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Kazem Malmir, Gholam Reza Olyaei, Saeed Talebian, Ali Ashraf Jamshidi and Majid Ashraf Ganguie

focused more on hoping in a forward direction. Athletes may injure their ankles when they are fatigued. 15 Ankle muscles, particularly peroneal muscles, may be fatigued under these conditions. Decline of function of the peroneal muscles due to fatigue may expose the ankle to injury through various

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Christine L. Berg, Joseph M. Hart, Riann Palmieri-Smith, Kevin M. Cross and Christopher D. Ingersoll

Context:

If ankle joint cryotherapy impairs the ability of the ankle musculature to counteract potentially injurious forces, the ankle is left vulnerable to injury.

Objective:

To compare peroneal reaction to sudden inversion following ankle joint cryotherapy.

Design:

Repeated measures design with independent variables, treatment (cryotherapy and control), and time (baseline, immediately post treatment, 15 minutes post treatment, and 30 minutes post treatment).

Setting:

University research laboratory.

Patients or Other Participants:

Twenty-seven healthy volunteers.

Intervention(s):

An ice bag was secured to the lateral ankle joint for 20 minutes.

Main Outcome Measures:

The onset and average root mean square amplitude of EMG activity in the peroneal muscles was calculated following the release of a trap door mechanism causing inversion.

Results:

There was no statistically significant change from baseline for peroneal reaction time or average peroneal muscle activity at any post treatment time.

Conclusions:

Cryotherapy does not affect peroneal muscle reaction following sudden inversion perturbation.

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Benjamin Henry, Todd McLoda, Carrie L. Docherty and John Schrader

Context:

Peroneal reaction to sudden inversion has been determined to be too slow to overcome the joint motion. A focused plyometric training program may decrease the muscle's reaction time.

Objective:

To determine the effect of a 6-wk plyometric training program on peroneus longus reaction time.

Design:

Repeated measures.

Setting:

University research laboratory.

Participants:

48 healthy volunteers (age 20.0 ± 1.2 y, height 176.1 ± 16.9 cm, weight 74.5 ± 27.9 kg) from a large Midwestern university. Subjects were randomly assigned to either a training group or a control group.

Interventions:

Independent variables were group at 2 levels (training and no training) and time at 2 levels (pretest and posttest). The dependent variable was peroneal latency measured with surface electromyography. A custom-made trapdoor device capable of inverting the ankle to 30° was also used. Latency data were obtained from the time the trapdoor dropped until the peroneus longus muscle activated. Peroneal latency was measured before and after the 6-wk training period. The no-training group was instructed to maintain current activities. The training group performed a 6-wk plyometric protocol 3 times weekly. Data were examined with a repeated-measures ANOVA with 1 within-subject factor (time at 2 levels) and 1 between-subjects factor (group at 2 levels). A priori alpha level was set at P < .05.

Main Outcome Measures:

Pretest and posttest latency measurements (ms) were recorded for the peroneus longus muscle.

Results:

The study found no significant group-by-time interaction (F 1,46 = 0.03, P = .87). In addition, there was no difference between the pretest and posttest values (pretest = 61.76 ± 14.81 ms, posttest = 59.24 ± 12.28 ms; P = .18) and no difference between the training and no-training groups (training group = 59.10 ± 12.18 ms, no-training group = 61.79 ± 15.18 ms; P = .43).

Conclusions:

Although latency measurements were consistent with previous studies, the plyometric training program did not cause significant change in the peroneus longus reaction time.

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Eli Isakov, Joseph Mizrahi, Pablo Solzi, Zev Susak and Moshe Lotem

The response of the peroneal muscles to sudden inversion of the ankle during standing was investigated. The variation of the inversion angle with time was measured by means of a potentiometer attached to a specially designed test apparatus. During the tests, volunteers were subjected to sudden and unexpected inversion of their ankle, during which the surface EMG of the peroneal muscles was also recorded. Two groups were tested, one of normal subjects and one consisting of subjects with recurrent ankle sprains. There were 8 females and 3 males in each group. The subjects in the second group, who suffered from recurrent ankle sprains, had been asymptomatic during the last 2 months prior to the tests. For each subject in the two groups, both ankles were tested. The results indicated a latency time ranging from 60 to 80 ms for both groups. It was concluded that the reflex contraction of the peroneal muscles due to a sudden stretch inversion motion has no role in protecting the ankle joint during sprain and that this protection is mainly provided by the passive tissues.

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Kazem Malmir, Gholam Reza Olyaei, Saeed Talebian and Ali Ashraf Jamshidi

Context:

Cyclic movements and muscle fatigue may result in musculoskeletal injuries by inducing changes in neuromuscular control. Ankle frontal-plane neuromuscular control has rarely been studied in spite of its importance.

Objective:

To compare the effects of peroneal muscle fatigue and a cyclic passive-inversion (CPI) protocol on ankle neuromuscular control during a lateral hop.

Design:

Quasi-experimental, repeated measures.

Setting:

University laboratory.

Participants:

22 recreationally active, healthy men with no history of ankle sprain or giving way.

