Characteristics of Acute Cartilage Response After Mechanical Loading in Patients with Early-Mild Knee Osteoarthritis.

This study determined whether the acute cartilage response, assessed by cartilage thickness and echo intensity, differs between patients with early-mild knee osteoarthritis (OA) and healthy controls. We recruited 56 women aged ≥ 50 years with Kellgren-Lawrence (KL) grade ≤ 2 (age, 70.6 ± 7.4 years; height, 153.7 ± 5.2 cm; weight, 51.9 ± 8.2 kg). Based on KL grades and knee symptoms, the participants were classified into control (KL ≤ 1, asymptomatic, n = 27) and early-mild knee OA groups (KL 1 and symptomatic, KL 2, n = 29). Medial femoral cartilage thickness and echo intensity were assessed using ultrasonographic B-mode images before and after treadmill walking (15 min, 3.3 km/h). To investigate the acute cartilage response, repeated-measures analysis of covariance (groups × time) with adjusted age, external knee moment impulse, steps during treadmill walking, and cartilage thickness at pre-walking was performed. A significant interaction was found at the tibiofemoral joint; after walking, the cartilage thickness was significantly decreased in the early-mild knee OA group compared to the control group (p = 0.002). At the patellofemoral joint, a significant main effect of time was observed, but no interaction was detected (p = 0.802). No changes in cartilage echo intensity at either the tibiofemoral or patellofemoral joints, and no interactions were noted (p = 0.295 and p = 0.063). As acute cartilage response after walking, the thickness of the medial tibiofemoral joint in the early-mild knee OA was significantly reduced than that in the control group. Thus, greater acute deformation after walking might be a feature found in patients with early-mild knee OA.

Understanding muscle coordination during gait based on muscle synergy and its association with symptoms in patients with knee osteoarthritis.

OBJECTIVE: We aimed to investigate the muscle coordination differences between a control group and patients with mild and severe knee osteoarthritis (KOA) using muscle synergy analysis and determine whether muscle coordination was associated with symptoms of KOA. METHOD: Fifty-three women with medial KOA and 19 control patients participated in the study. The gait analyses and muscle activity measurements of seven lower limb muscles were assessed using a motion capture system and electromyography. Gait speed and knee adduction moment impulse were calculated. The spatiotemporal components of muscle synergy were extracted using non-negative matrix factorization, and the dynamic motor control index during walking (walk-DMC) was computed. The number of muscle synergy and their spatiotemporal components were compared among the mild KOA, severe KOA, and control groups. Moreover, the association between KOA symptoms with walk-DMC and other gait parameters was evaluated using multi-linear regression analysis. RESULTS: The number of muscle synergies was lower in mild and severe KOA compared with those in the control group. In synergy 1, the weightings of biceps femoris and gluteus medius in severe KOA were higher than that in the control group. In synergy 3, the weightings of higher tibial anterior and lower gastrocnemius lateralis were confirmed in the mild KOA group. Regression analysis showed that the walk-DMC was independently associated with knee-related symptoms of KOA after adjusting for the covariates. CONCLUSIONS: Muscle coordination was altered in patients with KOA. The correlation between muscle coordination and KOA may be attributed to the knee-related symptoms. Key points • Patients with knee osteoarthritis (OA) experienced a deterioration in muscle coordination when walking. • Loss of muscle coordination was associated with severe knee-related symptoms in knee OA. • Considering muscle coordination as a knee OA symptom-related factor may provide improved treatment.

Effects of Low-Intensity Torque-Matched Isometric Training at Long and Short Muscle Lengths of the Hamstrings on Muscle Strength and Hypertrophy: A Randomized Controlled Study.

