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Edited by Christopher D. Ingersoll

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Edited by Christopher D. Ingersoll

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Edited by Christopher D. Ingersoll

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Christopher D. Ingersoll

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Christopher D. Ingersoll

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J. Ty Hopkins and Christopher D. Ingersoll

Objectives:

To define the concept of arthrogenic muscle inhibition (AMI), to discuss its implications in the rehabilitation of joint injury, to discuss the neurophysiologic events that lead to AMI, to evaluate the methods available to measure AM1 and the models that might be implemented to examine AMI, and to review therapeutic interventions that might reduce AMI.

Data Sources:

The databases MEDLINE, SPORTDiscus, and CIHNAL were searched with the terms reflex inhibition, joint mechanoreceptor, Ib interneuron, Hoffmann reflex, effusion, and joint injury. The remaining citations were collected from references of similar papers.

Conclusions:

AMI is a limiting factor in the rehabilitation of joint injury. It results in atrophy and deficiencies in strength and increases the susceptibility to further injury. A therapeutic intervention that results in decreased inhibition, allowing for active exercise, would lead to faster and more complete recovery.

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Kyung-Min Kim, Christopher D. Ingersoll and Jay Hertel

Context:

Focal ankle-joint cooling (FAJC) has been shown to increase Hoffmann (H) reflex amplitudes of select leg muscles while subjects lie prone, but it is unknown whether the neurophysiological cooling effects persist in standing.

Objective:

To assess the effects of FAJC on H-reflexes of the soleus and fibularis longus during 3 body positions (prone, bipedal, and unipedal stances) in individuals with and without chronic ankle instability (CAI).

Design:

Crossover.

Setting:

Laboratory.

Participants:

15 young adults with CAI (9 male, 6 female) and 15 healthy controls.

Intervention:

All subjects received both FAJC and sham treatments on separate days in a randomized order. FAJC was accomplished by applying a 1.5-L plastic bag filled with crushed ice to the ankle for 20 min. Sham treatment involved room-temperature candy corn.

Main Outcome Measures:

Maximum amplitudes of H-reflexes and motor (M) waves were recorded while subjects lay prone and then stood in quiet bipedal and unipedal stances before and immediately after each treatment. Primary outcome measures were Hmax:Mmax ratios for the soleus and fibularis longus. Three-factor (group × treatment condition × time) repeated-measures ANOVAs and Fisher LSD tests were performed for statistical analyses.

Results:

Significant interactions of treatment condition by time for prone Hmax:Mmax ratios were found in the soleus (P = .001) and fibularis longus (P = .003). In both muscles, prone Hmax:Mmax ratios moderately increased after FAJC but not after sham treatment. The CAI and healthy groups responded similarly to FAJC. In contrast, there were no significant interactions or main effects in the bipedal and unipedal stances in either muscle (P > .05).

Conclusions:

FAJC moderately increased H-reflex amplitudes of the soleus and fibularis longus while subjects were prone but not during bipedal or unipedal standing. These results were not different between groups with and without CAI.

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Kenneth L Knight, Christopher D Ingersoll and John Bartholomew

Problem:

Isokinetic contractions are thought to be superior to isotonic contractions for developing strength because resistance during them is greater. Because isokinetic resistance is accommodating, however, it decreases with fatigue. It is constant during multiple repetitions, so an aggressive isotonic procedure should produce more force as the muscle fatigues, which would be an advantage in strength development.

Purpose:

To compare force production in isokinetic and isotonic muscle contractions at the beginning and end of a set of fatiguing repetitions.

Methods:

Subjects performed 25 maximal-effort isokinetic knee extensions at 60°/s. After 25–72 hours, they performed maximal repetitions isotonically using 70% of the isokinetic peak torque with speed set at a maximum of 300°/s.

Results:

Peak force during the first 3 repetitions was greater isokinetically, but average force was similar. During the last 3 repetitions, isotonic force was higher than isokinetic force.

Conclusion:

Muscle is more active as it nears fatigue during an isotonic contraction. These data support the hypothesis that isotonic contractions recruit extra motor units at the point of fatigue.

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Teddy W. Worrell, Christopher D. Ingersoll and Jack Farr

The purpose of this case study was to determine the effect of patellar taping, patellar bracing, and control condition on (a) patellofemoral congruence angle (PFC), (b) lateral patellar angle (LPA), (c) lateral patellar displacement (LPD), and (d) pain, as determined by the visual analog scale (VAS) during an 8-in. step-down. The subject was a 15-year-old female with a 3-year history of recurrent patellar subluxations and anterior knee pain syndrome. Results revealed the following: control condition—PFC 41.4-1.1°, LPA 19.9-6.9°, LPD 18.6-8.3 mm, VAS 8.8 cm; tape—PFC 46.2-2.3°, LPA 25.1-2.9°, LPD 24.2-7.5 mm, VAS 0.8 cm; brace—PFC 3.4-16.5°, LPA 7.9-0.8°, LPD 9.4-4.7 mm, VAS 0.3 cm. Patellar bracing was effective in centralizing the patella as revealed by the PFC, LPA, and LPD measures; however, patellar taping did not improve patellar position, and in some positions taping actually worsened patellar position. A large reduction in pain as measured by the VAS occurred during an 8-in. step-down for both taping and bracing. More research is necessary to explain the pain reduction without a change in patellar position using tape.

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Joseph M. Hart, Jamie L. Leonard and Christopher D. Ingersoll

Context:

Despite recent findings regarding lower extremity function after cryotherapy, little is known of the neuromuscular, kinetic, and kinematic changes that might occur during functional tasks.

Objective:

To evaluate changes in ground-reaction forces, muscle activity, and knee-joint flexion during single-leg landings after 20-minute knee-joint cryotherapy.

Design:

1 × 4 repeated-measures, time-series design.

Setting:

Research laboratory.

Patients or Other Participants:

20 healthy male and female subjects.

Intervention:

Subjects performed 5 single-leg landings before, immediately after, and 15 and 30 minutes after knee-joint cryo-therapy.

Main Outcome Measures:

Ground-reaction force, knee-joint flexion, and muscle activity of the gastrocnemius, hamstrings, quadriceps, and gluteus medius.

Results:

Cryotherapy did not significantly (P > .05) change maximum knee-joint flexion, vertical ground-reaction force, or average muscle activity during a single-leg landing.

Conclusion:

Knee-joint cryotherapy might not place the lower extremity at risk for injury during landing.