[Show abstract][Hide abstract] ABSTRACT: 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.
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.
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).
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.
The Journal of Nutrition Health and Aging 01/2014; · 2.39 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Purpose
To examine the relationships between body mass to waist circumference (BM:W) ratio or body mass index (BMI) and muscularity, 140 overweight (BMI ≥ 25 kg/m2 and <30 kg/m2), 265 normal weight (BMI > 18.5 kg/m2 and <25 kg/m2) and 26 underweight (BMI ≤ 18.5 kg/m2) Japanese women aged 60–80 years volunteered (overall 431 women).
Muscle thickness was measured by ultrasound at six sites on the anterior and posterior aspects of the body. Total muscle mass (TMM) was estimated from an ultrasound-derived prediction equation. BMI and BM:W ratio were calculated using anthropometrical variables.
When the overall sample was used, BMI was positively correlated with the TMM (r = 0.573, p < 0.001) and TMM index (r = 0.659, p < 0.001). BM:W ratio was also positively correlated with the TMM (r = 0.566, p < 0.001) and TMM index (r = 0.400, p < 0.001). In normal weight women, BMI was positively correlated with the TMM (r = 0.460, p < 0.001) and TMM index (r = 0.496, p < 0.001). Similarly, BM:W ratio was positively correlated with the TMM (r = 0.514, p < 0.001) and TMM index (r = 0.318, p < 0.001). In overweight and underweight women, TMM was significantly and positively correlated with BM:W ratio (r = 0.442 and r = 0.715, respectively; p < 0.001), but not BMI (r = 0.077 and r = 0.315). TMM index was also positively correlated with BM:W ratio in both overweight (r = 0.184, p < 0.05) and underweight (r = 0.500, p < 0.01) women. BMI was positively correlated with TMM index (r = 0.230, p < 0.01) and inversely correlated to the percentage of TMM in body mass (r = −0.262, p < 0.01) in overweight women.
These results suggest that, compared to BMI, BM:W ratio may provide a simple and potential index for assessing muscularity in Japanese older underweight women. However, in normal and overweight women, BMI and BM:W ratio are both preferred in assessing muscularity.
Journal of Clinical Gerontology and Geriatrics. 01/2014;
[Show abstract][Hide abstract] ABSTRACT: The present study examined neuromuscular adaptations following 12-week maximal voluntary co-contraction training.
Sixteen young men were allocated to training (TG, n = 9) or control (CG, n = 7) group. TG conducted a training program (3 days/week), which consisted of 4-s maximal voluntary contractions of elbow flexors and extensors by simultaneously contracting both muscle groups at 90° of the elbow joint, followed by 4-s muscle relaxation (10 repetitions/set, 5 sets/day) for 12 weeks. In addition to the muscle thicknesses of elbow flexors and extensors, the torque and electromyograms (EMGs) of the two muscle groups during isometric maximal voluntary contraction (MVC) were determined before (Pre), after 4 weeks, and 12 weeks of intervention.
After intervention, CG showed no significant changes in all measured variables. In TG, MVC torque significantly increased in both elbow flexors (+13 % at 4 weeks and +15 % at 12 weeks) and extensors (+27 % at 4 weeks and +46 % at 12 weeks) from Pre. Muscle thickness also significantly increased in both elbow flexors (+4 %) and extensors (+4 %) at 12 weeks. Agonist EMG activities during MVC significantly increased in both elbow flexors (+31 % at 4 weeks and +44 % at 12 weeks) and extensors (+27 % at 4 weeks and +40 % at 12 weeks), without changes in antagonist involuntary coactivation level in both muscle groups.
These results indicate that maximal voluntary co-contraction is applicable as a training modality for increasing the size and strength of antagonistic muscle pairs without increasing involuntary coactivation level.
