Elsevier

Clinical Biomechanics

Volume 17, Issue 7, August 2002, Pages 536-540
Clinical Biomechanics

Stiffness and passive peak force changes at the ankle joint: the effect of different joint angular velocities

https://doi.org/10.1016/S0268-0033(02)00062-1Get rights and content

Abstract

Objective. To compare peak force and stiffness at the ankle joint in response to repetitive dorsiflexion at two joint angular velocities (5 and 25 deg s−1).

Design. Pre- post-repeated measures design.

Background. Stretching affects the biomechanical properties of tissues. In many instances, stretching is performed in a cyclic manner. An important factor that might influence the effects of stretching is the speed at which the tissues are lengthened.

Methods. Eighteen healthy subjects participated. A dynamometer repeatedly moved the ankle joint from 0 deg of dorsiflexion to 80% of maximum dorsiflexion over a 2 min period. Two joint angular velocities were examined: 5 and 25 deg s−1. Force and angle data were recorded simultaneously. Electromyographic activity from plantar and dorsiflexor muscles was monitored. The variables of interest were peak passive force and average stiffness at the first and last repetition of motion.

Results. Peak force was significantly higher (P<0.05) at 25 deg s−1 for the first repetition. At both joint angular velocities, peak passive force decreased significantly over the 2 min of motion. The decreases were 13% and 21% at 5 and 25 deg s−1 respectively. Peak passive force was not significantly different (P>0.05) across velocities at 2 min. Stiffness was greater at 25 deg s−1 initially (P<0.05), however, it decreased significantly across time. The magnitude of the decrease was 20% and 31% at 5 and 25 deg s−1 respectively. After 2 min of motion, there was no significant difference (P>0.05) in stiffness across the joint angular velocities examined.

Conclusion(s). The findings showed that while significant differences existed in stiffness and peak force across angular velocities at the start of the stretching motion, the differences decreased considerably with repeated motion, and were relatively similar within 2 min.
Relevance

It has long been thought that greater speeds of stretch are more likely to lead to muscle injury. Our findings suggest that it is most beneficial to stretch at a slow speed initially, thereafter, the speed of stretch may be increased.

Introduction

Stretching exercises are commonly undertaken in sports and rehabilitation settings. In many instances, repeated stretching activities are performed in a cyclic manner. These types of stretches have been termed ballistic or dynamic. Few studies have examined changes in biomechanical parameters when tissues are stretched in a cyclic manner. In a study involving animals, Taylor et al. [1] observed significant decreases in peak passive muscle tension across cycles. Using cadaveric spinal segments, Adams and Dolan [2] reported that repeated motion caused a steady fall in resistance to bending. In contrast to these findings, a study involving humans by Magnusson et al. [3] noted an increase in hamstring muscle's stiffness across 10 cycles of motion.

An important parameter that might influence biomechanical variables such as stiffness and peak passive tension is the speed of the stretch. In a study involving animals, Taylor et al. [1] reported that both stiffness and peak passive tension became greater as the speed of stretch increased. Similarly, in spinal segments, Adams and Dolan [2] noted increased resistance to bending as speed of motion increased. In humans, across joint angular velocities ranging from 1 to 40 deg s−1, Hufschmidt and Schwaller [4] noted significant increases in torque between 0 and 10 deg of dorsiflexion at the ankle joint. In contrast, Lamontagne et al. [5] reported no significant differences in torque until joint angular velocity reached 120 deg s−1. In the studies of Hufschmidt and Schwaller [4] and Lamontagne et al. [5] the joint range of motion was considerably less than that encountered when full range of motion stretches are undertaken at the ankle joint by individuals with normal motion or minor pathologies [6].

It has been stated that there is a need for more information on the prescription of stretching routines to enhance the safety and the results of stretching programs [7]. The time dependant nature of responses to stretch could provide important information allowing a more precise stretching prescription to be implemented. Hence, the purpose of the current study was to examine the effects of cyclic motion at two joint angular velocities on peak passive force and average stiffness at the ankle joint.

Section snippets

Subjects

Eighteen subjects (11 females, 7 males) volunteered to participate in this study. The mean age, height, and mass of the subjects is presented in Table 1. All subjects were recreational athletes who were not participating in a stretching program at the time of the study. No subjects had a history of participating in sports that demanded high levels of flexibility, and no subjects had recent injuries that may have affected the findings. All subjects signed a document of informed consent.

Procedures

The

Results

All subjects completed the protocols, and no subjects had EMG data that were in excess of 1% MVC. In respect to peak passive force, the findings showed that there was a significant difference across angular velocities for the first repetition. Peak force was significantly greater (P<0.05) at the higher speed (means: 74.5 N versus 84.7 N). The findings showed that at both 5 and 25 deg s−1, peak passive force decreased significantly (P<0.05) over the 2 min of motion (see Fig. 2). Qualitatively,

Discussion

The primary purpose of the current study was to examine differences in viscoelastic parameters associated with different velocities of stretching, and describe how these differences were affected by repeated motion. Our results showed that as the angular velocity was increased from 5 to 25 deg s−1, the peak passive force and average stiffness also increased. These findings were in agreement with the in vitro work of Taylor et al. [1] and the in vivo studies of Huffschmidt and Schwaller [4].

Conclusions

This study has provided new information related to the effect of stretching soft tissues repeatedly. The findings showed that while significant differences existed in stiffness and peak force across angular velocities at the start of the stretching motion, the differences decreased considerably with repeated motion and were relatively similar in a relatively short period of time. These findings suggest that it is most beneficial to stretch at a slow speed initially to maintain stiffness and

References (13)

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