“One Week of Unilateral Ankle Immobilisation Alters Plantarflexor Strength, Balance and Walking Speed: A Pilot Study in
Asymptomatic Volunteers” by Caplan N et al.
Journal of Sport Rehabilitation
© 2014 Human Kinetics, Inc.

Note: This article will be published in a forthcoming issue of the Journal of Sport Rehabilitation. The article appears here in its accepted, peer-reviewed form, as it was provided by the submitting author. It has not been copyedited, proofed, or formatted by the publisher.

Section: Original Research Report
Article Title: One Week of Unilateral Ankle Immobilisation Alters Plantarflexor Strength,
Balance and Walking Speed: A Pilot Study in Asymptomatic Volunteers
Authors: 1Nick Caplan, 1Andrew Forbes, 2Sarkhell Radha, 1Su Stewart, 1Alistair Ewen,
1
Alan St Clair Gibson, and 1,3Deiary Kader
Affiliations: 1Faculty of Health and Life Sciences, Northumbria University, Newcastle upon
Tyne, UK. 2Chelsea and Westminster Hospital, London. 3Gateshead Health NHS Foundation
Trust, Gateshead, UK.
Journal: Journal of Sport Rehabilitation
Acceptance Date: October 7, 2014
©2014 Human Kinetics, Inc.

DOI: http://dx.doi.org/10.1123/jsr.2013-0137

“One Week of Unilateral Ankle Immobilisation Alters Plantarflexor Strength, Balance and Walking Speed: A Pilot Study in
Asymptomatic Volunteers” by Caplan N et al.
Journal of Sport Rehabilitation
© 2014 Human Kinetics, Inc.

One week of unilateral ankle immobilisation alters plantarflexor strength, balance and walking speed: a pilot study in asymptomatic volunteers
1

Nick Caplan PhD, 1Andrew Forbes MSc, 2Sarkhell Radha MD, MSc, 1Su Stewart PhD,
1
Alistair Ewen PhD, 1Alan St Clair Gibson PhD, 1,3Deiary Kader MD

1
2
3

Faculty of Health and Life Sciences, Northumbria University, Newcastle upon
Tyne, UK
Chelsea and Westminster Hospital, 369 Fulham Road, London, SW10 9NH.
Gateshead Health NHS Foundation Trust, Gateshead, UK

Corresponding author:
Dr Nick Caplan
Faculty of Health and Life Sciences
Northumbria University
Northumberland Building
Newcastle upon Tyne
NE1 8ST
United Kingdom
Tel: +44 (0)191 243 7382
Email: nick.caplan@northumbria.ac.uk

Funding
This research received no specific grant from any funding agency in the public, commercial or not-for-profit sectors.

Competing interests
None declared.

“One Week of Unilateral Ankle Immobilisation Alters Plantarflexor Strength, Balance and Walking Speed: A Pilot Study in
Asymptomatic Volunteers” by Caplan N et al.
Journal of Sport Rehabilitation
© 2014 Human Kinetics, Inc.

Abstract
Context: Ankle immobilisation is often used following ankle injury. Objective:

To

determine the influence of one week’s unilateral ankle immobilisation on plantarflexor strength, balance and walking gait in asymptomatic volunteers. Design: Repeated measures laboratory study. Setting: University laboratory. Participants:

Six physically active male

participants with no recent history of lower limb injury. Interventions: Participants completed a one week period of ankle immobilisation achieved through wearing a below knee ankle cast. Before the cast was applied, as well as immediately following cast removal, at 24 hours after cast removal, and at 48 hours after cast removal, their plantarflexor 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 platarflexor torque and balance were used to determine any effect on muscle strength and proprioception following 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: Following cast removal, plantarflexor strength was reduced for the majority of participants (p=0.063, CI=-33.98-1.31) and balance performance was reduced in the immobilised limb (p<0.05, CI=0.84-5.16). Both strength and balance were not significantly different to baseline levels by 48 hours. Walking speed was not significantly different immediately following cast removal, but increased progressively above baseline walking speed over the following 48 hours. 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 immobilisation suggested compromised central and peripheral neural mechanisms. This suggestion appeared consistent with the delayed increase in walking speed which could occur as a result of the excitability of the neural pathways increasing towards baseline levels.
Key words: Ankle, cast, biomechanics, gait, immobilisation

“One Week of Unilateral Ankle Immobilisation Alters Plantarflexor Strength, Balance and Walking Speed: A Pilot Study in
Asymptomatic Volunteers” by Caplan N et al.
Journal of Sport Rehabilitation
© 2014 Human Kinetics, Inc.

