.
  2. Haugen T, Buchheit M. Sprint running performance monitoring: methodological and practical considerations. Sports Med. 2016;46(5):641.
  3. Bangsbo J, Iaia FM, Krustrup P. The Yo-Yo Intermittent Recovery Test: a useful tool for evaluation of physical performance in intermittent sports. Sports Med. 2008;38:37–51.
  4. Buchheit M. The Numbers Will Love You Back in Return—I Promise. Int J Sports Physiol & Perf, 2016, 11, 551 -554.

The influence of changes in acute training load on daily sensitivity of morning-measured fatigue variables in elite soccer players

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Thorpe RT, Strudwick AJ, Buchheit M, Atkinson G, Drust B, Gregson W. The influence of changes in acute training load on daily sensitivity of morning-measured fatigue variables in elite soccer players. IJSPP, In press

Full text here

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Abstract

Purpose To determine the sensitivity of a range of potential fatigue measures to daily training load accumulated over the previous two, three and four days during a short in-season competitive period in elite senior soccer players (n=10).

Methods Total high-speed running distance, perceived ratings of wellness (fatigue, muscle soreness, sleep quality), counter-movement jump height (CMJ), submaximal heart rate (HRex), post-exercise heart rate recovery (HRR) and heart rate variability (HRV: Ln rMSSD) were analysed during an in-season competitive period (17 days). General linear models were used to evaluate the influence of two, three and four day total high-speed running distance accumulation on fatigue measures.

Results Fluctuations in perceived ratings of fatigue were correlated with fluctuations in total high-speed running distance accumulation covered on the previous 2-days (r=-0.31; small), 3-days (r=-0.42; moderate) and 4-days (r=-0.28; small) (p<0.05). Changes in HRex (r=0.28; small; p= 0.02) were correlated with changes in 4-day total high-speed running distance accumulation only. Correlations between variability in muscle soreness, sleep quality, CMJ, HRR% and HRV and total high-speed running distance were negligible and not statistically significant for all accumulation training loads.

Conclusions Perceived ratings of fatigue and HRex were sensitive to fluctuations in acute total high-speed running distance accumulation, although, sensitivity was not systematically influenced by the number of previous days over which the training load was accumulated. The present findings indicate that the sensitivity of morning-measured fatigue variables to changes in training load is generally not improved when compared with training loads beyond the previous days training.

rt

@robbyt05

Player tracking technology: half-full or half-empty glass?

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Buchheit M & Simpson BM. Player tracking technology: half-full or half-empty glass? IJSPP, In press

This paper summarizes the main points of my talk in Aspire last year (Monitoring Load conference, Doha, Qatar, 2016) where I, among others, highlited the limitations of the metabolic power concept

Full text here

Abstract. With the ongoing development of (micro) technology, player tracking has become one of the most important components of load monitoring in team sports. The three main objectives of player tracking are the following: i) better understanding of practice (provide an objective, a posteriori evaluation of external load and locomotor demands of any given session or match), ii) the optimisation of training load patterns at the team level and iii) decision making on individual players training programs to improve performance and prevent injuries (e.g., top-up training vs. un-loading sequences, return to play progression). This paper, discusses the basics of a simple tracking approach and the need for the integration of multiple systems. The limitations of some of the most used variables in the field (including metabolic power measures) will be debated and innovative and potentially new powerful variables will be presented. The foundations of a successful player monitoring system are probably laid on the pitch first, in the way practitioners collect their own tracking data, given the limitations of each variable, and how they report and utilize all this information, rather than in the technology and the variables per se. Overall, the decision to use any tracking technology or new variable should always be considered with a cost/benefit approach (i.e., cost, ease of use, portability, manpower / ability to impact on the training program).

stride-symmetries

Figure. Example of Force load symmetry in a players during his return to play period following a right ankle sprain. The symmetry (with errors bars standing for typical error of measurement8) is calculated from the Force load of all foot impacts during all accelerated running phases (>2m.s-2) of each session. The star represents the date of the injury.

@benMsimpson

Metabolic power: powerful enough to drive Ferraris?

