Plantar Flexor Strength Research Articles

Feasibility of lower-limb muscle power training to enhance locomotor function poststroke.

Poststroke motor control is characterized by greatly reduced muscle power generation. To date, the extent to which muscle power limits walking performance or whether its remediation should be a primary component of locomotor rehabilitation has yet to be established. The purpose of this study was to examine the feasibility and the effects of Poststroke Optimization of Walking using Explosive Resistance training, an intervention aimed at improving poststroke muscular and locomotor function. Twelve subjects (6-60 mo poststroke) participated in 24 training sessions (3 sessions/wk for 8 wk). Exercises included leg press, calf raises, and jump training, all performed at high concentric velocity, as well as trials of fast walking. We measured self-selected and fastest comfortable walking speeds as well as knee extensor and plantar flexor strength and power at pretraining, posttraining, and 8 wk follow-up time points. In addition, we also performed a number of clinical assessments commonly used in poststroke rehabilitation trials. Following training, significant improvements in lower-limb muscle strength and power were realized and accompanied by improvements in self-selected as well as fastest comfortable walking speeds. No changes in clinical assessments resulted from training.

The Effect of Transcutaneous Electrical Nerve Stimulation (TENS) Applied to the Foot and Ankle on Strength, Proprioception and Balance: A Preliminary Study

Background: Transcutaneous electrical nerve stimulation (TENS) promotes upper motor neuron excitability which has the potential to improve function. As a precursor to clinical trials, we investigated the potential efficacy of TENS on strength, proprioception and balance in healthy older adults. Method: Design: A paired-sample randomized crossover trial. No stimulation was the control. Intervention: A one-off session of TENS (Modulated frequency: 70-130Hz, 5 second cycle) via a conductive sock. Participants: 25 healthy older volunteers with no pre-existing balance or mobility limitations or contra-indications to TENS. Outcomes: Dorsiflexor and plantarflexor strength and proprioception using an isokinetic dynamometer and balance (postural sway and forward reach test). Analysis: Paired t-tests Results: None of the parameters showed any significant changes with TENS (p>0.05). Conclusions: The stimulation of cutaneous sensory nerve endings of the foot with the application of TENS showed no immediate effect on the ankle proprioception, lower leg muscle strength, and postural stability. The concern that TENS would have a distracting impact on sensation and balance was not supported according to these results.

8주간의 체중을 이용한 저항운동 시 전신진동 유·무에 따른 노인 여성하지의 발바닥쪽굽힘근의 생체역학적 특성 변화

The aim of this study was to investigate the effect of resistance training with and without whole-body vibration(WBV) on the biomechanical properties of the plantarflexor in the elderly women (>60 yrs., n=35). Thirty-five volunteers were randomly assigned to a resistance training with WBV group (RVT, n=14), a resistance training without WBV (RT, n=11), and a non-training control group (CON, n=10). The RVT and the RT groups participated in the training sessions three times a week for 8 weeks, followed by a 4-week detraining period. The CON group was instructed to refrain from any type of resistance training. To assess strength and activation of the plantarflexor muscles, maximum isometric ankle plantarflexion torque and muscle activation of the triceps surae muscles were measured using dynamometry, twitch interpolation technique and electromyography at four different ankle joint angles. Also, the lower extremity function was assessed by vertical jumping. The measurements were performed prior to, 2 and 8 weeks after the training and after a 4-week detraining period. Following the 8-week training sessions, an increase in the isometric plantarflexion strength was found to be greater for the RVT compared with the RT group (p<.05). Muscle inhibition was significantly decreased after training than before training only for the RVT (p<.05). Following the detraining period, a decrease in isometric plantarflexors strength and a increases in muscle inhibition were significantly less in the RVT compared with the RT group. In conclusion, the exercise with WBV is a feasible training modality for the elderly and seems to have a boosting effect when used with conventional resistance training.

Predictors for the benefit of selective dorsal rhizotomy.