Introduction
Ankle injuries are the most commonly reported injuries in sport.1 Severe ankle injuries often require immobilisation through application of below knee ankle casts or shortleg walkers.2 Wearing of a below knee cast influences the biomechanics of the ankle joint.
Plantarflexion normally seen immediately after heel strike is prevented by the below knee cast, as is dorsiflexion in the second half of the stance phase of the gait cycle3. During midstance there is a delay before foot flat is achieved4. This reduced range of motion, caused by the cast, will have a direct influence on the function of the ankle joint and surrounding soft tissues. As a result, soft tissue adaptations are often seen.
Joint immobilisation has been shown to lead to muscle atrophy, and reduced muscle strength, range of motion and joint stiffness5,6. It has been suggested that muscle atrophy occurs most rapidly in the early days (2-3 days) of immobilisation7-9. Vandenborne et al10 reported reductions in calf muscle cross sectional area of between 5-8% per week in the first two weeks of immobilisation. They also observed significant reductions in both isometric and isokinetic torque generation following immobilisation5,10.

Altered motorneuronal

excitability has been reported following immobilisation through hindlimb suspension 11, longterm bed rest12 and spaceflight13, and neural adaptations have been suggested as making a larger contribution to reductions in muscle strength than muscle changes12, 14, 15.
The influence of wearing a cast or short-leg walker on the biomechanics of the lower limbs has been reported in participants whilst actually wearing a cast16, 17. The influence of a period of ankle immobilisation on lower limb function, however, has not been widely investigated. This study aimed to investigate the influence of seven days’ ankle

immobilisation on walking biomechanics, plantarflexion strength and balance in healthy volunteers as a pilot study to help inform future studies investigating the influence of

“One Week of Unilateral Ankle Immobilisation Alters Plantarflexor Strength, Balance and Walking Speed: A Pilot Study in
Asymptomatic Volunteers” by Caplan N et al.
Journal of Sport Rehabilitation
© 2014 Human Kinetics, Inc.

immobilisation in patients.

It was hypothesised that ankle immobilisation may cause

impairments to both gait, plantarflexion strength and balance performance.
Methods
Participants
Six healthy male participants took part in this study, with a mean (±SD) age, height and mass of 21.8 (±1.0) years, 1.77 (±0.05) m, and 80.1 (±6.9) kg, respectively.

All

participants were free from injury at the time of testing and none had previously worn a below knee cast.

The study was approved by the institutional review board and all

participants provided fully informed written consent.
Procedures
Participants were tested immediately before, immediately after, and at both 24 hours and 48 hours after wearing an ankle cast for seven days, weight bearing permitted. A below knee plaster cast was applied to the left leg of each participant (non-dominant in all participants) A ‘plaster sock’ and a layer of protective cotton wool was first applied to protect the skin and any bony prominences from discomfort and pain during the period of immobilisation. A combination of 3 inch and 4 inch 3M™ Scotchcast™ PolyPlus casting tape was used to immobilise the ankle in a neutral joint position. All casts were applied by the same orthopaedic surgeon. The below knee cast was removed immediately prior to the second testing session.
Each testing sessions consisted of a 3D walking gait analysis and an assessment of balance performance.

All biomechanical assessments were completed without the

participants wearing the cast.

