The aim of this study was to ascertain the effects of night shift work on athletic performance in cross country mountain bike racing.
The study model had participants (n=1) work a night shift at Rotorua ED followed by competition in the 2016 Nduro Winter Series XC race (42km). Study participants were not allowed sleep between work and racing. For analysis heart rate, strava segment times and self reported subjective scores were used as end points, with comparison made to data taken from a control race (2015 Nduro Winter Series round 1).
100% of athletes (n=1) self reported a higher suffer score during the race following the night shift when compared to the control. Suffering was rated highest in the first 30 minutes of the race. Subjects described an intense feeling of frustration as riders flew past on even slight inclines.
Heart rate data supports the reported early race difficulties with an inability to sustain an appropriate heart rate and low speeds despite a gravel road section near the start. The Fern Drive strava segment shows almost 3 minutes time loss to the leaders after only 7.3km.
Although not a primary endpoint of the study, participants (n=1) reported a slowing of reaction times and poor line choices on even easy sections of the trail during the first 30 minutes.
Performance improved somewhat through later sections of the course, though these improvements were largely restricted to singletrack portions. Climbing remained poor. Both of these were supported by objective data, with ascent time for Katore Road being 1 minute 40 seconds of the fastest recorded time for the study participant. Descent times were slower than previous pb’s but by a smaller percentage.
Results demonstrate that competing in XC mountain bike racing after a night shift contributes to poor performance based on both subjective and objective measures.
A number of potential confounders are present in the above study. The relatively small sample size (n=1) has the potential to influence results. The subject may also have just had a bad day, independent of the night shift. Recent training loads may have been inadequate or incorrect to prepare for a race such as the Winter Series XC.
Use of caffeine supplementation was not formally measured and may have had an impact. Further research is needed, currently a follow up study is planned for Nduro Winter XC round 2 in August.
Citation* (not accepted for publication):
Reynolds T (2016) The effect of night shift work of cross country mountain bike racing, Rotorua Journal of Mountain Biking Medicine, 1(1), online version.