Selective dorsal rhizotomy (SDR) is a spasticity reducing treatment option for children with spastic cerebral palsy. Selection criteria for this procedure are inconclusive to date. Clinical relevance of the achieved functional improvements and side effects like the negative impact on muscle strength are discussed controversially. In this prospective cohort study one and two year results of 54 children with a mean age of 6.9 (±2.9) years at the time of SDR are analyzed with regard to gross motor function and factors affecting the functional benefit. Only ambulatory children who were able to perform a gross motor function measure test (GMFM-88) were included in this study. Additionally, the modified Ashworth scale (MAS), a manual muscle strength test (MFT), and the body mass index (BMI) were evaluated as possible outcome predictors. MAS of hip adductors and hamstrings decreased significantly (p<0.001) and stayed reduced after two years, while GMFM improved significantly from 79% to 84% 12 months after SDR (p<0.001) and another 2% between 12 and 24 months (p=0.002). Muscle strength did improve significantly concerning knee extension (p=0.008) and ankle dorsiflexion (p=0.006). The improvement of function correlated moderately with age at surgery and preoperative GMFM and weakly with the standard deviation score of the BMI, the dorsiflexor and plantarflexor strength preoperatively as well as with the reduction of spasticity of the hamstrings and the preoperative spasticity of the adductors and hamstrings. Correctly indicated SDR reduces spasticity and increases motor skills sustainably in children with spastic cerebral palsy corresponding to clinically relevant changes of GMFM without compromising muscular strength. Outcome correlates to GMFM and age rather than to MAS and maximal strength testing. The data of this evaluation suggest that children who benefit the most from SDR are between 4 and 7 years old and have a preoperative GMFM between 65% and 85%.

Parallel Walk Test: Its Correlation With Balance and Motor Functions in People With Chronic Stroke

ObjectivesTo investigate (1) the intrarater, interrater, and test-retest reliability of the times and scores generated in the parallel walk test (PWT); (2) their correlations with impairments and activity limitations of individuals with stroke; and (3) the cutoff times that best discriminate individuals with stroke from healthy elderly subjects. DesignCross sectional study. SettingUniversity-based rehabilitation center. ParticipantsParticipants (N=72) comprised individuals with stroke (n=37) and healthy individuals (n=35). InterventionsNot applicable. Main Outcome MeasuresThe PWT was administered along with the Fugl-Meyer Motor Assessment of the Lower Extremities (FMA-LE), handheld dynamometer measurements of ankle dorsiflexor and plantarflexor muscle strength, the 5-Times-Sit-to-Stand Test, the Berg Balance Scale (BBS), a limits of stability (LOS) test, the 10-m walk test (10-MWT), and the timed Up and Go (TUG) test. ResultsPWT times and scores showed good to excellent intrarater, interrater, and test-retest reliability in individuals with stroke. PWT times using paths of 3 different widths significantly correlated with FMA-LE scores, 5-Times-Sit-to-Stand Test times, BBS scores, some LOS test results, 10-MWT gait speed, and TUG test times. PWT times of 6.30 to 7.48 seconds, depending on the path width, were shown reliably to discriminate individuals with stroke from healthy individuals. ConclusionThe PWT is a reliable, easy-to-administer clinical tool for assessing dynamic walking balance in individuals with chronic stroke.

The Changes of Muscle Strength and Functional Activities During Aging in Male and Female Populations

Aging is associated with the loss of muscle strength and difficulties in functional activities. The aim of this study was to investigate the changes of muscle strength and functional activities during aging in male and female individuals. This study was a cross-sectional study recruiting healthy individuals aged 40–89 years. The muscle strength of bilateral hip flexors, knee extensors, and ankle plantar flexors were measured. Activities including functional reach test, timed up and go test, and alternating stair stepping were also measured. A total of 373 male and 371 female individuals participated in this study. The muscle strength of hip flexors and knee extensors were all significantly decreased after age 80 years as compared with the age group of 40–49 years in both male and female groups. The abilities of functional reach and timed up and go task were significantly decreased after age 70 years in the male group and decreased after age 60 years in the female group as compared with the age group of 40–49 years. We noted that the muscle strength and functional activities were decreased earlier in female than male individuals. The decrease of functional activities during the aging process seems to be earlier than the decrease of muscle strength. It is important to implement functional activities training in addition to strengthening exercise to maintain functional levels of the geriatric population.

Effects of 1 Week of Unilateral Ankle Immobilization on Plantar-Flexor Strength, Balance, and Walking Speed: A Pilot Study in Asymptomatic Volunteers

Ankle immobilization is often used after ankle injury. To determine the influence of 1 week's unilateral ankle immobilization on plantar-flexor strength, balance, and walking gait in asymptomatic volunteers. Repeated-measures laboratory study. University laboratory. 6 physically active male participants with no recent history of lower-limb injury. 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. 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. 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.

