Sprint running performance monitoring: methodological and practical considerations

Haugen T & Buchheit M. Sprint running performance monitoring: methodological and practical considerations. Sports Med 2015, In press

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Fig 4 R2

Fig. Percentage changes in 10-m sprint time and maximal sprinting speed (best 10-m split during a 40-m sprint, MSS) in a well-trained young soccer player. Error bars represent the typical error of each variable (i.e., 1.6 and 2.9% for 10-m and maximal sprinting speed (MSS), respectively, Table 2). Details of the methods have been published elsewhere [34]. The grey area represents trivial changes. *: likely change, **: very likely change and ***: almost certain change. Multiples of the smallest worthwhile changes (SWC) were used to assess the magnitude of the changes based on Cohen’s effect size principle, where 1, 3 and 6 multiples of the SWC stand for small, moderate and large changes.

The aim of this review is to investigate methodological concerns associated with sprint performance monitoring, more specifically the influence and magnitude of varying external conditions, technology and monitoring methodologies not directly related to human physiology. The combination of different starting procedures and triggering devices can cause up to very large time differences, which may be many times greater than performance changes caused by years of conditioning. Wind, altitude, temperature, barometric pressure and humidity can all combine to yield moderate time differences over short sprints. Sprint performance can also be affected by the athlete’s clothing, principally by its weight rather than its aerodynamic properties. On level surfaces, the track compliance must change dramatically before performance changes larger than typical variation can be detected. An optimal shoe bending stiffness can enhance performance by a small margin. Fully-automatic timing systems, dual-beamed photocells, laser guns and high-speed video are the most accurate tools for sprint performance monitoring. Manual timing and single-beamed photocells should be avoided over short sprint distances (10-20 m) due to large absolute errors. The validity of today’s GPS technology is satisfactory for long distances (>30 m) and maximal velocity in team sports, but multiple observations are still needed due to questionable reliability. Based on different approaches used to estimate the smallest worthwhile performance change and the typical error of sprint measures, we have provided an assessment of the usefulness of speed evaluation from 5 to 40 m. Finally, we provide statistical guidelines to accurately assess changes in individual performance; i.e., considering both the smallest worthwhile change in performance and the typical error of measurement, which can be reduced while repeating the number of trials.

Key points
-Monitored sprint times over very short distances may vary up to 50-60% due to differences in equipment and methodology
-Presented calibration equations are needed to compare sprint times across varying settings
-We provide guidelines to accurately monitor and interpret sprint performance changes, based on established magnitude thresholds and practices to decrease typical errors with trials repetitions

The effect of body mass on eccentric knee flexor strength assessed with an instrumented Nordic hamstring device (Nordbord) in football players

Figure 1Buchheit M, Cholley Y, Nagel M and Poulos N. The effect of body mass on eccentric knee flexor strength assessed with an instrumented Nordic hamstring device (Nordbord) in football players. Int J Sports Physiol and Perf, In press – full text hereFigure 2Abstract
Purpose. The aims of the present study were to 1) examine the effect of body mass (BM) on eccentric knee flexor strength using the Nordbord, and 2) offer simple guidelines to control for effect of BM on knee flexors strength.
Methods. Data from 81 soccer players (U17, U19, U21, senior 4th French division and professionals) and 41 Australian Football League (AFL) players were used for analysis. They all performed one set of three maximal repetitions of the bilateral Nordic hamstring exercise, with the greatest strength measure used for analysis. The main regression equation obtained from the overall sample was used to predict eccentric knee flexor strength from a given BM (moderate TEE, 22%). Individual deviations from the BM-predicted score were used as a BM-free index of eccentric knee flexor strength.
Results. There was a large (r = 0.55, 90% confidence limits: 0.42;0.64) correlation between eccentric knee flexor strength and BM. Heavier and older players (professionals, 4th French division and AFL) outperformed their lighter and younger (U17-U21) counterparts, with the soccer professionals presenting the highest absolute strength. Professional soccer players were the only ones to show strength values likely slightly greater than those expected for their BM.
Conclusions. Eccentric knee flexor strength, as assessed with the Nordbord, is largely BM-dependent. To control for this effect, practitioners may compare actual test performances with the expected strength for a given BM, using the following predictive equation: eccentric strength (N) = 4 x BM (kg) + 26.1. Professional soccer players with specific knee flexors training history and enhanced neuromuscular performance may show higher than expected values.

Keywords: hamstring strength; injuries; Australian Football League; soccer; association football.

Figure 3