ABSTRACT: Nakao, S, Ikezoe, T, Taniguchi, M, Motomura, Y, Hirono, T, Nojiri, S, Hayashi, R, Tanaka, H, and Ichihashi, N. Effects of low-intensity torque-matched isometric training at long and short muscle lengths of the hamstrings on muscle strength and hypertrophy: A randomized controlled study. J Strength Cond Res 37(10): 1978-1984, 2023-This study investigated the effects of low-intensity torque-matched isometric training on muscle hypertrophy and strengthening at long (LL) and short muscle lengths (SL). Twenty-eight young subjects completed an 8-week hamstring isometric training program (30% of maximal voluntary contraction (MVC) × 5 s × 20 repetitions × 5 sets × 3 times/week) at 30° knee flexion (LL) or 90° knee flexion (SL). The cross-sectional area (CSA) of the hamstrings and MVC were measured before and after the intervention. The active torque because of muscle contraction was calculated by subtracting the passive torque at rest from the total torque (30% MVC). The active torque was significantly lower in the LL training group than in the SL training group (p < 0.01), whereas there was no between-group difference in total torque during training. For CSA and MVC at 30° knee flexion, the split-plot analysis of variance (ANOVA) showed no significant time × group interaction; however, it did show a significant main effect of time (p < 0.05), indicating a significant increase after training intervention. As for MVC at 90° knee flexion, there was a significant time × group interaction (p < 0.05) and a significant simple main effect of time in both the LL (p < 0.01; Cohen's d effect size [ES] = 0.36) and SL (p < 0.01; ES = 0.64) training groups. Therefore, low-intensity isometric training at LL can induce hypertrophy and strengthening, even in cases where the active torque production is lower than that at SL, whereas the training at SL may be more effective for muscle strengthening at SL.

Ultrasonographic echo intensity in the medial femoral cartilage is enhanced prior to cartilage thinning in women with early mild knee osteoarthritis.

PURPOSE: We aimed to determine whether altered cartilage echo intensity is associated with knee osteoarthritis (OA) severity and whether the alteration occurs before thinning of the femoral cartilage in knee OA. METHODS: The medial femoral cartilage thickness and echo intensity of 118 women aged ≥ 50 years were assessed using an ultrasound imaging device. Based on the Kellgren-Lawrence (KL) grade and knee symptoms, participants were classified into five groups: control (asymptomatic grades 0-1), early OA (symptomatic grade 1), grade 2, grade 3, and grade 4. Analysis of covariance, with adjusted age and height, and the Sidak post hoc test were used to assess the differences in cartilage thickness and echo intensity in knees with varying OA severity. RESULTS: The echo intensity on longitudinal images, equivalent to the tibiofemoral weight-bearing surface, was significantly higher in the grade 2 group than that in the control group (p = 0.049). However, no significant difference was noted in cartilage thickness (n.s.). In the grades 3 and 4 groups, cartilage thickness became thinner as OA progressed (p < 0.001 and p < 0.001, respectively). However, the cartilage echo intensity was not significantly enhanced compared with that of the grade 2 group (n.s.). There were no significant differences in the cartilage thickness and echo intensity between the early OA and control groups on the longitudinal images (n.s.). CONCLUSIONS: The echo intensity of the medial femoral cartilage was high in patients with KL grade 2, without decreased thickness. Our findings suggested that higher echo intensity is a feature of early cartilage degeneration in mild knee OA. Further studies are needed to establish this feature as a useful screening parameter of early cartilage degeneration in knee OA. LEVEL OF EVIDENCE: Level III.

Acute Effects of Low-intensity Isometric Exercise at Long and Short Muscle-tendon Unit Lengths.

Low-intensity training at long muscle-tendon unit lengths with a greater passive force may cause muscle swelling, which may be related to hypertrophy, even if the active force production is lower than that at short muscle-tendon unit lengths. This study compared muscle swelling after low-intensity torque-matched isometric exercises at long and short muscle-tendon unit lengths. Twenty-six volunteers performed isometric knee flexion exercises (30% of maximal voluntary contraction× 5 seconds×10 repetitions×9 sets) either at long or short lengths of the hamstrings (90° hip flexion and 30° knee flexion, or 90° hip and knee flexion, respectively). Active torque was calculated by subtracting passive torque from the total torque generated during exercise. Swelling-induced changes in cross-sectional area was assessed before and after exercise using ultrasonography. There was no between-group difference in the total torque during exercise; however, the active torque was significantly lower in the group trained at long than in the group trained at short muscle-tendon unit lengths. Muscle swelling occurred in both groups. The results suggest that exercise at long muscle-tendon unit lengths can cause similar muscle swelling as exercise at short muscle-tendon unit lengths, even in cases where active torque production is lower than that at short lengths.

Assessment of fore-, mid-, and rear-foot alignment and their association with knee symptoms and function in patients with knee osteoarthritis.

