Children with Low Handgrip Strength: A Narrative Review of Possible Exercise Strategies to Improve Its Development.

BACKGROUND: Handgrip strength (HGS) is a predictor of health in both children and adults. Evidence suggests that without a possible strategy, children with low HGS may become adults with low HGS. However, little is known about what strategies are effective for children with low HGS to achieve a higher baseline level in adulthood. This narrative review aimed to investigate whether physical exercise interventions could improve HGS in children. METHODS: The relevant databases/search engine was searched using keywords related to the main topics discussed throughout this review. RESULTS: Our findings suggest that it may not be possible to improve HGS over that observed from normal development with physical education or traditional resistance-training programs. However, if the training program includes exercises that directly stimulate the forearm/hand muscle groups to grip, it may be possible to obtain changes in HGS that exceed the changes due to normal developmental growth. CONCLUSION: Although there are associations between HGS and markers of health, no research could be identified that examined whether increasing HGS would lead to an improvement in health. If an increase in HGS really does represent an improvement in long-term health, then gripping exercise may need to be included into physical activity programs during the growth/development phase.

The Fat Fraction Percentage of White Adipose Tissue at various Ages in Humans: An Updated Review.

We recently reported the fat fraction percentage of white adipose tissue in adolescents and adults measured by the water-fat separation method, but there was limited discussion about the change in adipose tissue fat fraction with growth. The purpose of this updated review was to examine the fat content of white (subcutaneous) adipose tissue during the process from birth to adulthood by adding the latest available data. A relevant database was searched through November 2020. Nineteen studies were included. We found that calculated mean values of fat fraction percentage in white adipose tissue were 72.2% in neonates, 87.2% in children, and 87.4% in adults. In contrast, fat fraction percentage of truncal white adipose tissue in the fetuses was from 10% to 24% (29 and 34 wk of gestational age, respectively). Our results suggest that the fat fraction percentage of white adipose tissue may not undergo large changes during the process from birth to adulthood (neonates = 72.2%, children = 87.2%, adults = 87.4%), which was different from the results of a study utilizing a biopsy. The mean value and range of fat fraction percentages for children over 7 years old were especially similar to adults. Further, the fat fraction percentage for neonates was relatively close to the results of children and adults. At the moment, the characteristics of the changes in fat fraction percentage of adipose tissue from birth to preschool children are unclear and future research is needed to clarify this issue.

The mysterious values of adipose tissue density and fat content in infants: MRI-measured body composition studies.

Adipose tissue is a type of connective tissue composed of closely packed adipocytes with collagenous and elastic fibers. These adipocytes store triglycerides at a high percentage and the estimate of this amount is important for the calculation of body fat mass. For example, magnetic resonance imaging (MRI) measures adipose tissue volume, but adipose tissue density (fat content percentage and density) is required to calculate fat mass. However, in previously published studies, the conversion factor for white adipose tissue density varies from study to study. This paper aimed to investigate the different adipose tissue densities used as conversion factors to clarify differences between studies. Furthermore, we include a new proposal for adipose tissue density and fat content of infants based on the results of recent water-fat MRI studies. IMPACT: Magnetic resonance imaging (MRI) is one of the methods used to measure body composition in infants and the inherent density of tissue/organs is needed in order to calculate the mass of target organs and tissues. The conversion factor used for white adipose tissue density currently varies from study to study. This article includes a new recommendation for the adipose tissue density and fat content of infants based on the results of recent water-fat MRI studies.

Acute Muscular Responses to Practical Low-Load Blood Flow Restriction Exercise Versus Traditional Low-Load Blood Flow Restriction and High-/Low-Load Exercise.

