Sleep restriction between consecutive days of exercise impairs sprint and endurance cycling performance.

The study aim was to determine the effect of sleep restriction (3 h) between consecutive days of exercise on sprint and endurance cycling performance, wellness, and mood. A total of 10 well-trained males performed 2 consecutive-day trials separated by a normal night sleep (control [CONT]; mean [SD] sleep duration 3.0 [0.2] h) or sleep restriction (RES; mean [SD] sleep duration 3.0 [0.2] h). Experimental trials included a 90-min fixed-paced cycling bout and the respective sleep conditions on Day 1, followed by two 6-s peak power (6-s PP) tests, a 4- and 20-min time trial (TT) on Day 2. Profile of Mood States (POMS) and wellness questionnaires were recorded on Day 1 and Day 2. Blood lactate and glucose, heart rate (HR), and rating of perceived exertion were recorded throughout Day 2. Power output (PO) was significantly reduced for RES in the 6-s PP trial (mean [SD] 1159 [127] W for RES versus 1250 [186] W for CONT; p = 0.04) and mean PO during the 20-min TT (mean [SD] 237 [59] W for RES versus 255 [58] W for CONT; p = 0.03). There were no differences for HR, lactate and glucose, or POMS between CONT and RES in all experimental trials (p = 0.05-0.89). Participants reported a reduction in overall wellness prior to exercise on Day 2 following RES (mean [SD] 14.5 [1.6] au) compared to CONT (mean [SD] 16 [3.0] au; p = 0.034). Sleep restriction and the associated reductions in wellness, reduce cycling performance during consecutive days of exercise in a range of cycling tests that are relevant to both track and road cyclists.

Deception of cycling distance on pacing strategies, perceptual responses, and neural activity.

Pacing during exercise performance is well-established; however, little is known about the neural responses associated with changes in power output and the effect of exercise end-point knowledge. Therefore, the aim of this study was to examine the effect of deception of cycling distance on pacing, cerebral oxy- (O2Hb) and deoxy-haemoglobin concentrations, and alpha (α) wave activity. Ten well-trained male cyclists (23.7 ± 6.6 years) completed three cycling time trials (TT) on a stationary air-braked cycle ergometer and were informed the study was to examine the reliability of 3 × 30-km TT. Participants unknowingly completed three distances (24, 30, and 36 km) in a randomised order. Performance (power output; PO), physiological (heart rate; HR), perceptual (rating of perceived exertion; RPE), and neurological (O2Hb, HHb, and α activity) measures were recorded throughout each TT. Data were converted to a percentage relative to the total distance covered. At 100% completion, HR and PO were lower during the 36 km compared to the 30 km trial (P ≤ 0.01). Compared to the 24 km trial, α waves were reduced at 100% (effect size; ES = 1.01), while O2Hb was greater at 70% of completion in the 36 km trial (ES = 1.39). RPE was also higher for 36 km compared to 30-km trial at 80% and the 24-km trial at 10% and 40-100% of completion (P ≤ 0.02). We conclude that the increase in O2Hb and RPE during the 36-km trial, while a reduction in HR and PO is present, may indicate that the pre-frontal cortex may influence the regulation of exercise performance when deceived of the duration end-point by increasing perception of effort to reduce premature onset of physiological strain.

The influence of knowledge of performance endpoint on pacing strategies, perception of effort, and neural activity during 30-km cycling time trials.

It is understood that withholding information during exercise can alter performance during self-paced exercise, though less is known about neural activity during such exercise. The aim of this study was to compare the effects of withholding versus providing distance feedback on perception, muscular activation, and cerebral activity during cycling time trials (TT). Nine well-trained male cyclists randomly completed 2 x 30-km TT, with provision of performance information and distance feedback (known; KTT), and without performance information and remaining distance (unknown; UTT). Prefrontal cortex (PFC) hemoglobin concentration, electroencephalogy (EEG) responses of the parietal lobe (PL) and motor cortex (MC), and surface electromyogram (EMG) of the right thigh were monitored throughout the TTs, in addition to heart rate (HR), rating of perceived exertion (RPE), and power output (PO). Time to completion was shorter for the KTT compared to UTT (51.04 ± 3.26 vs. 49.25 ± 3.57 min, P = 0.01). There were no differences evident for RPE between conditions (P > 0.50). However, during the final 2 km, the KTT presented higher PO (P ≤ 0.05), HR (P = 0.03) and MC, and PL EEG activity (d = 0.51-0.71) in addition to increased tissue hemoglobin index (nTHI) and oxygen extraction (HHb) (d = 0.55-0.65) compared to the UTT. In conclusion, when withholding information pertaining to remaining distance, performance was reduced due to the application of a conservative pacing strategy. In addition, the increase in HHb across the PFC was strongly correlated with PO (r = 0.790; P < 0.001) suggesting knowledge about remaining distance may increase activation across the PFC. Further, it appears that changes within the PFC may play a role in the regulation of cycling performance.

