Strengthening recovery, enduring sleep. An ecologically valid assessment of sleep quantity and quality in hybrid...

PURPOSE: This study assessed sleep characteristics in a sample of experienced “hybrid” athletes (i.e., athletes who participate and train for competitions that combine endurance and resistance tasks, e.g., Hyrox, Cross-Fit) to investigate the influence of training mode (i.e., resistance training and endurance training) on sleep quality, quantity, and architecture. METHODS: Eight male “Hyrox” athletes (23–32 years) wore a validated, non-invasive, ambulatory sleep monitoring device after completing either a primarily resistance or endurance training bout, performed within a two-week period, consisting of a total two resistance and two endurance post-training nights evaluated. Objectively-measured sleep parameters analysed included: total sleep time (TST), sleep onset latency (SOL), wake after sleep onset (WASO), sleep architecture (sleep stages proportion), and the number and duration of cardiac arousals occurring before and after sleep onset. RESULTS: Despite reporting ‘good’ overall sleep quality, hybrid athletes experienced shorter TST (~ 6.6 h) and spent ~ 5% less time in REM compared to reference non-athletes, but in-line with other sport populations. Compared to endurance training, resistance training was associated with longer SOL (29 vs. 10 min, p = 0.003) and shorter WASO (31 vs. 48 min, p = 0.008), with corresponding differences in cardiac arousals before and after sleep onset (13 vs. 5 events before SO, 81 vs. 99 events after SO, respectively, p = 0.006 and p = 0.010). CONCLUSION: Hybrid athletes presented sleep characteristics that differed depending on the training mode of their exercise bout. In particular, sleep latency and WASO time were positively associated with cardiac autonomic responses before and after sleep onset.