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Masatoshi Nakamura, Tome Ikezoe, Takahiro Tokugawa and Noriaki Ichihashi

Context:

Hold–relax stretching (HRS) and static stretching (SS) are commonly used to increase joint range of motion (ROM) and decrease muscle stiffness. However, whether there are differences between acute effects of HRS and SS on end ROM, passive torque, and muscle stiffness is unclear. In addition, any differences between the mechanisms by which HRS and SS lead to an increase in end ROM are unclear.

Objective:

To compare the acute effects of HRS and SS on the passive properties of the gastrocnemius muscle–tendon unit (MTU), end ROM, passive torque, and muscle stiffness in vivo and to investigate the factors involved in increasing end ROM.

Design:

Crossover experimental design.

Participants:

30 healthy men (21.7 ± 1.2 y) with no history of neuromuscular disease or musculoskeletal injury involving the lower limbs.

Intervention:

Both HRS and SS of 30 s were repeated 4 times, lasting a total of 2 min.

Main Outcome Measures:

End ROM, passive torque, and muscle stiffness were measured during passive ankle dorsiflexion using a dynamometer and ultrasonography before and immediately after HRS and SS.

Results:

The results showed that end ROM and passive torque at end ROM significantly increased immediately after both HRS and SS, whereas muscle stiffness significantly decreased. In addition, the percentage change in passive torque at end ROM on use of the HRS technique was significantly higher than that after use of the SS technique. However, the percentage change in muscle stiffness after SS was significantly higher than that with HRS.

Conclusion:

These results suggest that both HRS and SS can effectively decrease muscle stiffness of the gastrocnemius MTU and that HRS induces a change in the passive torque at end ROM—ie, sensory perception—rather than changing muscle stiffness.

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Kevin M. Cross

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Dale J. Butterwick

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R. McNeill Alexander

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Thomas S. Buchanan, David G. Lloyd, Kurt Manal and Thor F. Besier

This paper provides an overview of forward dynamic neuromusculoskeletal modeling. The aim of such models is to estimate or predict muscle forces, joint moments, and/or joint kinematics from neural signals. This is a four-step process. In the first step, muscle activation dynamics govern the transformation from the neural signal to a measure of muscle activation—a time varying parameter between 0 and 1. In the second step, muscle contraction dynamics characterize how muscle activations are transformed into muscle forces. The third step requires a model of the musculoskeletal geometry to transform muscle forces to joint moments. Finally, the equations of motion allow joint moments to be transformed into joint movements. Each step involves complex nonlinear relationships. The focus of this paper is on the details involved in the first two steps, since these are the most challenging to the biomechanician. The global process is then explained through applications to the study of predicting isometric elbow moments and dynamic knee kinetics.

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Sarah Ritchie

Column-editor : Jeff G. Konin

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Tariq Awan, Stephanie G. Marsh, Peter Miller and Stephen E. Lemos

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Rohit Shah and Amanda Sinclair

Edited by Tricia Hubbard

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Yoshiko Hasebe, Yoshie Tanabe and Kazunori Yasuda

Context:

Anterior cruciate ligament (ACL) reconstruction with doubled hamstring autograft might not sufficiently improve fundamental sports abilities of patients with ACL-deficient knees.

Objective:

To clarify whether ACL reconstruction using the hamstring graft can improve fundamental sports abilities.

Design:

Patients were examined twice, preoperatively and 2 years postoperatively, using the conventional evaluation scales and performance tests.

Participants:

15 athletic patients with ACL reconstruction using hamstring autograft.

Measurements:

A stairs-run test and figure-8 one-leg hop test. Muscle strength and knee stability were measured with Cybex® II and KT-2000® arthrometers, respectively.

Results:

There were no significant differences between the preoperative and postoperative results in the performance tests. The degree of postoperative recovery in the subjective score, the anterior translation of the tibia, and the isokinetic muscle strength was not significantly correlated with the degree of restoration in each performance test.

Conclusions:

Postoperative restoration as measured by conventional evaluation scales is not correlated with restoration of sports abilities in patients with ACL insufficiency.