Allometric scaling of isometric biceps strength in adult females and the effect of body mass index

The ratio standard is not adequate for scaling handgrip strength in judo athletes and nonathletes

This study aimed to analyze if the ratio standard or the allometry is the best scaling methods of handgrip strength (HGS) for body mass (BM) in judo athletes and nonathletes, and to verify if the HGS mean values are higher in judo athletes than nonathletes when the BM effect is removed. One hundred forty-two individuals, being 88 judo athletes and 54 non-athletes participated in this study. The maximal isometric HGS was measured in judo athletes and nonathletes in the preferred hand. Only the allometry method was able to remove the BM effect of HGS. The al-lometric exponents found for athletes was b=0.68 and b=0.563 for non-athletes. A common allometric exponent was identified as (b=0.64) for comparing judo athletes and nonathletes. However, neither was able to allow for the comparison between groups due to a distortion of (bias; P<0.01). Thus, an index (HGS_INDEX) was proposed to allow within-group (judo athletes and nonathletes) and between-group (judo athletes vs. nonathletes) comparison, removing the effect of BM. In summary, the allometric exponent based on the theory of geometric similarity (b=0.67) was able to remove the BM effect of HGS in judo athletes. An index (HGS_INDEX) is suggested for classification (or rank) of the judoka in relation to the expected average of HGS.

Influência da obesidade nos critérios de classificação de sarcopenia em idosos

Resumo Objetivo identificar a prevalência de obesidade sarcopênica em idosos residentes na comunidade e analisar a relação da obesidade com os critérios de classificação da sarcopenia. Método Trata-se de um corte transversal analítico vinculado ao projeto “Atenção Integral à Saúde do Idoso”. A avaliação da sarcopenia foi realizada a partir dos critérios do Consenso Europeu de Sarcopenia. Para classificação dos idosos como obesos sarcopênicos considerou-se aqueles que se apresentaram como provável sarcopênico, sarcopênico ou sarcopênico severo associado ao percentual de gordura >27% para homens e >38% para mulheres. Os dados foram analisados utilizando estatística bivariada e um modelo de regressão linear. Resultados Dos 209 idosos residentes na comunidade foi verificado uma prevalência de 23,9% de sarcopenia, 28,2% de obesidade e 4,3% de obesidade sarcopênica. Ainda, pode-se observar que os homens apresentaram maior prevalência de sarcopenia (p=0,006) e de obesidade (p=0,005) que as mulheres; os obesos tiveram menor prevalência de perda de massa muscular que os idosos não obesos (p<0,001); e os obesos apresentaram incremento na força (p=0,003) e na massa muscular (p<0,001) em relação aos não obesos, mesmo quando ajustado para sexo, faixa etária, multicomorbidades e incapacidade funcional. Conclusão levando em consideração a prevalência de obesidade sarcopênica na população estudada e a influência positiva da obesidade na predição de força e massa muscular, destaca-se a importância da avaliação multidimensional do idoso, a fim de averiguar a real necessidade de intervenções para perda de peso corporal, com intuito de prevenção de perda de força e massa muscular.

Maturity status effects on torque and muscle architecture of young soccer players

This study investigated the effects of maturity status on knee extensor torque and vastus lateralis architecture of young soccer players. Thirty-four males aged 13-18 years were divided into two groups: pubescent (PUB, n = 15) and postpubescent (POSP, n = 19). Torque by angle interaction was established for absolute [F(2.649, 84.771) = 9.066, p < 0.05] and relative to body mass [F(2.704, 86.533) = 4.050, p < 0.05] isometric torque with the POSP group showing greater values. Muscle volume torque-angle relationship was similar between groups. Absolute, relative to body mass, and relative to muscle volume concentric and eccentric torque-velocity relationship showed a non-significant interaction but a significant group effect in favour the POSP group for absolute and concentric torque relative to body mass. Torque-angle and torque-velocity relationship normalized by body mass allometric exponents showed a non-significant interactions and group effects. Muscle thickness (3.6 ± 0.6 vs. 3.8 ± 0.6 cm), fascicle length (8.3 ± 1.4 vs. 8.9 ± 1.6 cm) and pennation angle (15.0 ± 2.3 vs. 14.3 ± 3.2 degrees) was similar between PUB and POSP groups, respectively. Maturity status did not show a significant effect on muscle architecture and on isometric and dynamic torques when allometrically normalized.

