Maximal Knee Extensor Strength Research Articles

30-sit-to-stand power is a better tool than isometric knee extensor strength to detect motor impairment in people with haemophilic arthropathy.

Regular assessment of motor impairments is crucial in people with haemophilic arthropathy (PwHA). This study aimed to determine if there are differences in 30-secondssit-to-stand (30-STS) power and maximal voluntary isometric contraction (MVIC) of the knee extensors between PwHA and healthy control group (CG). The secondary aims were to investigate the correlation between 30-STS power and MVIC of knee extensors with clinical characteristics and to assess their effectiveness in identifying motor impairment in PwHA. A cross-sectional study was conducted by collecting data from PwHA (n=17) and a sedentary CG (n=15). MVIC (torque) and 30-STS power were normalised to body mass. Correlation analysis and simple linear regression adjusted for age were used to assess the association between tests and clinical variables. Using z-scores derived from the mean and standard deviation of the CG, we compared the MVIC and the 30-STS power in PwHA. PwHA showed lower MVIC and 30-STS power compared to CG (p<.001; large effect size d>.8). Lower 30-STS power was associated with greater joint impairment and greater fear of movement, whereas MVIC showed no association with clinical variables. 30-STS power showed a lower z-score compared to MVIC (p<.001). In addition, 30-STS power detected 47% of PwHA with motor impairment compared to 0% for MVIC (p=.002). Our results suggest that 30-STS power may be more effective than knee extensors MVIC in detecting motor impairment in PwHA. Consequently, lower limb skeletal muscle power, rather than maximum knee extensor strength, appears to be more affected in PwHA.

RELATIONSHIP BETWEEN QUADRICEPS ECHOGENICITY AND KNEE EXTENSOR STRENGTH IN OLDER ADULTS: A SYSTEMATIC REVIEW

Abstract The clinical availability of assessing muscle quality through diagnostic ultrasound provides a viable screening tool for geriatric syndromes that impair mobility. However, relationships between muscle echogenicity and clinical assessments require further inquiry. The authors aimed to systematically identify and synthesize the literature regarding the relationship between quadriceps echogenicity and maximal knee extensor strength in older adults. A total of 12 extracted articles (N=701, 73.6±5.4 years) independently assessed the relationship between quadriceps echogenicity and peak knee extensor torque. Correlations were weak to moderately negative between knee extensor strength and rectus femoris echogenicity in older adults (mean ±standard deviation; r=-0.398±0.159 [range=-0.681 to -0.080]). While the limited number studies did not warrant advanced analyses, but it appears that the echogenicity of the vastus medialis (study n=3, r=-0.426±1.97 [range=-0.640 to -0.253]) and vastus lateralis (n=3, r=-0.411±0.095 [range=-0.511 to -0.322]) may be superior to the vastus intermedius (n=4, r=-0.341±0.166 [range=-0.484 to -0.120]) and rectus femoris (n=7, r=0.290±0.140 [range=-0.460 to -0.080]) for predicting knee extension strength in older adults. Furthermore, averaging across multiple quadriceps muscles generally improved correlations (n=4, r=-0.544±0.154 [range=-0.681 to -0.334]). Overall, correlations with knee extensor strength were stronger when echogenicity was corrected for subcutaneous fat thickness (n=3, r=-0.491±0.04 [range=-0.521 to -0.453]). However, results regarding fat correction were inconsistent within studies (n=2, uncorrected r=-0.120 and -0.527 versus corrected r=-0.500 and -0.453, respectively). Future studies should aim to report correlations for all quadriceps muscles and for both corrected and uncorrected echogenicity values to allow for more thorough analytical approaches.

