Muscle Echo Intensity Research Articles

Relationship between longitudinal changes in skeletal muscle characteristics over time and functional recovery during intensive rehabilitation of patients with subacute stroke

ABSTRACT Background Stroke is a disease that easily impairs skeletal muscle characteristics, resulting in low quantity, low quality, and poor strength. However, the recovery process of skeletal muscles in patients with stroke is not well established. Objectives We aimed to determine the longitudinal changes in skeletal muscle characteristics in patients with stroke during intensive rehabilitation and examine their relationship with functional recovery. Methods Eighty-five patients with stroke were prospectively recruited. We defined muscle quantity and quality as ultrasonographic muscle thickness and echo intensity, respectively, and muscle strength as knee extension strength. These skeletal muscle characteristics were compared at four time points: on admission, after 2 weeks, after 4 weeks, and at discharge. We also explored the relationship between changes in skeletal muscle characteristics and functional recovery. Results Non-paretic knee extension torque (F = 5.838, P = .001), paretic quadriceps thickness (F = 2.943, P = .039), and paretic tibialis anterior thickness (F = 4.654, P = .004) improved over time, and changes in the paretic side quadriceps thickness were significantly associated with recovery for balance ability (odds ratio, 1.05; 95% confidence interval, 1.00–1.09; P = .048). Conclusions The present study revealed that knee extension muscle strength on the non-paretic side and quadriceps and tibialis anterior thickness on the paretic side significantly improved over time and that changes in the paretic side quadriceps thickness were associated with the recovery of balance ability.

Effects of Transdermal Methylsulfonylmethane on Muscle Damage and Recovery Following Eccentric Exercise

PURPOSE:The present study aimed to investigate the effects of transdermal application of methylsulfonylmethane (MSM) on muscle damage and recovery following eccentric exercise in young men.METHODS: Eleven college-aged men without any cardiovascular or orthopedic disorders underwent two sessions consisting of a control session (CS) and an experimental session (ES) in a random order with at least 2 weeks of wash-out between the sessions. The participants performed 30 maximal eccentric exercises involving their non-dominant elbow flexors in each session. Circumference, muscle soreness, range of motion, maximal voluntary isometric contraction (MVIC), and muscular echo intensity (EI) were measured to evaluate the changes in the level of exercise-induced muscle damage (EIMD). All measurements were performed at 24, 48, 72, and 96 hours after exercise and also immediately before and after exercise.RESULTS:Transdermal application of MSM in ES attenuated muscle swelling and decreased MVIC after eccentric exercise when compared with CS. Muscle soreness and EI tended to increase less rapidly and decrease more rapidly in ES than in CS.CONCLUSIONS: Transdermal application of MSM may induce relatively positive effects on EIMD and recovery following eccentric exercise when compared with the treatment that has been widely used previously.

Ultrasound Imaging Analysis of the Lumbar Multifidus Muscle Echo Intensity: Intra-Rater and Inter-Rater Reliability of a Novice and an Experienced Rater

Background and Objectives: Ultrasound echo intensity (EI) of the lumbar multifidus muscle (LMM) could offer valuable insights regarding muscle quality in people with low back pain (LBP). However, whether the rater’s experience noticeably influences the reliability and precision of LMM EI measurements has not been established. The aims of this study were to investigate the intra-rater and inter-rater reliability of LMM EI measurements, and to compare the reliability and SEM between a novice and an experienced rater. Materials and Methods: Twenty athletes (10 females, 10 males) with a history of LBP were included in this study. Transverse ultrasound images of LMM were taken at L5 in prone. LMM EI measurements were obtained bilaterally by tracing the maximum ROI representing the LMM cross-sectional area (CSA), avoiding the inclusion of bone or surrounding fascia. All measurements were performed by two novice raters and an experienced researcher. Each measurement was acquired by each rater three times for each side on three different images, and the average was used in the analyses. Raters were blinded to each other’s measurements and the participant’s clinical information. Intra-class correlation coefficients (ICCs) were obtained to assess the intra-rater and inter-rater reliability. Results: The intra-rater ICC values for the LMM measurements for the experienced rater were excellent (ICC all > 0.997). The inter-rater reliability ICC values showed moderate to excellent reliability (0.614 to 0.994) and agreement between the novice raters and the experienced rater, except for Novice 1 for the right LMM, which revealed lower ICCs and a wider 95% CI. Intra-rater and inter-rater reliability results were similar when separately looking at the right and left side of the muscle and participant gender. Conclusions: Our findings support the clinical use of ultrasound imaging for the assessment of LMM EI in individuals with LBP.