[Show abstract][Hide abstract] ABSTRACT: The purpose of this study was to examine the age-related site-specific muscle loss of the upper and lower extremities and trunk in men and women. Japanese nonobese adults aged 20-79 (n = 1559, 52 % women) had muscle thickness (MTH) measured by ultrasound at nine sites on the anterior and posterior aspects of the body. An MTH ratio located in the anterior and posterior aspects of the upper arm, upper leg, lower leg, and trunk was calculated. Site-specific muscle loss was defined as a ratio of MTH > 2 standard deviations below the mean for young adults in each segment. Age was inversely correlated (p < 0.001) to upper-leg MTH ratio in men (r = -0.463) and women (r = -0.541). Age was correlated positively to upper-arm MTH ratio and inversely to trunk MTH ratio in men (r = 0.191 and r = -0.238, both p < 0.001) and women (r = 0.102, p = 0.004 and r = -0.446, p < 0.001). Weak correlations were observed between age and lower-leg MTH ratios in men (r = 0.015, p = 0.682) and women (r = 0.086, p = 0.015). The prevalence of site-specific upper-leg muscle loss showed an age-related increasing pattern in men (6 % for ages 30-39, 21 % for ages 50-59, and 38 % for ages 70-79) and women (15 % for ages 30-39, 32 % for ages 50-59, and 50 % for ages 70-79). For other segments, however, the prevalence rate of site-specific muscle loss was relatively low throughout the age groups in men and women, although higher rates were observed in the older group. These results suggest that the anterior/posterior MTH ratio of the upper leg may be useful in providing an earlier diagnosis for site-specific muscle loss.
[Show abstract][Hide abstract] ABSTRACT: The 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.
MTs 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 x (MTSUMxL) (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.
The 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.
Journal of PHYSIOLOGICAL ANTHROPOLOGY 09/2013; 32(1):12. · 0.63 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The present study aimed to examine the effect of short-term training utilizing voluntary co-contraction with maximal efforts. 23 healthy young men (training group: TG, n=13; control group: CG, n=10) participated in this study. TG conducted a 4-week training program (3 days/week), which consisted of 4s simultaneous maximal voluntary contractions of elbow flexors and extensors at 90°of the elbow joint, followed by 4s muscle relaxation (10 repetitions/set, 5 sets/day). Before and after the intervention, maximal voluntary isometric and isokinetic torques and the muscle thicknesses of the elbow flexors and extensors were determined. The electromyograms (EMGs) of the 2 muscle groups during isometric maximal voluntary contraction (MVC) were also recorded. After the intervention, CG did not show any significant changes in all measured variables. In TG, significant increases were found in the agonist EMG activities during MVC, and maximal isometric and isokinetic torques of the elbow flexors and extensors, without significant changes in the muscle thicknesses and involuntary coactivation levels during MVC. The current results indicate that the training mode with maximal voluntary co-contraction is effective for improving the force-generating capabilities of the exercising muscles, without any increases in the level of involuntary coactivation during MVC.
International Journal of Sports Medicine 07/2013; · 2.27 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The purpose of this study was to compare the prevalence of severe sarcopenia detected by total skeletal muscle mass (SM) index and of site-specific thigh sarcopenia for differing age groups in men and women. Japanese nonobese men and women aged 20 to 85 (n = 1,994, 55 % women) had muscle thickness (MTH) measured by ultrasound at six sites on the anterior and posterior aspects of the body. SM was estimated from ultrasound-derived prediction equations. Site-specific thigh sarcopenia was calculated using ultrasound-measured MTH at the anterior and posterior aspects of the thigh (MTH ratio, anterior 50 %/posterior 50 % thigh MTH (A50/P50 MTH)). Sarcopenia was defined as a SM index (SM divided by height(2)) of >2 standard deviations (SD) below the mean for young adults. Site-specific thigh sarcopenia was defined as a ratio of A50/P50 MTH of >2 SD below the mean for young adults. Age was inversely correlated to SM index and A50/P50 MTH in men (r = -0.480 and r = -0.522) and women (r = -0.243 and r = -0.516). The prevalence rate of sarcopenia was less than 3 % for women under the age of 60, 7 % for ages 60-69, and 24 % for ages 70-80. In men, the prevalence rate of sarcopenia was less than 7 % under the age of 50, 18 % for ages 50-59, 33 % for ages 60-69, and 47 % for ages 70-85. Compared to the sarcopenia estimated by SM index, there was a higher prevalence of site-specific thigh sarcopenia observed in both sexes. These results suggest that site-specific thigh sarcopenia appears before it is able to be detected at the whole body level.
