Effect of sauna-based heat acclimation on plasma volume and heart rate variability

Stanley, J., Halliday, A., D’Auria, S., Buchheit, M. and Leicht, AS. Effect of sauna-based heat acclimation on plasma volume and heart rate variability. Eur J App Physiol, In press.

PV EAJP Full text here / Video of the talk here

Abstract
Purpose: We investigated the effect of post-exercise sauna bathing on plasma volume (PV) expansion and whether such responses can be tracked by changes in heart rate (HR) based measures.
Methods: Seven, well-trained, male cyclists were monitored for 35 consecutive days (17 d baseline training, 10d training plus sauna, 8d training). Sauna exposure consisted of 30 min (87°C, 11% relative humidity) immediately following normal training. Capillary blood samples were collected to assess PV changes while resting seated. HR (HRwake) and vagal-related HR variability (natural logarithm of square-root mean squared differences of successive R−R intervals, ln rMSSDwake) were assessed daily upon waking. A sub-maximal cycle test (5 min at 125 W) was performed on days 1, 8, 15, 22, 25, 29, and 35 and HR recovery (HRR60s) and ln rMSSDpostex were assessed post-exercise. Effects were examined using magnitude-based inferences.
Results: Compared with baseline, sauna resulted in: 1) peak PV expansion after 4 exposures with a likely large increase [+17.8% (90% confidence limits, 7.4;29.2)]; 2) reduction of HRwake by a trivial-to-moderate amount [−10.2% (−15.9;−4.0)]; 3) trivial-to-small changes for ln rMSSDwake [4.3% (1.9;6.8)] and ln rMSSDpostex [−2.4% (−9.1;4.9)]; and 4) a likely moderate decrease in HRR60s [−15.6% (−30.9;3.0)]. Correlations between individual changes in PV and HR measures were all unclear.
Conclusions: Sauna-bathing following normal training largely expanded PV in well-trained cyclists after just 4 exposures. The utility of HR and HRV indices for tracking changes in PV was however uncertain. Future studies will clarify mechanisms and performance benefits of post-training sauna bathing.
Keywords: heat exposure; blood volume; cardiac parasympathetic activity; post-exercise; cyclists.

@jamiestanley85

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Relative match intensities at high altitude in highly-trained young soccer players (isa3600)

qantas-joeys-held-to-scoreless-draw-in-bolivia_00048620-leadimageMartin Buchheit, Kristal Hammond, Pitre C. Bourdon, Ben M. Simpson, Laura A. Garvican-Lewis, Walter F. Schmidt, Christopher J. Gore and Robert J. Aughey. Relative match intensities at high altitude in highly-trained young soccer players (isa3600). Journal of Sports Science and Medicine, In press.

Figure 1Full text here

ABSTRACT

To compare relative match intensities of sea-level versus high-altitude native soccer players during a 2-week camp at 3600 m, data from 7 sea-level (Australian U17 National team, AUS) and 6 high-altitude (a Bolivian U18 team, BOL) native soccer players were analysed. Two matches were played at sea-level and three at 3600 m on Days 1, 6 and 13. The Yo-Yo Intermittent recovery test (vYo-YoIR1) was performed at sea-level, and on Days 3 and 10. Match activity profiles were measured via 10-Hz GPS. Distance covered >14.4 km.h-1 (D>14.4 km.h-1) and >80% of vYo-YoIR1 (D>80%vYo-YoIR1) were examined.

Upon arrival at altitude, there was a greater decrement in vYo-YoIR1 (Cohen’s d +1.0, 90%CL ± 0.8) and D>14.4 km.h-1 (+0.5 ± 0.8) in AUS. D>14.4 km.h-1 was similarly reduced relative to vYo-YoIR1 in both groups, so that D>80%vYo-YoIR1 remained similarly unchanged (-0.1 ± 0.8). Throughout the altitude sojourn, vYo-YoIR1 and D>14.4 km.h-1 increased in parallel in AUS, so that D>80%vYo-YoIR1 remained stable in AUS (+6.0%/match, 90%CL ± 6.7); conversely D>80%vYo-YoIR1 decreased largely in BOL (-12.2%/match ± 6.2).

In sea-level natives competing at high-altitude, changes in match running performance likely follow those in high-intensity running performance. Bolivian data confirm that increases in ‘fitness’ do not necessarily translate into greater match running performance, but rather in reduced relative exercise intensity.

Key words: association football; hypoxia; match running performance

Cardiac Parasympathetic Activity and Race Performance: An Elite Triathlete Case Study

Stanley J, D’Auria S, Buchheit M. Cardiac Parasympathetic Activity and Race Performance: An Elite Triathlete Case Study. Int J Sports Physiol Perform. 2014 Oct 29. [Epub ahead of print]

2s Men's caloundra enduro triathlon 2011 fs 2s-12-MAbstract

We examined whether changes in heart rate (HR) variability (HRV) could consistently track adaptation to training and race performance during a 32-week competitive season. An elite male long-course triathlete recorded resting HR (RHR) each morning and vagal-related indices of HRV (natural logarithm of square-root of mean squared differences of successive R-R intervals; ln rMSSD and the ratio of ln rMSSD to R-R interval length; ln rMSSD:RR) were assessed. Daily training load was quantified using a power meter and wrist-top GPS device. Trends in HRV indices and training load were examined by calculating standardised differences (ES). The following trends in week-to-week changes were consistently observed: 1) when the triathlete was coping to a training block, RHR decreased [ES, -0.38 (90% confidence limits, -0.05;-0.72)] and ln rMSSD increased [+0.36 (0.71;0.00)], 2) when the triathlete was not coping, RHR increased [+0.65 (1.29;0.00)] and ln rMSSD decreased [-0.60 (0.00;-1.20)], 3) optimal competition performance was associated with moderate decreases in ln rMSSD [-0.86 (-0.76;-0.95)] and ln rMSSD:RR [-0.90 (-0.60;-1.20)] in the week prior to competition, and 4) sub-optimal competition performance was associated with small decreases in ln rMSSD [-0.25 (-0.76;-0.95)] and trivial changes in ln rMSSD:RR [-0.04 (0.50;-0.57)] in the week prior to competition. To conclude, in this triathlete, a decrease in RHR concurrent with increased ln rMSSD compared with the previous week consistently appears indicative of positive training adaptation during a training block. A simultaneous reduction in ln rMSSD and ln rMSSD:RR during the final week preceding competition appears consistently indicative of optimal performance.