CONTEXT: Blood flow restriction (BFR) increases muscle size and strength when combined with low loads, but various methods are used to produce this stimulus. It is unclear how using elastic knee wraps can impact acute muscular responses compared with using nylon cuffs, where the pressure can be standardized. OBJECTIVE: Investigate how elastic knee wraps compare with nylon cuffs and high-load (HL)/low-load (LL) resistance exercise. DESIGN: A randomized cross-over experimental design using 6 conditions combined with unilateral knee extension. SETTING: Human Performance Laboratory. PARTICIPANTS: A total of 9 healthy participants (males = 7 and females = 2) and had an average age of 22 (4) years. INTERVENTION: LL (30% of 1-repetition maximum [1-RM]), HL (70% 1-RM), BFR at 40% of arterial occlusion pressure (BFR-LOW), BFR at 80% of arterial occlusion pressure (BFR-HIGH), elastic knee wraps stretched by 2 in (PRACTICAL-LOW), and elastic knee wraps stretched to a new length equivalent to 85% of thigh circumference (PRACTICAL-HIGH). BFR and practical conditions used 30% 1-RM. MAIN OUTCOME MEASURES: Muscle thickness, maximum voluntary isometric contraction, and electromyography amplitude. Bayesian statistics evaluated differences in changes between conditions using the Bayes factor (BF10), and median and 95% credible intervals were reported from the posterior distribution. RESULTS: Total repetitions completed were greater for BFR-LOW versus PRACTICAL-HIGH (BF10 = 3.2, 48.6 vs 44 repetitions) and greater for PRACTICAL-LOW versus BFR-HIGH (BF10 = 717, 51.8 vs 36.3 repetitions). Greater decreases in changes in maximum voluntary isometric contraction were found in PRACTICAL-HIGH versus HL (BF10 = 1035, ∼103 N) and LL (BF10 = 45, ∼66 N). No differences in changes in muscle thickness were found between LL versus PRACTICAL-LOW/PRACTICAL-HIGH conditions (BF10 = 0.32). Greater changes in electromyography amplitude were also found for BFR-LOW versus PRACTICAL-HIGH condition (BF10 = 6.13, ∼12%), but no differences were noted between the other BFR conditions. CONCLUSIONS: Overall, elastic knee wraps produce a more fatiguing stimulus than LL or HL conditions and might be used as an alternative to pneumatic cuffs that are traditionally used for BFR exercise.

Body fat percentage assessment by ultrasound subcutaneous fat thickness measurements in middle-aged and older adults.

BACKGROUND & AIMS: B-mode ultrasound accurately measures both muscle mass, body density and percent body fat (% BF) in younger adults, but how well it can estimate % BF in middle-aged and older adults using DXA-derived %BF as the criterion is unclear. We sought to develop % BF prediction equations for middle-aged and older adults using ultrasound subcutaneous fat thickness (SFT). METHODS: A cross-sectional study of Japanese adults (n = 414, 50-79 years) where 276 subjects were randomly assigned to a model development group and the other 138 subjects were assigned to a cross-validation group. B-mode ultrasound measured SFT at nine sites. Dual energy X-ray absorptiometry (DXA) measured % BF, arm fat mass (FM) and leg FM. Stepwise multiple linear regression developed prediction equations from anthropometric data (body mass, height, waist and hip circumference) and ultrasound SFT sites. Bland-Altman plots assessed validity of the prediction equations to measure % BF in the cross-validation group. RESULTS: The best prediction equation for % BF was the following: [% BF = 15.709 + (1.753*anterior trunk SFT) + (5.626*Sex) + (3.635*posterior upper arm SFT) - (4.428*anterior lower leg SFT) - (0.170*height) + (0.264*waist) + (anterior thigh SFT*2.241); r2 = 0.809, standard error of the estimate (SEE) = 3.3 kg]. Arm FM and leg FM prediction equations had r2 values ranging from 0.690 to 0.812 and SEEs of 0.29 and 0.75 kg. A small mean bias was noted for estimating % BF (-0.14%), but large limits of agreement were found (-8.0-7.7%) and systematic error was noted in all of the equations (r = 0.275 to 0.515, p < 0.05). CONCLUSIONS: Despite high r2 values and a small mean bias found between predicted and DXA % BF, wide limits of agreement were found with some systematic error present. Therefore, these prediction equations for middle-aged and older adults may not be sufficiently accurate to use in a clinical setting.

The impact of DXA-derived fat-free adipose tissue on the prevalence of low muscle mass in older adults.

