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Jamie Stanley, Shaun D’Auria and Martin Buchheit

The authors examined whether changes in heart-rate (HR) variability (HRV) could consistently track adaptation to training and race performance during a 32-wk competitive season. An elite male long-course triathlete recorded resting HR (RHR) each morning, and vagal-related indices of HRV (natural logarithm of the 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 standardized differences (ES). The following trends in week-to-week changes were consistently observed: (1) When the triathlete was coping with 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 before competition. (4) Suboptimal 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 before 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.

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Samuel T Tebeck, Jonathan D Buckley, Clint R Bellenger and Jamie Stanley

Purpose:

To investigate the effect of a 5-day short-term heat acclimation (STHA) protocol in dry (43˚C and 20 % RH) or humid (32˚C and 80 % RH) environmental conditions on endurance cycling performance in temperate conditions (21˚C).

Methods:

In a randomised, cross-over design, eleven cyclists completed each of the two, 5-day blocks of STHA matched for heat index (44˚C) and total exposure time (480 min), separated by 30-days. Pre- and post-temperate endurance performance (4-min mean max power, lactate threshold 1 and 2) was assessed in addition a heat stress test used to assess individual levels of heat adaptation.

Results:

Differences in endurance performance were unclear. Following dry STHA, gross mechanical efficiency was likely reduced [between-condition effect size dry vs humid (90 % confidence interval) [-0.59 (-1.05, -0.15)], oxygen uptake was likely increased for a given workload [+0.64 (0.14, 1.07)] and energy expenditure likely increased [+0.59 (0.17, 1.03)]. Plasma volume expansion at Day 5 of acclimation was similar (within-condition outcome +4.6 ± 6.3 % and +5.3 ± 5.1 % dry and humid respectively) but was retained for 3-4 days longer after the final humid STHA exposure (-0.2 ± 8.1 % and +4.5 ± 4.2 % dry and humid respectively). Sweat rate was very likely increased during dry STHA [+0.57 (0.25, 0.89)] and possibly increased [+0.18 (-0.15; 0.50)] during humid STHA.

Conclusion:

STHA induced divergent adaptations between dry and humid conditions, but did not result in differences in temperate endurance performance.

Open access

Avish P. Sharma, Philo U. Saunders, Laura A. Garvican-Lewis, Brad Clark, Jamie Stanley, Eileen Y. Robertson and Kevin G. Thompson

Purpose:

To determine the effect of training at 2100-m natural altitude on running speed (RS) during training sessions over a range of intensities relevant to middle-distance running performance.

Methods:

In an observational study, 19 elite middle-distance runners (mean ± SD age 25 ± 5 y, VO2max, 71 ± 5 mL · kg–1 · min–1) completed either 4–6 wk of sea-level training (CON, n = 7) or a 4- to 5-wk natural altitude-training camp living at 2100 m and training at 1400–2700 m (ALT, n = 12) after a period of sea-level training. Each training session was recorded on a GPS watch, and athletes also provided a score for session rating of perceived exertion (sRPE). Training sessions were grouped according to duration and intensity. RS (km/h) and sRPE from matched training sessions completed at sea level and 2100 m were compared within ALT, with sessions completed at sea level in CON describing normal variation.

Results:

In ALT, RS was reduced at altitude compared with sea level, with the greatest decrements observed during threshold- and VO2max-intensity sessions (5.8% and 3.6%, respectively). Velocity of low-intensity and race-pace sessions completed at a lower altitude (1400 m) and/or with additional recovery was maintained in ALT, though at a significantly greater sRPE (P = .04 and .05, respectively). There was no change in velocity or sRPE at any intensity in CON.

Conclusion:

RS in elite middle-distance athletes is adversely affected at 2100-m natural altitude, with levels of impairment dependent on the intensity of training. Maintenance of RS at certain intensities while training at altitude can result in a higher perceived exertion.