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After many requests following my talk in Aspire last year (Monitoring Load conference, Doha, Qatar, 2016) where I takled the metabolic power concept, I have just put together a written version of this specific section (that will also partly be inlcuded in a IJSPP paper written with Ben Simpson now available here)

Since Osgnagh et al. in 2010,13 who showed the potential application of the metabolic power (MP) concept8 for load monitoring in soccer, the interest for this variable has grown exponentially and is now used across many other team sports.6, 7, 12, 16 In fact, most GPS brands offer now the ability to monitor players’ MP, and a majority of practitioners use this variable when reporting.1 While we have been the firsts to be excited about the potential of this monitoring approach, we have since reconsidered our opinion and question now its usefulness in the field to monitor elite players (i.e., “Ferraris”). This is essentially related to i) recent research findings questioning its validity in the context of team sports-specific movements and ii) the fact that it is only an incomplete metabolic measure of internal load and probably too broad a marker of external load.

What do we actually measure?

It has now been shown by four distinct and independent research groups that locomotor-related MP assessed via either GPS or local positioning system (PGPS or Pmet in the figure below) differs largely from the true metabolic demands as assessed via indirect calorimetry (VO2 measures, PVO2). PGPS was actually reported to be very largely greater than PVO2 during walking,3 but very largely lower during shuttle runs at low speed15 and during soccer-,4 rugby-11 or team-sports3 specific circuits.

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While some may see the consistency of such conclusions as a kind of consensus, Osgnach et al. wished to write a letter to the editor to defend their approach and criticize our methodology.14 Since we were not given the chance to respond to this letter by the IJSM editor (“you will not be invited to respond to this letter, but I am sure that you will discuss directly this interesting issue with the di Prampero group”), we wished to comment on their main critics in the present post. This should clarify some discussions and confirm the limitations of MP in the context of interest, i.e., monitoring team-sports specific efforts with the available technology on the market.

  • Resting VO2
    • Osgnagh et al.: “Buchheit et al. have included resting VO2 in their calculations; using net VO2 as in the original methodology would reduce the difference observed and PGPS won’t appear to be underestimated anymore.”14
    • Response: we have in fact used net VO2, as clearly written p1151, 2nd paragraph “Average net VO2 and the respiratory exchange ratio (RER) were calculated for each of the three 1-min efforts and the following 30-s recovery periods”4

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  • Anaerobic energy contribution
    • Osgnagh et al.: “Anaerobic energy contribution is not appropriately accounted for in the calculation (the intensity of some efforts may be greater than VO2max, so that they are missed in the overall metabolic cost).”14
    • Response: Agree. But in this case, the actual (true) metabolic demands would have been even greater than those measured, which suggests that the PGPS underestimation would have actually been even greater than that reported in our paper!4

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  • Impact of non-locomotor actions
    • Osgnagh et al.: “as shown in Buchheit’s Figure 2, VO2 increases markedly at several points, while the simultaneously determined MP remains close to zero.”14 They suggest that something was wrong with our data.
    • Response: Soccer as most other team sports often includes intense but static movements (passing a ball for example, as in our circuit). It is therefore obvious to observe a rise in VO2 that is not associated with locomotor movements and in turn, changes in MP. This is an important limitation of MP – which may only reflect locomotor-related metabolic activity. But if that was the case, what would be the value of such an impartial measure of metabolic load? This is at odds with all attempts to use MP outputs for overall load monitoring or nutritional (post training/matches recovery) guidelines.6

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  • Sampling frequency
    • Osgnagh et al.: “The low sampling frequency of the GPS device used is problematic and explains the underestimation of PGPS.”14
    • Response: while we agree that 4 Hz as used in our study can be considered as low, we don’t believe that this may be the cause of the underestimation since the other researchers have all reported the same underestimation using higher sampling frequencies (i.e., 500,15 1011 and 53 Hz). Note also that we have shown that sampling frequency per se was not the most important factors when it comes to precision and validity.5

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Added value to load monitoring systems?

Considering that the agreement between PGPS and PVO2 has only been shown to be acceptable during continuous and linear jog and runs (but neither during walking nor intermittent changes of direction runs)3, the metabolic underestimation may be related to the fact that the current equation initially developed for maximal and linear sprint acceleration8 may not be well suited for team-sport specific running patterns (e.g., including rest, irregular step frequency and stride length, turns, upper body muscle activity, static movements).4

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This suggests that the value of PGPS per se to monitor training load in team sports may be questionable. Its usefulness may also be limited with respect to practitioners’ expectations in the field. In fact, practitioners are likely seeking for:

  • Overall estimates of internal load, which are satisfactorily assessed through HR and RPE measures1 – information on the metabolic load of exclusively locomotor-related actions as with PGPS may not be comprehensive enough.
  • Precise measures of external load, which directly relate to specific mechanical constraints on players’ anatomy, which, in turn target specific muscle groups. This has direct implications for training, recovery and injury risk. However:
    • PGPS is clearly dissociated from actual muscle activation, as exemplified by very large variations in the PGPS/EMG ratio during accelerated vs. decelerate running.10

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  • PGPS, if it was to be used as a global marker of mechanical work, wouldn’t allow deciphering the underlying mechanisms of the load – we rather use distance while accelerating, decelerating and while running at high-speed since those variables may relate directly to the load of specific muscle groups.