Enhanced echo intensity and a higher extracellular water-to-intracellular water ratio are helpful clinical signs for detecting muscle degeneration in patients with knee osteoarthritis

Enhanced muscle echo intensity (EI) with ultrasound imaging and a higher extracellular water-to-intracellular water (ECW/ICW) ratio with segmental-bioelectrical impedance spectroscopy (S-BIS) represent muscle quality loss. This study aimed to clarify quadriceps muscle degeneration characteristics, focusing on muscle quality changes in patients with knee osteoarthritis (OA). Forty-one women with knee OA (mean age, 71.4±6.0 years) and 27 healthy women (mean age, 75.6±4.9 years) participated. Ultrasonography was used to evaluate the muscle thickness (MT) and the EI of each quadriceps compartment. The ECW/ICW ratio was obtained by S-BIS. MT, EI, and ECW/ICW ratio differences between the two groups were tested using univariate analysis of variance, adjusting for age and body mass index. Logistic regression analyses were performed with the group as the dependent variable, and the MT and EI of the vastus medialis (VM) and the ECW/ICW ratio as independent variables. Patients with knee OA had a significant decrease in VM MT, enhanced VM, and vastus intermedius EIs and a higher ECW/ICW ratio compared with healthy participants. Logistic regression analysis showed that the VM EI (odds ratio [OR], 1.19; 95% confidence interval [CI], 1.06-1.35) and the ECW/ICW ratio were independently associated with knee OA (OR, 1.19; 95% CI, 1.00-1.42). VM EI and the ECW/ICW ratio, rather than VM MT, characterised quadriceps muscle degeneration in patients with knee OA. Therefore, enhanced EI and a higher ECW/ICW ratio are helpful clinical signs for detecting muscle degeneration in patients with knee OA. Key Points •Echo intensity (EI) of the vastus medialis and the extracellular-to-intracellular water (ECW/ICW) ratio significantly increased in patients with knee osteoarthritis OA). •Enhanced EI and a higher ECW/ICW ratio are useful clinical signs for detecting muscle degeneration in patients with knee OA.

The time course of recovery of indirect markers of exercise-induced muscle damage induced by multi- and single-joint exercises

Strength training is performed using multi-joint (MJ) or single-joint (SJ) exercises; however, it is not clear whether different time of recovery is necessary between the two types of exercise. The aim of the present study was to compare the time course of recovery of indirect markers of exercise-induced muscle damage (EIMD) in the elbow flexors after performing MJ and SJ exercises. Twenty-four (n = 24) untrained men were randomized in to the MJ (n = 12) or SJ group (n = 12). Exercise protocol to induce muscle damage consisted of four sets of ten repetitions at 80% of one repetition maximum (1RM) in front pull-down (MJ exercise) or biceps curl (SJ exercise). Maximal voluntary isometric contraction, muscle soreness during elbow extension, ultrasound imaging (muscle thickness and echo intensity) and creatine kinase (CK) were measured before and up to 96 h after exercise. Significant effect of time (p < 0.05) at all times after exercise was observed for isometric strength, muscle soreness, muscle thickness and at 48, 72 and 96 h for echo intensity, with no time × group interaction. However, significant time × group interaction (p = 0.03) was observed only for CK activity at 96 h (MJ = 3348 ± 2911 IU/l vs. SJ = 890 ± 1426 IU/l; p < 0.05). In addition, there was a significant increase in CK after MJ at 48 h, 72 h and 96 h after exercise (p < 0.05), while SJ increased only at 48 h after exercise. Despite a dissimilar time course of CK response, MJ and SJ exercises induced a similar recovery pattern for muscle strength, thickness, echo intensity and soreness.