The association between physical characteristics of the ankle joint and the mobility performance in elderly people with type 2 diabetes mellitus

Previous studies showed that older adults with diabetes have a worse mobility performance as compared with those without diabetes. Studies also demonstrated that older adults with diabetes have weakened ankle muscle strength, reduced joint range in ankle dorsiflexion and worsened ankle joint proprioception as compared with control population. The purpose of the present study was to examine the relationship between the physical characteristics of the ankle joint and the mobility performance in older adults with type 2 diabetes. Older adults with type 2 diabetes (n=85) were recruited, and Timed Up and Go test (TUG) for mobility assessment was performed. Active ankle joint repositioning test was used for assessing the ankle joint proprioception sense; peak torque of ankle dorsiflexors and plantar flexors were tested by using a Cybex Norm dynamometer, and weight-bearing lunge test (WBLT) was used for assessing the stiffness of ankle dorsiflexion. Our results showed that age, body mass index (BMI), normalized peak torque of plantar flexors and dorsiflexors, active ankle joint repositioning test errors and the WBLT distance were significantly correlated with the TUG (all p<0.001). These ankle characteristics, together with the demographic data of the subjects, contributed 59.9% of the variance in the TUG by multiple regression analysis. Body mass, ankle plantar flexors strength and ankle joint proprioception are important factors contributing to the physical mobility of the older adults with type 2 diabetes.

The effect of rowing ergometry and resistive exercise on skeletal muscle structure and function during bed rest

Exposure to microgravity causes functional and structural impairment of skeletal muscle. Current exercise regimens are time-consuming and insufficiently effective; an integrated countermeasure is needed that addresses musculoskeletal along with cardiovascular health. High-intensity, short-duration rowing ergometry and supplemental resistive strength exercise may achieve these goals. Twenty-seven healthy volunteers completed 5 wk of head-down-tilt bed rest (HDBR): 18 were randomized to exercise, 9 remained sedentary. Exercise consisted of rowing ergometry 6 days/wk, including interval training, and supplemental strength training 2 days/wk. Measurements before and after HDBR and following reambulation included assessment of strength, skeletal muscle volume (MRI), and muscle metabolism (magnetic resonance spectroscopy); quadriceps muscle biopsies were obtained to assess muscle fiber types, capillarization, and oxidative capacity. Sedentary bed rest (BR) led to decreased muscle volume (quadriceps: -9 ± 4%, P < 0.001; plantar flexors: -19 ± 6%, P < 0.001). Exercise (ExBR) reduced atrophy in the quadriceps (-5 ± 4%, interaction P = 0.018) and calf muscle, although to a lesser degree (-14 ± 6%, interaction P = 0.076). Knee extensor and plantar flexor strength was impaired by BR (-14 ± 15%, P = 0.014 and -22 ± 7%, P = 0.001) but preserved by ExBR (-4 ± 13%, P = 0.238 and +13 ± 28%, P = 0.011). Metabolic capacity, as assessed by maximal O2 consumption, (31)P-MRS, and oxidative chain enzyme activity, was impaired in BR but stable or improved in ExBR. Reambulation reversed the negative impact of BR. High-intensity, short-duration rowing and supplemental strength training effectively preserved skeletal muscle function and structure while partially preventing atrophy in key antigravity muscles. Due to its integrated cardiovascular benefits, rowing ergometry could be a primary component of exercise prescriptions for astronauts or patients suffering from severe deconditioning.

The reliability of isokinetic strength of ankle dorsal and plantar flexors in patients with peripheral arterial disease

The reliability of isokinetic strength of ankle dorsal and plantar flexors in patients with peripheral arterial disease

