Plantar Flexor Strength Research Articles

Plantar flexor strength and size decrease following single-leg disuse in uninjured adults: A meta-analysis.

Plantar flexors play a pivotal role in human locomotion and balance. Several original research studies and systematic reviews have characterised the impact of single-leg disuse on plantar flexor strength and size. However, no meta-analysis has quantified the effects of single-leg disuse on changes in plantar flexor strength and size in uninjured adults. To quantify changes in plantar flexor strength and size in response to single-leg disuse. Data were extracted from 19 studies captured in our previous systematic review on studies that employed a unilateral lower limb immobilisation model (cast or brace) and were published up to January 30, 2022. Random-effects meta-analyses were performed on original research studies reporting measures of plantar flexor strength (isometric, isokinetic, or repetition maximum) and size (magnetic resonance imaging or computed tomography) in uninjured adults. Single-leg disuse decreased plantar flexor strength (Hedges gav = -0.71 [95% confidence interval: -0.93, -0.48], p < 0.001, 7-28 days, N = 16 studies, n = 121 participants including ≥13 females, ages 19-29) and plantar flexor size (-0.33 [-0.50, -0.15], p < 0.001, 14-35 days, N = 6, n = 49, 10 females, ages 22-27) across all durations of disuse. Single-leg disuse decreases plantar flexor strength and size in uninjured adults. This work adds to recent meta-analytic findings demonstrating the declines in knee extensors strength and size following single-leg disuse. The paucity of female and participants >30 years old in the single-leg disuse literature examining plantar flexors represents a priority of future work.

Reliability of isokinetic dynamometer for isometric assessment of ankle plantar flexor strength.

ObjectiveTo evaluate isokinetic dynamometer reliability for isometric assessment of plantar flexor (PF) strength. DesignCross-sectional. SettingTesting by the same physiotherapist twice during a first session (repeatability) and once during a second session (reproducibility). ParticipantsTwenty-two healthy subjects (44 ankles, 11 men/11 women). Main Outcome MeasuresIsometric PF peak torque, with and without body mass normalization, at 0° and +20° of plantar flexion. Measurement reliability was evaluated using intraclass correlation coefficient (ICC), standard error of measurement (SEM) and minimal detectable change (MDC). ResultsWithout normalization, measurement repeatability was excellent at 0° of plantar flexion (ICC, 0.94; SEM, 6.6%; MDC, 18.4%) compared with good repeatability at +20° (ICC, 0.85; SEM, 11.1%; MDC 30.6%). Measurement repeatability following normalization was good at 0° (ICC, 0.88; SEM, 5.2%; MDC, 14.4%) and +20° (ICC, 0.79; SEM, 10.2%; MDC, 28.1%). While reproducibility was good at 0° with normalization (ICC, 0.84; SEM, 5.9%; MDC, 16.3%) or excellent without (ICC 0.92; SEM 7.5%; MDC, 20.8%), it was moderate at +20° with normalization (ICC 0.71; SEM 11.3%; MDC, 31.3%) or good without (ICC 0.78; SEM 13.0%; MDC, 36.1%). ConclusionThe reliability of PF maximal isometric strength is good/excellent at 0° of plantar flexion but moderate/good at +20°.

How Does Standing Anteroposterior Stability Limits Correlate to Foot/ankle Functions in Bilateral Spastic Cerebral Palsy?

To determine whether foot and ankle functions are correlated with the limits of stability (LoS) while standing in individuals with bilateral spastic cerebral palsy (BSCP). Eighteen people who could walk and with BSCP and 18 people without disability participated. Anteroposterior LoS was measured using a force platform. To quantify ankle and foot functions, spasticity, isometric muscle strength, passive range of motion, and plantar light touch-pressure sensation were assessed. In the BSCP group, anteroposterior LoS was significantly decreased, and anterior LoS reduction was correlated with decreases in plantar flexor and toe flexor strength and in sensitivity of the forefoot to light touch-pressure sensation, whereas the posterior LoS reduction was correlated with reduced dorsiflexor strength. The present findings suggest that improvement in these foot and ankle functions in BSCP may increase LoS while standing.

The Effects of Heat Therapy During Immobilization and Rehabilitation on Muscle Atrophy and Strength Loss at Return to Sports in Healthy Humans.