[Show abstract][Hide abstract] ABSTRACT: Abstract To better understand the cascade from neural activation up to force production within in vivo contracting muscle-tendon units, we estimated activation of contractile elements from experimentally measured human fascicle length change and force using a Hill-type muscle model. The experiment was conducted with respect to twitch contractions of the tibialis anterior muscle at three joint angles. As muscle contractile element force is a function of its length and velocity, the activation of contractile elements was calculated using a Hill-type muscle model and measured data. The results were able to reproduce the continuous rising activation of contractile elements after termination of electromyographic activity, the earlier shift of peak activation in time compared to twitch force, and the differences in time-course activation at three different joint angles. These findings are consistent with the predicted change in the activation of contractile elements from previous reports. Also, the results suggest that the time-course of the activation of contractile elements was greatly influenced by the change in force generating capacities related to both length and velocity, even in fixed end contractions, which could result from muscle-tendon interaction.
Journal of Sports Sciences 03/2013; · 2.08 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Body mass index (BMI), expressed as the ratio of body mass to height squared (kg/m2), involves not only fat but also lean mass. The present study aimed to clarify how BMI is associated with total muscle mass (TMM) in older Japanese women and men.
Using a B-mode ultrasound apparatus, muscle thickness was measured at nine sites (forearm, upper arm anterior and posterior, thigh anterior and posterior, lower leg anterior and posterior, abdomen, and subscapular) for 346 women (BMI 16.40 to 33.11 kg/m2) and 286 men (BMI 16.86 to 31.18 kg/m2) aged 60.0 to 79.5 yrs. TMM was estimated using the product of the sum of the muscle thicknesses at the nine sites with height as an independent variable. For both sexes, the estimated TMM relative to height squared was significantly correlated with BMI (r = 0.688, P<0.0001 for women; r = 0.696, P<0.0001 for men), but the percentage of the estimated TMM in body mass was not.
These results indicate that, for older Japanese women and men, BMI is a simple and convenient index for assessing total muscularity.
Journal of PHYSIOLOGICAL ANTHROPOLOGY 01/2013; 32(1):4. · 0.63 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The purpose of this study was to examine the relationship between muscle architecture of the triceps brachii (TB) and joint performance during concentric elbow extensions. Twenty-two men performed maximal isometric and concentric elbow extensions against various loads. Joint torque and angular velocity during concentric contractions were measured, and joint power was calculated. Muscle length, cross-sectional areas and volume of TB were measured from magnetic resonance images. Pennation angle (PA) of TB at rest was determined by ultrasonography. The PA was significantly correlated with the maximal isometric torque (r = 0.471), but not to the torque normalized by muscle volume (r = 0.312). A significant correlation was found between PA and the angular velocity at 0 kg load (r = 0.563), even when the angular velocity was normalized by the muscle length (r = 0.536). The PA was significantly correlated with the maximal joint power (r = 0.519), but not with the power normalized by muscle volume (r = 0.393). These results suggest that PA has a positive influence on the muscle shortening velocity during an unloaded movement, but does not have a significant influence on the maximum power generation in untrained men.