Effect of isometric exercises on the masseter muscle in older adults with missing dentition: a randomized controlled trial

Maintaining oral function in older individuals with missing teeth is important for leading a healthy and independent life. This study aimed to evaluate whether simple isometric exercises can maintain and improve the oral function [maximum occlusal force (MOF) and masticatory ability (MA)] and the masticatory muscle properties [masseter muscle thickness (MMT) and echo intensity (MMEI)] in older adults during the maintenance phase of removable prosthetic treatment. Participants were randomly categorized into the intervention and control groups. The mouthpieces were distributed, and participants were instructed to use them for exercising. The intervention group was instructed to perform maximum clenching for 10 s, whereas the control group was instructed to tap the teeth at an arbitrary speed for 10 s. Both were repeated five times at an interval of 5 s between each activity and twice daily for 4 weeks. The outcomes were measured after a month of exercise. The intervention group showed a significant improvement in the MOF, MMT during contraction, MMT at rest and MMEI during contraction. There were no significant differences in the MA and MMEI at rest. In the control group, no improvement was observed in any of the parameters. When the isometric exercises were performed using a mouthpiece, there was an improvement in the oral function and masseter muscle properties in older individuals with Eichner B status who used dentures.

Quantification of immobilization-induced changes in human calf muscle using speed-of-sound ultrasound: An observational pilot study.

Short-term immobilization leads to fatty muscular degeneration, which is associated with various negative health effects. Based on literature showing very high correlations between MRI Dixon fat fraction and Speed-of-Sound (SoS), we hypothesized that we can detect short-term-immobilization-induced differences in SoS.Both calves of 10 patients with a calf cast on one side for a mean duration of 41 ± 26 days were examined in relaxed position using a standard ultrasound machine. Calf perimeters were measured for both sides. A flat Plexiglas-reflector, placed vertically on the opposite side of the probe with the calf in-between, was used as a timing reference for SoS. SoS was both manually annotated by two readers and assessed by an automatic annotation algorithm. The thickness values of the subcutaneous fat and muscle layers were manually read from the B-mode images. Differences between the cast and non-cast calves were calculated with a paired t test. Correlation analysis of SoS and calf perimeter was performed using Pearson's correlation coefficient.Paired t test showed significant differences between the cast and non-cast side for both SoS (P < .01) and leg perimeter (P < .001). SoS was reduced with the number of days after cast installment (r = −0.553, P = .097). No significant differences were found for muscle layer thickness, subcutaneous fat layer thickness, mean fat echo intensity, or mean muscle echo intensity.Short-term-immobilization led to a significant reduction in SoS in the cast calf compared to the healthy calf, indicating a potential role of SoS as a biomarker in detecting immobilization-induced fatty muscular degeneration not visible on B-mode ultrasound.

Measuring muscle quality: associations between echo intensity and normalized strength and power

Objective. Muscle quality has received considerable attention within the literature due to its influence on health and performance. However, it has been assessed by various measures (e.g. ultrasound imaging, normalized strength), contributing to a lack of a consensus definition. The purpose of this study was to investigate the association between common muscle quality measures: vastus lateralis echo intensity (EI) and peak torque (PT) and power (PP) normalized to thigh lean mass (TLM) and thigh fat mass (TFM). Approach. Participants’ (n = 39; age = 32.7 ± 8.2 years; %BF = 24.1% ±8.1%) whole body and leg composition was assessed via dual-energy x-ray absorptiometry and custom thigh analyses. Subcutaneous fat-corrected muscle EI was assessed via ultrasonography. Maximal PT and PP of the dominant leg extensors were examined on a calibrated dynamometer and were normalized to both TLM and TFM, respectively. Pearson product-moment correlations were used to examine the associations between EI and PT/TLM, PT/TFM, PP/TLM, and PP/TFM. Main results. Greater muscle EI was significantly related with lower PT/TFM and PP/TFM (r = −0.74 to −0.70, P < 0.001), but unrelated to PT/TLM or PP/TLM (P ≥ 0.205). Significance. These findings suggest that ultrasound imaging (muscle EI) and normalized strength and power may not be used interchangeably to define muscle quality, and muscle EI may be more sensitive to the adiposity of the limb than TLM. Future research should consider using separate and consistent definitions when referring to imaging-derived or normalized strength and power values of muscle quality.