Animal research suggests that repeated heat exposures may stimulate skeletal muscle protein synthesis and downregulate protein degradation. Repeated heat exposures during ankle immobilization and rehabilitation would preserve human muscle strength and mass. Controlled laboratory study. A total of 20 male participants (age, 33.6 ± 2.8 years; weight, 83.8 ± 9.2 kg; height, 182 ± 6 cm) underwent 4 weeks of supervised training, 2 weeks of single-lower leg immobilization, and 2 weeks of supervised rehabilitation before return to sports (RTS). Participants were split into 2 groups: (1) whole-body heat therapy (HEAT) and (2) sham treatment (SHAM) throughout the immobilization and rehabilitation periods. Measures of muscle strength (isometric and isokinetic), volume (magnetic resonance imaging and ultrasound), and muscle biopsies were obtained preimmobilization, postimmobilization, and at RTS. Maximal isometric strength of the plantarflexors was lower at RTS compared with preimmobilization in SHAM (P = .027) but not HEAT (P = .301). Isokinetic strength during a fatigue test was higher at RTS compared with preimmobilization in HEAT (P = .039) but not SHAM (P = .245). Pennation angle and muscle thickness were lower at postimmobilization compared with preimmobilization only in SHAM (P≤ .027). Muscle cross-sectional area decreased in soleus and both gastrocnemius medialis and lateralis (all P≤ .035) in SHAM, but only in gastrocnemius medialis in HEAT. There was a large (d = 0.91) but not significant (P = .054) decrease in the ratio of phosphorylated/total nuclear factor-kappa B (NFκB) from preimmobilization to postimmobilization in HEAT only. There was an increase in phosphorylated fork head box O proteins (FoxO) only in HEAT (P = .034), suggesting a decrease in FoxO activity. Caspase 3 expression increased from preimmobilization to postimmobilization in SHAM only (P = .004). These results indicate that using heat therapy throughout immobilization and rehabilitation reduces skeletal muscle atrophy and maintains plantarflexor strength in healthy humans. Moreover, heat therapy may lead to the inactivation of the FoxO and NFκB signaling pathways involved in atrophy. Repeated heat exposures should be considered a novel therapeutic intervention to counteract muscle atrophy during immobilization.

Looking Beyond the Number of Repetitions: An Observational Cross-Sectional Study on Calf Raise Test Outcomes in Children Aged 10–17 Years

Aims The calf raise test (CRT) assesses plantarflexor strength and endurance, but normative data for children are scarce. Furthermore, contradictions exist on which factors are associated with total repetitions, with repetitions being the only metric considered. We quantified three of the main CRT outcomes (repetitions, total work, and peak height) in children 10–17 years and explored their relationship with various factors. Methods Healthy children (n = 165, 50.3% female) completed single-legged calf raises on a 10° incline, once on each leg. Test outcomes were extracted using the valid and reliable Calf Raise application. Results CRT outcomes were not significantly different between legs (p ≥ .19). The only covariates significantly associated with outcomes based on stepwise quantile regressions were body mass index centile for repetitions, meeting physical activity recommendations for total work and peak height, and age for total work. Outcomes did not significantly differ based on sex or maturation. Median values were around 26 for repetitions, 640–1460 J for total work (age dependent), and 10.1 cm for peak height for children meeting physical activity recommendations. Conclusion Children who were older, had lower body mass indices, and were more active exhibited superior CRT outcomes. Meeting physical activity recommendations appears beneficial for plantarflexor function and should continue to be prioritized in children.

Functional Performance and Tendon Morphology After Operative or Nonoperative Treatment of Achilles Tendon Ruptures.

