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Blaine C. Long and J. Ty Hopkins

Context:

It is reported that thermotherapy decreases motoneuron-pool recruitment. Any decrease in recruitment might have a significant impact on an athlete’s ability to return to competition.

Objective:

To determine whether moist heat application influences involuntary motoneuron-pool recruitment or voluntary plantar-flexion peak torque of the soleus muscle immediately or 30 min after application.

Design:

A 3 × 3 crossover design.

Setting:

Biomechanics laboratory.

Participants:

Eighteen healthy subjects with no history of lower extremity surgery or injury 12 months before the study volunteered.

Intervention:

A series of short-duration, high-intensity stimuli was delivered to the tibial nerve to find the Hmax and Mmax measures. Immediately after the Hmax and Mmax measures, subjects were positioned on an isokinetic dynamometer where they performed 5 submaximal warm-up repetitions. Immediately after the warm-up, 5 maximum-intensity peak plantar-flexion torque repetitions were performed. After the dynamometer measures, subjects returned to the table, where a moist heat pack, no heat pack, or a dry nonheated heat pack was applied.

Main Outcome Measures:

Hmax, Mmax, peak plantar-flexion torque, surface temperature (°C), and ambient temperature (°C).

Results:

Moist heat did not influence the H:Mmax ratio or peak plantar-flexion torque. Temperature increased with moist heat pack. Ambient temperature remained constant.

Conclusions:

Moist heat did not influence involuntary motoneuron-pool recruitment or voluntary peak plantar-flexion torque of the soleus muscle immediately or 30 min after application.

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Daniel P. Ferris, Joseph M. Czerniecki and Blake Hannaford

We developed a pneumatically powered orthosis for the human ankle joint. The orthosis consisted of a carbon fiber shell, hinge joint, and two artificial pneumatic muscles. One artificial pneumatic muscle provided plantar flexion torque and the second one provided dorsiflexion torque. Computer software adjusted air pressure in each artificial muscle independently so that artificial muscle force was proportional to rectified low-pass-filtered electromyography (EMG) amplitude (i.e., proportional myoelectric control). Tibialis anterior EMG activated the artificial dorsiflexor and soleus EMG activated the artificial plantar flexor. We collected joint kinematic and artificial muscle force data as one healthy participant walked on a treadmill with the orthosis. Peak plantar flexor torque provided by the orthosis was 70 Nm, and peak dorsiflexor torque provided by the orthosis was 38 Nm. The orthosis could be useful for basic science studies on human locomotion or possibly for gait rehabilitation after neurological injury.

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Nick Caplan, Andrew Forbes, Sarkhell Radha, Su Stewart, Alistair Ewen, Alan St Clair Gibson and Deiary Kader

Context:

Ankle immobilization is often used after ankle injury.

Objective:

To determine the influence of 1 week’s unilateral ankle immobilization on plantar-flexor strength, balance, and walking gait in asymptomatic volunteers.

Design:

Repeated-measures laboratory study.

Setting:

University laboratory.

Participants:

6 physically active male participants with no recent history of lower-limb injury.

Interventions:

Participants completed a 1-wk period of ankle immobilization achieved through wearing a below-knee ankle cast. Before the cast was applied, as well as immediately, 24 h, and 48 h after cast removal, their plantar-flexor strength was assessed isokinetically, and they completed a single-leg balance task as a measure of proprioceptive function. An analysis of their walking gait was also completed

Main Outcome Measures:

Peak plantar-flexor torque and balance were used to determine any effect on muscle strength and proprioception after cast removal. Ranges of motion (3D) of the ankle, knee, and hip, as well as walking speed, were used to assess any influence on walking gait.

Results:

After cast removal, plantar-flexor strength was reduced for the majority of participants (P = .063, CI = −33.98 to 1.31) and balance performance was reduced in the immobilized limb (P < .05, CI = 0.84−5.16). Both strength and balance were not significantly different from baseline levels by 48 h. Walking speed was not significantly different immediately after cast removal but increased progressively above baseline walking speed over the following 48 h. Joint ranges of motion were not significantly different at any time point.

Conclusions:

The reduction in strength and balance after such a short period of immobilization suggested compromised central and peripheral neural mechanisms. This suggestion appeared consistent with the delayed increase in walking speed that could occur as a result of the excitability of the neural pathways increasing toward baseline levels.

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Jake A. Melaro, Ramzi M. Majaj, Douglas W. Powell, Paul DeVita and Max R. Paquette

ground reaction force (GRF), lower peak plantar flexor torque, peak ankle positive power, peak ankle angular velocity, and positive ankle angular work compared with young adults. 13 – 15 Although many pathologies and other factors contribute to declines in the health of aging adults, poor propulsive