For the 3D gait analysis, sixteen retroreflective markers

(diameter = 14 mm) were attached to the pelvis and lower limbs (Plugin Gait, Vicon Motion
Systems, Oxford). A 12 camera motion capture system (MX-T20, Vicon Motion Systems,

“One Week of Unilateral Ankle Immobilisation Alters Plantarflexor Strength, Balance and Walking Speed: A Pilot Study in
Asymptomatic Volunteers” by Caplan N et al.
Journal of Sport Rehabilitation
© 2014 Human Kinetics, Inc.

Oxford) was used to measure kinematics at 200 Hz.

Participants were instructed to walk at

their preferred velocity along a walkway that ran centrally along the laboratory.

Each

participant completed three trials in order to extract data for one complete gait cycle for each leg during each trial. The gait cycle for one leg was defined as starting when the foot made initial contact with the ground, and ended when the same foot came into contact with the ground again. Heel strike and toe off were determined by visual inspection of the heel and toe markers, respectively. Heel strike was identified as the point at which the heel marker reached its lowest vertical position. Toe off was identified as the point at which the toe marker started to move vertically away from the its lowest position. Three complete gait cycles were used for each limb. Each gait cycle was time normalised in Polygon (Vicon
Motion Systems, Oxford) and ensemble averaged across the three gait cycles for each participant. For each gait cycle, maximum and minimum ankle, knee and hip joint angles of the ensemble averaged data were used to calculate the range of joint motion during the gait cycle in each plane of motion. Walking speed was also extracted for each gait cycle included in the analysis.
Balance was assessed using a stabilometer (Stability System SD, Biodex, Shirley,
NY). Participants balanced on each leg for 30 seconds while their centre of pressure was tracked to produce a stability index. The stability index is measured as a standard deviation of deviations of the centre of pressure in the anteroposterior and mediolateral directions18, and gives an indication of proprioceptive function19. Participants completed all balance trials barefoot to avoid any confounding influence of footwear between pre- and postimmobilisation trials. Balance trials were completed with eyes closed in order to increase the demands on the proprioceptive system.
Strength of the plantarflexor muscles was assessed using an isokinetic dynamometer
(Cybex Norm, Cybex, Massachusetts). Participants were supine and their left ankle was

“One Week of Unilateral Ankle Immobilisation Alters Plantarflexor Strength, Balance and Walking Speed: A Pilot Study in
Asymptomatic Volunteers” by Caplan N et al.
Journal of Sport Rehabilitation
© 2014 Human Kinetics, Inc.

secured into an ankle attachment. Three maximal effort plantarflexions were performed at an angular velocity of 120 degrees per second.

Overall concentric peak torque was then

extracted for later analysis.
Data analysis
The independent variable in this study was the time point at which each test was completed (i.e. pre-cast, 0 hrs post-cast, 24 hrs post-cast and 48 hrs post-cast).

The

dependent variables included plantarflexor peak torque, stability index, walking speed and range of motion about the ankle, knee and hip in flexion/extension, adduction/abduction and internal/external rotation. All variables were checked for normality of distribution using Q-Q and box plots. One way analysis of variance with repeated measures was used to evaluate changes in each variable as a function of ankle immobilisation and recovery following cast removal (i.e. pre-cast, 0 hrs post-cast, 24 hrs post-cast and 48 hrs post-cast). LSD post hoc tests were used to determine the significance of each pairwise comparison. Significance was set at 95%.
Results
Peak torque during plantarflexion in the limb that underwent immobilisation (Figure
1) showed a significant main effect of time (F3,15=5.640, p<0.01). Peak torque reduced by
22% immediately following cast removal compared to baseline, and despite this not being statistically significant (p=0.063), the confidence interval suggested that this would be a clinically meaningful reduction in torque for the vast majority of participants (Table 1). At
24 hours post cast removal, plantarflexor strength had returned slightly towards baseline, although it was still lower than baseline (p=0.050). By 48 hours post cast removal, peak plantarflexor torque had returned to baseline (p=0.390).

“One Week of Unilateral Ankle Immobilisation Alters Plantarflexor Strength, Balance and Walking Speed: A Pilot Study in
Asymptomatic Volunteers” by Caplan N et al.
Journal of Sport Rehabilitation
© 2014 Human Kinetics, Inc.