Journal of applied biomechanics 08/2012; · 1.26 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Abstract Background: It is unknown whether severe sarcopenia produces unfavorable effects on cardiovascular risk factors. To examine the influence of severe and moderate sarcopenia on selected cardiovascular risk factors, 687 men were screened; those exhibiting clinically relevant diseases and higher body fat percentage (>25% fat) were excluded. A total of 410 men aged 40-76 years (mean age 56.0 years) were used for data analyses. Methods: Sarcopenia was defined as a skeletal muscle mass (SM) index (muscle mass/height squared) of 1-2 standard deviations (SD) below (moderate) or <2 SDs below (severe) the mean for young adult men. Ultrasound-measured subcutaneous fat and muscle thicknesses were used to estimate the SM, percent body fat, and fat-free mass. Serum total cholesterol (TC) and high-density lipoprotein cholesterol (HDL-C) levels were determined using fasting blood samples. Systolic blood pressure and diastolic blood pressure were also measured. Results: HDL-C was similar among the groups, but TC was lower in severe and moderate sarcopenia groups compared to the normal group. As a result, the TC:HDL-C ratio was lower in the moderate and severe sarcopenia groups than in the normal group. After adjusting for age, body mass index (BMI), waist circumference, and percent body fat, HDL-C was lower in both sarcopenia groups compared to the normal group, but other parameters were similar among the groups. A low prevalence of high HDL-C and high prevalence of moderate HDL-C were observed in the severe and the moderate sarcopenia groups. Conclusion: Our results suggest that moderate and severe sarcopenia may influence the HDL-C level, although the values are still maintained in the clinically normal range.
[Show abstract][Hide abstract] ABSTRACT: The purpose of the present study was to examine a hypothesis that the musculotendinous behavior during a propelling action with a countermovement can be altered by a single practice session through modulation of neuromuscular activities.
Eight males performed unilateral maximal plantarflexion with (CMJ) and without (noCMJ) countermovement before and after a practice consisting of six sets of three repetitions of unilateral CMJ exercises. Measurements included EMG activities of the triceps surae and tibialis anterior muscles and the fascicle behavior of the gastrocnemius by ultrasonography, and impulse was calculated from the force-time data. The change in tendon length was also estimated.
The impulse in CMJ increased after the practice, but that in noCMJ did not. After the practice, the magnitude of fascicle lengthening and shortening in CMJ decreased, which was accompanied by an increase in tendon shortening without change in the ankle joint range of motion. The time lag from the onset of reaction force to that of EMG activities of the triceps surae muscles was shortened after the practice.
The results support the hypothesis and indicate that, as a neural modulation through a single practice, the muscle-tendon unit behavior during CMJ can be optimized to improve the performance.
Medicine and science in sports and exercise 03/2012; 44(8):1512-8. · 4.48 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Asians seem to have less skeletal muscle mass (SMM) than other ethnic groups, but it is not clear whether relative SMM, i.e., SMM / height square or SMM to fat-free mass (FFM) ratio, differs among different ethnic groups at the same level of body mass index (BMI).
To compare the SMM to fat-free mass (FFM) ratio as well as anthropometric variables and body composition among 3 ethnic groups.
Three hundred thirty-nine Japanese, 343 Brazilian, and 183 German men and women were recruited for this cross-sectional study.
Muscle thickness (MTH) and subcutaneous fat thickness (FTH) were measured by ultrasound at nine sites on the anterior and posterior aspects of the body. FTH was used to estimate the body density, from which fat mass and fat-free mass (FFM) was calculated by using Brozek equation. Total SMM was estimated from ultrasound-derived prediction equations.
Percentage body fat was similar among the ethnic groups in men, while Brazilians were higher than Japanese in women. In German men and women, absolute SMM and FFM were higher than in their Japanese and Brazilians counterparts. SMM index and SMM:FFM ratios were similar among the ethnic groups in women, excluding SMM:FFM ratio in Brazilian. In men, however, these relative values (SMM index and SMM:FFM ratio) were still higher in Germans. After adjusting for age and BMI, the SMM index and SMM:FFM ratios were lower in Brazilian men and women compared with the other two ethnic groups, while the SMM index and SMM:FFM ratios were similar in Japanese and German men and women, excluding SMM:FFM ratio in women.
Our results suggest that relative SMM is not lower in Asian populations compared with European populations after adjusted by age and BMI.
