The effects of partial sleep restriction on biomechanical, physiological and perceptual responses during an early morning cycling time trial Dale Edwards; Cathy Munro; Travis Steenkamp; Dr Jonathan Davy Department of Human Kinetics and Ergonomics Rhodes University, Grahamstown

Background Effective growth Energy conservation Recovery 7-9 hours (Mignot, 2008) SLEEP LOSS Mood Cognitive performance

Background and problem identification What about athletic performance? Sleep loss before a competition is a common problem among athletes performance but the effect on athletic performance is still unclear. Sleep loss before a competition is a common problem among athletes Previous research has focused on total sleep deprivation (24 hours or more) The effect of partial sleep restriction (less than 7 hours) on physical endurance performance remains poorly understood. Total sleep deprivation (24 hours or more)- Most research Partial sleep restriction (less than 6 hours)- Limited research

Methodology – Experimental Design Sleep restricted Normal sleep 4 hours time in bed Laboratory Bed: 02h00 or 02h45 Wake: 06h00 or 06h45 Normal sleep (7 – 9 hrs) Home Bed ≈ 22h00 to 23h00 Wake: 06h00 or 06h45 Cycling time trial @06h30 or 07h15 Order randomised 5 – 7 day wash out

Cycling protocol and dependent variables 16.1km time trial (Atkinson & Brunskill, 2000) Air resistance relative to BW Blinded except for distance covered Maximal effort required Time Power output Heart rate Central RPE Average every 2km Average every 2km Taken every 2km

Participants and experimental procedure 13 participants (5 female and 8 male); age range18-25 Uninjured, non-smoking, no sleep disorders, oral contraceptives (Females) Sleep restricted condition = entered lab at 00h00 Recruit, consent habituate Testing session 1 Testing session 2 Fasted 5 min warm up Power output, HR, RPE taken every 2km Resistance setting 16.1 km practise Female participant characteristics: age 22yrs±1.36; mass 56.5kg±6.74; height 159.8cm±6.78 Male participant characteristics: age 22yrs±1; mass 79kg±8; height 177cm±7

Results: Time to completion Condition effect: p=0.09; Sex effect: p<0.01; Condition*Sex: p=0.58 * (p<0.01 Figure 1: Mean time to completion for both conditions (Error bars denote 95% CI) Figure 2: Mean time to completion by sex for both conditions (Error bars denote 95% CI)

Time to completion

Results: Power output End spurt Condition effect: p=0.09; Distance: p<0.01; Sex effect: p<0.01; Condition*Distance: p=0.98 End spurt Figure 3: Mean power output for both conditions over the time trial (Error bars denote 95% CI)

Results: Heart rate Increased steadily No steady state reached Condition effect: p=0.34; Distance: p<0.01; Sex effect: p=0.08; Condition*Distance: p=0.72 Increased steadily No steady state reached Figure 4: Mean heart rate for both conditions over the time trial (Error bars denote 95% CI)

Results: Ratings of perceived exertion Condition effect: p=0.67; Distance: p<0.01; Sex effect: p=0.23; Condition*Distance: p=0.85 Increased steadily Figure 5: Mean RPE for both conditions over the time trial (Error bars denote 95% CI)

Discussion Sleep restriction of 4 hours enough to cause performance decrements? Adapted from Steenekamp & Davy (2014) Used fixed pace protocol 4 hours partial sleep restriction Sleep restriction as opposed to fragmented sleep 16.1 km time trial intensity and duration?

Limitations Small sample size (n=13) Access to well trained cyclists Student population Chronotype was not accounted for

Recommendations Exploring boundaries of sleep restriction and exercise Sleep fragmentation Chronotype Individual data

Conclusion Current findings suggest that partial sleep deprivation of up 4 hours has no significant influence on biomechanical, physiological and perceptual responses during a cycling time trial. However performance is meaningful in the context of cycling. Methodological inconsistencies within previous literature make it challenging to draw conclusions. More research needed. These finding should be seen in light of the limitations of this study.

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