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  • Injuries are most generally related to inappropriate volumes of accelerations2 or high-speed running;9 there is in contrast little evidence to suggest that spikes in overall energy consumption per se may play a role in injury etiology.

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Until new evidences are provided regarding the validity of PGPS as a valid measure of overall energy expenditure during team-sport specific movements, and given the conceptual limitations (difficulties in deciphering the underlying mechanisms of the load), metabolic power assessed via the current technology (PGPS) may not be as powerful as we though to drive Ferraris.

References

  1. Akenhead R, Nassis GP. Training Load and Player Monitoring in High-Level Football: Current Practice and Perceptions. Int J Sports Physiol Perform. 2016;11(5):587-93.
  2. Bowen L, Gross AS, Gimpel M, Li FX. Accumulated workloads and the acute:chronic workload ratio relate to injury risk in elite youth football players. Br J Sports Med. 2016.
  3. Brown DM, Dwyer DB, Robertson SJ, Gastin PB. Metabolic Power Method Underestimates Energy Expenditure in Field Sport Movements Using a GPS Tracking System. Int J Sports Physiol Perform. 2016.
  4. Buchheit M, Manouvrier C, Cassirame J, Morin JB. Monitoring Locomotor Load in Soccer: Is Metabolic Power, Powerful? Int J Sports Med. 2015;36(14):1149-55.
  5. Buchheit M, Allen A, Poon TK, Modonutti M, Gregson W, Di Salvo V. Integrating different tracking systems in football: multiple camera semi-automatic system, local position measurement and GPS technologies. J Sports Sci. 2014;32(20)(20):1844-57.
  6. Coutts AJ, Kempton T, Sullivan C, Bilsborough J, Cordy J, Rampinini E. Metabolic power and energetic costs of professional Australian Football match-play. J Sci Med Sport. 2015;18(2):219-24.
  7. Cummins C, Gray A, Shorter K, Halaki M, Orr R. Energetic and Metabolic Power Demands of National Rugby League Match-Play. Int J Sports Med. 2016;37(7):552-8.
  8. di Prampero PE, Fusi S, Sepulcri L, Morin JB, Belli A, Antonutto G. Sprint running: a new energetic approach. J Exp Biol. 2005;208(Pt 14):2809-16.
  9. Duhig S, Shield AJ, Opar D, Gabbett TJ, Ferguson C, Williams M. Effect of high-speed running on hamstring strain injury risk. Br J Sports Med. 2016.
  10. Hader K, Mendez-Villanueva A, Palazzi D, Ahmaidi S, Buchheit M. Metabolic Power Requirement of Change of Direction Speed in Young Soccer Players: Not All Is What It Seems. PLoS One. 2016;11(3):e0149839.
  11. Highton J, Mullen T, Norris J, Oxendale C, Twist C. Energy Expenditure Derived From Micro-Technology is Not Suitable for Assessing Internal Load in Collision-Based Activities. Int J Sports Physiol Perform. 2016.
  12. Malone S, Solan B, Collins K, Doran D. The metabolic power and energetic demands of elite Gaelic football match play. J Sports Med Phys Fitness. 2016.
  13. Osgnach C, Poser S, Bernardini R, Rinaldo R, di Prampero PE. Energy cost and metabolic power in elite soccer: a new match analysis approach. Med Sci Sports Exerc. 2010;42(1):170-8.
  14. Osgnach C, Paolini E, Roberti V, Vettor M, di Prampero PE. Metabolic Power and Oxygen Consumption in Team Sports: A Brief Response to Buchheit et al. Int J Sports Med. 2016;37(1):77-81.
  15. Stevens TG, de Ruiter CJ, van Maurik D, van Lierop CJ, Savelsbergh GJ, Beek PJ. Measured and Estimated Energy Cost of Constant and Shuttle Running in Soccer Players. Med Sci Sports Exerc. 2015;47(6):1219-24.
  16. Vescovi JD. Locomotor, Heart-Rate, and Metabolic Power Characteristics of Youth Women’s Field Hockey: Female Athletes in Motion (FAiM) Study. Research quarterly for exercise and sport. 2016;87(1):68-77.