The Journal of Nutrition Health and Aging 01/2012; 16(6):534-8. · 2.39 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The purpose of this study was to examine if the regional difference in muscle hypertrophy after chronic resistance training is associated with muscle activation after one session of resistance exercise. Twelve men performed one session of resistance exercise of elbow extensors. Before and immediately after the exercise, transverse relaxation time (T2)-weighted magnetic resonance (MR) images of upper arm were recorded to evaluate the muscle activation along its length. In the MR images, T2 for the pixels within the triceps brachii muscle was quantified. The number of pixels with T2 greater than the threshold (mean + 1SD of T2 before the exercise) was expressed as the ratio to the number of pixels occupied by the muscle (%activated area). Another 12 subjects completed 12 weeks of training intervention (3 days per week), which consisted of the same program variables as used in the experiment for the T2 measurement. The cross-sectional areas of the triceps brachii before and after the training intervention were measured from MR images of upper arm. The %activated area of the triceps brachii induced by one session of the exercise was found to be significantly lower in the distal region than the middle and proximal regions. Similarly, the relative increase in muscle cross-sectional area after the 12 weeks of training intervention was significantly less in the distal region than the middle and proximal regions. The results suggest that the regional difference in muscle hypertrophy after chronic resistance training is attributable to the regional difference in muscle activation during the exercise.
[Show abstract][Hide abstract] ABSTRACT: The purpose of this study was to compare the age-related muscle loss in both the appendicular and trunk regions in 207 Japanese and 111 German men aged 20-62 years. Ultrasound-measured muscle thickness (MTH) was taken at eight sites from the anterior and posterior aspects of the body, and the MTH was expressed in terms relative to limb length (MTH/L) or standing height (MTH/Ht). In both the Japanese and Germans, age was correlated with quadriceps MTH (Japanese, r = -0·347; Germans, r = -0·292; both P<0·01) and abdomen MTH (Japanese, r = -0·300, P<0·01; Germans, r = -0·232; P<0·05). On the other hand, hamstring MTH was correlated with age in the Japanese (r = -0·188, P<0·01), but not in the Germans (r = 0·100). There were no significant correlations between age and other limb (i.e. triceps surae MTH/L, Japanese, r = 0·04; Germans, r = 0·05) and trunk sites (subscapula MTH/Ht, Japanese, r = -0·09; Germans, r = -0·02). In conclusion, age-related skeletal muscle loss was strongly observed in the quadriceps and abdominal sites in both the Japanese and German men, although the rate of regular physical activity was different between the two groups.
[Show abstract][Hide abstract] ABSTRACT: The present study investigated the effect of movement frequencies on the behavior of fascicles and tendons of synergistic muscles. Seven male subjects performed ankle bending (calf-raise) exercises at four movement frequencies (1.33, 1.67, 1.84, and 2.00 Hz), performed with an identical range of ankle joint motion. The fascicle and tendon behavior of medial gastrocnemius (MG) and soleus (SOL) was measured by ultrasonography while kinematic and kinetic parameters of the ankle were recorded. The torque of ankle joint was larger at higher exercise frequencies. The length change of muscle decreased and that of tendon increased at higher frequencies both for MG and for SOL, with no significant inter-muscle differences in the relative changes of muscle or tendon lengths to that of MTU. Changes of pennation angles and electromyographic activities as a function of movement frequency were also comparable for MG and SOL. These results suggest that under a stretch-shortening cycle action, the muscle-tendon interaction is altered by the movement frequency toward greater use of tendon elastic energy to provide greater MTU power at a higher frequency. Results also suggest that the movement frequency dependence of fascicle and tendon behavior is comparable between MG and SOL.
