Emika Kato

Changes in ankle joint stiffness due to stretching: The role of tendon elongation of the gastrocnemius muscle

Abstract The purpose of this study was to investigate changes in ankle joint stiffness and the associated changes in the gastrocnemius muscle and tendon due to static stretching. Seven healthy male participants lay supine with the hip and knee joints fully extended. The right ankle joint was rotated into dorsiflexion from a 30° plantar flexed position and the torque measured by a dynamometer. The ankle joint was maintained in a dorsiflexed position for 20 min (static stretching of the calf muscles). We performed surface electromyography of the medial and lateral gastrocnemii, the soleus, and the tibialis anterior of the right leg to confirm no muscle activity throughout static stretching and the passive test (passive dorsiflexion). During static stretching, the ankle joint angle and elongation of the gastrocnemius were recorded by goniometry and ultrasonography, respectively. Tendon elongation of the gastrocnemius was calculated based on the changes in the ankle joint angle and muscle elongation. In addition, the relationships between passive torques and ankle joint angles, and elongation of muscle and tendon, were examined before and after static stretching. The ankle dorsiflexion angle and tendon elongation increased significantly by 10 min after the onset of static stretching, while there was no further increase in muscle length. In addition, ankle dorsiflexion angle and tendon elongation at an identical passive torque (30 N · m) increased significantly (from 24±7° to 33±5° and from 17±2 mm to 22±1 mm, respectively) after static stretching. However, muscle elongation was unchanged. In conclusion, the current results suggest that an increase in the ankle joint dorsiflexion angle due to static stretching is attributable to a change in tendon not muscle stiffness.

Relationships Between Muscle Strength and Indices of Muscle Cross-sectional Area Determined During Maximal Voluntary Contraction in Middle-aged and Elderly Individuals

Akagi, R, Takai, Y, Kato, E, Fukuda, M, Wakahara, T, Ohta, M, Kanehisa, H, Kawakami, Y, and Fukunaga, T. Relationships between muscle strength and indices of muscle cross-sectional area determined during maximal voluntary contraction in middle-aged and elderly individuals. J Strength Cond Res 23(4): 1258-1262, 2009-The present study examined how muscle cross-sectional area (CSA) indices determined at rest and during maximal voluntary contraction (MVC) are related to muscle strength in middle-aged and elderly individuals (22 men and 36 women, 51-77 years). The muscle thickness (MT) of elbow flexors and circumference (C) at the level 60% distal to the upper arm was measured by ultrasonography and a measuring tape, respectively, both at rest and during isometric MVC of elbow flexion. The muscle strength (F) of elbow flexors was calculated by dividing the torque developed during MVC by the forearm length of each subject. The product of MT and C (MT×C) and the square of MT (MT2) were defined as the muscle CSA indices. The F was significantly correlated with MT×C during MVC (r = 0.905, p ≤ 0.001) and at rest (r = 0.778, p ≤ 0.001), with the former relationship significantly stronger than the latter (p ≤ 0.001). Similarly, F was significantly correlated with MT2 both during MVC (r = 0.896, p ≤ 0.001) and at rest (r = 0.780, p ≤ 0.001), and there was also a significant difference between the correlation coefficients (p ≤ 0.01). These findings show that, in middle-aged and elderly individuals, muscle strength is more closely related to muscle CSA indices during MVC than at rest. It is concluded that the present muscle CSA indices taken during MVC enable easy and practical evaluation of the muscle strength per size of elbow flexors in middle-aged and elderly individuals.

Validity of ultrasound muscle thickness measurements for predicting leg skeletal muscle mass in healthy Japanese middle-aged and older individuals

BackgroundThe skeletal muscle mass of the lower limb plays a role in its mobility during daily life. From the perspective of physical resources, leg muscle mass dominantly decreases after the end of the fifth decade. Therefore, an accurate estimate of the muscle mass is important for the middle-aged and older population. The present study aimed to clarify the validity of ultrasound muscle thickness (MT) measurements for predicting leg skeletal muscle mass (SM) in the healthy Japanese middle-aged and older population.FindingsMTs at four sites of the lower limb and the bone-free lean tissue mass (LTM) of the right leg were determined using brightness-mode ultrasonography and dual-energy X-ray absorptiometry (DXA), respectively, in 44 women and 33 men, 52- to 78-years old. LTM was used as a representative variable of leg skeletal muscle mass. In the model-development group (30 women and 22 men), regression analysis produced an equation with R2 and standard error of the estimate (SEE) of 0.958 and 0.3 kg, respectively: LTM (kg) = 0.01464 × (MTSUM×L) (cm2) - 2.767, where MTSUM is the sum of the product of MTs at four sites, and L is length of segment where MT is determined. The estimated LTM (7.0 ± 1.7 kg) did not significantly differ from the measured LTM (7.0 ± 1.7 kg), without a significant systematic error on a Bland-Altman plot. The application of this equation for the cross-validation group (14 women and 11 men) did not yield a significant difference between the measured (7.2 ± 1.6 kg) or estimated (7.2 ± 1.6 kg) LTM and systematic error.ConclusionThe developed prediction equation may be useful for estimating the lean tissue mass of the lower extremity for the healthy Japanese middle-aged and older population.