While controversy remains as to the relative benefit of operative (OM) versus non-operative management (NOM) of Achilles tendon (AT) ruptures (ATR), few studies have examined the effect on high impact maneuvers such as jumping and hopping. The purpose of this study was to determine if functional performance including strength, jumping, and hopping outcomes differed between OM and NOM of acute ATR. The secondary objective was to assess the degree of association between AT morphology and performance outcomes. Retrospective cohort with a single prospective evaluation. All patients were treated at an institutional secondary care center. Eligible participants (n=12 OM; 12 NOM) who were treated with OM or NOM of ATR within three weeks of injury were evaluated a minimum 20 months following ATR. AT length, thickness and gastrocnemius muscle thickness were assessed with B-mode ultrasound. Isokinetic plantar flexor strength, hop tests and countermovement and drop jumps were completed. Two-way ANOVAS were completed on all tests with unilateral values, independent t-tests were used for bilateral outcomes, and linear regressions were completed to assess the relationship between normalized AT length and performance. Affected limb AT was elongated and thickened (p\<0.01), gastrocnemius was atrophied (p\< 0.01) and angle-specific plantar flexor torque was reduced at 120°/s when measured at 20° plantar flexion (p = 0.028). Single leg drop vertical jump was higher in OM (p = 0.015) with no difference for hop and jump tests. AT length was related to plantar flexor torque but had no relationship with hopping performance. Hop test performance was maintained despite plantarflexion weakness, gastrocnemius atrophy, and AT elongation. This may be the result of compensatory movement patterns. AT length holds limited explanatory power in plantar flexor strength, although this relationship should be evaluated further. Level III.

Peripheral artery disease patients with chronic kidney disease have lower muscle strength and mitochondrial function compared to those with normal kidney function

Introduction: Chronic kidney disease is a significant risk factor for both the development of peripheral artery disease (PAD) and major adverse limb events. However, little is known about how the coalescence of these two conditions impacts limb muscle pathophysiology. The objective of the current study was to determine the impact of CKD on skeletal muscle strength and mitochondrial health in patients with and without PAD. Methods: A cross-sectional prospective study design was employed to assess plantar flexor muscle strength, muscle fiber cross-sectional area (CSA), and mitochondrial health in four groups of patients (61 males and 29 females): PAD only (Toe brachial index, TBI&lt;0.5 and eGFR&gt;60 mL/min), CKD only (TBI&gt;0.75 and eGFR:15-45 mL/min), PAD with CKD (TBI&lt;0.5 and eGFR:15-45 mL/min), and adult controls without PAD and CKD (TBI&gt;0.75 and eGFR&gt;60 mL/min). Results: Plantar flexor muscle strength was lowest in PAD patients with CKD compared to adult controls ( P&lt;0.0001), PAD only ( P=0.001), and CKD only ( P=0.003). No differences in the mean muscle fiber CSA were detected. The percentage of COX+ fibers was significantly lower in PAD patients with CKD compared to adult controls ( P=0.03). High resolution respirometry analysis of mitochondrial oxidative phosphorylation (OXPHOS) function demonstrated that CKD has a significant negative impact on muscle bioenergetics. PAD patients with CKD had lower OXPHOS function than adult controls ( P=0.0016) and PAD patients without CKD ( P=0.0015). Notably, CKD patients without PAD also had lower OXPHOS function than adult controls ( P=0.0054) and PAD patients without CKD ( P=0.005). Conclusion: The current results demonstrate a profound negative impact of CKD on the associated myopathy of PAD patients. This study was supported by National Institutes of Health (NIH) grant R01-HL149704 (T.E.R.). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

The effects of plantarflexor weakness and reduced tendon stiffness with aging on gait stability.

Falls among older adults are a costly public health concern. Such falls can be precipitated by balance disturbances, after which a recovery strategy requiring rapid, high force outputs is necessary. Sarcopenia among older adults likely diminishes their ability to produce the forces necessary to arrest gait instability. Age-related changes to tendon stiffness may also delay muscle stretch and afferent feedback and decrease force transmission, worsening fall outcomes. However, the association between muscle strength, tendon stiffness, and gait instability is not well established. Given the ankle's proximity to the onset of many walking balance disturbances, we examined the relation between both plantarflexor strength and Achilles tendon stiffness with walking-related instability during perturbed gait in older and younger adults-the latter quantified herein using margins of stability and whole-body angular momentum including the application of treadmill-induced slip perturbations. Older and younger adults did not differ in plantarflexor strength, but Achilles tendon stiffness was lower in older adults. Among older adults, plantarflexor weakness associated with greater whole-body angular momentum following treadmill-induced slip perturbations. Weaker older adults also appeared to walk and recover from treadmill-induced slip perturbations with more caution. This study highlights the role of plantarflexor strength and Achilles tendon stiffness in regulating lateral gait stability in older adults, which may be targets for training protocols seeking to minimize fall risk and injury severity.