Is skeletal muscle echo intensity more indicative of voluntary or involuntary strength in young women?

Is skeletal muscle echo intensity more indicative of voluntary or involuntary strength in young women?

Increased muscle echointensity correlates with clinical disability and muscle strength in chronic inflammatory demyelinating polyneuropathy.

We evaluated muscle echointensity as a marker for secondary axonal damage in patients with chronic inflammatory demyelinating polyneuropathy (CIDP) using ultrasonography. Findings were correlated with clinical disability and muscular strength. Eighty patients with CIDP (40 with typical and 40 with atypical CIDP) were examined clinically, including assessment of Medical Research Council (MRC) sum score and Inflammatory Neuropathy Cause and Treatment Overall Disability Sum Score (INCAT-ODSS). Echointensity in eight proximal and distal muscles of the arms and legs was evaluated by muscle ultrasonography using the Heckmatt scale. Alterations of echointensity occurred most frequently in the distal leg muscles, with a median (range) Heckmatt score of 1.5 (1-4). There were no differences between typical and atypical CIDP patients with regard to Heckmatt score. Alterations of echointensity correlated to disability and muscle strength. The arm score of the INCAT-ODSS correlated to Heckmatt score for the distal arm muscles (r=0.23, p=0.046) and the leg score of the INCAT-ODSS correlated to Heckmatt scores for the proximal (r=0.34, p=0.002) and distal leg muscles (r=0.33, p=0.004). MRC sum score, as well as individual MRC scores for arm and leg muscles, correlated to Heckmatt scores of the corresponding muscle groups (r=-0.25, p=0.02 for MRC sum score). Increased muscle echointensity, reflecting fibrosis and fatty infiltration due to secondary axonal damage, correlated to muscular strength and disability in a large cohort of CIDP patients. Alterations of echointensity occur in both typical and atypical CIDP patients and are pronounced in the distal leg muscles.

Relationship between muscle echo intensity on ultrasound and isokinetic strength of the three superficial quadriceps femoris muscles in healthy young adults.

[Purpose] The purpose of this study was to clarify the relationship between muscle echo intensity measured with ultrasound and the isokinetic strength of each of the three superficial quadriceps femoris muscles in healthy young adults. [Participants and Methods] We measured the echo intensity of the three superficial muscles of the quadriceps femoris in 25 healthy adults (10 males and 15 females; mean age, 22.3 years) using ultrasound. Moreover, we obtained the maximum force during isokinetic knee extension at 60°/s using an isokinetic dynamometer. [Results] In males and females, a significant negative correlation between echo intensity and muscle strength was found in the VM (r=−0.65 and r=−0.63, respectively). [Conclusion] In both males and females, only the muscle echo intensity of the vastus medialis was found to have a negative correlation with the maximum force during isokinetic knee extension at 60°/s. Our data lay the foundation for simplifying and rationally performing the measurement of muscle echo intensity of the quadriceps femoris. And it would therefore be sufficient to only measure the VM to clarify a relationship between EI and maximum isokinetic force in the quadriceps.

Effects of physical activity in muscle ultrasound evaluation of an older adult population – a pilot study

INTRODUCTION: Population aging has become an increasing challenge in society and inactive aging populations are especially challenging. OBJECTIVE: The main aim of this study is to conduct ultrasound evaluation of the effects of an intervention program on muscle architecture in older adults. METHODS: A total of thirty-four individuals of both sexes aged over 60 years were divided into two groups as follows: an intervention group (n = 18), who took part in a physical activity program for 8 weeks, three sessions per week, lasting approximately 20 min on each occasion, and a control group, whose members were encouraged to maintain their usual daily routines (outdoor aerobic exercise) (n = 16). Only six of the 18 participants from the intervention group were available for a second evaluation session. All the participants were submitted to bilateral quadriceps muscle ultrasound evaluations; thickness and echo-intensity of muscles were analyzed. RESULTS: Muscle thickness showed a significant negative correlation with age and echo-intensity showed a significant positive correlation with age. Echo-intensity showed a significant negative correlation with muscle thickness. Comparing the groups at the baseline evaluation, there were no significant differences between them (p &lt; 0.05) for either measurement. CONCLUSIONS: We can highlight three points regarding post-intervention status in the intervention group: 1. There were significant differences in echo-intensity. It is therefore essential to establish early strategies to promote active aging, thus preventing dependence and inactivity in the older adult population; 2. Ultrasound is a good method for evaluating the musculoskeletal system and its changes in response to aging and physical activities; 3 Physical activities are important to maintain the muscles healthy and the older adult population independent.