OBJECTIVE: Hallux valgus, flatfoot, and rearfoot eversion are well-known major complications of knee osteoarthritis (OA). However, there is no consensus on the association between these foot malalignments and knee symptoms or function. Thus, this study aimed to examine the association between foot alignment and knee symptoms or function in patients with knee OA. METHODS: Female patients aged ≥ 50 years with symptomatic knee OA participated in this study. Knee symptoms and function were assessed using the Knee Society Scoring System (KSS). Hallux valgus, navicular/foot ratio, and leg heel alignment were used as the forefoot, midfoot, and rearfoot alignment indices, respectively. The navicular/foot ratio was defined as the ratio of the navicular height to the total foot length. We performed multiple linear regression analysis to examine the associations between foot alignment and knee symptoms or function. RESULTS: Seventy-eight participants participated our study. KSS symptom score was significantly associated with navicular/foot ratio (regression coefficient [ß], -0.30; 95% confidence interval [CI], -109.2 to -20.5; P = 0.005), knee extensor strength (ß, 0.32; 95% CI, 0.02 to 0.09; P = 0.004), and age (ß, 0.24; 95% CI, 0.01 to 0.32; P = 0.036). KSS function score was not associated with foot alignments but with knee extensor strength (ß, 0.40; 95% CI, 0.10 to 0.33; P = 0.001) and body mass index (ß, -0.35; 95% CI, -2.82 to -0.66; P = 0.002). CONCLUSIONS: Knee symptoms were significantly associated with midfoot alignment in patients with medial knee OA. This suggests that lower navicular height in patients with medial knee OA may relate with the alleviation of knee symptoms. Key Points • In patients with medial knee OA, midfoot alignment was significantly associated with knee symptoms in patients with medial knee OA; however, knee function was not associated with foot alignment. • Lower navicular height in patients with medial knee OA may relate with the alleviation of knee symptoms.

Enhanced echo intensity in vastus medialis is associated with worsening of functional disabilities and symptoms in patients with knee osteoarthritis: a 3 years longitudinal study.

Patients with knee osteoarthritis (OA) experience muscle quality loss, and is characterized by the enhanced echo intensity (EI) of the vastus medialis (VM) muscles and a high extracellular water-to-intracellular water (ECW/ICW) ratio of the thigh. This study aimed to elucidate the association between muscle degeneration and the worsening of functional disabilities and symptoms in patients with KOA over 3 years duration. Thirty-three patients with KOA who completed follow-up over 3 years were included in the analysis. The knee scoring system (KSS) was used to evaluate the functional abilities and symptoms. Based on the 3 years change in KSS scores, patients were classified into progressive or non-progressive groups. Muscle thickness (MT) and EI of the VM were determined using ultrasonography. The ECW/ICW ratio was measured using segmental-bioelectrical impedance spectroscopy. Multivariable logistic regression analyses were conducted with the groups as the dependent variables and VM-MT, VM-EI, and ECW/ICW ratio at baseline as independent variables, including potential confounders. Thirteen (39.4%) patients showed progressive features. VM-EI at baseline was significantly associated with the progression of functional disabilities (adjusted odds ratio [OR] 1.24; 95% confidence interval [CI] 1.03 - 1.50) and symptoms (adjusted OR 1.13; 95% CI 1.01 - 1.25). Enhanced VM-EI was associated with the worsening of functional disabilities and symptoms in patients with KOA over a period of 3 years. Therefore, the assessment of VM-EI using ultrasonography is a useful indicator for predicting the future worsening of KOA.

The effect of Liquid ice after high-intensity exercise on muscle function compared to Block ice.

Cryotherapy is used to recover muscle damage after exercise and to treat acute sports injuries. Liquid ice (LI) can keep cold for a long time, and is assumed more effective than block ice (BI). From this, the aim of this study was to investigate the effects of LI on the change of passive stiffness (PS) as muscle function and to validate the effectiveness of LI compared to BI. We performed the experiment as part of a case series of verification of the effects of cryotherapy. 22 healthy men (target area: right leg) were randomized to two groups: LI group and BI group. PS was measured three times during experiment protocol, pre: before exercise; post; after treating each cryotherapy after exercise; 48h: 48 hours after pre. Statistical analysis compared the PS, the amount of change in PS, and the rate of change in PS between the two groups. The rate of change between pre and 48h in LI was significantly lower compared to that in BI (p = 0.03). There was no significant difference regarding other results between groups. It revealed that the difference of effect between LI and BI for PS of muscles after high-intensity exercises. These results could be helpful for the choice of intervention for reducing muscle stiffness after exercise and at sports field.

