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The purpose of this study was to investigate different intensities of unilateral fatiguing dynamic quadriceps contractions on non-exercised, contralateral quadriceps performance. In a randomized crossover study design with 12 recreationally trained male (1.78 ± 0.05 m, 84.5 ± 7.6 kg, 30.0 ± 8.5 yrs) participants, maximal voluntary contraction (MVC) force, force developed in the first 100 ms (F100), and electromyography of the non-exercised contralateral knee extensors were measured before and after fatiguing protocols performed by ipsilateral knee extensors. Non-exercised knee extensors’ endurance was also measured post-intervention. The fatigue protocols consisted of four sets of dynamic knee extensions each to task failure with 40% and 70% MVC on separate days. Both the 40% (p = 0.009, Effect Size [ES] = 0.72) and 70% (p = 0.001, ES = 2.03) conditions exhibited 23.7% and 34.6% decreases in F100 respectively with the non-exercised contralateral knee extensors. A significant time effect (p = 0.002) demonstrated that both the 40% (and 70% (conditions exhibited 4.4% (ES = 0.29) and 7.1% (ES = 0.53) force decreases from pre- to post-intervention, respectively. However, the condition * time interaction only showed a trend (p = 0.09) with moderate (40%: ES = 0.62) to large (70%: ES = 0.82) effect sizes for decreased contralateral limb force compared with control session. The 40% (p = 0.09, ES = 0.65) and 70% (p = 0.07, ES = 0.79) protocols had a tendency to induce greater contralateral force variation during sustained submaximal isometric contraction compared with control. In conclusion, this study highlighted that unilateral lower limb fatigue induced by low intensity as well as high intensity dynamic knee extensions provided some evidence of crossover fatigue with the contralateral non-exercised limb. |