Development and validation of a portable articulated dynamometry system to assess knee extensor muscle strength

Muscle strength assessment is important in predicting clinical and functional outcomes in many disorders. Manual muscle testing, although commonly used, offers suboptimal accuracy and reliability. Isokinetic dynamometers (IKDs) have excellent accuracy and reliability; but are bulky and expensive, offering limited accessibility. This study aimed to design a portable dynamometer that is accessible, accurate and reliable, and to validate the device in a general population. The portable articulated dynamometry system (PADS) is a portable device with an embedded high-precision load cell, designed to measure muscle strength with optimal accuracy. Seventy-two participants underwent maximal isometric and isokinetic knee extensor torque measurement with the PADS and IKD, respectively. The PADS results were cross-validated against IKD results using change in mean (CIM). Interrater and intra-rater reliabilities were assessed using intraclass correlation coefficients, standard error of measurement, and minimal detectable change. The PADS maximal knee extensor strength results were not significantly different from those by IKD (CIM: − 2.13 Nm; 95% CI − 4.74, 0.49 Nm). The PADS showed interrater reliability (Pearson’s r: 0.958; ICC: 0.979; SEM: 5.51%) and excellent intra-rater reliability (Pearson’s r: 0.912; ICC: 0.954; SEM: 8.38%). The proposed PADS may be an effective alternative to IKD, offering good accuracy, reliability, and potentially better accessibility.

Decrements of mobility and power in recreationally active septuagenarians is related to loss of force, but not slowing of the muscle: a 5-year longitudinal study

A lesser 6-min walk distance (6MWD) and timed up-and-go (TUG) in old compared with young adults was previously linked to slowing of muscle contractile properties. The purpose of the present study was to determine whether any further reductions in 6MWD and TUG over a 5-year period in septuagenarians are associated with further slowing of muscle contractile properties. We measured muscle function by a countermovement jump, isometric maximal knee extensor strength (MVC) on a dynamometer and quadriceps muscle size by magnetic resonance imaging (MRI) in 17 older women (71.1 ± 2.8 y) and 17 older men (71.3 ± 4.1y). Performance in TUG and 6MWD were reduced over the 5-year period, irrespective of sex (P < 0.001), and both were correlated with power at both baseline and follow-up (R ≥ 0.53; P ≤ 0.001). Jump take-off velocity (VCMJ) was slower at follow-up (P < 0.01) and correlated with 6MWD and TUG at both baseline and follow-up in both sexes (R ≥ 0.54; P ≤ 0.001). However, the relationship between ‘body mass: maximal muscle force ratio’ with VCMJ was not significantly changed, indicating that the lower VCMJ was attributable to muscles working at a higher relative load, hence a lower part of the force–velocity relationship, due to a reduction in MVC (body mass had not changed significantly), rather than slowing of the muscle. The lower VCMJ in women than men (P < 0.001) was likewise attributable to a lower MVC rather than slower contractile properties in women. In conclusion, the decrement in 6MWD and TUG in septuagenarians is due to a loss of muscle mass, rather than further loss of muscle quality.

How limb dominance influences limb symmetry in ACL patients: effects on functional performance

BackgroundTiming for return to sport (RTS) after anterior cruciate ligament (ACL) injury is paramount for the avoidance of a secondary injury. A common criterion in RTS decision-making is the limb symmetry index (LSI) which quantifies (a)symmetries between the affected and unaffected limb. Limb dominance is one of many factors that may contribute to the recovery of the LSI after ACL reconstruction. The purpose of this study was to examine how limb dominance affects the LSI of functional performance tasks nine months following ACL reconstruction (time of RTS).MethodsAt time of return to sport, n = 100 patients (n = 48 injured the dominant limb, n = 52 injured the non-dominant limb, n = 34 female, n = 66 male) with ACL reconstruction surgery performed isokinetic strength measurements of the knee extensors and flexors, and drop jumps (DJ), single leg hop for distance (SHD) and 6 m timed hop (6MTH) testings.ResultsThe findings indicated that injury of the dominant leg led to significantly higher LSI values in maximal isokinetic knee extensor strength (p = 0.030). No significant differences were observed for maximal isokinetic knee flexor strength, DJ, SHD or 6MTH performance. Stratifying for sex revealed no significant differences. Simple regression analyses demonstrated that LSI in maximal knee extensor strength significantly predicted LSIs in DJ and SHD while explaining 14% and 18% of the respective variance.ConclusionsGiven that limb dominance affects the LSI of muscle strength suggests that a differentiated interpretation of the LSI with respect to limb dominance should be considered for a safe return to sport. Monoarticular knee extensor strength and multiarticular hop test performance are interrelated and thus can show asymmetries which are not maladaptive but established during years of habituation or training.

