Affiliations: Department of Exercise Science, University of Puget Sound, Tacoma, WA, USA
Correspondence:
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Corresponding author: Barbara L. Warren, 1500 N. Warner #1047, Department of Exercise Science, University of Puget Sound, Tacoma, WA 98416, USA. Tel.: +1 253 879 3710; Fax: +1 253 879 3254; E-mail:blwarren@pugetsound.edu
Abstract: BACKGROUND: The effects of circadian rhythms on aerobic exercise
have been well documented, but little research has been conducted during
isokinetic exercise. OBJECTIVE: The purpose of this study was to examine how isokinetic
peak torque of the knee extensors changes throughout the day. METHODS: Twenty-five college-aged recreational athletes (14
females, 11 males) completed one familiarization and three experimental
sessions on a Cybex NORM isokinetic dynamometer, with start times of
08:00-09:00, 13:00-14:00, and 18:00-19:00. Each session began with a
five-minute warmup on a cycle ergometer and three sets of four submaximal
concentric discrete knee extensions at 60, 180 and 300°/s, with knee flexion
held constant at 300°/s and a one minute rest between velocity sets. This
was followed by four maximal concentric discrete knee extensions with the
same parameters as the warmup. Peak torque was recorded for each velocity.
Data were analyzed using a two-way 3 (time) × 3 (velocity) repeated measures
ANOVA (α ≤ 0.05). RESULTS: There were no significant differences in peak torque by
time of day at any velocity among females (n= 14), males (n= 11), or the
entire group (n= 25). CONCLUSIONS: When measuring knee extension peak torque in these
college-aged subjects, time of day was not a factor.
Keywords: Isokinetic, peak torque, knee extension, time of day
