Masters Thesis

Effects of Prolonged Sitting on a Lifting Task

Low back pathologies are some of the most prevalent in western society. Two factors that have shown to influence low back pain are sitting and lifting; however, little research has identified how sitting effects muscle activation during these tasks. The purpose of this study was to investigate the effects of prolonged sitting on muscle activation and muscle involvement of the biceps femoris (BF), rectus femoris (RF), erector spinae (ES) and gluteus maximus (GM) muscles during a lifting task. Twenty-one recreationally active males (24 ± 2 years, 1.80 ± 0.06 m, 81.0 ± 12.50 kg, 25.16 ± 3.34 kg/m2 ) completed 5 lifts with a 22.68 kg crate before and after two hours of sitting. Surface electromyography (EMG) was used to measure muscle activation during the concentric and eccentric phases of the lifts. Muscle activation ratios were calculated for each muscle during the lift. No significant differences were found in muscle activation ratios (p > 0.05) post sitting. There were no significant differences in RMS EMG for the GM, ES, and RF (p > 0.05) muscles; however, the BF muscle decreased 17% (p = 0.046) during the eccentric phase of the lift. Prolonged sitting significantly decreases muscle activation of the BF muscle. Therefore, altered pathologies could be expected in populations that sit for two hours or more.

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