A significant main effect of time was found for stability index (Figure 2) for the limb that underwent immobilisation (F3,15=8.560, p<0.01), but not for the contralateral limb
(F3,15=0.723, p=0.554).

In the limb that underwent immobilisation, stability index was

significantly impaired immediately post cast removal (p<0.05) and returned gradually to baseline over the following 48 hours. Mean differences in stability index, and confidence intervals, between pre-cast and each of the three post-cast assessments are shown in Table 1.
Significant main effects of time were also seen for walking speed (F3,15=8.288, p<0.01; Figure 3). Post hoc analysis showed that walking speed was not changed from baseline immediately post cast removal, however walking speed did subsequently increase significantly by 24 hours post cast removal (p<0.01). Mean differences in walking speed, and confidence intervals, between pre-cast and each of the three post-cast assessments are shown in Table 1.
Ankle, knee and hip range of motion was not changed in the limb undergoing immobilisation in flexion/extention (ankle: F3,15=1.108, p=0.377; knee: F3,15=0.866, p=0.480; hip: F3,15=0.101, p=0.958), adduction/abduction (ankle: F3,15=0.868, p=0.479; knee:
F3,15=1.572, p=0.238; hip: F3,15=2.651, p=0.087) or internal/external rotation (ankle:
F3,15=0.607, p=0.621; knee: F3,15=1.607, p=0.230; hip: F3,15=1.532, p=0.247). Similarly, no differences were seen in the contralateral limb in flexion/extension (ankle: F3,15=1.376, p=0.288; knee: F3,15=0.503, p=0.686; hip: F3,15=0.619, p=0.613), adduction/abduction (ankle:
F3,15=0.713, p=0.559; knee: F3,15=1.731, p=0.204; hip: F3,15=1.867, p=0.178) or internal/external rotation (ankle: F3,15=0.577, p=0.639; knee: F3,15=2.200, p=0.130; hip:
F3,15=0.130, p=0.941).

“One Week of Unilateral Ankle Immobilisation Alters Plantarflexor Strength, Balance and Walking Speed: A Pilot Study in
Asymptomatic Volunteers” by Caplan N et al.
Journal of Sport Rehabilitation
© 2014 Human Kinetics, Inc.

Discussion
The aim of this study was to determine the influence of a seven day period of unilateral ankle immobilisation on the biomechanics of the lower limbs during walking and single leg stance, as well as on the strength of the plantarflexors. The main findings of this study were that, despite no changes in ankle, knee or hip range of motion during walking following ankle immobilisation, plantarflexor strength was reduced and balance performance was impaired immediately following cast removal, with both returning to baseline levels by
48 hours post cast removal. Walking speed was not different following cast removal, but increased over the course of the following two days.
Plantarflexor torque reduced by almost one quarter after just seven days of immobilisation through wearing a below knee cast, which would equate to approximately 3% per day. Muller20 previously reported similar daily reductions (1-6% per day) in the upper limbs, although it must be remembered that the upper limbs are not weightbearing as in the lower limbs. Larger reductions in strength have been observed following longer periods of immobilisation in humans14, 21, 22. To our knowledge, however, this is the first study to report such large reductions in plantarflexor torque during the first week of ankle immobilisation.
Although calf muscle cross sectional area was not measured in this study, it is likely that some atrophy had occurred7-9. The amount of atrophy that could have occurred in this study, however, is probably less than that reported in previous studies as participants were weightbearing during the period of immobilisation. Even with some muscle atrophy, it is unlikely to have been sufficient to elicit such large reductions in plantarflexor strength.
Muscle atrophy will influence muscle strength, however alterations in neural pathways have also been suggested following periods of immobilisation. Duchateau and
Hainut14 observed reductions in the maximal motor unit firing rate following immobilisation of the adductor pollicis and the first dorsal interosseous in humans.