Body Composition, Strength, and Dietary Intake of Patients with Hip or Knee Osteoarthritis

PURPOSE

To describe body composition (fat mass (FM) and fat-free mass (FFM)), strength, and nutritional characteristics of patients with hip or knee osteoarthritis undergoing total joint arthroplasty.

METHODS

In this prospective pilot study, osteoarthritic patients underwent body composition assessment using bioelectrical impedance analysis, grip strength measurement, and completed a 24-h dietary recall during their pre-operative assessment.

RESULTS

Fifty-five patients were included (∼66% females, age 43-89 years). Mean ± SD body mass index (BMI) was 32.79 ± 6.48 kg/m(2) and 62% were obese. Compared with hip osteoarthritis patients, knee osteoarthritis patients had a higher BMI (P = 0.018) and males with knee osteoarthritis had a lower grip strength (P = 0.028). There was a wide range in FM and FFM values across the BMI spectrum. Patients with a higher FM index (FMI, FM/height in m(2)) had higher levels of pain (P = 0.036) and females with higher FMI had a lower grip strength (P = 0.048). Dietary under-reporting was common and many patients did not meet recommendations for protein, vitamins C and E, or omega-3 fatty acids. Those who consumed less protein than the recommended dietary allowance were older (P = 0.018).

CONCLUSIONS

A wide variability of body composition and dietary intake was observed which may impact strength and ultimately affect physical function. As such, patients with osteoarthritis may benefit from targeted nutrition and physical activity interventions before and after surgery.

Influences of Obesity on Job Demands and Worker Capacity

Evidence suggests that the growing prevalence of obesity in the workforce has resulted in an increase in the incidence and cost of musculoskeletal injuries. Obesity can modify job demands and affect worker capacity in terms of anthropometry and occupational biomechanics, which may place workers at greater risk of injury. This paper presents a review of studies quantifying the work-relevant impacts of obesity, specifically related to work task demands, capacities, and their potential imbalance. The increased body fat that accompanies obesity leads to larger anthropometric dimensions and inertial parameters, particularly in the trunk and thigh areas. Consequently, individuals who are obese adjust their work postures and motions as an accommodation. These changes may affect the biomechanical demands on the joints and increase the burden on the musculoskeletal system. Independent of job demands, obesity-related differences also occur with respect to strength, fatigue, and task performance. Directions for future research are provided, focusing on the need for workplace redesign to account for changing workforce demographics.

Effect of BMI on Knee Joint Torques in Ergometer Rowing

Although an authoritative panel recommended the use of ergometer rowing as a non-weight-bearing form of exercise for obese adults, the biomechanical characterization of ergometer rowing is strikingly absent. We examined the interaction between body mass index (BMI) relative to the lower extremity biomechanics during rowing in 10 normal weight (BMI 18–25), 10 overweight (BMI 25–30 kg·m−2), and 10 obese (BMI > 30 kg·m−2) participants. The results showed that BMI affects joint kinematics and primarily knee joint kinetics. The data revealed that high BMI leads to unfavorable knee joint torques, implying increased loads of the medial compartment in the knee joint that could be avoided by allowing more variable foot positioning on future designs of rowing ergometers.