[Show abstract][Hide abstract] ABSTRACT: Findings from animal experiments are sometimes contradictory to the idea that the tendon structure is a simple elastic spring in series with muscle fibers, and suggest influence of muscle contraction on the tendon mechanical properties. The purpose of the present study was to investigate the influence of muscle contraction levels on the force-length relationship of the human Achilles tendon during lengthening of the triceps surae muscle-tendon unit. For seven subjects, ankle dorsiflexion was performed without (passive condition) and with contraction of plantar flexor muscles (eccentric conditions, at 3 contraction levels) on an isokinetic dynamometer. Deformation of the Achilles tendon during each trial was measured using ultrasonography. The Achilles tendon force corresponding to the tendon elongation of 10mm in the passive condition was significantly smaller than those in the eccentric conditions (p<0.05 or p<0.01). Within the eccentric conditions, the Achilles tendon force corresponding to the tendon elongation of 10mm was significantly greater in the maximal contraction level than those in submaximal eccentric conditions (p<0.05 or p<0.01). In addition, the tendon stiffness was greater in higher contraction levels (p<0.05 or p<0.01). Present results suggest that the human tendon structure is not a simple elastic spring in series with muscle fibers.
Journal of biomechanics 06/2011; 44(11):2168-71. · 2.66 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The present study aimed to clarify how the force-generating capability of quadriceps femoris (QF) is associated to its surface EMG activity during a body mass-based squat movement.
Isometric knee extension torque (KET) during maximal voluntary contraction and EMG activities of the rectus femoris and vastus lateralis muscles during a body mass-based squat movement were determined in 53 men and 48 women age 19-90 yr, including 18 frail elderly persons who used the long-term care insurance system. The rectified EMG signals during the squat movement were averaged and normalized as the relative value (%EMG(max)) to that during maximal voluntary contraction. The %EMG(max) values for rectus femoris and vastus lateralis were averaged and used as an index representing the level of muscular activities of QF during the squat movement (QF %EMG(max)).
QF %EMG(max) was nonlinearly related to KET relative to body mass (KET/BM). Linear piecewise continuous regression analysis showed that there was a breakpoint of 1.9 N·m·kg(-1) in the relationship between the two variables. In individuals with KET/BM less than 1.9 N·m·kg(-1), QF %EMG(max) rapidly increased as KET/BM decreased.
The current results indicate that the activity level of QF during a body mass-based squat movement is influenced by its force generation capability. For individuals with a KET/BM less than 1.9 N·m·kg(-1), body mass-based squat movement is considered to be a fairly high-intensity exercise. The breakpoint of 1.9 N·m·kg(-1) may be assumed to be a threshold level of knee extensor strength, which should be maintained for performing the activities of daily living without great difficulty.
Medicine and science in sports and exercise 05/2011; 43(12):2328-34. · 4.48 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The present study determined in vivo deformation of the entire Achilles tendon in the longitudinal and transverse directions during isometric plantar flexions. Twelve young women and men performed isometric plantar flexions at 0% (rest), 30%, and 60% of the maximal voluntary contraction (MVC) while a series of oblique longitudinal and cross-sectional magnetic resonance (MR) images of the Achilles tendon were taken. At the distal end of the soleus muscle belly, the Achilles tendon was divided into the aponeurotic (ATapo) and the tendinous (ATten) components. The length of each component was measured in the MR images. The widths of the Achilles tendon were determined at 10 regions along ATapo and at four regions along ATten. Longitudinal and transverse strains were calculated as changes in relative length and width compared with those at rest. The ATapo deformed in both longitudinal and transverse directions at 30%MVC and 60%MVC. There was no difference between the strains of the ATapo at 30%MVC and 60%MVC either in the longitudinal (1.1 and 1.6%) or transverse (5.0∼11.4 and 5.0∼13.9%) direction. The ATten was elongated longitudinally (3.3%) to a greater amount than ATapo, while narrowing transversely in the most distal region (-4.6%). The current results show that the magnitude and the direction of contraction-induced deformation of Achilles tendon are different for the proximal and distal components. This may be related to the different functions of Achilles tendon, i.e., force transmission or elastic energy storage during muscle contractions.
Journal of Applied Physiology 03/2011; 110(6):1615-21. · 3.48 Impact Factor