Association between Sprint and Jump Performance and Maximum Strength in Standing Calf Raise or Squat in Elite Youth Soccer Players.

Soccer is a complex sports discipline that requires players to engage in diverse high-intensity and multidirectional activities. The optimization of strength and conditioning programs requires a comprehensive understanding of the physical attributes influencing player performance. While previous research has demonstrated the influence of knee and hip extensor muscles on the performance in sprints and other explosive movements, this study aimed to establish the relationship between plantar flexor muscle strength and high-intensity actions. Back squat (BS) and calf raise (CR) one-repetition maxima as well as linear sprint (5-, 10-, 30 m) and drop jump performance from different heights (15, 30, 45 and 60 cm) were measured in 45 elite youth players (age: 16.62 ± 1.1 years). Results showed significant negative correlations between BS strength and sprint times (r = -0.60 to -0.61), confirming the importance of lower limb extensor muscle strength in short-distance sprints. While no significant correlations were found with sprint performances, CR strength was significantly associated with drop jump test results from 45 and 60 cm drop height (r = 0.36 to 0.46). These findings demonstrate that isolated CR strength positively influences the performance in actions involving rapid stretch-shortening cycles, which suggests that current strength and conditioning programs for youth soccer players should be extended to also include exercises specifically targeting the plantar flexor muscles. While this cross-sectional study provides novel insights into the complex interplay between muscle strength and soccer-specific performance, its findings need to be corroborated in longitudinal studies directly testing the impact of plantar flexor strength training.

Effects of plyometric training techniques on vertical jump performance of basketball players.

The aim of our study was to compare the effects of two different plyometric training programs (targeting knee extensors or plantar flexors) on jump height and strength of leg muscles. Twenty-nine male basketball players were assigned to the knee-flexed (KF), knee-extended (KE), or control groups. In addition to regular training, the KF group performed plyometric jumps (10 sets of 10 jumps, 3 sessions/week, 4weeks) from 50cm boxes with the knee flexed (90°-120°), whereas the KE group performed the jumps from 30cm boxes with the knee much more extended (130°-170°). Jumping ability was evaluated with squat jumps (SJs), countermovement jumps (CMJs), and drop jumps from 20cm (DJ20) and 40cm (DJ40). Knee and ankle muscles were assessed during maximal isokinetic and isometric tests, and EMG activity was recorded from vastus lateralis and medial gastrocnemius. The KF group increased SJ (+10%, d=0.86) and CMJ (+11%, d=0.70) but decreased DJ40 height (-7%, d=-0.40). Conversely, the KE group increased DJ20 (+10%, d=0.74) and DJ40 (+12%, d=0.77) but decreased SJ height (-4%, d=-0.23). The reactivity index during DJs increased (+10% for DJ20, d=0.47; +20% for DJ40, d=0.91) for the KE group but decreased (-10%, d=-0.48) for the KF group during DJ40. Plantar flexor strength increased for the KE group (d=0.72-1.00) but not for the KF group. Negative transfer across jumps is consistent with the principle of training specificity. Basketball players interested to perform fast rebounds in their training should avoid plyometric jumps with large knee flexions and long contact times.

Muscle strength and foot pressure vary depending on the type of foot pain

This study compared muscle strength and foot pressure among patients with metatarsalgia, patients with plantar fasciitis, and healthy controls. A total of 31 patients with foot pain (14 metatarsalgia and 17 plantar fasciitis) and 29 healthy controls participated in the study. The strengths of the plantar flexor and hip muscles were measured using isokinetic and handheld dynamometers, respectively. Foot pressure parameters, including the pressure–time integral (PTI) and foot arch index (AI), were assessed using pedobarography. Compared with the healthy control group, plantar flexor strength was significantly reduced in the affected feet of the metatarsalgia and plantar fasciitis groups (F = 0.083, all p < 0.001); however, hip strength was significantly decreased only in the affected feet of the metatarsalgia group (F = 20.900, p < 0.001). Plantar flexor (p < 0.001) and hip (p = 0.004) strength were significantly lower in the metatarsalgia group than in the plantar fasciitis group. The PTI was lower in the forefeet of the affected feet in the metatarsalgia (p < 0.001) and plantar fasciitis (p = 0.004) groups. Foot AI (p < 0.001) was significantly reduced only in the metatarsalgia group. These results suggest the need to consider the evaluation of muscle strength and foot pressure in both feet for the diagnosis and treatment of foot pain.