Duchateau12 also

“One Week of Unilateral Ankle Immobilisation Alters Plantarflexor Strength, Balance and Walking Speed: A Pilot Study in
Asymptomatic Volunteers” by Caplan N et al.
Journal of Sport Rehabilitation
© 2014 Human Kinetics, Inc.

reported a 46% reduction in maximal voluntary contraction torque during plantarflexion following five weeks of bed rest. This reduction in torque was associated with a 33% reduction in central activation but only a 19% reduction in estimated force generating capacity of the muscle. More recently, Stevens et al15 used regression analyses to show that the reduction in plantarflexor torque induced by seven weeks of unilateral ankle immobilisation was mostly due to altered muscle activation rather than reduced muscle cross sectional area. These neural changes have been found to recover more rapidly than the changes seen in the muscle12,

15

, with the time course for neural recovery, relative to the

duration of immobilisation, reported by Duchateau12 being consistent with that observed in this study.
It was interesting to note that peak plantarflexor torque showed a greater difference in mean value compared to baseline immediately following cast removal than at 24 hours post cast removal, yet the difference compared to baseline was only significant at 24 hours post cast removal.

Despite the larger mean difference from baseline immediately post cast

removal, closer inspection of the statistical data revealed that the standard error was twice that of the standard error at 24 hours cast removal, despite similar standard deviations as illustrated in Figure 1. Similar confidence intervals were also found, which pointed towards there being a meaningful reduction in torque at both time points. In order to improve the reliability of plantarflexor torque measurements, it would be beneficical to conduct a number of pre-intervention trials to ensure to negate any learning effects being seen in the data.
The ability to maintain a controlled upright stance was reduced following seven days of ankle immobilisation, as indicated by an increase amount of sway. This increased sway could be due to alterations in peripheral or central neural drive to the plantarflexor muscles.
Altered central drive to the plantarflexors during maximal activity is likely to be reduced, as discussed above in relation to plantarflexor strength reductions, however, the unilateral

“One Week of Unilateral Ankle Immobilisation Alters Plantarflexor Strength, Balance and Walking Speed: A Pilot Study in
Asymptomatic Volunteers” by Caplan N et al.
Journal of Sport Rehabilitation
© 2014 Human Kinetics, Inc.

adaptations seen in balance suggest that this cannot be the case entirely. Reductions in central drive to the muscles would cause changes to balance performance in both limbs.
Changes were only seen, however, in the limb that underwent immobilisation. This unilateral response could be caused by altered proprioception at the ankle, or alterations in the motorneurons. Anderson et al11 investigated muscular and reflex adaptations of the soleus following hindlimb suspension in rats. H and T reflexes were elicited by transcutaneous submaximal stimulation and a tap to the Achilles tendon, respectively. Following hindlimb suspension, the H reflex amplitude was increased. Conversely, the T reflex amplitude was supressed. As the H reflex only involves the motorneurons as opposed to the T reflex which involves the entire stretch reflex pathway (including the muscle spindles), it was suggested that immobilisation reduces the excitability of the muscle proprioceptors rather than affecting the motorneurons11. With this in mind, the reduction in balance performance seen here in the immobilised limb suggests that the muscle spindles of the plantarflexor muscles have adapted to the period of disuse and have become hypoexcitable. Whilst walking in below knee casts, reductions in muscle activity of the plantarflexors have been observed23.

Due to the

immobilisation of the ankle joint, length changes of the plantarflexor muscle fibres will be minimised, leaving the muscle spindles in a relatively rested state during the seven days of immobilisation in this study. This would diminish the stretch reflex contribution to muscle activity normally seen during the walking gait cycle and could contribute to a possible reduction in muscle spindle excitability.
Walking speed immediately following cast removal was not different to baseline, despite the likely reduced central drive to the plantarflexors and the potentially reduced excitability of the muscle spindles. It is possible that the participants adapted to walking with the additional mass and constraints of the below knee cast during the week of immobilisation.

“One Week of Unilateral Ankle Immobilisation Alters Plantarflexor Strength, Balance and Walking Speed: A Pilot Study in
Asymptomatic Volunteers” by Caplan N et al.
Journal of Sport Rehabilitation
© 2014 Human Kinetics, Inc.