Abstract 13472: Physical Incapacity in Heart Failure Patients is Associated With Skeletal Muscle Mitochondrial Dysfunction

Introduction: The role of skeletal muscle mitochondrial dysfunction in exercise intolerance in heart failure patients is unknown. Therefore, this study aimed to identify the relationship between physical capacity and skeletal muscle mitochondrial function in patients with heart failure and reduced ejection fraction (HFrEF). Methods A total of 53 HFrEF patients and 20 age- and sex-matched controls underwent dual-energy X-ray absorptiometry to assess muscle mass by the appendicular lean mass index (ALMI), cardiopulmonary exercise testing (peakVO2), 6-minute walking test (6MWD) and maximal isometric knee-extensor strength test. In skeletal muscle biopsies from vastus lateralis, mitochondrial respiratory capacity was measured by high resolution respirometry. We performed Pearson correlations to examine the relationships between physical capacity tests and mitochondrial function. Results Mean age of the study cohort was 71.7 ±7.0 years. Compared with healthy controls, HFrEF patients had a lower peakVO2 (14.6 ±4.1 vs. 26.2 ±8.0 mL/kg/min, p &lt;0.001) and a shorter 6MWD (429 ±106 vs. 581 ±93 m, p &lt;0.001). HFrEF patients had a lower ALMI (0.74 ±0.15 vs. 0.86 ±0.16 kg/(kg/m 2 ), p = 0.005). Maximal coupled mitochondrial respiration was decreased in HFrEF patients compared with healthy controls (59.1 ±19.0 vs. 92.6 ±38.8 ρmol O 2 *s -1 mg -1 , p &lt;0.001) as well as the respiratory control ratio (7.2 ±2.5 vs. 9.7 ±3.1). Maximal coupled mitochondrial respiration was correlated to peakVO2 (r = 0.58, p &lt;0.001) and 6MWD (r = 0.44, p &lt;0.001), but not to muscle mass or maximal knee-extensor strength. Conclusions HFrEF patients had a lower peakVO2, shorter 6MWD and impaired skeletal muscle mitochondrial function as compared with controls. Maximal coupled mitochondrial respiration was correlated with physical capacity across the population of HFrEF patients and healthy controls establishing an association between skeletal muscle mitochondrial dysfunction and physical incapacity.

The relationship between muscle capacity utilization during gait and pain in people with symptomatic knee osteoarthritis

BackgroundMuscle capacity utilization reflects the percentage of maximal knee extensor strength required to complete physical activities. Research questionIs pain associated with muscle capacity utilization during walking in older adults with knee osteoarthritis? Secondarily, is muscle capacity utilization in older adults with knee osteoarthritis sex-specific? MethodsTwenty-three participants (15 females) with symptomatic knee OA completed this study [age 67 ( ± 8) years, body mass index 29.7 ( ± 3.9) kg/m2, gait speed during the Six Minute Walk test 1.25 ( ± 0.25) m/s]. Pain was measured using the Knee injury and Osteoarthritis Outcome Score. Muscle capacity utilization was quantified as the peak external knee flexor moment during level walking normalized to knee extensor maximum voluntary isometric contraction. The knee flexor moment was calculated from kinematic and kinetic data during barefoot level walking at a self-selected speed and at 1.1 m/s. Knee extensor maximum voluntary isometric contraction was measured on a dynamometer. Multiple linear regressions were used to determine the relationship between pain and muscle capacity utilization after adjusting for age, sex, body mass index, and gait speed. Independent sample t-tests examined sex differences. ResultsPain was not associated with muscle capacity utilization during self-selected and standardized walking speeds (p = 0.38 and p = 0.36, respectively). Females did not require a greater muscle capacity utilization than males to complete gait at self-selected and standardized speeds (p = 0.28, and p = 0.40, respectively). SignificanceMuscle capacity utilization was not associated with pain during walking in people with knee osteoarthritis. Future work should explore more challenging activities of daily living in knee OA.

Habitual side-specific loading leads to structural, mechanical, and compositional changes in the patellar tendon of young and senior lifelong male athletes.