Cross-Education Effects of Isokinetic Eccentric Plantarflexor Training on Flexibility, Strength, and Muscle-Tendon Mechanics.

Large increases in joint range of motion (ROM) have been reported after eccentric resistance training; however, limited data exist describing the associated mechanisms or potential cross-education effects in the contralateral limb. Therefore, the effects of a 6-wk isokinetic eccentric plantarflexor training program were examined in 26 participants. Before and after the training program, dorsiflexion ROM, plantarflexor strength, and muscle-tendon unit (MTU) morphology and mechanics were measured in control ( n = 13) and experimental ( n = 13) young adult groups. Training consisted of 5 sets of 12 maximal isokinetic eccentric plantarflexor contractions twice weekly on the right limb. Significant ( P < 0.05) increases in dorsiflexion ROM (4.0-9.5°), stretch tolerance (40.3-95.9%), passive elastic energy storage (47.5-161.3%), and isometric (38.1-40.6%) and eccentric (46.7-67.0%) peak plantarflexor torques were detected in both trained and contralateral limbs in the experimental group. Significant increases in gastrocnemius medialis and soleus thickness (5.4-6.1%), gastrocnemius medialis fascicle length (7.6 ± 8.5%), passive plantarflexor MTU stiffness (30.1 ± 35.5%), and Achilles tendon stiffness (5.3 ± 4.9%) were observed in the trained limb only. Significant correlations were detected between the changes in trained and contralateral limbs for dorsiflexion ROM ( r = 0.59) and both isometric ( r = 0.79) and eccentric ( r = 0.73) peak torques. No significant changes in any metric were detected in the control group. Large ROM increases in the trained limb were associated with neurological, mechanical, and structural adaptations, with evidence of a cross-education effect in the contralateral limb being primarily driven by neurological adaptation (stretch tolerance). The large improvements in ROM, muscle size, and strength confirm that isokinetic eccentric training is a highly effective training tool, with potential for use in athletic and clinical populations where MTU function is impaired and current therapies are ineffective.

Self-Massage Acute Effects on Pressure Pain Threshold, Muscular Electrical Activity, and Muscle Force Production: A Systematic Review and Meta-Analysis.

Furlan, MR, Machado, E, Petter, GdN, Barbosa, IM, Geremia, JM, and Glänzel, MH. Self-massage acute effects on pressure pain threshold, muscular electrical activity, and muscle force production: a systematic review and meta-analysis. J Strength Cond Res 38(3): 620-635, 2024-Self-massage (SM) is often used in physiotherapy and sports training programs. However, the SM acute effects on pressure pain threshold (PPT), muscle electrical activity (MEA), and muscle force production remain unclear. A meta-analytical review was performed to verify the SM acute effects on neuromuscular responses in healthy adults or athletes. The review (CRD42021254656) was performed in the PubMed, Web of Science, and Embase databases. A synthesis of the included studies was performed, and both the risk of bias and the evidence certainty level were assessed through the PEDro scale and Grading of Recommendations Assessment, Development, and Evaluation approach, respectively. Nineteen studies were included, 5 evaluated the PPT, 7 the thigh muscles' MEA, and 15 the lower-limb strength. The SM application induces moderate increases in quadriceps' PPT (5 studies; standardized mean difference [SMD]: 0.487; 95% CI 0.251-0.723; p < 0.001; I2 = 0%). We found no SM effects on the hamstrings and plantar flexors' MEA. Also, we observed small increases in knee extensors' concentric torque (2 studies; SMD: 0.288; 95% CI 0.088-0.489; p = 0.005; I2 = 0%), without effects in isometric muscle strength, eccentric torque, and rate of force development. Grading of recommendations assessment, development, and evaluation analysis showed high and low certainty levels for the SM effects on quadriceps' PPT and muscle strength, respectively. Self-massage pressure-volume application seems to be a determining factor in inducing changes in these parameters, and it may vary among the treated muscles, where a higher pressure-volume application is required for increasing knee flexors and plantar flexors' PPT and strength. Thus, new studies with better methodological quality should be performed to strengthen this evidence.