Obesity-related differences in muscular capacity during sustained isometric exertions

Over one-third of the world adult population is overweight or obese, and the prevalence continues to increase. Obesity is a risk factor for injury, and the growing prevalence may be associated with increases in the future incidence and cost of injuries. In this study, we examined obesity-related differences in muscular capacity during sustained isometric exertions involving hand grip, shoulder flexion, and trunk extension. Thirty-six young individuals who were obese or not obese (aged 18-29) completed these exertions at fixed levels of absolute loads involving low-moderate levels of effort. Individuals who were obese had an overall ∼20% higher absolute strength, but ∼20% lower relative strength. These differences were most evident in the hand grip and shoulder exertions. Parameters of fitted exponential relationships between endurance time and task demands (as a percentage of strength) were similar in both groups. Perceptual and performance responses were also consistent between groups. Accordingly, we conclude that obesity may not substantially influence muscular capacity for these tasks.

The effects of anthropometric scaling parameters on normalized muscle strength in uninjured baseball pitchers

CONTEXT

Muscle force must be normalized for between-subjects comparisons of strength to be valid. The most effective method for normalizing muscle strength has not, however, been systematically evaluated.

OBJECTIVE

To evaluate the effects of normalizing muscle strength using a spectrum of anthropometric parameters.

DESIGN

Cross-sectional.

SETTING

Laboratory.

PARTICIPANTS

50 uninjured high-school-age baseball pitchers.

INTERVENTIONS

Shoulder-rotation strength was tested at 0° and 90° abduction with a handheld dynamometer. Muscle force was normalized to parameters including subject height, weight, height × weight, body-mass index (BMI), forearm length, and forearm length × height.

OUTCOME MEASURES

Statistical analysis included evaluating the coefficient of variation, skewness, and kurtosis of the nonnormalized and normalized muscle force. The most effective normalization method was determined based on the scaling factor that yielded the lowest variability for the data set and promoted the most normal distribution of the data set.

RESULTS

Using body weight to scale muscle force was the most effective anthropometric parameter for normalizing strength values based on the group of statistical measures of variability. BMI, height × weight, and forearm length × weight as scaling factors also yielded less variable values for muscle strength compared with nonnormalized strength, but less consistently than body weight. Height and forearm length were least effective in reducing the variability of the data set relative to nonnormalized muscle force.

CONCLUSION

This study provides objective support for scaling muscle strength to subject body weight. This approach to normalizing muscle strength uses methods readily accessible to clinicians and researchers and may facilitate the identification of differences in strength between individuals with diverse physical characteristics.

Normalizing hip muscle strength: establishing body-size-independent measurements

OBJECTIVE

To investigate the effectiveness of computing body-size-independent hip strength measures using muscle-specific allometric scaling and ratio standard normalization methods.

DESIGN

Cross-sectional study.

SETTING

University laboratory.

PARTICIPANTS

A convenience sample of healthy participants (N=113; 42 men, 71 women).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Anthropometric measurements of the leg and thigh were obtained, and maximal hip strength was tested (medial and lateral rotation, abduction, adduction, flexion, extension). Strength was measured isometrically as force (kg) and then converted to torque (Nm).

RESULTS

The allometric scaling analysis resulted in exponents for normalizing body mass (BM) in each muscle group assessed. In addition, a 6-muscle average exponent was also computed (bavg) for force (men, .554; women, .335) and torque (men, .792; women, .482). The nonsignificant results of the linear regression analysis revealed that normalizing hip strength to BM(bavg) (hip strength/BM(bavg)) effectively removed the influence of BM on force and torque. However, sex should be factored into analyses of allometric scaling because men have higher b-values than women for both force and torque. The linear regression analyses also demonstrated that force normalized to BM (P=.162-.895) and torque normalized to BM × Height (P=.146-.889) were body-size-independent measures. Force normalized to BM⁰·⁶⁷ (P=.001-.191) and body mass index (BMI) (P=<.001-.066), and torque normalized to BM (P=.004-.415) and BMI (P<.001) were significantly related to BM and therefore were not body-size independent.

CONCLUSIONS

Normalizing force and torque to BM(bavg) is the most effective method of removing body-size dependence and allowing comparisons of persons with differing body sizes.