Interventions:

Participants performed a lateral hop before and after 2 interventions on a Biodex dynamometer. They were randomly assigned to intervention order and interventions were 1 wk apart. A passive intervention included 40 CPIs at 5°/s through 80% of maximum range of motion, and a fatigue intervention involved an isometric eversion at 40% of the maximal voluntary isometric contraction until the torque decreased to 50% of its initial value.

Main Outcome Measures:

Median frequency of the peroneus longus during the fatigue protocol, energy absorption by the viscoelastic tissues during the CPI protocol, and feedforward onset and reaction time of the peroneus longus during landing.

Results:

A significant fall in median frequency (P < .05) and a significant decrease in energy absorption (P < .05) confirmed fatigue and a change in viscoelastic behavior, respectively. There was a significant main effect of condition on feedforward onset and reaction time (P < .05). No significant main effect of intervention or intervention × condition interaction was noted (P > .05). There was a significant difference between pre- and postintervention measures (P < .0125), but no significant difference was found between postintervention measures (P > .0125).

Conclusions:

Both fatigue and the CPI may similarly impair ankle neuromuscular control. Thus, in prolonged sports competitions and exercises, the ankle may be injured due to either fatigue or changes in the biomechanical properties of the viscoelastic tissues.

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Nicholas E. Clark, Linda S. Bobo and Christine A. Ho

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Cynthia J. Wright and Brent L. Arnold

Context:

Force sense (FS), the proprioceptive ability to detect muscle-force generation, has been shown to be impaired in individuals with functional ankle instability (FAI). Fatigue can also impair FS in healthy individuals, but it is unknown how fatigue affects FS in individuals with FAI.

Objective:

To assess the effect of fatigue on ankle-eversion force-sense error in individuals with and without FAI. Design: Case control with repeated measures.

Setting:

Sports medicine research laboratory.

Participants:

32 individuals with FAI and 32 individuals with no ankle sprains or instability in their lifetime. FAI subjects had a history of ≥1 lateral ankle sprain and giving-way ≥1 episode per month.

Interventions:

Three eversion FS trials were captured per load (10% and 30% of maximal voluntary isometric contraction) using a load cell before and after a concentric eversion fatigue protocol.

Main Outcome Measures:

Trial error was the difference between the target and reproduction forces. Constant error (CE), absolute error (AE), and variable error (VE) were calculated from 3 trial errors. A Group × Fatigue × Load repeated-measures ANOVA was performed for each error.

Results:

There were no significant 3-way interactions or 2-way interactions involving group (all P > .05). CE and AE had a significant 2-way interaction between load and fatigue (CE: F 1,62 = 8.704, P = .004; AE: F 1,62 = 4.024, P = .049), and VE had a significant main effect for fatigue (F 1,62 = 5.130, P = .027), all of which indicated increased FS error with fatigue at 10% load. However, at 30% load only VE increased with fatigue. The FAI group had greater error as measured by AE (F 1,62 = 4.571, P = .036) but not CE or VE (P > .05).

Conclusions:

Greater AE indicates that FAI individuals are less accurate in their force production. Fatigue impaired force sense in all subjects equally. These deficits provide evidence of impaired proprioception with fatigue and in individuals with FAI.

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Mark A. Feger, Luke Donovan, C. Collin Herb, Geoffrey G. Handsfield, Silvia S. Blemker, Joseph M. Hart, Susan A. Saliba, Mark F. Abel, Joseph S. Park and Jay Hertel

.45] cm 3 /m·kg and PRE: 1.55 [0.11] cm 3 /m·kg; POST: 1.94 [0.17] cm 3 /m·kg, respectively, Figure  1 ). Rehabilitation resulted in large increases in all foot and ankle extrinsic muscle volumes, except for the flexor hallucis longus and peroneals (PRE: 0.87 [0.22] cm 3 /m·kg; POST: 0.66 [0.18] cm 3 /m

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Cathleen Brown, Scott Ross, Rick Mynark and Kevin Guskiewicz

Context:

Functional ankle instability (FAI) is difficult to identify and quantify.

Objective:

To compare joint position sense (JPS), time to stabilization (TTS), and electromy-ography (EMG) of ankle musculature in recreational athletes with and without FAI.

Design:

Case-control compared with t tests and ANOVAs.

Setting:

Sports medicine research laboratory.

Participants:

20 recreational athletes.

Main Outcome Measures:

Passive angle reproduction, TTS, and mean EMG amplitude of the tibialis anterior, peroneals, lateral gastrocnemius, and soleus muscles during single-leg-jump landing.

Results:

No differences in JPS or medial-lateral TTS measures between groups. Significantly longer anterior-posterior TTS (P < .05) in the unstable ankle group. The stable ankle group had significantly higher mean EMG soleus amplitude after landing (P < .05). No other significant differences were found for mean EMG amplitudes before or after landing.

Conclusions:

Subjects with FAI demonstrated deficits in landing stability and soleus muscle activity during landing that may represent chronic adaptive changes following injury.