Unique Characteristics of Quadriceps Muscle Morphology and Function in Older Tennis Players.

We investigated the quadriceps muscle size and quantitative characteristics in older tennis players. Thirty-eight senior tennis players (70.8 ± 5.3years) and 38 controls (71.6 ± 5.1years) were included. To measure the muscle size and quality, we measured muscle thickness in the rectus femoris (RF), vastus lateralis, and vastus intermedius, and muscle echo intensity in the RF and vastus lateralis using B-mode transverse ultrasound, respectively. We measured knee extension peak torque for muscle function. Muscle thickness in the RF, vastus lateralis, and vastus intermedius were significantly larger in tennis players than in controls. Tennis players had a lower echo intensity in RF and a higher knee extension peak torque compared to controls. Stepwise multiple linear regression analysis implied that echo intensity and muscle thickness were predictors of knee extension peak torque. Higher muscle quality contributes to a higher knee extension peak torque in tennis players. Playing tennis may prevent age-related muscle atrophy and maintain muscle quality in older individuals.

Effect of performing daily activities while standing on the quantity and quality of the thigh muscles in adults with severe cerebral palsy: a cross-sectional study.

[Purpose] To observe the effect of daily standing, as indicated by gross motor function, on the quantity and quality of the thigh muscles in adults with severe cerebral palsy and to obtain data to determine an appropriate intervention that will improve their quality of life. [Participants and Methods] Thirty-three adults with severe cerebral palsy participated in the study. We assessed the gross motor function using the GMFM-66-IS. We then evaluated the quadriceps muscle thickness and the rectus femoris muscle echo intensity using ultrasonography. We divided the participants into the standing and non-standing groups and then examined the correlations of the GMFM-66-IS score to muscle thickness and echo intensity. We calculated the difference in mean muscle thickness and echo intensity between the two groups using an independent t-test. [Results] Significant positive correlations were found between the GMFM-66-IS score and muscle thickness and echo intensity. In the group-specific analysis, no significant correlation was found between echo intensity and the GMFM-66-IS score in either group. Muscle thickness and echo intensity were greater in the participants of the standing group. [Conclusion] Daily standing, as indicated by gross motor function, affected muscle thickness and echo intensity. Quantitative and qualitative data might need to be evaluated when assessing the muscles of adults with severe cerebral palsy using ultrasonography.

The utility of the ultrasonographic assessment of the lower leg muscles to evaluate sarcopenia and muscle quality in older adults

AbstractBackgroundThe assessment of muscle quality is expected to help predict the prognosis of sarcopenia and examine the response to intervention. Ultrasonography can be used to evaluate approaches for determining muscle quantity and quality. We focused on the lower leg muscles and examined the relationship between the ultrasonographic assessments and the components of sarcopenia and muscle quality by comparing them with those of the quadriceps muscle (QFM).Methods47 physically healthy older participants aged 78.3 ± 6.0 years (53% male) were enrolled in this cross‐sectional study. Muscle thickness (MT) and echo intensity (EI) of the lower leg muscles and QFM were assessed with ultrasonography. Muscle mass, grip strength, and gait speed, and lower leg muscle strength were measured. Muscle quality was calculated using a formula: leg muscle strength/leg muscle mass.ResultsThe MTs and EIs of the tibialis anterior muscle (TA) and QFM were significantly associated with grip and leg strength. We observed a significant correlation in the MTs and EIs of the lower leg muscles and QFM. The EIs of the lower leg muscles and QFM showed significant negative correlations with muscle quality. In the multiple linear regression model, the EI of the TA and QFM was extracted as an independent factor of muscle quality (TA: β = −0.35, p = 0.0358; QFM: β = −0.30, p = 0.0327).ConclusionsThe ultrasonographic assessments of the lower leg muscles, especially the TA, were associated with sarcopenia components and muscle quality equal to or greater than those of the QFM.

