Affiliations: [a] Clinical Kinesiology Laboratory, The Physical Therapy
Department, The University of Montana, Missoula, MT 59812 4680, USA. Tel.: +1
406 243 4753/5183; Fax: +1 406 243 2795; E-mail: rgajdos@selway.umt.edu | [b] St. Patrick Hospital, Missoula, MT 59802, USA | [c] Northern Rockies Rehabilitation & Athletic
Training Center, Missoula, MT 59804, USA
Abstract: The purpose of this study was to examine the influence of short
hamstring muscles (hamstrings) on gravitational torque of the leg (GT) and on
knee extension and knee flexion concentric isokinetic torque. Fifteen
non-disabled men (ages: 18 to 37 years) with clinically short hamstrings
(passive straight-leg-raising ≤ 65°) were measured
for the GT in two positions: 1) seated position that included a passive stretch
of the hamstrings, and 2) supine position that did not include a passive
stretch of the hamstrings. Subjects performed three trials of maximal
concentric knee extension and flexion in the seated position under four
randomly ordered conditions
(60°·s^{-1} with seated GT,
60°·s^{-1}with supine GT,
180°·s^{-1} with seated GT,
and 180°·s^{-1} with supine
GT). One-way ANOVA analysis showed that the GT measured while seated
(36.00 ± 9.58 Nm) was greater than the GT measured while
supine (21.00 ± 3.90 Nm) (P < 0.001).
The greater GT while seated was explained by the sum of the passive hamstring
torque and the true GT. Knee flexion peak torque, knee flexion average torque,
and the hamstring/quadriceps average torque ratios were decreased at
60°·s^{-1} (P ≤
0.023) using the seated GT compared to using the supine GT. The same
torque characteristics did not differ significantly for knee flexion at
180°·s^{-1}, or for knee
extension at either isokinetic speed. We concluded that hamstring passive
torque contributed to greater GT in the seated position, which caused invalid
knee flexion torque measurements when tested at
60°·s^{-1}. This evidence
supports weighing the leg supine in order to remove hamstring passive torque
and to ensure valid knee concentric isokinetic torque measurements when testing
at 60°·s^{-1}.
Keywords: Isokinetic testing, knee muscles, short hamstring muscles