BACKGROUND/OBJECTIVES: To investigate the impact of eliminating fat-free adipose tissue (aFFAT) on the prevalence of low muscle mass in older adults. SUBJECTS/METHODS: Three hundred and forty-three (153 men and 190 women) well-functioning Japanese older adults (aged 65-79) had their appendicular lean mass (aLM) and appendicular fat mass (aFM) measured using dual-energy X-ray absorptiometry (DXA). aFFAT was then estimated from DXA-derived aFM (aFM = (FM/0.15)*0.85). Both traditional cutoffs and those corrected for aFFAT were used for diagnosing low muscle mass. RESULTS: With traditional cutoff values, the prevalence of low muscle mass using the unadjusted aLM index was 20.1%. After adjusting the aLM index for aFFAT, the prevalence increased to 49.0% (p < 0.001). However, when the cutoff values were also adjusted for aFFAT, the prevalence of low muscle mass only increased to 23.0% (p < 0.001). Further, ~5% of the participants (7 men and 8 women) were newly classified as having low muscle mass after correction for aFFAT. However, several women (n = 5) were not classified as having low muscle mass using the corrected cutoff value, although they would have been when using the non-corrected cutoff. CONCLUSIONS: Adjusting for the effect of aFFAT on DXA-derived aLM significantly increases the prevalence of low muscle mass in older adults. For clinical research and practice, the influence of aFFAT on DXA-derived aLM may need to be taken into consideration when diagnosing low muscle mass.

The Bigger the Hand, the Bigger the Difference? Implications for Testing Strength With 2 Popular Handgrip Dynamometers.

CONTEXT: Studies developed the frail elderly handgrip strength (HGS) diagnostic criteria using multiple types of handgrip dynamometers. If different handgrip dynamometers report different values, then this would have the potential to misclassify people into the wrong diagnostic category. OBJECTIVE: To examine the characteristics of HGS measured by 2 standard handgrip dynamometers and to investigate the influence of hand size on HGS. SETTING: University research laboratory. PARTICIPANTS: A total of 87 young and middle-aged adults between the ages of 20 and 60 years participated in this study. MAIN OUTCOME MEASURES: Standard methods of HGS measurements were used for hydraulic and Smedley spring-type dynamometers, although the participants were instructed to maintain an upright standing position in both tests. RESULTS: Test-retest reliability of hydraulic and Smedley dynamometers provided comparable results to that observed with previous studies. However, the difference in HGS between the 2 dynamometers (Hydraulic-Smedley difference) was positively associated (r = .670, P < .001) with the mean of the 2 dynamometers. The participants who had relatively low HGS (at least <35 kg) produced similar HGS values when the 2 dynamometers were compared, whereas persons who had relatively higher HGS (at least >45 kg) produced greater strength values with the hydraulic compared with the Smedley. The hand and palm lengths were weakly correlated (r = .349 and r = .358, respectively, both Ps < .001) with the difference in HGS between the 2 dynamometers. CONCLUSIONS: Test-retest reliability of hydraulic and Smedley dynamometers provides comparable results to previous studies. However, the difference in HGS between the 2 dynamometers was positively associated with the mean of the 2 dynamometers. This Hydraulic-Smedley difference would not affect persons who have relatively low HGS (at least <35 kg), while when HGS is relatively high, the comparison between dynamometers should be done with caution.

Fat-Free Adipose Tissue Mass: Impact on Peak Oxygen Uptake (VO2peak) in Adolescents with and without Obesity.

Fat-free body mass (FFM) is a surrogate for skeletal muscle mass and is often used for the normalization of several physiological variables (e.g., oxygen uptake). However, FFM includes non-skeletal muscle components such as the fat-free component of adipose tissue fat cells. As the amount of adipose tissue mass increases, the FFM will also increase and be included in the measurement of FFM. Therefore, FFM may not be an appropriate indicator of muscle mass when targeting individuals with a large amount of body fat. This review aimed (1) to examine the fat-free adipose tissue (FFAT) in adolescents with and without obesity and (2) to investigate the impact of FFAT on peak oxygen uptake (VO2peak) by comparing VO2peak expressed relative to FFM and FFM minus FFAT between adolescents with and without obesity. Calculated FFAT was threefold higher in adolescents with obesity compared to those without obesity (mean ± SD; 6.94 ± 1.40 vs. 2.22 ± 0.58 kg). The VO2peak expressed relative to FFM-FFAT was similar between the two groups (56.5 ± 6.7 vs. 57.4 ± 8.9 ml min-1 kg-1 FFM-FFAT, respectively). On the other hand, VO2peak expressed relative to FFM was approximately 8% different between groups. When normalizing VO2peak by FFM, eliminating the FFAT component from FFM may be needed, especially when comparing groups with different body fat mass.

Validity of wrist-worn consumer products to measure heart rate and energy expenditure.

