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Electromyographic Analysis of the Hamstrings during the 'Nordic' Hamstring Exercise

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Fruer, Steven A. (2008) Electromyographic Analysis of the Hamstrings during the 'Nordic' Hamstring Exercise. Masters thesis, University of Gloucestershire.

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7466 Fruer (2008) Electromyographic Aalysys of the Hamstrings during the Nordic Hamstring Exercise.pdf - Accepted Version
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Abstract

Training using the Nordic Hamstring Exercise (NHE) has been shown to improve factors that may help prevent hamstrings injury, despite this no research group has examined the recruitment characteristics of the hamstrings muscles during this exercise and considered the specificity of training adaptations. The aim of the present investigation was to study the electromyographic (EMG) activity of the hamstrings muscles during the NHE and then to investigate the effect of a 4 week NHE training programme on isokinetic eccentric hamstring peak torque production in both limbs at velocities 60, 120 and 240°/s. Eighteen male professional soccer players (mean ± SD; age, 22.8 ± 3.5 yrs) were randomly assigned to a training or control group. A paired sample t-test indicated no difference in the normalised RMS amplitude of the hamstrings between the dominant (DOM) and non dominant (NDOM) limbs (t 37 = 0.137; P = 0.413) during the NHE. Two-way repeated measures ANOVA demonstrated no interaction between the medial (MED) and lateral (LAT) muscle regions and the knee position (phase 1, 1st 1 /3 of the movement; phase 2, 2nd 1/3 of the movement; phase 3, yct 1/3 of the movement) for the RMS EMG amplitude of the hamstrings in the DOM limb (F 2, 35 = 1.775, P = 0.184). Although no main effect for muscle region was observed (F 1, 36 = 1.605, P = 0.213), main effects for knee position during the movement on RMS EMG amplitude were demonstrated (F 2, 35 = 154.354, P < 0.001). Bonferroni corrected post-hoc t-tests indicated that the normalised RMS EMG amplitude was significantly higher at phase 2 (11.1±3.8%) and phase 3 (8.6±3.0%) of the movement when compared to phase 1 (3.7±1.8%) of the movement. For the training study, a two-way (2 x 2) between (group) within (time) ANOVA demonstrated an interaction effect for time by group of the DOM and NDOM limbs in isokinetic hamstring peak torque production across assessment velocities (60°/s, DOM F 1, 16 = 5.11, P = 0.04; NDOM F 1, 16 6.84, P = 0.02; 120°/s, DOM F 1, 16 = 4.46, P = 0.05; 240°/s DOM, F 1, 16 = 8.10, P = 0.01; 240°/s, NDOM, F 1, 16 5.68, P = 0.03). Main effects for time for the DOM limb were observed for the slowest velocity (60°/s, DOM, F 1, 16 = 5.58, P = 0.03), but not for the faster velocities (120°/s, DOM, F 1, 16 = 2.73 P = 0.12; 240°/s, DOM, F 1, 16 = 1.24, P = 0.28). Main effects for time for the NDOM limb were observed across all velocities (60°/s, NDOM, F 1, l6 = 10.96, P < 0.001; 120°/s, NDOM, F 1, 16 = 6.75, P = 0.02; 240°/s, NDOM, F 1, 16 = 12.24, P < 0.001). A two-way (2 x 2) repeated measures ANOVA indicated no interaction effects for time by limb across velocities in the training group (60°/s, F 1, 18 = 0.20, P = 0.66; 120°/s, F 1, l8 = 0.026 P = 0.88; 240°/s, F 1, 18 = 2.48, P = 0.13). Main effects for time across all velocities were observed (F 1, 18 = 23.65, P < 0.001) although no main effects for limb across all velocities were observed (F 1, 18 = 0.75, P = 0.40). EMG data demonstrates that the hamstrings muscles in both limbs are recruited to a similar extent and the activity levels of the LAT and MED hamstrings were similar during the NHE; with the highest activation levels being observed in the more extended knee joint positions. Isokinetic peak torque data demonstrates that 4 weeks NHE training significantly increases eccentric peak torque production in the hamstrings of both the DOM and NDOM limbs. These results have implications for injury prevention and rehabilitation as increasing eccentric hamstring strength has been identified to reduce hamstrings injuries.

Item Type:

Thesis (Masters)

Thesis Advisors:

Thesis Advisor	Email	URL
Iga, John	jiga@glos.ac.uk	UNSPECIFIED
Deighan, Martine	mdeighan@glos.ac.uk	https://www.glos.ac.uk/staff/profile/martine-deighan/
James, David	djames@glos.ac.uk	https://www.glos.ac.uk/staff/profile/david-james/