Relationship between lifting capacity and back and knee strength in normal Chinese male adults

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Relationship between lifting capacity and back and knee strength in normal Chinese male adults

 

Author: Yeung, Kit-chi
Title: Relationship between lifting capacity and back and knee strength in normal Chinese male adults
Degree: M.Sc.
Year: 1999
Subject: Lifting and carrying -- Physiological aspects
Muscle strength -- Measurement
Back -- Muscles
Knee -- Muscles
Chinese
Men
Hong Kong Polytechnic University -- Dissertations
Department: Multi-disciplinary Studies
Jockey Club Rehabilitation Engineering Centre
Pages: ix, 66 leaves : col. ill. ; 30 cm
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b1483443
URI: http://theses.lib.polyu.edu.hk/handle/200/1941
Abstract: It is believed that global lifting capacity and the corresponding individual joint strength are interrelated. It is expected that the knowledge of their relationship could help in the analysis of contributing factors for lifting performance and provide insight into methods for devising optimal individual strengthening programs. Therefore, the relationship between global lifting capacity and individual joint strength was investigated by correlation and regression methods in 24 normal Chinese male adults. The global lifting capacity was measured in both static symmetrical and dynamic asymmetrical testing conditions using torso and leg lifting techniques. The static lifting capacity was measured using the Acuforce system, which involved symmetrical isometric lifting in fixed leg and torso lifting postures. The dynamic lifting capacity was measured using the Blankenship system, which involved asymmetrical dynamic lifting of a box with varied weight through a range of motion using leg and torso lifting techniques. To quantify knee strength, the isokinetic approach was utilized. The knee strengths were measured in terms of the isokinetic extension and flexion peak torques under concentric and eccentric contractions at slow (60o/s) and fast (180o/s) speeds using the Cybex 6000 machine. The back strengths were quantified utilizing isometric and isoinertial approaches. For the isometric back strength, back isometric peak torques at three orthogonal planes of motion, namely flexion/extension, side flexion and axial rotation, were measured using the B200 isostation. For the isoinertial back strength, the maximal isoinertial velocities of the trunk under 25% and 50% isometric peak torques determined in the three orthogonal planes were measured using the B200 isostation. The dynamic asymmetrical leg and torso lifting capacities were found to be significantly correlated with all of the isometric back strength (in flexion/extension, side flexion and axial rotation) (r=0.51 to 0.62, p<0.05) and isokinetic knee strength (in flexion and extension) (r=0.46 to 0.65, p<0.05). The static symmetrical leg and torso lifting capacities were found to be significantly correlated with all the isometric back strength parameters (r=0.53 to 0.69, p<0.05) and the isokinetic knee strength parameters (r=0.49 to 0.51, p<0.05) except the isometric back strength in axial rotation and the isokinetic knee strength in flexion. Most of the isoinertial back strength parameters were not significantly correlated with both of the static symmetrical and dynamic asymmetrical lifting capacities using leg and torso lifting techniques. From the derived multiple linear regression equation, it was noted that both of the dynamic asymmetrical leg (r=0.98) and torso(r=0.99) lifting capacities could be predicted using isokinetic peak torque of the knee under concentric extension at 180o/s and isometric peak torque of the back in side flexion. This finding suggests that among the numerous strength parameters being studied, the 'isometric peak torque of the back in side flexion' and the 'isokinetic peak torque of the knee in concentric extension at 180o/s' are important in predicting the asymmetrical dynamic lifting capacity. From the training point of view, these two identified parameters might support that the lifting capacities might enhance through specific back and knee strengthening. It is proposed that for back strengthening, in addition to the traditional emphasis for back extension training, strength in back side flexion should also be emphasized especially for targeting at enhancing the dynamic lifting capacity. For knee strengthening, it is proposed that training targeted at improving the isokinetic peak torque of the knee in concentric extension at 180o/s might enhance the global asymmetrical dynamic lifting capacity.

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