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Article Title

EFFECTS OF FATIGUE ON LOWER EXTREMITY BIOMECHANICS DURING SQUATTING

Abstract

Resistance training can induce muscular fatigue, which has the potential to influence balance and proper form during exercise. PURPOSE: This study sought to analyze lower extremity biomechanics while squatting when fatigued. METHODS: Subjects consisted of 6 males, and 5 females between the ages of 18-48y (26 ± 7.3y), who performed back squats regularly. Brightly colored stickers were placed on the left side of the body on the humeral head, greater trochanter, lateral femoral condyle, and lateral malleolus of the fibula, and in the front on both tibial tuberosities. Subjects were video recorded on mounted tablet computers from the front and side view, while performing 5 back squats with an unloaded 20.5 kg barbell. Using 75% of their self-reported 1RM, they then performed a descending ladder from 10 reps down to 1, reducing their number by 1 each set. If a set could not be completed without re-racking, the next set was reduced by 5% (e.g. 70% 1RM). Participants performed another 5 reps with the unloaded barbell post-fatigue. Ankle, knee, and hip flexion angles were determined in side view for the 5 reps pre- and post-fatigue using a validated tablet app. Hip adduction/rotation was approximated in the front view by an angle with the apex at the subject’s chin down to the tibial tuberosities. The highest and lowest angles were removed and the middle three repetitions were averaged for each joint. Dependent t-tests determined differences in pre- vs post-fatigue for ankle, knee, hip flexion, and hip adduction/rotation angles at p < 0.05. RESULTS: The results showed no significant differences in degrees of hip, knee, and ankle flexion between the pre- and the post-fatigue tests. The results for the pre- and post-test mean of the hip angle remained nearly unchanged, 69.4 ± 12.1° vs. 69.9 ± 10.1°, for pre- vs. post- fatigue, respectively (p>0.05). Knee angle increased slightly pre- to post- (74.5 ± 12.6° vs. 76.2 ± 11.8°), as did the ankle angle (56.6 ± 5.5° vs. 57.2 ± 6.2°), although neither reached statistical significance (p>0.05). Subjects displayed greater hip adduction and internal rotation after fatigue (54.2 ± 10.8° vs. 53.2 ± 12.0°) although this was also not significant (p>0.05). CONCLUSION: Our results showed that there was no significant change in lower extremity biomechanics after a fatiguing back squat workout, which is in contrast to previous studies. Our data suggests that participants had a tendency to squat shallower and collapse their knees inward after fatigue, but our data lacked statistical power. Future studies should use more secure joint markers, a more precise method of analyzing video data, and a weighted barbell during testing to observe effects of fatigue.

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