Effective muscle elongation positions for the neck extensor muscles: An ultrasonic shear wave elastography study.

This study aimed to clarify the effective stretching positions for neck extensor muscles. Fifteen healthy men were measured shear moduli of the right neck extensor muscles using ultrasound shear wave elastography in following positions: rest (Rest), flexion (Flex), contralateral bending (Bend), flexion + contralateral bending (Flex â†’ Bend), flexion + contralateral bending + contralateral rotation (Flex â†’ Bend â†’ ConRot), and flexion + contralateral bending + ipsilateral rotation (Flex â†’ Bend â†’ IpsRot). The increase in the shear modulus indicated a greater muscle elongation. Regarding the upper trapezius and splenius capitis, the shear moduli at Flex â†’ Bend, Flex â†’ Bend â†’ ConRot, and Flex â†’ Bend â†’ IpsRot were significantly higher than those at Rest. The shear moduli at stretching positions, including contralateral bending, were significantly higher than those at Rest and Flex in the levator scapulae. The results indicated that the stretching position with a combination of flexion and contralateral bending could be effective for elongation of the upper trapezius and splenius capitis. Furthermore, the stretching positions including contralateral bending could be effective for the levator scapulae.

Epimuscular myofascial force transmission from biarticular rectus femoris elongation increases shear modulus of monoarticular quadriceps muscles.

This study aimed to examine the effect of rectus femoris (RF) elongation with passive hip angle change on the shear moduli of the vastus lateralis (VL) and medialis (VM) to verify whether Epimuscular myofascial force transmission (EMFT) occurs in the human quadriceps. Fourteen healthy men participated in this study. The shear moduli of the RF, VL, and VM were measured in four hip positions: flexion (Flex), extension and abduction (Ext-Abd), extension (Ext), and extension and adduction (Ext-Add). As the behavior of shear moduli may differ depending on the parts of the vasti muscles, we measured the medial and lateral parts of the VL (Medial-VL and Lateral-VL) and VM (Medial-VM and Lateral-VM). The shear moduli at the Ext and Ext-Add positions were higher than at the Flex position in the RF, VL, and VM. The shear moduli during Ext and Ext-Add were higher than at the Ext-Abd in the RF, VL, and Lateral-VM. Moreover, the shear modulus of the Lateral-VM was higher than of the Medial-VM (Flex: 8.5% higher; Ext-Abd: 15.6%; Ext: 30.2%; Ext-Add: 32.6%). The shear moduli of the VL and VM, which are monoarticular muscles of the knee, increased with passive hip extension or adduction with extension, even when the knee angle was kept constant. The results suggest that EMFT occurs in the quadriceps, and EMFT had a great impact in the Lateral-VM, which is anatomically adjacent to the RF, but it had little effect in the Medial-VM, which is further away from the RF.

Differences in shear elastic modulus of the latissimus dorsi muscle during stretching among varied trunk positions.

The latissimus dorsi (LD) can be divided into the upper, middle, and lower parts, but the effective stretching positions for each part are unknown. In this study, we aimed to investigate effective trunk positions for stretching of the LD. A total of 14 healthy males participated in this study. The following seven trunk positions were chosen as the LD stretching positions; upright of the trunk (Baseline), flexion of the trunk (Flex), contralateral bending of the trunk (LB), contralateral rotation of the trunk (Rot), flexion and contralateral bending of the trunk (Flex + LB), flexion and contralateral rotation of the trunk (Flex + Rot), and contralateral bending and contralateral rotation of the trunk (LB + Rot). Maximal elevation of the upper limb was passively added to all positions. The shear elastic modulus, used as the index of muscle elongation, was measured at the four parts (upper, middle, lower, distal parts) of the LD. The shear elastic moduli showed obviously high values in Rot and LB + Rot at the upper, middle, and distal parts, and also in LB, Rot, and LB + Rot at the lower part. These findings suggest that contralateral trunk rotation, or a combination of contralateral trunk bending and rotation are effective trunk positions for stretching all parts of the LD. Contralateral trunk bending was also effective for stretching the lower part of the LD.

Effects of trunk lean and foot lift exercises in sitting position on abdominal muscle activity and the contribution rate of transversus abdominis.