Exploring the interplay between ankle muscle strength, postural control, and pain intensity in chronic ankle instability: A comprehensive analysis

BackgroundChronic Ankle Instability (CAI) is a common musculoskeletal condition characterized by recurring ankle sprains and impaired postural control (PC). Understanding the relationship between ankle muscle strength, PC, and the role of pain is essential for effective management. ObjectivesThis prospective cross sectional study aimed to 1. Compare ankle isometric muscle strength (IMS) and PC between CAI and asymptomatic sides. 2. Assess the correlations between ankle IMS and PC and explore the potential mediating effect of pain in individuals with CAI. MethodsA total of 44 individuals with CAI, were enrolled in the study. Ankle IMS (dorsiflexors, plantar flexors, invertors, and evertors) was measured using a dynamometer, while PC was evaluated using sway parameters (anterior-posterior and medial-lateral sway, ellipse area). Pain levels were reported using a Visual Analog Scale. ResultsThe CAI ankles exhibited significantly lower ankle IMS in all muscle groups compared to the asymptomatic ankles (p < 0.001). Additionally, the CAI side showed increased postural sway and a larger ellipse area (p < 0.001), indicating reduced PC. Negative correlations were observed between ankle IMS and PC parameters on the CAI side, with dorsiflexor strength showing correlations ranging from −0.423 to −0.387, plantar flexor strength ranging from −0.423 to −0.371, invertor strength ranging from −0.412 to −0.238, and evertor strength ranging from −0.451 to −0.365 (p < 0.001). Mediation analysis revealed that pain played a significant mediating role in connecting ankle IMS and PC parameters among individuals with CAI, with statistical significance (p < 0.05). ConclusionsIndividuals with CAI exhibit weaker ankle IMS and diminished PC in comparison to their healthy side. Moreover, pain was identified as a mediator in the relationship between ankle IMS and PC in CAI. These findings underscore the importance of addressing both ankle IMS and pain in the rehabilitation and management of CAI.

Effectiveness of functional or biomechanical bandages with athletic taping and kinesiotaping in subjects with chronic ankle instability: a systematic review and meta-analysis.

The aim of the study was to analyze the effects of functional or biomechanical bandages, whether elastic or inelastic, in Chronic Ankle Instability (CAI). This review used PubMed, WoS, SCOPUS, and CINAHL following PRISMA and registering in Prospero. Main PICOS: (1) CAI; (2) intervention, functional/biomechanical bandages; (3) comparison, taping effect versus placebo/no taping, or another functional taping; (4) outcomes, improvement of CAI functionality (dynamic/static balance, ankle kinematic, perception, agility and motor control, endurance and strength; (5) experimental and preexperimental studies. The meta-analyses considered mean and s.d. of the results per variable; effect size (ES) of each study and for each type of intervention. Homogeneity (Q), heterogeneity (H 2 and I 2), and 95% CI were calculated. In total, 28 studies were selected. Significant differences were found for dynamic balance (66.66%) and static balance (87.5%), ankle kinematics (75.00%), perceptions (88.88%), plantar flexor strength (100%), muscle activity (66.6%), endurance (100%), functional performance (100%), and gait (66.6%). The main results of meta-analyses (eight studies) are as follows - h/M ratio soleus, ES: 0.080, 95% CI: -5.219-5.379; h/M ratio peroneus, ES: 0.070, 95% CI: -6.151-6.291; posteromedial KT, ES: 0.042 95% CI: -0.514-0.598; posteromedial-overall, ES: -0.006 95% CI: -1.071-0.819; mSEBT-KT, ES: 0.057 95% CI: -0.281-0.395; mSEBT-overall, ES: -0.035 95% CI: -0.190-0.590. All biomechanical or functional bandages, whether elastic or inelastic, applied in CAI were favorable, highlighting patient perception, dynamic and static balance, kinematics and agility and motor control, for its effectiveness and evidence. Thus, bandages increase ankle functionality. The meta-analyses found no statistical significance. Clinically, soleus muscle activity, h-reflex/M-responses using fibular reposition with rigid tape, and dynamic balance with combined kinesiotaping during the modified star excursion balance test and with the posteromedial direction found improvements. Level of evidence according to Scottish Intercollegiate Guidelines Network: 1+. Level of evidence according to the Oxford Centre for Evidence-Based Medicine 2011: 1.

