Effects of Sleep Loss and Strenuous Physical Activity on the Rest–Activity Circadian Rhythm

Abstract

A period of 3 days of little and fragmented sleep (3-4 hr of total rest per day), in which subjects were engaged in a prolonged physical effort, was enough to significantly affect the rest-activity rhythm. A longer period (5 days) in such a condition induced even more accentuated alterations, with a disturbance in nocturnal sleep. Disrupted sleep is common among hospitalized patients and those working long shifts. This study demonstrates changes in the structure of the rest-activity circadian rhythm that can result and may suggest opportunities for intervention.

Health challenges in long-distance dog sled racing: A systematic review of literature

“…With respect to the research design described in the different studies, eight were descriptive field studies with repeated measurements [10–17] (two of which were defined as “case” studies based on reports of one or two participants [16,17]) and two were surveys [18,19] (of which, one was designed as a perspective longitudinal study [19]). In most studies, measurements were done during or shortly before/after the race, while three studies included follow-up measurements over 1 week [10,11] and 1 month [19] after completion of the race. The studies accounted for a total of 185 subjects (accounting for overlapping samples), among which at least 66 were males and 48 were females, while for 71 subjects the sex was not specified.…”

“…During the race, the participants slept about 4-hours per day, accumulating a sleep-debt of ~ 8–28 hours. Overall, the sleep-wake patterns and alertness levels were impoverished after completion of the race, especially among the participants who were engaged in the race for a longer span.Calogiuri et al [11]5.5010 mushers (2 M and 8 F, Age: 43±11 years) participating in the Finnmarksløp 500K and 1000K Descriptive field study with baseline assessments, repeated measurements and comparisons between participants in the short and long racePsychophysical workloadSleep & alertnessContinuous HR-monitoringActigraphy (analysed using Activity-analysis, Sleep-analysis and NPCRA) with sleep logsThe average estimated workload was of relatively low intensity. However, the long duration alongside the little resting time makes the race extremely demanding.…”

“…Three studies by Calogiuri and Weydahl have carried out continuous monitoring of the participants heart rate (HR) throughout the race (or part of it) and cross-matched this information with the official race reports in order to estimate the exercise intensity during the different legs [10,11,17]. These studies reveal that, on average, the exercise intensity sustained by the participants in long-distance dog sled races is not particularly high per se : the mean HR measured during the legs ranges between 50% and 65% of the participants maximal HR, although at times very high levels of intensity were achieved (HR above 90% of the maximum) [10,11,17].…”

“…These studies reveal that, on average, the exercise intensity sustained by the participants in long-distance dog sled races is not particularly high per se : the mean HR measured during the legs ranges between 50% and 65% of the participants maximal HR, although at times very high levels of intensity were achieved (HR above 90% of the maximum) [10,11,17]. However, these studies also reveal that the participants engage in few and brief bouts of rest (on average two bouts per day, accounting for an overall rest-time of about 3–4 hours per day) [10,11], which, alongside the long duration of the race and the challenging environmental conditions, makes the overall load quite strenuous. These findings are in line with two studies carried out by Cox and her colleagues, in which the energy expenditure of the participants was assessed using doubly labelled water [14] and by combining energy intake data with weight loss data [16].…”

“…Finnmarksløp 500K and 1000K, respectively): the mushers in the shorter race engage in higher exercise intensities as compared to the mushers in the longer race [11]. Such differences in load probably depend on the fact that the mushers in the shorter race are allowed a smaller number of dogs than the musher in the longer race (seven and 12, respectively), but it could also be explained by different pacing strategies adopted by the participants in the different races.…”