Effects of lifelong physical activity on tendon function have been investigated in cross-sectional studies, but these are at risk of "survivorship" bias. Here, we investigate whether lifelong side-specific loading is associated with greater cross-sectional area (CSA), mechanical properties, cell density (DNA content), and collagen cross-link composition of the male human patellar tendon (PT), in vivo. Nine seniors and six young male lifelong elite badminton players and fencers were included. CSA of the PT obtained by 3-tesla MRI and ultrasonography-based bilateral PT mechanics were assessed. Collagen fibril characteristics, enzymatic cross links, nonenzymatic glycation (autofluorescence), collagen, and DNA content were measured biochemically in PT biopsies. The elite athletes had a ≥15% side-to-side difference in maximal knee extensor strength, reflecting chronic unilateral sport-specific loading patterns. The PT CSA was greater on the lead extremity compared with the nonlead extremity (17%, P = 0.0001). Furthermore, greater tendon stiffness (18%, P = 0.0404) together with lower tendon stress (22%, P = 0.0005) and tendon strain (18%, P = 0.0433) were observed on the lead extremity. No effects were demonstrated from side-to-side for glycation, enzymatic cross link, collagen, and DNA content (50%, P = 0.1160). Moreover, tendon fibril density was 87 ± 28 fibrils/μm2 on the lead extremity and 68 ± 26 fibrils/μm2 on the nonlead extremity (28%, P = 0.0544). Tendon fibril diameter was 86 ± 14 nm on the lead extremity and 94 ± 14 nm on the nonlead extremity (-9%, P = 0.1076). These novel data suggest that lifelong side-specific loading in males yields greater patellar tendon size and stiffness possibly with concomitant greater fibril density but without changes of collagen cross-link composition.NEW & NOTEWORTHY The present data demonstrate that lifelong side-specific loading yields greater patellar tendon structure on the lead extremity without affecting glycation that is associated with aging. These novel data suggest that lifelong side-specific habitual loading induce structural alterations that may serve to improve the mechanical properties of the tendon.

Novel approaches to reduce the risk of falling in community dwellings: effects of two multimodal programs in lower-body strength—a pilot study

Abstract Background Muscle weakness is a key risk factor for falls and strength exercises should be included in fall prevention programs. A psychomotor intervention promoting motor stimulation and the whole-body vibration (WBV) providing muscle contractions may reduce the incidence of falls. Our hypothesis relies on the greater benefits of a combined program. This study aimed to evaluate the effectiveness and the feasibility of two 12-week multimodal programs in lower-body strength in community dwellings fallers or with balance impairment. Methods Thirty-seven participants (34 women; mean age 74.3 ± 5.2 years) were allocated into: experimental group 1 [EG1] (psychomotor intervention), or experimental group 2 [EG2] (combined program: psychomotor intervention plus WBV), 3x/week. Maximal strength of knee extensors and flexors was assessed by an isokinetic dynamometer at 60°/s. Wilcoxon and Mann-Whitney tests were performed. Results The overall adherence rate was high (86.3%), with a level intensity in the rating of perceived exertion of 12.1 ± 0.3 points, in EG1, and 12.5 ± 0.4 points, in EG2. Significant changes between the pre-post intervention were observed exclusively in EG2, in the variables ‘Peak torque extension’ (71.7 ± 28.6 Nm vs. 79.2 ± 23.5 Nm, P = 0.042) and ‘Agonist/Antagonist ratio’ (60.2 ± 13.0 vs. 53.5 ± 8.6, P = 0.013). The effect size (r) in both variables was medium. No significant changes between groups were detected. Conclusions This pilot results indicate that both programs were feasible and well-tolerated. The combined program demonstrates larger effectiveness, since the WBV may positively influence the lower-body strength, reducing the risk of falls. Trial Registration: ClinicalTrials.gov Identifier: NCT03446352. Funding: This pilot was granted by the ESACA Project (Grant ALT20-03-0145-FEDER-000007) and by FCT (SFRH/BD/147398/2019).

Knee Extensor Muscle Strength Is More Important Than Postural Balance for Stair-Climbing Ability in Elderly Patients with Severe Knee Osteoarthritis.