A Portable, Neurostimulation-Integrated, Force Measurement Platform for the Clinical Assessment of Plantarflexor Central Drive.

Plantarflexor central drive is a promising biomarker of neuromotor impairment; however, routine clinical assessment is hindered by the unavailability of force measurement systems with integrated neurostimulation capabilities. In this study, we evaluate the accuracy of a portable, neurostimulation-integrated, plantarflexor force measurement system we developed to facilitate the assessment of plantarflexor neuromotor function in clinical settings. Two experiments were conducted with the Central Drive System (CEDRS). To evaluate accuracy, experiment #1 included 16 neurotypical adults and used intra-class correlation (ICC2,1) to test agreement of plantarflexor strength capacity measured with CEDRS versus a stationary dynamometer. To evaluate validity, experiment #2 added 26 individuals with post-stroke hemiparesis and used one-way ANOVAs to test for between-limb differences in CEDRS' measurements of plantarflexor neuromotor function, comparing neurotypical, non-paretic, and paretic limb measurements. The association between paretic plantarflexor neuromotor function and walking function outcomes derived from the six-minute walk test (6MWT) were also evaluated. CEDRS' measurements of plantarflexor neuromotor function showed high agreement with measurements made by the stationary dynamometer (ICC = 0.83, p < 0.001). CEDRS' measurements also showed the expected between-limb differences (p's < 0.001) in maximum voluntary strength (Neurotypical: 76.21 ± 13.84 ft-lbs., Non-paretic: 56.93 ± 17.75 ft-lbs., and Paretic: 31.51 ± 14.08 ft-lbs.), strength capacity (Neurotypical: 76.47 ± 13.59 ft-lbs., Non-paretic: 64.08 ± 14.50 ft-lbs., and Paretic: 44.55 ± 14.23 ft-lbs.), and central drive (Neurotypical: 88.73 ± 1.71%, Non-paretic: 73.66% ± 17.74%, and Paretic: 52.04% ± 20.22%). CEDRS-measured plantarflexor central drive was moderately correlated with 6MWT total distance (r = 0.69, p < 0.001) and distance-induced changes in speed (r = 0.61, p = 0.002). CEDRS is a clinician-operated, portable, neurostimulation-integrated force measurement platform that produces accurate measurements of plantarflexor neuromotor function that are associated with post-stroke walking ability.

Multifactorial assessment of braking time predictors in a driving simulator among older adults according to gender

Vehicle driving depends on the integration of motor, visual, and cognitive skills to respond appropriately to different situations that occur in traffic. To analyze a model of performance predictor for braking time in the driving simulator, using a battery of tests divided by gender. Selected were 100 male drivers with a mean age of 72.6 ± 5.7 years. Sociodemographic variables, braking time in the driving simulator, and motor, visual, and cognitive skills were evaluated. Comparing genders, men were older than women (p = 0.002) and had longer driving times (p = 0.001). Men had more strength in hand grip (p ≤ 0.001). In the linear regression analysis, the model explained 68 % of the braking time in men and 50.8 % in women. In the stepwise multiple linear regression analysis, the variable that remained in the model was the strength of the right plantar flexors, which explained 13 % of the braking time in women and men, and the cognitive variables explained 38.9 %. Sociodemographic, motor, visual, and cognitive variables, explained a substantial portion of the variability in braking time for both older women and men, the specific variables driving this performance differed between the sexes. For older women, factors such as muscle strength emerged as critical determinants of braking ability, highlighting the importance of physical health in maintaining driving skills. On the other hand, cognitive conditions emerged as the primary predictor of braking performance in older men, underscoring the role of mental acuity and decision-making processes in safe driving.

A longer Achilles tendon moment arm length is not associated with superior hopping performance.