Sleep quantity and quality during consecutive day heat training with the inclusion of cold-water immersion recovery.

Exercise in the heat is a common occurrence among athletes and often is intentional in order to gain heat acclimation benefits, however, little is known about how such training may affect sleep. Therefore, this study investigated five days of training in the heat of varying intensity and duration and inclusion of cold-water immersion (CWI) recovery on sleep quantity and quality. Thirty recreationally-trained male participants completed five days of heat training (HT) and were randomised into three interventions including (i) 90 min cycling at 40% power at maximal aerobic capacity (Pmax) with 15 min passive recovery (90HT); (ii) 90 min cycling at 40% Pmax with 15 min CWI recovery (90CWI); or (iii) 30 min cycling alternating between 40% and 70% Pmax, with 15 min passive recovery (30HT). Sleep quality and quantity were assessed using Actigraphy and sleep diaries during five baseline nights (BASE) and five nights of HT which included subjective sleep quality and objective assessments of sleep quantity and quality. Total time asleep and perceived sleep quality were reduced, while awake duration and wake after sleep onset (WASO) were increased (p = 0.001-0.01) during HT compared to BASE. Latency was shorter for 30HT compared to 90HT during HT (p = 0.02), however, no differences between interventions for all other sleep variables (p > 0.05). The reduction in total sleep time due to increases in average wake duration during HT may be due to the unaccustomed increased in training frequency. Of note, reducing training in the heat duration per day improved sleep latency and sleep quality with no effect on total sleep time, while the addition of CWI has minimal effect on sleep quality or quantity.

The effect of high versus low intensity heat acclimation on performance and neuromuscular responses.

This study examined the effect of exercise intensity and duration during 5-day heat acclimation (HA) on cycling performance and neuromuscular responses. 20 recreationally trained males completed a 'baseline' trial followed by 5 consecutive days HA, and a 'post-acclimation' trial. Baseline and post-acclimation trials consisted of maximal voluntary contractions (MVC), a single and repeated countermovement jump protocol, 20km cycling time trial (TT) and 5×6s maximal sprints (SPR). Cycling trials were undertaken in 33.0 ± 0.8°C and 60 ± 3% relative humidity. Core (Tcore), and skin temperatures (Tskin), heart rate (HR), rating of perceived exertion (RPE) and thermal sensation were recorded throughout cycling trials. Participants were assigned to either 30min high-intensity (30HI) or 90min low-intensity (90LI) cohorts for HA, conducted in environmental conditions of 32.0 ± 1.6°C. Percentage change time to complete the 20km TT for the 90LI cohort was significantly improved post-acclimation (-5.9 ± 7.0%; P=0.04) compared to the 30HI cohort (-0.18 ± 3.9%; P<0.05). The 30HI cohort showed greatest improvements in power output (PO) during post-acclimation SPR 1 and 2 compared to 90LI (546 ± 128W and 517 ± 87W, respectively; P<0.02). No differences were evident for MVC within 30HI cohort, however, a reduced performance indicated by % change within the 90LI (P=0.04). Compared to baseline, mean Tcore was reduced post-acclimation within the 30HI cohort (P=0.05) while mean Tcore and HR were significantly reduced within the 90LI cohort (P=0.01 and 0.04, respectively). Greater physiological adaptations and performance improvements were noted within the 90LI cohort compared to the 30HI. However, 30HI did provide some benefit to anaerobic performance including sprint PO and MVC. These findings suggest specifying training duration and intensity during heat acclimation may be useful for specific post-acclimation performance.