Detrended fluctuation analysis to determine physiologic thresholds, investigation and evidence from incremental cycling test.

PURPOSE: Training zones are generally assessed by gas-exchange thresholds (GET). Several mathematical analyses of heart rate variability (HRV) are proposed for indirect GET determination. Our study aimed to investigate the accordance of the detrend fluctuation analysis (DFA α1) for determining GET with first (VT1) and second ventilatory (VT2) thresholds in well-trained subjects. METHODS: Eighteen female and 38 male sub-elite cyclists performed a maximal incremental cycling test of 2-min stage duration with continuous gas exchange and HR measurements. Power output (PO), Oxygen uptake ( V ˙ O2) and HR at VT1 and VT2 were compared with DFA α1 0.75 (HRVT1) and 0.50 (HRVT2). Agreements between PO, V ˙ O2 and HR values were analyzed using Bland-Altman analysis. RESULTS: Large limits of agreement between VT1 and HRVT1 were observed for measures of V ˙ O2 expressed in mL.min-1.kg-1 [- 21.3; + 14.1], HR [ 39.2; + 26.9] bpm and PO [- 118; + 83] watts. Indeed, agreements were also low between VT2 and HRVT2 for measures of V ˙ O2 [- 26.7; + 4.3] mL.min-1.kg-1, HR [- 45.5; + 10.6] bpm and PO [- 157; + 35] watts. Our results also showed a sex effect: women obtained worst predictions based on DFA α1 than men for HR (p = 0.014), PO (p = 0.044) at VT1 and V ˙ O 2 (p = 0.045), HR (p = 0.003) and PO (p = 0.004) at VT2. CONCLUSION: There was unsatisfactory agreement between the GET and DFA α1 methods for VT1 and VT2 determination in both sex well-trained cyclists. Trial registration number 2233534 on 2024/03/05 retrospectively registered.

Gradual Advance of Sleep-Wake Schedules Before an Eastward Flight and Phase Adjustment After Flight in Elite Cross-Country Mountain Bikers: Effects on Sleep and Performance.

ABSTRACT: Garbellotto, L, Petit, E, Brunet, E, Guirronnet, S, Clolus, Y, Gillet, V, Bourdin, H, and Mougin, F. Gradual advance of sleep-wake schedules before an eastward flight and phase adjustment after flight in elite cross-country mountain bikers: effects on sleep and performance. J Strength Cond Res 37(4): 872-880, 2023-Strategies, for alleviating jet lag, specifically targeted to competitive athletes have never been studied, in ecological conditions. This study aimed to assess the effects of a phase advance before a 7-hour eastward flight followed by a strategy of resynchronization at destination on sleep and physical performance in professional mountain bikers. Six athletes participated in this study divided into 4 periods: (i) baseline (usual sleep-wake rhythm); (ii) phase advance (advance sleep-wake schedules of 3 hours for 6 days); (iii) travel (flight: Paris-Tokyo); and (iv) phase adjustment (resynchronization of sleep-wake schedules). Melatonin pills and light therapy were administrated during the phase advance and phase adjustment. Sleep was recorded by polysomnography and actigraphy, core body temperature (CBT) rhythm was assessed by ingestible capsules, and physical performances were tested by the Wingate and 5-minute maximal exercise tests. Results showed that bedtime was advanced by 2.9 hours at the end of the phase advance ( p ≤ 0.01) with a batyphase of CBT advanced by 2.5 hours ( p = 0.07). Bedtime was similar at destination compared with baseline. Total sleep time and sleep composition were unchanged at the end of the phase advance or at destination, compared with baseline. Physical performances were maintained after phase advance and at destination. The phase advance enabled to preshift part of the time zones without disturbing sleep and physical performances and contributed to preserving them once at destination. A phase advance before eastward travel represents an effective strategy to counter harmful effects of jet lag.

Complete sleep evaluation of top professional cross-country mountain bikers' athletes.

BACKGROUND: Despite growing interest in athletes' sleep, few studies have focused on professional athletes, especially in individual sports. Moreover, limited investigations included female athletes. This study aimed to evaluate sleep chronotype, as well as objective and subjective sleep characteristics in male and female professional cross-country mountain bikers. METHODS: Thirteen athletes (7 males and 6 females) of the French national team took part in this study. The Chronotype was assessed by the Horne and Östberg Morningness-Eveningness Questionnaire and sleep by actigraphy for one month, by ambulatory polysomnography (PSG) for one night and by the Pittsburgh Sleep Quality Index. RESULTS: Most athletes (77%) are classified as moderately morning type and a minority of athletes (23%) are intermediate type. Athletes sleep on average 8 hours per night and during the night recorded by PSG, N3 and REM sleep stages represented 21.2±3.4% and 20.9±3.1% of the total sleep time, respectively. These good sleep parameters were confirmed by subjective data with 77% good sleepers. Except the poorer subjective sleep quality in female athletes (5.7±1.6) compared to male athletes (2.6±1.7, P<0.05), no significant sex difference was found for all characteristics evaluated. CONCLUSIONS: The professional status of these athletes and the organization of mountain bike calendar may explain their good sleep characteristics.