INTRODUCTION: The ability to monitor physical activity throughout the day and during various activities continues to improve with the development of wrist-worn monitors. However, the accuracy of wrist-worn monitors to measure both heart rate and energy expenditure during physical activity is still unclear. The purpose of this study was to determine the accuracy of several popular wrist-worn monitors at measuring heart rate and energy expenditure. METHODS: Participants wore the TomTom Cardio, Microsoft Band and Fitbit Surge on randomly assigned locations on each wrist. The maximum number of monitors per wrist was two. The criteria used for heart rate and energy expenditure were a three-lead electrocardiogram and indirect calorimetry using a metabolic cart. Participants exercised on a treadmill at 3.2, 4.8, 6.4, 8 and 9.7 km/h for 3 minutes at each speed, with no rest between speeds. Heart rate and energy expenditure were manually recorded every minute throughout the protocol. RESULTS: Mean absolute percentage error for heart rate varied from 2.17 to 8.06% for the Fitbit Surge, from 1.01 to 7.49% for the TomTom Cardio and from 1.31 to 7.37% for the Microsoft Band. The mean absolute percentage error for energy expenditure varied from 25.4 to 61.8% for the Fitbit Surge, from 0.4 to 26.6% for the TomTom Cardio and from 1.8 to 9.4% for the Microsoft Band. CONCLUSION: Data from these devices may be useful in obtaining an estimate of heart rate for everyday activities and general exercise, but energy expenditure from these devices may be significantly over- or underestimated.

Relationships between central arterial stiffness, lean body mass, and absolute and relative strength in young and older men and women.

Relationships between muscular strength and arterial stiffness as well as between muscle mass and arterial stiffness have been observed suggesting a link between the neuromuscular system and vascular health. However, the relationship between central arterial stiffness and absolute and relative strength along with muscle mass has not been investigated in both sexes across a broad age range. The purpose of this study was to examine the relationship between central arterial stiffness and absolute and relative strength as well as between central arterial stiffness and lean body mass (LBM) in men and women across a broad age range. LBM, central arterial stiffness and strength were measured on 36 men and 35 women between the ages of 18 and 75 years. Strength was measured on five machine resistance exercises and summed as one measure of overall strength (absolute strength). Relative strength was calculated as total strength divided by LBM (relative strength). Central arterial stiffness was inversely related to both absolute (r = -0·230; P = 0·029) and relative strength (r = -0·484; P < 0·001) but not LBM (r = 0·097; P = 0·213). The relationship between central arterial stiffness and relative strength was attenuated but still present when controlling for either age, per cent body fat, LBM or mean arterial pressure. These results suggest that, across a wide age range, the expression of relative muscular strength has a stronger relationship with central arterial stiffness compared to either LBM or absolute strength. This suggests that muscle function more than muscle mass may be coupled with vascular health.

Prediction and Validation of DXA-Derived Appendicular Fat-Free Adipose Tissue by a Single Ultrasound Image of the Forearm in Japanese Older Adults.

OBJECTIVES: To develop regression-based equations for estimating dual-energy x-ray absorptiometry (DXA) derived appendicular fat-free adipose tissue (FFAT) using a single ultrasound image in the forearm, and to investigate the validity of those equations to calculate FFAT-free appendicular lean mass (aLM-minus-FFATappendicular ) in 311 Japanese adults aged 60 to 79 years. METHODS: Subjects were randomly separated into two groups: 215 in the model-development group (91 men and 124 women) and 96 in the cross-validation group (42 men and 54 women). Appendicular fat mass and aLM were measured by the DXA, and subcutaneous adipose tissue (AT-forearm) and muscle (MT-ulna) thicknesses were measured by ultrasound. Appendicular FFAT was calculated based on the results of a previous study (appendicular FFAT = appendicular fat mass/0.85 x 0.15). The aLM was estimated from MT-ulna using a previously published equation (aLM = 4.89 x MT-ulna x body height - 9.15). Stepwise linear regression analysis was used to determine predictive models for DXA-derived appendicular FFAT from AT-forearm, sex, age, and anthropometrical variables. The best ultrasound prediction equation for estimation of appendicular FFAT was developed and then cross-validated in a subsample of older adults. RESULTS: There was no significant difference between the DXA-derived and ultrasound-predicted aLM-minus-FFATappendicular . A strong correlation was observed between the DXA-derived and ultrasound-predicted aLM-minus-FFATappendicular (r = 0.935, P < .001). Bland-Altman analysis did not indicate a bias in the prediction of the aLM-minus-FFATappendicular for the validation group. CONCLUSIONS: Our results indicated that a single ultrasound forearm measurement can be used to accurately estimate DXA-derived aLM-minus-FFATappendicular in Japanese older adults, which may be advantageous for community-based physical examinations.