Knee osteoarthritis is a chronic joint disease which damages articular cartilage. In its severe stages, it results in impairments in balance and muscle strength loss, which affect daily life activities such as walking or climbing stairs. This study sought to investigate associated factors with stair-climbing ability in this population, with special interest in measuring the relevance of postural balance for this task. Forty-four patients scheduled to undergo unilateral total knee arthroplasty were assessed. Timed up and go test, stair ascent–descent test, three different isometric strength tests (knee flexion, knee extension and hip abduction), active knee extension and flexion range of movement and static postural balance assessment were evaluated. Spearman’s correlation coefficients and multiple linear regression analysis determined the strength of association between the different variables and stair-climbing time. No significant association between the stair-climbing time and static balance was found. Significant associations were found between stair-climbing time and timed up and go (r = 0.71; p < 0.0001) and maximal knee extensor strength (r = –0.52; p = 0.0003). One-year increase in age was associated with 0.15 s (95% CI 0.00 to 0.30) slower stair-climbing time. In conclusion, muscle strength is more important than postural balance for stair-climbing ability in this population.

Synergetic Effect of NO Precursor Supplementation and Exercise Training.

Nitric oxide (NO) precursor supplementation has been shown to increase NO bioavailability and can potentially improve vascular function and exercise performance. It remains unclear whether the combination of NO precursor supplementation and exercise training has synergic effects on exercise performance. This study aims to assess the effect of chronic nitrate and citrulline intake on exercise training adaptations in healthy young individuals. In this randomized, double-bind trial, 24 healthy young (12 females) subjects performed vascular function assessment (blood pressure, pulse wave velocity, postischemia vasodilation, and cerebrovascular reactivity) and both local (submaximal isometric unilateral knee extension) and whole-body (incremental cycling) exercise tests to exhaustion before and after a 2-month exercise training program and daily intake of a placebo or a nitrate-rich salad and citrulline (N + C, 520 mg nitrate and 6 g citrulline) drink. Prefrontal cortex and quadriceps oxygenation was monitored continuously during exercise by near-infrared spectroscopy. N + C supplementation had no effect on vascular function and muscle and cerebral oxygenation during both local and whole-body exercise. N + C supplementation induced a significantly larger increase in maximal knee extensor strength (+5.1 ± 3.5 vs +0.2 ± 5.5 kg, P = 0.008) as well as a trend toward a larger increase in knee extensor endurance (+35.2 ± 26.1 vs +24.0 ± 10.4 contractions, P = 0.092) than placebo, but no effect on exercise training-induced maximal aerobic performance improvement. These results suggest that chronic nitrate and citrulline supplementation enhances the effect of exercise training on quadriceps muscle function in healthy active young individuals, but this does not translate into improved maximal aerobic performances.

Effects of Vastus Lateralis Muscle Fascicle Length on Isokinetic Muscle Strength and Dynamic Balance in Youth Soccer Players

PURPOSE The purpose of this study was to determine the effect of vastus lateralis muscle fascicle length on isokinetic muscle strength and dynamic balance in youth soccer players. METHODS Fourteen youth soccer players were divided into long fascicle length group (LFG, n=7) and short fascicle length group (SFG, n=7) by fascicle length of vastus lateralis muscle using ultrasound imaging. And measurements of muscle thickness, fascicle pennation angle, and physiological cross-sectional area were taken at the same location. Additionally, maximal isokinetic strength of knee extensors was assessed at 60°/sec and 120°/sec and a Y-balance test was completed. RESULTS Fascicle length and ratio of fascicle length/lower limb length were significantly greater in LFG than that in SFG (p<.001). Fascicle pennation angle (p<.01) and physiological cross-sectional area (p<.05) were significantly greater in SFG than that in LFG. The isokinetic maximal strength of knee extensors at 120°/sec was significantly greater in SFG than that in LFG (p<.05). The composite score of Y-balance was significantly greater in SFG than that in LFG (p<.05). CONCLUSIONS Our results show differences in architectural characteristics of the vastus lateralis. Further, the maximal isokinetic strength of knee extensors at 120°/sec and the ability of dynamic balance were greater in short vastus lateralis fascicle length of youth soccer players. 색인어: 외측광근, 근속길이, 등속성 ê·¼ë ¥, ë™ì ê· í˜•, ìœ ì†Œë „ ì¶•êµ¬ì„ ìˆ˜ Keywords: Vastus lateralis, Fascicle length, Isokinetic strength, Dynamic balance, Youth soccer players