Following removal of the cast, walking could simply have felt easier, enabling the participants to walk at their baseline speed. In the following two days, however, walking speed increased. This increase in speed occurred as plantarflexor strength and balance performance returned to baseline levels.

Assuming that the reductions in strength and

balance were, in fact, linked to reduced central drive and muscle spindle hypoexcitability, respectively, their recovery towards baseline could lead to a relative increase in plantarflexor muscle activation by 24 hours and 48 hours, which could lead to the observed increases in walking speed.
Grey et al24 demonstrated the importance of the plantarflexor muscle spindles during locomotion. Following perturbation of the ankle into plantarflexion during the stance phase of the walking gait cycle, a reduction in soleus muscle activity was recorded due to reduced stretch of the muscle fibres, and thus supressed the response of the muscle spindles. This would support our suggestion that changes in muscle spindle excitability towards baseline during the two days following cast removal could influence plantarflexor muscle activation during walking.

If the muscle spindles do, in fact, show hypoexcitability following

immobilisation11, any subsequent increase in their excitability would lead to increases in plantarflexor muscle activity during the walking gait cycle which could elicit increases in walking speed24.
Ankle, knee and hip ranges of motion during the walking gait cycle were not influenced by one week’s immobilisation of the ankle joint. This was surprising as a number of previous studies have reported kinematic and kinetic differences whilst walking in below knee casts or low leg walkers 4, 16, 17. Walking kinematics would have been altered during the week of immobilisation, although perhaps seven days might not have been sufficient to elicit changes in lower limb kinematic following cast removal, regardless of any changes that could have occurred in the contractile properties of the plantarflexors or neural drive to the muscles.

“One Week of Unilateral Ankle Immobilisation Alters Plantarflexor Strength, Balance and Walking Speed: A Pilot Study in
Asymptomatic Volunteers” by Caplan N et al.
Journal of Sport Rehabilitation
© 2014 Human Kinetics, Inc.

Current rehabilitative practices following periods of immobilisation focus on the recovery of joint range of motion.25 The data presented here, suggest that joint range of motion during the functional task of walking are not affected by one week of ankle immobilisation. Future studies are needed to determine whether a longer period of

immobilisation could lead to kinematic changes. The findings of reduced plantarflexor strength coupled with impaired balance performance, that were suggested to be linked to altered motor control and proprioception suggest that an additional early emphasis on proprioceptive training might be appropriate. Strength and balance returned to baseline levels within a short time period following only a week of immobilisation, although a longer period of joint immobilisation could increase the duration of any neural recovery. Again, more research is needed to identify exactly how the duration of immobilisation affects neural recovery. At the very least, patients should be educated about the proprioceptive deficits that are likely to affect them for the period immediately following cast removal, in order to reduce risk of further injury through falls.
Although this pilot study presents useful information about the effects of ankle immobilisation on the biomechanics of the ankle joint, it was conducted on asymptomatic volunteers. Following injury, it is reported that arthrogenic muscle inhibition can occur following injury or effusion of a joint (typically the knee), which can lead to reductions in muscle size and functional impairment. In the ankle, however, Palmieri et al26 observed arthrogenic facilitation of the soleus, peroneus longus and tibialis anterior when ankle joint effusion was simulated. This facilitation of the ankle musculature could, therefore, further exaggerate the adaptations seen here in asymptomatic volunteers, in terms of walking speed.
Conversely, however, McVey et al27 observed arthrogenic inhibition in patients with functional ankle instability.

If muscular inhibition does occur, then the suggested

hyperexcitability of the neural pathways, discussed as a potential mechanism for the

“One Week of Unilateral Ankle Immobilisation Alters Plantarflexor Strength, Balance and Walking Speed: A Pilot Study in
Asymptomatic Volunteers” by Caplan N et al.
Journal of Sport Rehabilitation
© 2014 Human Kinetics, Inc.

increased walking speed seen here in the two days following cast removal in asymptomatic volunteers, could actually be supressed in patients with functional ankle instability. Further research is clearly warranted to extend the current work to look at how a period of ankle immobilisation affects the biomechanics and motor control of the ankle in ankle injury patients. Although the findings of this study demonstrate a number of potential influences of ankle joint immobilisation in terms of strength, balance and walking speed, clinicians must consider whether these are outweighed by the clinical benefits of immobilising the joint.
Conclusion
In conclusion, one week of ankle immobilisation leads to a reduction in plantarflexor strength and impaired balance performance.