Muscle activation and heart rate responses to a side-step interval exercise.

BACKGROUND: The side-step test is commonly used to assess agility. Side-step interval exercise may also be a potential way to improve cardiorespiratory and muscular fitness. However, the acute heart rate and muscle activation response to this type of exercise is not well established. In addition, different tempos can influence these responses. The purpose of this study was to determine the acute heart rate and muscle activation responses of a side-step interval exercise to different exercise tempos. METHODS: Ten participants completed a V˙O2 max test and performed a side-step interval exercise for 4 × 1 min intervals separated by 1-min rest intervals at a slow (84 bpm) and fast (112 bpm) tempo. Muscle activation of the vastus lateralis and vastus medialis and heart rate were measured during exercise. RESULTS: During the slow tempo, vastus lateralis muscle activation varied from 45% to 48% of maximum muscle activation (EMGmax ) while vastus medialis muscle activation varied from 51% to 54% EMGmax . During the fast tempo, vastus lateralis muscle activation varied from 53% to 65% EMGmax while vastus medialis muscle activation varied from 64% to 76% EMGmax . Heart rates varied from 80-84% HRmax from set 1 to set 4 for the fast tempo and varied from 67% to 72% HRmax from set 1 to set 4 for the slow speeds. CONCLUSION: Exercise intensity of a side-step interval exercise reached adequate levels to suggest that it may be possible to use this type of exercise to improve cardiorespiratory and muscular fitness.

Can Handgrip Strength Improve Following Body Mass-Based Lower Body Exercise?

Knee extension strength (KES) improves following body mass-based lower body exercise training; however, it is unknown whether this type of exercise increases handgrip strength (HGS) as a result of a cross-education effect in older individuals. Our aim was to investigate the effect of a body mass-based exercise intervention on HGS and KES in older adults. At baseline, 166 subjects started a 12-week intervention program, and 160 (108 women and 52 men) subjects completed the study. A self-selected group of 37 older adults (21 women and 16 men) served as a control group. HGS, KES, and ultrasound-derived anterior thigh muscle thickness (anterior thigh MT) were measured at baseline and post-testing, and relative strength of the knee extensor (KES/anterior thigh MT) was calculated. A linear regression model controlling for baseline values of body-mass index, % body fat, fat-free mass, HGS, chair stand time, anterior thigh MT, and KES/body mass ratio found a significant difference between control and training groups for KES post-testing values (p = 0.001) and anterior thigh MT post-testing values (p = 0.012), but not for HGS post-testing values (p = 0.287). Our results suggest that increases in lower body strength and muscle size following a 12-week lower body mass-based exercise intervention fail to translate into improvements in HGS.

Time-course of muscle growth, and its relationship with muscle strength in both young and older women.

AIM: The time-course for changes in muscle size and strength is not well understood, particularly in women. In addition, contributions of muscle size to strength are commonly assessed utilizing a pre-post change score; however, a more appropriate within-subject correlational analysis has never been used. METHODS: To determine the time-course for thigh muscle size and strength in young (aged 18-25 years) and older (aged 50-65 years) women, and determine the relationship between size and strength after 8 weeks of training carried our three times per week. RESULTS: Anterior muscle thickness at the 50% site increased after 1 week of training, and exceeded the measurement error after 2 weeks (mean difference 0.23 cm, 95% CI 0.12-0.34 cm). Anterior muscle thickness at the 70% site increased and exceeded the measurement error after 2 weeks (mean difference 0.30 cm, 95% CI 0.15-0.45 cm). Posterior muscle thickness at the 50% site increased after 1 week of training, and exceeded the measurement error after 2 weeks (mean difference 0.24 cm, 95% CI 0.03-0.44 cm). Posterior muscle thickness at the 70% site increased after 1 week, and exceeded the measurement error after 3 weeks (mean difference 0.21 cm, 95% CI 0.07-0.35 cm). Muscle strength, assessed through one-repetition maximum, increased by 2 weeks in most measurements, and the within-subject variance explained by changes in muscle size ranged between 9% and 35%. CONCLUSIONS: Muscle growth appeared to occur early into a training program in both young and older women. Furthermore, although a large portion remains unexplained, the variance in muscle strength explained by muscle size is greater than previous studies not utilizing within-subject correlations. Geriatr Gerontol Int 2017; 17: 2000-2007.