Reliability and validity of knee extensor strength measurements using a portable dynamometer anchoring system in a supine position

BackgroundMuscle strength measurements using hand-held dynamometry (HHD) can be affected by the inadequate strength of the tester and lack of stabilization of the participants and the device. A portable HHD anchoring system was designed that enabled the measurement of isometric knee extensor muscle strength in a supine position. This can be used with individuals who are unable to assume the sitting position required for the measurement of knee extensor strength in conventional isokinetic dynamometry (IKD). The aim of this study was to evaluate the reliability and validity of knee extensor strength measurements using this device.MethodsThe maximal knee extensor isometric strength of the dominant leg in healthy adults aged 20 to 40 years was tested. Three trials of three contractions were assessed by two raters using the portable dynamometer anchoring system whilst the participant was in the supine position. After the three measurement trials, peak knee extensor torque was evaluated using IKD. The intraclass correlation coefficient (ICC) and 95% limits of agreement (LOA) for intra- and inter-rater reliability were obtained.ResultsThirty-nine participants (19 male and 20 female, aged 30.08 ± 4.16 y), completed the three measurement trials. The ICC for intra-rater reliability was 0.98 for the maximum measurements of knee extensor strength (95% confidence interval [CI]: 0.96–0.98) and 0.98 (95% CI: 0.96–0.99) for inter-rater reliability. The mean difference (%) between the maximum knee extensor strength measurements of each trial was 1.02% (LOA range: − 11.13 to 13.16%) for intra-rater and − 1.44% (LOA range: − 13.98 to 11.08%) for inter-rater measurements. The Pearson correlation coefficient of the maximum voluntary peak torque measurements with the portable dynamometer anchoring system and IKD was 0.927.ConclusionsThe portable dynamometer anchoring system is a reliable and valid tool for measuring isometric knee extensor strength in a supine position. Future clinical feasibility studies are needed to determine if this equipment can be applied to people with severe illness or disabilities.Trial registrationKCT0003041.

Evaluation of 18-Week Whole-Body Vibration Training in Normobaric Hypoxia on Lower Extremity Muscle Strength in an Elderly Population.

Therapeutic benefits of hypoxic training have been suggested for clinical populations, such as elderly who could suffer loss of lower limb muscle strength and higher risk of falling. This study investigated the effects of 18 weeks of whole-body vibration (WBV) training in normobaric hypoxia on the strength parameters of an elderly population. Thirty-one healthy elderly participants were randomly assigned to a hypoxic whole-body vibration group (HWBV; n = 10), normoxic whole-body vibration group (NWBV; n = 11), or control group (n = 10). The experimental groups received the same vibration treatment in a hypoxia chamber (HWBV: 16.1% fraction of inspired oxygen [FiO2]; NWBV: 21.0% FiO2). Isokinetic leg muscle strength was evaluated using a Biodex System-3 isokinetic dynamometer. Body composition was obtained with dual-energy X-ray absorptiometry. There were no significant differences between groups in either strength or body composition parameters. The NWBV group showed statistically significant improvements in the maximal strength of knee extensors, with a small effect size (p = 0.004; d = 0.54). No significant differences were found in any variable of the HWBV group. The combination of WBV training and exposure to normobaric cyclic hypoxia carried out in the present study did not have an effect on strength parameters in healthy elderly subjects.