인체 족저굴곡근의 근력과 아킬레스 건의 경도, 기능적 능력 간 상관관계 분석

Tendon elasticity is an important factor affecting muscle function and thus human movements. It has been reported that the mechanical properties of tendon are adaptable to external loading condition. Based on the adaptability of muscle and tendon to external loading conditions, one can assume that there might be an optimum ratio between muscle strength and tendon stiffness. The present study aimed to investigate whether there is correlation between plantar flexor muscle strength and stiffness of the achilles tendon (AT). Twenty two male subjects (age: 23.2±1.5 yrs, height: 175.5±6.2 cm, weight: 75.4±9.8 kg) performed max- imum voluntary isometric plantarflexion on a custom-built dynamometer and muscle-tendon junction of the medial gastrocnemius muscle was simultaneously monitored using a real-time ultrasound imaging machine. The averages of muscle force and tendon stiffness were 366.38±79.37 N, 35.34±10.42 N/mm, respectively. Significant positive correlation was observed between muscle strength and tendon stiffness (r=0.8507), indicating that the muscle force is proportional to tendon stiffness. The results might have been used in computational modeling and criterion of training progress level in the fields of training and rehabilitation

Ankle voluntary movement enhancement following robotic-assisted locomotor training in spinal cord injury.

BackgroundIn incomplete spinal cord injury (iSCI), sensorimotor impairments result in severe limitations to ambulation. To improve walking capacity, physical therapies using robotic-assisted locomotor devices, such as the Lokomat, have been developed. Following locomotor training, an improvement in gait capabilities—characterized by increases in the over-ground walking speed and endurance—is generally observed in patients. To better understand the mechanisms underlying these improvements, we studied the effects of Lokomat training on impaired ankle voluntary movement, known to be an important limiting factor in gait for iSCI patients.MethodsFifteen chronic iSCI subjects performed twelve 1-hour sessions of Lokomat training over the course of a month. The voluntary movement was qualified by measuring active range of motion, maximal velocity peak and trajectory smoothness for the spastic ankle during a movement from full plantar-flexion (PF) to full dorsi-flexion (DF) at the patient’s maximum speed. Dorsi- and plantar-flexor muscle strength was quantified by isometric maximal voluntary contraction (MVC). Clinical assessments were also performed using the Timed Up and Go (TUG), the 10-meter walk (10MWT) and the 6-minute walk (6MWT) tests. All evaluations were performed both before and after the training and were compared to a control group of fifteen iSCI patients.ResultsAfter the Lokomat training, the active range of motion, the maximal velocity, and the movement smoothness were significantly improved in the voluntary movement. Patients also exhibited an improvement in the MVC for their ankle dorsi- and plantar-flexor muscles. In terms of functional activity, we observed an enhancement in the mobility (TUG) and the over-ground gait velocity (10MWT) with training. Correlation tests indicated a significant relationship between ankle voluntary movement performance and the walking clinical assessments.ConclusionsThe improvements of the kinematic and kinetic parameters of the ankle voluntary movement, and their correlation with the functional assessments, support the therapeutic effect of robotic-assisted locomotor training on motor impairment in chronic iSCI.

Coping with heat stress during match-play tennis: Does an individualised hydration regimen enhance performance and recovery?

ObjectivesTo determine whether an individualised hydration regimen reduces thermal, physiological and perceptual strain during match-play tennis in the heat, and minimises alterations in neuromuscular function and physical performance postmatch and...

Plantarflexor Weakness Negatively Impacts Walking in Persons With Multiple Sclerosis More Than Plantarflexor Spasticity

ObjectivesTo determine whether plantarflexor (PF) spasticity or ankle strength best predicts variance in walking capacity or self-perceived limitations in walking in persons with multiple sclerosis (MS) and whether persons with MS with PF spasticity are weaker and have greater walking dysfunction than do persons with MS without PF spasticity. DesignCross-sectional study. SettingUniversity research laboratory. ParticipantsForty-two adults with MS (mean age, 42.9±10.1y; Expanded Disability Status Scale score, median=3.0, range=0–6) and 14 adults without disability (mean age, 41.9±10.1y). InterventionNot applicable. Main Outcome MeasuresPF spasticity and dorsiflexion and PF maximum voluntary isometric torque were assessed using the modified Ashworth Scale and a computerized dynamometer, respectively. The Timed 25-Foot Walk Test was the primary outcome measure of walking capacity. Secondary measures included the 6-Minute Walk Test and the 12-item Multiple Sclerosis Walking Scale. ResultsPF strength was the most consistent predictor of variance in walking capacity (Timed 25-Foot Walk Test: R2 change=.23–.29, P≤.001; 6-Minute Walk Test: R2 change=.12–.29, P≤.012), and self-perceived limitations of walking (12-item Multiple Sclerosis Walking Scale: R2 change=.04–.14, P<.18). There were no significant differences (P>.05) between persons with MS with PF spasticity and persons with MS without PF spasticity for any of the outcome measures. ConclusionsOur study suggests a unique contribution of PF weakness to walking dysfunction in persons with MS, and highlights the importance of evaluating PF strength in this clinical population.