PURPOSE: Abdominal hollowing exercise has been recommended to improve trunk stability. Trunk lean and foot lift exercises while sitting may easily promote abdominal muscle activity even in people who cannot perform abdominal hollowing consciously. The purpose of the present study was to examine the changes in abdominal muscle activity and contribution rate of the transversus abdominis muscle (TrA) when leaning the trunk and lifting the foot during sitting. METHODS: The muscle stiffnesses (indicators of muscle activity) of the right rectus abdominis, external oblique, internal oblique, and TrA of 14 healthy men were measured during abdominal hollowing and the following nine sitting tasks: reference posture, 15° and maximal posterior trunk lean, 20° and maximal ipsilateral and contralateral trunk lean, and ipsilateral and contralateral foot lift. The TrA contribution rate was calculated by dividing the TrA stiffness by the sum of the abdominal muscles' stiffnesses. RESULTS: The TrA stiffness was significantly higher in abdominal hollowing than in reference posture, posterior and ipsilateral trunk lean, and ipsilateral foot lift, but not higher than in contralateral trunk lean and contralateral foot lift. There was no significant difference in the TrA contribution rates between abdominal hollowing and ipsilateral or contralateral foot lift. CONCLUSION: The contralateral trunk lean or contralateral foot lift could enhance TrA activity for people who cannot perform abdominal hollowing consciously. The contralateral foot lift could particularly be beneficial to obtain selective activity of TrA.

Muscle size-scaled shear elastic modulus: A muscle force index independent of maximal voluntary contraction, assessed during elbow extension.

Shear elastic modulus (G) can differ among individuals due to muscle size and other factors, even for constant muscle force. Inter-individual comparisons of G usually require normalization by maximal voluntary contraction (MVC), but MVC procedures may not be appropriate for certain clinical populations including those presenting with pain or other compromised functionality. This study aimed to test whether muscle size-scaled G, which does not require MVC testing, would yield stronger correlation with absolute torque than unscaled G. Twelve-healthy males performed isometric elbow extension across a range of torque magnitudes (from 5 Nm until 60% MVC). G of the triceps brachii was measured using shear wave elastography during each trial. Cross-sectional area (CSA) and muscle thickness (MT) of the triceps brachii were measured at rest. Scaled G was calculated as a product of G and CSA or MT ("G-CSA" and "G-MT", respectively). Within-individual linear regressions were conducted between absolute torque and the three force indicator variables. The regression slopes' coefficient of variation (CV) was calculated for each indicator across individuals. Between-individual correlation coefficients were calculated, after pooling all data across individuals into a single regression analysis for each indicator. Linear regression found that inter-individual slope variation increased in the following order: G-CSA, G-MT, and unscaled G (CV = 0.15, 0.18, and 0.29, respectively). Pooled-individual correlation coefficients were significantly higher in G-CSA and G-MT than in unscaled G (r = 0.948, 0.924, and r = 0.783, respectively). These results suggest that muscle size-scaled G may be more appropriate than unscaled G when comparing shear moduli across individuals.

Effect of static stretching with different rest intervals on muscle stiffness.

The aim of the study was to investigate the effect of static stretching (SS) with different rest intervals on muscle stiffness. Fifteen healthy males participated in the study. Four bouts of thirty-second SS for the gastrocnemii were performed at the maximal dorsiflexion using dynamometer with two different rest intervals between stretches, namely 0 s (R0) and 30 s (R30). Each participant underwent both stretching protocols at least 48 h apart in a random order. Between each bout of SS, the ankle was moved to 20°-plantar-flexion in 3 s, held for each rest interval time, and then returned to the stretching position in 3 s. The shear elastic modulus of the medial gastrocnemius was measured before (PRE) and immediately after (POST) four bouts of SS to assess muscle stiffness of the medial gastrocnemius. Two-way repeated measures analysis of variance (protocol × time) indicated a significant interaction effect on the shear elastic modulus. The shear elastic modulus significantly decreased after SS in both protocols [R0, PRE: 11.5 ±â€¯3.3 kPa, POST: 10.0 ±â€¯2.6 kPa, amount of change: 1.6 ±â€¯0.9 kPa (13.0 ±â€¯5.2%); R30, PRE: 11.0 ±â€¯2.8 kPa, POST: 10.2 ±â€¯2.1 kPa, amount of change: 0.8 ±â€¯1.3 kPa (6.0 ±â€¯10.4%)]. Furthermore, the SS with 0-s rest interval induced greater decrease in shear elastic modulus when compared to SS with 30-s rest interval (p = 0.023). Thus, when performing SS to decrease muscle stiffness, rest intervals between stretches should be minimized.