Is muscle strength in a painful limb affected by knee pain status of the contralateral limb? — Data from the Osteoarthritis Initiative

Contralateral knee pain has been suggested to be associated with muscle weakness in a pain-free knee, potentially through a mechanism of central nervous inhibition. Whether contralateral knee pain also affects muscle strength in a painful knee, however, is unknown. Here we study the extent to which isometric muscle strength differs between matched painful limbs of people with unilateral knee pain vs. matched painful limbs people with bilateral knee pain. To that end, 163 participants with unilateral knee pain were identified from the Osteoarthritis Initiative. Unilaterally painful (UP) limbs were defined as having numerical rating scale (NRS) ≥4/10, infrequent/frequent pain in the painful limb, while contralateral pain-free limbs were defined by NRS=0-1, no/infrequent pain and Western Ontario and McMaster Universities Arthritis Index (WOMAC) ≤1. The comparator group were matched bilaterally painful (BP) limbs. Maximum isometric muscle strength (N) was compared between 1:1 matched BP and UP limbs. Extensor strength was found to be lower in BP limbs than in UP limbs, (−2.9%; p=0.39) but this difference was not statistically significant. Extensor strength was significantly lower in the UP vs. contralateral pain-free limbs (−6.2%; p<0.001). No differences were observed between BP and contralateral painful limbs (0.6%; p=0.87). In conclusion, the current results identify a slight reduction of maximum knee extensor strength in a painful limb, when the contralateral knee is also painful. In contrast to pain-free limbs, this effect did not reach statistical significance, but the overall findings support the concept of central nervous inhibition of muscle strength by contralateral knee pain.

No association of leg strength asymmetry with walking ability, fatigability, and fatigue in multiple sclerosis.

This cross-sectional study aims to determine whether leg strength asymmetries are associated with walking ability, objective measures of fatigability, or subjective perceptions of fatigue. Maximal knee extensor strength was assessed in 19 patients with multiple sclerosis (PwMS), and a symmetry index was calculated. Walking ability was determined through the total distance covered during a 6-min walk test (6MWT) and fatigability by calculating the change in distance covered between minutes 6 and 1. Perceptions of fatigue were assessed using the Fatigue Severity Scale and by obtaining ratings of perceived exertion during the first and final minute of the 6MWT. PwMS covered less distance (P=0.01) and perceived greater exertion (P<0.01) during minute 6 compared with minute 1. Knee extensor strength was asymmetric (P<0.01). The magnitude of asymmetry did not correlate with walking ability, fatigability, or measures of fatigue. Knee extensor strength asymmetry may not play an important role in prolonged walking performance in PwMS.

Relationship between occlusal force and falls among community-dwelling elderly in Japan: a cross-sectional correlative study

BackgroundFalls may cause serious health conditions among older population. Fall-related physical factors are thought to be associated with occlusal conditions. However, few studies examined the relationship between occlusal force and falls. To identify the association between occlusal force and falls among community-dwelling elderly individuals in Japan, public health nurses conducted a cross-sectional descriptive study.MethodsWe performed extensive physical assessments of five items: maximum occlusal force, handgrip strength, maximal knee extensor strength, one-leg standing time with eyes open and body sway. We also conducted a questionnaire survey concerning the participants’ demographic characteristics, health status and fall experience during the past year. Mean scores and standard deviations were calculated for age and the total points of the index of activities of daily living. Associations were examined using Mann-Whitney tests and logistic regression.ResultsWe examined 159 community-dwelling people aged ≥65 years, who were independent and active, including 38 participants (24.5%) with experience of falls in the past year. Maximum occlusal force had significant correlation with handgrip strength, maximal knee extensor strength, and one-leg standing time and body sway (P < .05, respectively). We found weak associations between participants with and without a history of falls in terms of the five physical measurements. Logistic regression analysis showed that fall experience was significantly associated with maximum occlusal force (P = 0.004).ConclusionsThis is the first study, led by public health nursing researchers, to examine the associations between maximum occlusal force and falls among community-dwelling elderly in Japan. The results showed that maximum occlusal force was significantly related to the other four extensive physical assessments, and might also suggest that maximum occlusal force assessment by public health nurses could contribute to more sophisticated and precise prediction of fall risks among the community-dwelling elderly. The latest occlusal force measurement device is non-invasive and easy to use. Public health nurses can introduce it at periodical community health checkup assembly events, which might contribute to raising awareness among community-dwelling elderly individuals and public health nurses about fall prevention and prediction.

Increase in echo intensity and extracellular-to-intracellular water ratio is independently associated with muscle weakness in elderly women.