Appendicular lean mass and site-specific muscle loss in the extremities correlate with dynamic strength.

BACKGROUND: Previous studies have reported the non-homogenous loss of muscle mass (site-specific muscle loss) with ageing, but this relationship to the loss of strength is not totally understood. PURPOSE: To investigate the relationship between maximal dynamic strength and site-specific muscle mass of the thigh and upper arm. METHODS: Thirty-five recreationally active men were separated into young-aged (YG, 20-39 years, n = 12), middle-aged (MG, 40-59 years, n = 13) and old-aged groups (OG, 60-75 years, n = 10). One-repetition maximum strength (1-RM; leg press, chest press, knee flexion, lat pull-down, and knee extension), muscle thickness (MTH, anterior and posterior thigh and upper arm) and appendicular lean mass (aLM) index were obtained from participants. Site-specific thigh MTH ratio was determined by dividing anterior thigh MTH (50% of thigh length) by posterior thigh MTH (50% of thigh length). RESULTS: aLM index was not significantly different between age groups, but a significantly smaller site-specific MTH thigh ratio was found in the OG. Collapsed across age groups both site-specific thigh MTH ratio and aLM index were significantly correlated with leg press, knee extension and knee flexion1-RM strength (r = 0·390-0·699), but not with knee extension: knee flexion (KE:KF) 1-RM strength ratios (r = 0·037-0·081). Separated by age groups only aLM index was correlated with KE:KF 1-RM ratio for the OG (r = 0·780). CONCLUSIONS: Site-specific thigh MTH ratio may be an important assessment tool in older individuals as it is different among age groups and is significantly related to dynamic maximal strength. However, maximal dynamic strength ratios appear to be less sensitive to differences in site-specific MTH ratios.

The influence of exercise load with and without different levels of blood flow restriction on acute changes in muscle thickness and lactate.

The aim of this study was to compare exercise with and without different degrees of blood flow restriction (BFR) on acute changes in muscle thickness (MTH) and whole blood lactate (WBL). Forty participants were assigned to Experiment 1, 2 or 3. Each experiment completed protocols differing by pressure, load and/or volume. MTH and WBL were measured pre and postexercise. The acute changes in MTH appear be maximized at 30% one repetition maximum (1RM) with BFR, although the difference between 20% 1RM and 30% 1RM at the lateral site was small (0·1 versus 0·2 cm, P = 0·09). Increasing the exercise load from 20% to 30% 1RM with BFR produces clear changes in WBL (3·7 versus 5·5 mmol l-1 , P<0·001). The acute changes in MTH and WBL for 30% 1RM in combination with BFR were similar to that observed with 70% 1RM and 20 and 30% to failure, albeit at a lower exercise volume. These findings may have implications for designing future studies as it suggest that exercise load (to a point) may have a greater influence on acute changes in MTH and metabolic accumulation than the applied relative pressure.

Ultrasound-Derived Forearm Muscle Thickness Is a Powerful Predictor for Estimating DXA-Derived Appendicular Lean Mass in Japanese Older Adults.

To test the validity of published equations, anterior forearm muscle thickness (MT-ulna) of 158 Japanese older adults (72 men and 86 women) aged 50-79 y was measured with ultrasound. Appendicular lean soft tissue mass (aLM) was estimated from MT-ulna using two equations (body height without [eqn 1] and with [eqn 2]) previously published in the literature. Appendicular lean mass was measured using dual-energy X-ray absorption (DXA), and this method served as the reference criterion. There was a strong correlation between DXA-derived and ultrasound-estimated aLM in both equations (r = 0.882 and r = 0.944). Total error was 2.60 kg for eqn (1) and 1.38 kg for eqn (2). A Bland-Altman plot revealed that there was no systematic bias between DXA-derived and ultrasound-estimated aLM; however, eqn (1) overestimated aLM compared with DXA-derived aLM. Our results suggest that an ultrasound MT-ulna equation that includes body height is appropriate and useful for estimating aLM in Japanese adults.