Variability in musculoskeletal and lower leg structure has the potential to influence hopping height. Achilles tendon moment arm length and plantarflexor muscle strength can influence ankle joint torque development and, consequently, hopping performance. While most studies have examined the connection of the Achilles tendon moment arm with hopping performance including the resting length, in this study we attempted to explore how the changes in Achilles tendon moment arm are related to hopping performance. Therefore, the purpose of this study was to test for correlations between foot and lower leg muscle structure parameters (i.e., muscle mass, volume, cross-sectional area and Achilles tendon moment arm length) and hopping height performance in relation to changes in Achilles tendon moment arm length. Eighteen participants (10 males 8 female) performed repetitive bilateral hopping on a force platform while sagittal plane kinematics of the lower leg were recorded. Additionally, maximal isometric plantarflexion was measured. To obtain structural parameters of the lower leg, the right lower leg of each participant was scanned with magnetic resonance imaging. The cross-sectional areas of the Achilles tendon, soleus, lateral and medial gastrocnemius were measured, while muscle volumes, muscle mass, and Achilles tendon moment arm length were calculated. Contrary to our initial assumption, longer Achilles tendon moment arm did not result in superior hopping performance. Interestingly, neither maximal isometric plantarflexion force nor muscle size correlated with repetitive bilateral hopping performance. We can assume that the mechanical characteristics of the tendon and the effective utilization of the stored strain energy in the tendon may play a more important role in repetitive hopping than the structural parameters of the lower leg.

Effect of Whole-body Vibration frequency on muscle tensile state during graded plantar flexor isometric contractions

BackgroundAcute physiological and biomechanical alterations have been reported following whole-body vibration (WBV). Stiffening of muscles has only been anecdotally reported in response to WBV. Accordingly, this study investigated active plantar flexor muscle stiffness in response to a single WBV bout at four mechanical vibration frequencies. MethodsThirteen healthy adults (37.1 ± 14.4 years old) randomly received WBV in 4 different frequencies (6, 12, 24, and 0 Hz control) for 5 min. Shear wave speed (SWS) in longitudinal and transverse projections, architecture, and electric muscle activity were recorded in the medial gastrocnemius (MG) and soleus (SOL) muscle during graded plantar flexor contraction. Subjective rating of perceived muscle stiffness was assessed via Likert-scale. ResultsSWS of the MG at rest was enhanced in response to 5 min of 24 Hz WBV (p = 0.025), while a small reduction in SOL SWS was found during contraction (p = 0.005) in the longitudinal view. Subjective stiffness rating was increased following 12 Hz intervention. After 24 Hz WBV, pennation angle for MG was decreased (p = 0.011) during contraction. As a secondary finding, plantar flexor strength was significantly increased with each visit, which, however, did not affect the study's main outcome because of balanced sequence allocation. ConclusionSWS effects were solely limited to 24 Hz mechanical vibration and in the longitudinal projection. The observed effects are compatible with an interpretation by post-activation potentiation, warm-up, and force-distribution within the triceps surae muscles following 5 min WBV. The outcome may suggest SWS as a useful tool for assessing acute changes in muscle stiffness.

Foot and Ankle Muscle Isometric Strength in Nonrearfoot Compared With Rearfoot Endurance Runners.

Transitioning to a forefoot strike pattern can be used to manage running-related knee injuries. However, adopting a nonrearfoot strike induces a higher load on foot and ankle structures than rearfoot strike. Sufficient foot muscle strength is also necessary to prevent excessive longitudinal arch (LA) deformation when running with nonrearfoot strike. The aim of this study was to investigate the potential differences in foot-ankle muscle strength between RF and NRF runners. A cross-sectional study including 40 RF and 40 NRF runners was conducted. The foot posture and the maximal voluntary isometric strength (MVIS) of 6 foot-ankle muscles were measured. The footstrike pattern was determined using a 2-D camera during a self-paced run on a treadmill. NRF had higher MVIS for ankle plantar flexor (+12.5%, P = .015), ankle dorsiflexor (+17.7%, P = .01), hallux flexor (+11%, P = .04), and lesser toe flexor (+20.8%, P = .0031). We found a small positive correlation between MVIS of ankle plantar flexor with MVIS of hallux flexor (r = 0.26; P = .01) and lesser toe flexor (r = 0.28; P = .01). In this cross-sectional study, we found that NRF runners on average have a higher MVIS of hallux and lesser toe flexor compared with RF runners. NRF runners also have a higher MVIS of ankle plantar flexor and dorsiflexor than RF runners. We found only a small correlation between ankle plantar flexor and foot muscle strength. Level III, case-control study.