The changes in muscle composition and its heterogeneity during aging are associated with muscle weakness in elderly persons independent of decreases in muscle mass or muscle thickness (MT). Both the assessment of echo intensity (EI) with ultrasound imaging and the evaluation of the extracellular water/intracellular water (ECW/ICW) ratio with segmental bioelectrical impedance spectroscopy (BIS) are non-invasive and convenient methods and seem valuable for muscle quality determination. However, no previous study has evaluated both EI and the ECW/ICW ratio simultaneously to investigate their relationship to muscle strength. The purpose of the present study was to investigate whether both EI and the ECW/ICW ratio are independently associated with muscle strength in elderly women. A total of 179 elderly women with a mean age of 74.1±4.9years, living independently in the community, were enrolled. The MT and EI of the quadriceps femoris were measured using transverse ultrasound imaging. The ECW/ICW ratio in the upper thigh was calculated from segmental BIS. The maximum knee extensor strength and the presence of knee pain were also assessed. Knee extensor strength showed a significant positive correlation with MT, and significant negative correlations with EI, the ECW/ICW ratio, and age. Stepwise regression analysis revealed that knee extensor strength in elderly women was predicted by MT, EI, and the ECW/ICW ratio. This study suggests that the simultaneous application of EI and the ECW/ICW ratio is useful in assessing muscle strength, and accurately estimates the changes in muscle quality related to muscle weakness.

The relationship between the physical cost index and knee extensor strength in children with hemiplegic cerebral palsy.

[Purpose] Lower extremity strength is a contributing factor to energy efficiency of gait. However, this contribution has not previously been evaluated in children with hemiplegic cerebral palsy (CP). The aim of this study was to evaluate the association between energy consumption, measured by the physical cost index (PCI), and strength of lower extremity, measured by the maximum knee extensor strength (MKES), in children with hemiplegic CP. [Subjects and Methods] Subjects were 10 children (4 males and 6 females; age, 7–17 years) with hemiplegic CP, but no history of orthopedic intervention or botulinum toxin treatment over the 1 year prior to the assessment. The PCI was measured during a 6-min walk test, and MKES using hand-held dynamometry, with the highest of two measures used for analysis. [Results] A negative correlation was identified between the PCI and MKES (R-value, −0.81 (affected) and −0.83 (unaffected) lower limb). [Conclusion] Higher lower extremity strength was associated with lower fatigability during a 6-min walk test in children with hemiplegic CP, providing evidence for the inclusion of strengthening exercises for both the affected and unaffected extremities in the rehabilitation of these children.

Effects of age and sex on neuromuscular-mechanical determinants of muscle strength

The aim of this study was to concurrently assess the effect of age on neuromuscular and mechanical properties in 24 young (23.6±3.7years) and 20 older (66.5±3.8years) healthy males and females. Maximal strength of knee extensors (KE) and flexors (KF), contractile rate of torque development (RTD) and neural activation of agonist-antagonist muscles (surface EMG) were examined during maximal voluntary isometric contraction (MVIC). Tissue stiffness (i.e. musculo-articular stiffness (MAS) and muscle stiffness (MS)) was examined via the free-oscillation technique, whereas muscle architecture (MA) of the vastus lateralis and subcutaneous fat were measured by ultrasonography. Males exhibited a greater age-related decline for KE (47.4%) and KF (53.1%) MVIC, and RTD (60.4%) when compared to females (32.9, 42.6 and 34.0%, respectively). Neural activation of agonist muscles during KE MVIC falls markedly with ageing; however, no age and sex effects were observed in the antagonist co-activation. MAS and MS were lower in elderly compared with young participants and in females compared with males. Regarding MA, main effects for age (young 23.0±3.3 vs older 19.5±2.0mm) and sex (males 22.4±3.5 vs females 20.4±2.7mm) were detected in muscle thickness. For fascicle length, there was an effect of age (young 104.6±8.8 vs older 89.8±10.5mm), while for pennation angle, there was an effect of sex (males 13.3±2.4 vs females 11.5±1.7°). These findings suggest that both neuromuscular and mechanical declines are important contributors to the age-related loss of muscle strength/function but with some peculiar sex-related differences.