Age-Related Change in Muscle Characteristics and Resistance Training for Older Adults.

In older adults, muscle weakness contributes greatly to functional restrictions on daily living activities, increased risk of falls, and adverse physiological changes. It has been suggested that not only muscle mass but also muscular infiltration of noncontractile elements may influence muscular performance such as strength and rapid force production. It is proved that resistance training may provoke substantial increases in muscle size even if it is performed at low intensities in older individuals. Also, recent studies have demonstrated the effectiveness of resistance training on muscle quality such as muscular infiltration of noncontractile elements for older people. This review shows the age-related changes in muscle mass and muscle quality, which were measured by muscle echo intensity on ultrasound images, and low-intensity resistance training effects on muscle volume and muscle quality.

Fast-Velocity Eccentric Cycling Exercise Causes Greater Muscle Damage Than Slow Eccentric Cycling.

This study aims to investigate muscle damage occurring in the early and recovery phases after fast-velocity and slow-velocity eccentric cycling. Eleven untrained men (age, 20.0 ± 1.7 years; height, 171.3 ± 6.8 cm; weight, 61.8 ± 7.7 kg; and %body fat, 13.2 ± 2.9%) performed slow-velocity maximal isokinetic eccentric cycling (slow-velocity; 30°/s) with one leg and fast-velocity (fast-velocity; 210°/s) isokinetic eccentric cycling with the other leg. Changes in maximal voluntary isokinetic concentric contraction (MVCC) torque at velocities of 30 and 210°/s, range of motion (ROM), and muscle soreness were assessed by pressure using a digital muscle stiffness instrument; thigh circumference, muscle echo intensity, and muscle stiffness were assessed before exercise, and immediately after exercise, 1 day, and 4 days after exercise. Comparing with the results obtained for slow-velocity cycling (post: 215.9 ± 32.3 Nm, day 1: 192.9 ± 47.4 Nm, day 4: 184.3 ± 47.2 Nm) and before exercise, MVCC after fast-velocity cycling significantly decreased at immediately (160.4 ± 43.5 Nm), 1 day (143.6 ± 54.1 Nm), and 4 days (150.1 ± 44.5 Nm) after exercise (p < 0.05). Significant increase in muscle soreness for vastus lateralis was observed after fast-velocity cycling (41.2 ± 16.9 mm) compared with slow-velocity cycling (23.7 ± 12.2 mm) 4 days after exercise (p < 0.05). However, no significant difference in muscle soreness was observed for rectus femoris and vastus medialis at any time points after exercise. In addition, no significant differences were observed in the ROM, thigh circumference, muscle echo intensity, and muscle stiffness. In conclusion, fast-velocity eccentric cycling causes a decrease in muscle strength and an increase in soreness as compared to slow-velocity eccentric cycling.

Correlation between Quantitative Ultrasonography on Small Muscles of the Foot in Diabetic Peripheral Neuropathy and Electrodiagnostic Study

Abstract Background: DPN is worthy of study as it's a leading cause for disability due to foot ulceration and amputation, gait disturbance, and fall-related injury. That makes the early diagnosis of DPN invaluable. Aim of Study: To assess the correlation between quantita-tive muscle ultrasonography (US) findings and electrodiag-nostic study results in patients with diabetic peripheral neu-ropathy (DPN). The clinical importance of quantitative muscle US in DPN was also evaluated. Patients and Methods: Twenty-five patients with DPN and 25 healthy volunteers were recruited. All control and DPN subjects underwent a bilateral peroneal and tibial motor nerve conduction study (NCS) and quantitative muscle US. Ultrasound images of the abductor haullicis (AH) muscle and the extensor digitorum brevis (EDB) muscle were obtained to measure thickness, muscle cross-sectional area (CSA) and echo intensity (EI). Differences in muscle thickness, CSA, and EI between the control and DPN patients' groups were analyzed. Relationships between electrodiagnostic study results and quantitative US parameters were evaluated. Results: A close relations observed between US findings (EI, CSA and muscle thickness) and NCS neuro-physiological findings indicating that we can use both examinations to detect muscle atrophy, and that US can expect changes in neurophys-iologic parameters in diabetics (muscle thickness and CSA were decreased, and EI was increased). The findings in the peroneal nerve were more significant than those in tibial nerve. Comparison between cases and controls regarding quantitative muscle US revealed a statistically insignificant difference in most the parameters, but some parameters showed statistically significant difference. However, there was a clinical importance of the US examination despite the insig-nificant statistics. Conclusion: These findings suggest that quantitative muscle ultrasound may be useful for detecting muscle changes in DPN. Further studies are needed to confirm the findings in larger groups of diabetic patients and to evaluate peripheral muscles by using quantitative muscle US in other types of neuropathy and neuromuscular diseases.