Abdominal girth as an index of muscle tension during abdominal hollowing: Selecting the optimal training intensity for the transversus abdominis muscle.

The abdominal hollowing technique is used for training the transversus abdominis (TrA). However, the optimal intensity of hollowing is still unclear. The objective of the present study is to verify the validity of estimating the tension of the TrA by measuring the girth of the abdomen with a tape and to determine the optimum intensity of hollowing to effectively train the TrA. Sixteen healthy males performed hollowing with an intensity of 0%, 25%, 50%, 75%, and 100%, estimated from the girth of the abdomen. The shear elastic modulus was measured for the rectus abdominis (RA), external oblique (EO), internal oblique (IO), and TrA at all intensities via ultrasonic shear wave elastography. The shear elastic modulus was considered as the index of the tension of the abdominal muscles at each intensity, and the ratio of the TrA to RA, EO, and IO respectively was calculated as the index of TrA selectivity. As the intensity of hollowing increased, the girth of abdomen decreased and tension of all the four muscles increased. The ratio of TrA to the RA, EO, and IO did not exhibit a significant variation among hollowing intensities of 25% to 100%. It is rational to estimate the tension of the TrA by measuring the girth of the abdomen. Moreover, considering both TrA contraction intensity and selectivity, abdominal hollowing performed at maximum intensity was effective for the maximum contraction training of the TrA.

Effect of different knee flexion angles with a constant hip and knee torque on the muscle forces and neuromuscular activities of hamstrings and gluteus maximus muscles.

PURPOSE: This study examined the effect of different knee flexion angles with a constant hip and knee torque on the muscle force and neuromuscular activity of the hamstrings and gluteus maximus. METHODS: Twenty healthy males lay in prone position and held their lower limb with hip flexion at 45° and knee flexion at either 10° or 80°. At these angles, the hip and knee torques are identical. Under three load conditions: passive (referred to as Unloaded), active (Loaded), and active with 3-kg weight added to the shank (Loaded + 3 kg), the muscle stiffness (i.e., an indicator of muscle force) and neuromuscular activity of the hamstrings and gluteus maximus were measured using shear wave elastography and surface electromyography. RESULTS: The muscle stiffness and neuromuscular activity of the hamstrings and gluteus maximus increased significantly with the load. Muscle stiffness in the hamstrings was significantly lower at knee flexion of 80° than at 10° for Unloaded, but not for either Loaded or Loaded + 3 kg. The neuromuscular activity of the hamstrings was significantly greater at knee flexion of 80° than at 10° for both Loaded and Loaded + 3 kg. The muscle stiffness or neuromuscular activity of the gluteus maximus showed no significant differences between knee angles. CONCLUSIONS: When the passive force in the hamstrings decreases with knee flexion, sufficient muscle force to maintain the hip and knee torques against an external load is generated by preferentially increasing the neuromuscular activity of the hamstrings, rather than increasing the synergetic muscle force.

Improvement in muscle strength with low-load isotonic training depends on fascicle length but not joint angle.

INTRODUCTION: In this study we investigate whether low-load isotonic training will elicit greater improvement in muscle strength at the same fascicle length, rather than at the same joint angle. METHODS: Sixteen healthy men (24.1 ± 2.5 years of age) were randomly divided into intervention and control groups. Pre- and posttraining maximum isometric and isokinetic strengths and fascicle lengths of the medial gastrocnemius muscle were measured. Isotonic resistance training at 15 ° to 30 ° ankle plantarflexion at low intensity was conducted for 4 weeks. RESULTS: The maximum isometric and isokinetic strength of the intervention group increased significantly only at 15 ° dorsiflexion and 8 ° to 12 ° dorsiflexion. Fascicle length during maximum voluntary contraction at 15 ° dorsiflexion to 0 ° was similar to fascicle length under training conditions. DISCUSSION: It is possible that the improvement in muscle strength with low-load training depends on fascicle length rather than joint angle. Muscle Nerve 57: 83-89, 2018.