Effect of a four-week isocaloric ketogenic diet on physical performance at very high-altitude: a pilot study.

BACKGROUND: A ketogenic diet (KD) reduces daily carbohydrates (CHOs) ingestion by replacing most calories with fat. KD is of increasing interest among athletes because it may increase their maximal oxygen uptake (VO2max), the principal performance limitation at high-altitudes (1500-3500 m). We examined the tolerance of a 4-week isocaloric KD (ICKD) under simulated hypoxia and the possibility of evaluating ICKD performance benefits with a maximal graded exercise bike test under hypoxia and collected data on the effect of the diet on performance markers and arterial blood gases. METHODS: In a randomised single-blind cross-over model, 6 recreational mountaineers (age 24-44 years) completed a 4-week ICKD followed or preceded by a 4-week usual mixed Western-style diet (UD). Performance parameters (VO2max, lactate threshold [LT], peak power [Ppeak]) and arterial blood gases (PaO2, PaCO2, pH, HCO3-) were measured at baseline under two conditions (normoxia and hypoxia) as well as after a 4-week UD and 4-week ICKD under the hypoxic condition. RESULTS: We analysed data for all 6 participants (BMI 19.9-24.6 kg m-2). Mean VO2max in the normoxic condition was 44.6 ml kg-1 min-1. Hypoxia led to decreased performance in all participants. With the ICKD diet, median values for PaO2 decreased by - 14.5% and VO2max by + 7.3% and Ppeak by + 4.7%. CONCLUSION: All participants except one could complete the ICKD. VO2max improved with the ICKD under the hypoxia condition. Therefore, an ICKD is an interesting alternative to CHOs dependency for endurance performance at high-altitudes, including high-altitude training and high-altitude races. Nevertheless, decreased PaO2 with ICKD remains a significant limitation in very-high to extreme altitudes (> 3500 m). Trial registration Clinical trial registration Nr. NCT05603689 (Clinicaltrials.gov). Ethics approval CER-VD, trial Nr. 2020-00427, registered 18.08.2020-prospectively registered.

Is Recovery Optimized by Using a Cycle Ergometer Between Ski-Mountaineering Sprints?

PURPOSE: To optimize the recovery phase between heats in ski-mountaineering sprint competitions, this study investigated whether an active recovery protocol on an ergocycle could improve subsequent performance compared with a self-selected recovery strategy. METHODS: Thirteen elite ski mountaineers (9 men and 4 women) performed 3 sprints with 2 different recovery conditions (Ergo vs Free) in a randomized order. The Ergo condition involved a 10-minute constant-intensity exercise on an ergocycle performed at 70% of maximum heart rate. For the Free condition, the athlete was asked to self-select modality. At the end of the third sprint, a passive recovery (seated) was prescribed for both protocols. Sprint performance (time) and physiological parameters (lactate concentration [La], heart rate [HR], and rating of perceived exertion [RPE]) were recorded from each sprint and recovery phase. RESULTS: In the Ergo vs Free protocols, sprint times (177 [24] s vs 176 [23] s; P = .63), recovery average HR (70% [2.9%] vs 71% [5.2%] of maximal HR), and RPE (16.7 [1.5] vs 16.8 [1.5]; P = .81) were not significantly different. However, [La] decreased more after Ergo (-2.9 [1.8] mmol·L-1) and Free (-2.8 [1.8] mmol·L-1) conditions compared with passive recovery (-1.1 [1.6] mmol·L-1; P < .05). CONCLUSIONS: The use of an ergocycle between heat sprints in ski mountaineering does not provide additional benefits compared with a recovery strategy freely chosen by the athletes. However, active conditions provide a faster [La] reduction compared with passive recovery and seem to be a more suitable strategy between multiple-heat sprints.

Repeated Sprint Training in Hypoxia: Case Report of Performance Benefits in a Professional Cyclist.

Repeated sprint training in hypoxia (RSH) has gained unprecedented popularity among the various strategies using hypoxia as an additional stimulus to improve performance. This case study reports the benefits of 150 repeated sprints in normobaric hypoxia over 10 days in a professional cyclist. After 3 weeks of endurance training in November, the cyclist performed five RSH sessions at a simulated altitude of 3,300 m on his own bicycle attached to an indoor trainer in a hypoxic chamber (FiO2 14.1 ± 0.1%, PiO2 94.6 ± 1.4 mm Hg). Each session consisted of four blocks of seven all-out sprints of 6 s interspersed with 14 s active recovery (for a total of 126 s per block). After 12 min of warm-up with a single isolated 6 s reference sprint, the sessions included a first and a second sprinting block with 4 min 54 s active recovery in-between. After 9 min 54 s active recovery including an isolated 6 s reference sprint, a third and a fourth block were performed with 4 min 54 s active recovery in-between, before an active cool-down of 9 min 54 s. The total duration was thus of 50 min per session for a total hypoxic exposure of 250 min exercising. Power output and heart rate were monitored at 1 Hz. Lactate concentration ([La]) and pulse oxygen saturation (SpO2) were measured at the start and end of each block during the first and fifth training session. Basal SpO2 was of 83% during session one and 85.5% during session five. When comparing the first and fifth training session, peak power increased for the best 1 s value (+8%) and the best 5 s average (+10%) to reach 1,041 W and 961 W, respectively. Average power for all blocks (including active recoveries) increased from 334 to 354 W with a similar average heart rate during the sessions (146'.min-1). Peak [La] was increased from 12.3 to 13.8 mmol.l-1. In conclusion, this case report illustrates a 10-days RSH intervention perceived as efficient in a professional cyclist and shown to improve total work (6-s sprints) produced for a similar physiological strain.