These negative effects recovered towards

normal levels over the two days following cast removal. It was suggested that the reductions in strength are most likely due to reduced central drive to the muscles, and that reduced balance performance was likely due to initial hypoexcitability of the muscle spindles in the immobilised limb, although these were not measured directly. Clearly further research is warranted to identify what exact mechanisms are leading to these changes. As strength and balance recovered towards normal levels, walking speed increased.

This lends further

support to the notion that neural mechanisms are contributing to the observed changes, as the increase in walking speed could be due to an increase in excitability of the muscle spindles over the two days following cast removal.

“One Week of Unilateral Ankle Immobilisation Alters Plantarflexor Strength, Balance and Walking Speed: A Pilot Study in
Asymptomatic Volunteers” by Caplan N et al.
Journal of Sport Rehabilitation
© 2014 Human Kinetics, Inc.

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Asymptomatic Volunteers” by Caplan N et al.
Journal of Sport Rehabilitation
© 2014 Human Kinetics, Inc.

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“One Week of Unilateral Ankle Immobilisation Alters Plantarflexor Strength, Balance and Walking Speed: A Pilot Study in
Asymptomatic Volunteers” by Caplan N et al.
Journal of Sport Rehabilitation
© 2014 Human Kinetics, Inc.

Figure 1. Mean (±SD) plantarflexor peak torque shown for baseline, immediately following cast removal, and at 24 hours and 48 hours following cast removal. * indicates a significant change from baseline.

“One Week of Unilateral Ankle Immobilisation Alters Plantarflexor Strength, Balance and Walking Speed: A Pilot Study in
Asymptomatic Volunteers” by Caplan N et al.
Journal of Sport Rehabilitation
© 2014 Human Kinetics, Inc.

Figure 2. Mean (±SD) stability index shown for baseline, immediately following cast removal, and at 24 hours and 48 hours following cast removal for the casted (black bars) and non-casted (white bars) limbs. * indicates a significant change from baseline.

“One Week of Unilateral Ankle Immobilisation Alters Plantarflexor Strength, Balance and Walking Speed: A Pilot Study in
Asymptomatic Volunteers” by Caplan N et al.
Journal of Sport Rehabilitation
© 2014 Human Kinetics, Inc.

Figure 3. Mean (±SD) walking speed shown for baseline, immediately following cast removal, and at 24 hours and 48 hours following cast removal. * indicates a significant change from baseline.

“One Week of Unilateral Ankle Immobilisation Alters Plantarflexor Strength, Balance and Walking Speed: A Pilot Study in
Asymptomatic Volunteers” by Caplan N et al.
Journal of Sport Rehabilitation
© 2014 Human Kinetics, Inc.

Table 1. Mean differences from baseline and 95% confidence intervals for plantarflexor peak torque, stability index and walking speed.
Mean
difference

Confidence interval
Lower
Upper

Plantarflexor peak torque (Nm)
0 hours post cast removal
24 hours post cast removal
48 hours post cast removal

-16.333
-8.500
7.500

-33.977
-16.993
-13.008

1.311
-0.007
28.008

Left leg stability index
0 hours post cast removal
24 hours post cast removal
48 hours post cast removal

3.000
1.683
-0.017

0.843
-0.627
-1.874

5.157
3.993
1.841

Right leg stability index
0 hours post cast removal
24 hours post cast removal
48 hours post cast removal

0.033
0.883
0.017

-2.236
-1.754
-1.845

2.302
3.521
1.878

Speed (m/s)
0 hours post cast removal
24 hours post cast removal
48 hours post cast removal

-0.019
0.083
0.110

-0.041
-0.124
-0.189

0.079
-0.041
-0.031