Healthy older adults have insufficient hip range of motion and plantar flexor strength to walk like healthy young adults

Limited plantar flexor strength and hip extension range of motion (ROM) in older adults are believed to underlie common age-related differences in gait. However, no studies of age-related differences in gait have quantified the percentage of strength and ROM used during gait. We examined peak hip angles, hip torques and plantar flexor torques, and corresponding estimates of functional capacity utilized (FCU), which we define as the percentage of available strength or joint ROM used, in 10 young and 10 older healthy adults walking under self-selected and controlled (slow and fast) conditions. Older adults walked with about 30% smaller hip extension angle, 28% larger hip flexion angle, 34% more hip extensor torque in the slow condition, and 12% less plantar flexor torque in the fast condition than young adults. Older adults had higher FCU than young adults for hip flexion angle (47% vs. 34%) and hip extensor torque (48% vs. 27%). FCUs for plantar flexor torque (both age groups) and hip extension angle (older adults in all conditions; young adults in self-selected gait) were not significantly <100%, and were higher than for other measures examined. Older adults lacked sufficient hip extension ROM to walk with a hip extension angle as large as that of young adults. Similarly, in the fast gait condition older adults lacked the strength to match the plantar flexor torque produced by young adults. This supports the hypothesis that hip extension ROM and plantar flexor strength are limiting factors in gait and contribute to age-related differences in gait.

Balance and muscle power of children with Charcot-Marie-Tooth.

BACKGROUND: In certain diseases, functional constraints establish a greater relationship with muscle power than muscle strength. However, in hereditary peripheral polyneuropathies, no such relationship was found in the literature. OBJECTIVE: In children with Charcot-Marie-Tooth (CMT), to identify the impact of muscle strength and range of movement on the static/dynamic balance and standing long jump based on quantitative and functional variables. METHOD: The study analyzed 19 participants aged between 6 and 16 years, of both genders and with clinical diagnoses of CMT of different subtypes. Anthropometric data, muscle strength of the lower limbs (hand-held dynamometer), ankle and knee range of movement, balance (Pediatric Balance Scale) and standing long jump distance were obtained by standardized procedures. For the statistical analysis, Pearson and Spearman correlation coefficients were used. RESULTS: There was a strong positive correlation between balance and the muscle strength of the right plantar flexors (r=0.61) and dorsiflexors (r=0.59) and a moderate correlation between balance and the muscle strength of inversion (r=0.41) and eversion of the right foot (r=0.44). For the long jump and range of movement, there was a weak positive correlation with right and left plantar flexion (r=0.20 and r=0.12, respectively) and left popliteal angle (r=0.25), and a poor negative correlation with left dorsiflexion (r=-0.15). CONCLUSIONS: The data on the patients analyzed suggests that the maintenance of distal muscle strength favors performance during balance tasks, while limitations in the range of movement of the legs seem not to be enough to influence the performance of the horizontal long jump.

Knee muscle strength – A challenge to measure

The aims were to assess the reliability of knee extensor and flexor muscle strength measurements using the Strength Measuring Chair (SMC) in children and adults, and to assess agreement between the SMC and an isokinetic dynamometer (ID). 20 healthy children (10/10 boys/girls, 5–13 years) and 23 adults (10/13 men/women, 23–60 years) were included. Muscle strength tests were performed in the SMC and in the ID. The intra-subject reliability was shown to be excellent in both instruments (ICC 0.93–0.99) and an excellent test–retest reliability of measurements in the SMC was found (ICC 0.87–0.93). Agreement between instruments was evaluated with ICC, paired t-test and Bland–Altman 95% limits of agreement plots. In both adults’ and children's groups, disagreements were found between the two instruments, with more in the children's group. The SMC, which has previously shown to be valid and reliable for measuring plantarflexor muscle strength, reliably measured knee muscle strength in healthy children and adults. However, the large disagreement found between the instruments, especially in the children's group, warrants care in standardizing measuring positions for different body size and warrants caution in comparing one's muscle strength measured using different assessment methods.

