Degree Name
Master of Science in Education
Graduate Program
Kinesiology
Advisor
Olson, Micheal W
Abstract
TITLE: RECOVERY OF FORCE OUTPUT AND ELECTROMYOGRAPHY FROM TRUNK MUSCLES AFTER CYCLIC PASSIVE LOADING
Major Advisor: Michael W. Olson
TITLE: RECOVERY OF FORCE OUTPUT AND ELECTROMYOGRAPHY FROM TRUNK MUSCLES AFTER CYCLIC PASSIVE LOADING
Major Advisor: Michael W. Olson
Continuous loading of the low back tissues results in modified neuromuscular and kinetic output during trunk extension efforts. It is believed that the viscoelastic behavior of these low back tissues is modified, but the ramifications of these loading schemes needs further study for longer durations. The purpose of this research project was to observe force output and muscle activation pattern changes during trunk extension efforts before and up to 60 minutes after passive cyclic loading of the lumbar spine during trunk flexion-extension exercise. Sixteen healthy male and female volunteers (20.3 ± 2.1 yrs, 1.63 ± 0.04 m, 50.2 ± 9.3 kg) participated in the study. An isokinetic dynamometer was used in performing a 10 min set of cyclic trunk flexion-extension at a preset velocity of 0.17rad/s through each participant’s range of trunk flexion from seated upright position. Participants performed maximum voluntary isometric contraction (MVIC) trunk extension efforts before, immediately after, and at 15 minute intervals (T15 – T60 ) for 60 min after cessation of the passive loading scheme. Maximum and average torque output, as well as surface electromyography (EMG) from thoracic (TP) lumbar paraspinal (LP), rectus abdominis (RA) and external oblique (EO) muscles (bilaterally), were recorded. One way ANOVAs were used to identify changes at each time period of testing compared to baseline values. Alpha was set at < 0.05. Maximum and average torque measures did not change over time (p > 0.05). Rate of force development did not change over time (p > 0.05). Average EMG did not change over time (p>0.05) in TP,LP and RA muscles. There was significant difference across time for the LEO muscle (p < 0.04). Average EMG at T15 and T30 were significantly lower than the initial pre-loading values. Similarly, a significant difference was present in the right EO over time (p < 0.01). Average EMG values at T15, T30 and T45 were significantly lower than at the initial pre-loading values. All peak EMG data during recovery were significantly reduced compared to the initial value all (p 0.05) Range of motion did not significantly change from pre to post trials. These data provide inconclusive results as to the force output and EMG modifications when the passive viscoelastic tissues are cyclically loaded in flexion-extension. There are indications of modifications in the EMG detected from EO, providing further potential evidence of neuromuscular modification to potentially compensate for increased compliance of the viscoelastic tissues.