Applicability of ultrasound muscle thickness measurements for predicting fat-free mass in elderly population

Objective: This study aimed to examine the applicability of ultrasound muscle thickness (MT) measurements for predicting whole body fat-free mass (FFM) in elderly individuals. Design and setting: Crosssectional study of 77 healthy elderly individuals. Methods: MTs at nine sites of the body and FFM were determined using B-mode ultrasound and dual-energy x-ray absorptiometry (DXA), respectively, in 44 women and 33 men aged 52 to 78 yrs. Stepwise multiple regression analysis produced two equations for predicting DXA-based FFM with sex (dummy: woman = 0 and man = 1) and either MTs at the anterior and posterior of thigh and lower leg (Eq1) or the product of MT and limb length (MT×LL) at thigh anterior and posterior, lower leg posterior, and upper arm anterior (Eq2) as independent variables. Results: The R2 and SEE for each of the two equations were 0.929 and 2.5 kg for Eq1 and 0.955 and 2.0 kg for Eq2. The estimated FFM from each of Eq1 (44.4 ± 8.9 kg) and Eq2 (44.4 ± 9.0 kg) did not significantly differ from that of the DXA-based FFM (44.4 ± 9.2 kg), without systematic error. However, the absolute value of the difference between the DXA-based and estimated FFM was significantly greater with Eq1 (2.0 ± 1.5 kg) than with Eq2 (1.5 ± 1.3 kg). Conclusion: The current results indicate that ultrasound MT measurement is useful to predict FFM in the elderly, and its accuracy is improved by using the product of MT and limb length as an independent variable.

Variability of limb muscle size in young men

The purpose of this study was to determine the interindividual variability of the upper and lower limb muscle size in young men. Subjects were 655 Japanese men aged 18–39 years. They were sedentary and mildly to highly active individuals, including college athletes of various sports. Muscle thicknesses at each of the anterior and posterior portions of the upper arm, thigh, and lower leg were measured using B‐mode ultrasonography. Interindividual variability of muscle thickness was evaluated by coefficients of variation (CVs). The CVs of muscle thicknesses were found to be in the order of upper arm posterior (17.7%), thigh anterior (14.8%), thigh posterior (12.6%), upper arm anterior (12.2%), lower leg anterior (9.8%), and lower leg posterior (9.4%). The CVs were significantly different between each pair of measurement sites except for those of upper arm anterior‐thigh posterior and lower leg anterior‐posterior. These differences remain significant even when the muscle thicknesses were normalized to the segment length. The observed differences in the size variability can be interpreted as muscle‐related differences in hypertrophic responsiveness to resistance training. The muscle‐dependent size variability may be related to the differences in the fiber‐type composition and/or muscle usage in daily life among examined muscle groups. Am. J. Hum. Biol. 2010.

Sex differences in relationship between passive ankle stiffness and leg stiffness during hopping.

The goal of this study was to examine the hypothesis that the relationships between passive ankle stiffness and leg stiffness would be different between males and females. 10 males and 10 females performed hopping in place on two legs at three frequencies of 2.0, 2.5, and 3.0 Hz. Based on a spring-mass model, leg stiffness, which is defined as the ratio of maximum ground reaction force to maximum center of mass displacement at the middle of the stance phase, was calculated using the vertical ground reaction force. Further, passive ankle stiffness was calculated as the slope of the passive ankle torque-angle relationship, which results from controlled passive ankle dorsiflexion. There was no significant difference in the leg stiffness between males and females at three hopping frequencies; however, females displayed less passive ankle stiffness than males. Further, significant positive linear relationships were found between the passive ankle stiffness and the leg stiffness for females at all hopping frequencies; however, there were no significant correlations between the passive ankle stiffness and the leg stiffness in males for all hopping frequencies. These results suggest that the relationship between the passive ankle stiffness and the leg stiffness are not the same between males and females, which may lead to a greater risk of anterior cruciate ligament injuries in females.

Combined Effects of Stretching and Resistance Training on Ankle Joint Flexibility

The purpose of the present study was to clarify the combined effects of stretching and resistance training on the active and passive dorsiflexion range of motion of ankle joint. Sixteen young adult men were randomly assigned to a training () or a control () group. The training group trained one leg for the combined program of static calf stretching and dorsiflexors resistance training program (STR

Regional Difference In Gastrocnemius Tension During Passive Stretching As Assessed With Shear Wave Elastography: 3154 Board #219 June 3, 3: 30 PM - 5: 00 PM.

Muscle strain injuries occur when the muscle is either stretched passively or activated during stretch. Calf strain injuries are most commonly found in the medial gastrocnemius (MG), especially at the distal musculotendinous junction. One of the reasons for the susceptibility of musculotendinous junction for strain injuries may be that the distal region of MG is stretched more than the medial belly region. Muscle tension during passive stretching can be estimated from shear elastic modulus measured by shear wave elastography. PURPOSE: To investigate the regional difference in MG tension during passive stretching, shear elastic modulus at the distal and medial belly regions of the MG was assessed by shear-wave elastography. METHODS: Twenty-two healthy men and 25 healthy women participated in this study. Shear elastic moduli at the distal and medial belly regions of the MG were measured with the ankle joint positions at 30° plantarflexion (PF), a neutral anatomical position (NE), and 20° dorsiflexion (DF). The regional differences in the shear elastic modulus were tested with a two-way analysis of variance (region of the MG × ankle joint position), followed by t-tests with Bonferroni correction, with the significance set at P < 0.05. RESULTS: Shear elastic modulus was not significantly different between the distal and medial belly regions at PF (distal region: 5.7 ± 2.0 kPa; medial belly region: 5.0 ± 1.4 kPa) and NE (distal region: 9.8 ± 1.6 kPa; medial belly region: 9.9 ± 1.8 kPa), but it was significantly higher at the distal region (40.7 ± 10.1 kPa) compared with the medial belly region (35.9 ± 9.1 kPa) at DF. CONCLUSIONS: Regional difference in MG tension during passive stretching was observed in the ankle joint position where the MG is sufficiently lengthened, which could lead to muscle strain injuries at the distal musculotendinous junction of the MG. The study was supported by JSPS KAKENHI (Grant Number 15K16500).