Cardiac Autonomic Responses and Adaptation to Repeated Bouts of Eccentric Exercise

PURPOSE:The current study was performed to examine the effects of acute eccentric resistance exercise (ERE) on heart rate variability (HRV) and to determine whether cardiac autonomic regulation adapts to the repeated bout effect.METHODS: Isokinetic eccentric exercise consisted of five sets of six maximal contractions of the knee extensor with an angular velocity of 90°/second. College-aged men (n=11) underwent two sessions of ERE with a 3-week interval. Muscle damage indicators such as the range of motion (ROM) and muscle echo intensity (EI) were measured. The post-exercise cardiac autonomic response was assessed by spectral analysis of HRV. Low frequency (LF) and high frequency (HF) bands, the normalized unit (nu) for each band power, and the LF-to-HF (LF/HF) ratio were determined. All variables were recorded at 24, 48, 72, and 96 hours post-exercise as well as before and immediately after ERE.RESULTS:The EI and ROM of the rectus femoris changed significantly after the maximal ERE. There was a significant interaction effect between the time and bout for EI. Significant changes in LF and HF nu were observed at 72 (1st ERE) and 96 hours (2nd ERE) after each ERE. The LF/HF ratio was also significantly increased at 24 (1st ERE) and 72 hours (2nd ERE) after each ERE. However, no interaction effects on changes in the HRV indices were observed.CONCLUSIONS: The present study suggests that acute ERE leads to cardiac autonomic imbalance for a sustained period and that repeated bouts of ERE cannot alleviate cardiac autonomic responses to exercise.

Site-specific skeletal muscle echo intensity and thickness differences in subcutaneous adipose tissue matched older and younger adults.

Age-related deterioration of muscle mass does not occur uniformly across the body. However, there is limited knowledge on the uniformity of age-related muscle composition changes across the body. Our primary objective was to evaluate muscle composition differences between younger and older adults across multiple muscle groups. We re-analysed data from a previously published cohort to evaluate differences in ultrasound muscle composition (echo intensity) between younger (<45years) and older (>60years) adults, when matched for adipose tissue mass at the anterior upper arm, anterior upper leg and abdominal muscles. Analysis of echo intensity is confounded by subcutaneous adipose tissue (SAT) thickness overlaying the muscle; we accounted for these effects by matching older and younger adults (1:1), stratified by sex, for absolute SAT thickness at each landmark. From 96 adults (n=females), 58 (n=34) were SAT matched at the anterior upper arm, 52 (n=30) at the anterior upper leg and 60 (n=30) at the abdominal region; thus, there were no age group differences in SAT thickness at each landmark. In comparison with younger adults, older adults presented with greater echo intensity at the anterior upper leg (females:40.3±6.8 vs. 52.4±7.6; males:35.7±8.0 vs. 54.3±9.8, p<.01) and abdominal (females:38.7±27.6 vs. 73.4±31.0; males:18.7±15.2 vs. 60.9±23.4, p<.01) muscles, but not anterior upper arm muscles (females:47.0±6.5 vs. 53.2±13.1; males:43.4±8.9 vs. 48.9±10.1, p=.18). Distinct age-related differences in trunk and lower limb muscle composition were evident compared to upper limb muscles; highlighting the importance of quantifying specific muscle groups when evaluating age-associated muscle characteristics.