The maximum force output of skeletal muscle exhibits a circadian rhythm and is associated with time-of-day differences in athletic performance. We investigated whether the diurnal difference in force output is associated with changes to the post-translational state of muscle proteins using non-targeted proteomic techniques. Ten physically active men (mean ± SD; age 26.7 ± 3.7 y, height 1.77 ± 0.08 m, body mass 74.9 ± 9.8 kg) performed experimental sessions in the morning (0800 h) and evening (1700 h) that were counterbalanced in order of administration and separated by at least 72 h. Each session included measurements of maximal voluntary contraction (MVC; including twitch-interpolation) and peak rate of force development (RFD) of the knee extensors. Samples of vastus lateralis were collected immediately after exercise and were analysed by ‘top-down’ and ‘bottom-up’ proteomic methods. Muscle force in the evening (754.4 ± 112.9 N) was significantly (P..

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