Are Repeated Single-Limb Heel Raises and Manual Muscle Testing Associated With Peak Plantar-Flexor Force in People With Inclusion Body Myositis?

Repeated heel raises have been proposed as a method of ankle plantar-flexor strength testing that circumvents the limitations of manual muscle testing (MMT). The study objective was to examine the relationships among ankle plantar-flexion isometric maximum voluntary contraction (MVC), repeated single-limb heel raises (SLHRs), and MMT in people with myositis. This was a cross-sectional study with a between-group design. The ability to complete 1 SLHR determined group assignment (SLHR group, n=24; no-SLHR group, n=19). Forty-three participants with myositis (13 women; median age=64.9 years) participated. Outcome measures included MVC, predicted MVC, Kendall MMT, and Daniels-Worthingham MMT. The Kendall MMT was unable to detect significant ankle plantar-flexor weakness established by quantitative methods and was unable to discriminate between participants who could and those who could not perform the SLHR task. Ankle plantar-flexion MVC was not associated with the number of heel-raise repetitions in the SLHR group (pseudo R(2)=.13). No significant relationship was observed between MVC values and MMT grades in the SLHR and no-SLHR groups. However, a moderate relationship between MVC values and MMT grades was evident in a combined-group analysis (ρ=.50-.67). The lower half of both MMT grading scales was not represented in the study despite the profound weakness of the participants. Both Kendall MMT and Daniels-Worthingham MMT had limited utility in the assessment of ankle plantar-flexor strength. Repeated SLHRs should not be used as a proxy measure of ankle plantar-flexion MVC in people with myositis.

Effect of ankle taping on angle and force matching and strength of the plantar flexors

ObjectiveInvestigate the effect of ankle taping on plantar-flexion strength, angle matching and force matching. DesignSingle group, repeated measures. SettingLaboratory of an educational institution. ParticipantsTwenty uninjured females (22.9 ± 3.6 years). Main Outcome MeasuresTape was applied to the ankle using a conventional hindfoot technique. Angle and force matching, and plantar-flexor strength were assessed using the purpose built dual ankle dynamometer, and measures were taken prior to and following taping. Angle matching was assessed passively and actively at 10, 15 and 20° of plantar-flexion. Participants were required to match the angle of the reference leg with the contralateral leg. Force matching was assessed at 10° of plantar-flexion and participants matched the torque of the reference leg with the contralateral leg. ResultsTaping had no effect on absolute errors during active or passive angle matching. Regardless of taping, the ankle angle tested had a significant effect on passive angle matching (p < 0.001); subjects were most accurate at matching a plantar-flexion angle of 20°. Ankle taping had no effect on force matching. Taping significantly improved peak plantar-flexion strength by 20% (p = 0.028). ConclusionAnkle taping has little effect on contralateral force and angle matching, but it can enhance peak plantar-flexion strength.

Influence of ankle plantar flexor muscle architecture and strength on gait in boys with haemophilia in comparison to typically developing children

Altered gait patterns, muscle weakness and atrophy have been reported in young boys with severe haemophilia when compared to unaffected peers. The aim of this study was to determine whether lateral gastrocnemius muscle size and architecture influenced biomechanical walking patterns of boys with haemophilia and if these relationships differed from age-matched typically developing boys. Biomechanical function of the knee and ankle during level walking, lateral gastrocnemius anatomical cross-sectional area, thickness, width, fascicle length and pennation angle and ankle plantar flexor muscle strength were recorded in 19 typically developing boys aged 7-12years and 19 age-matched haemophilic boys with a history of ankle joint bleeding. Associations between gait, strength and architecture were compared using correlations of peak gait values. Haemophilic boys walked with significantly larger (P<0.05) ankle dorsi flexion angles and knee flexion moments. The ankle plantar flexor muscles of haemophilic boys were significantly weaker and smaller when compared to typically developing peers. In the typically developing boys there was no apparent association between muscle architecture, strength and walking patterns. In haemophilic boys maximum muscle strength and ACSA normalized torque of the ankle plantar flexors together with the muscle width, thickness, fascicle length and angulation (P<0.05) were associated with motion at the ankle and peak moments at the knee joint. Muscle strength deficits of the ankle plantar flexors and changes in muscle size and architecture may underpin the key biomechanical alterations in walking patterns of haemophilic boys with a history of ankle joint bleeding.