Efficacies of ultrasound and a handheld dynamometer to predict one-repetition maximum

Factors Involved in Higher Knee Extension Torque Induced by Repetitive Peripheral Magnetic Stimulation

OBJECTIVE

The study aimed to determine the relationship between knee extension torque induced by repetitive peripheral magnetic stimulation and the characteristics of the participants.

DESIGN

This was a basic study with noninvasive intervention. Knee extension torque induced by repetitive peripheral magnetic stimulation (repetitive peripheral magnetic stimulation-induced torque) and maximum voluntary contraction were measured. Stepwise method of multiple regression was performed to determine the factors affecting repetitive peripheral magnetic stimulation-induced torque at 100% intensity and repetitive peripheral magnetic stimulation-induced torque divided by maximum voluntary contraction (percent maximum voluntary contraction). Subcutaneous fat thickness, vastus lateralis muscle thickness measured by ultrasound, maximum voluntary contraction, and mean power frequency of electromyography during maximum voluntary contraction were selected as independent variables.

RESULTS

Repetitive peripheral magnetic stimulation was applied to the right vastus lateralis of 30 young healthy adults (average age, 21.1 ± 0.3 yrs). In the multiple regression analysis, repetitive peripheral magnetic stimulation-induced torque ( P < 0.001) was shown to be independently and significantly associated with maximum voluntary contraction (β = 0.510), subcutaneous fat thickness (β = -0.358), and vastus lateralis muscle thickness (β = 0.208), while percent maximum voluntary contraction value ( P < 0.05) was independently and significantly associated with vastus lateralis muscle thickness (β = 1.059).

CONCLUSIONS

Repetitive peripheral magnetic stimulation-induced torque decreases with thicker subcutaneous fat and increases with stronger maximum voluntary contraction or with thicker muscle.

Characteristics of muscle contraction of the rectus femoris using tensiomyography by sex in healthy college students: a cross-sectional study

Background

Tensiomyography (TMG) is a non-invasive instrument for measuring mechanical muscle contraction characteristics and measuring the maximum displacement of the muscle belly in the radial direction with respect to the muscle and the time needed to achieve this from electrical stimulation. There have been only been a reports of TMG in healthy adults. A systematic review of TMG reported a low proportion of female participants, with a small sample size. Therefore, it is unclear whether there is a difference in TMG parameters according to sex and between dominant and non-dominant feet. Furthermore, the relationship between TMG parameters and evaluations commonly used in clinical practice has not been clarified. This study aimed to clarify the characteristics of muscle contraction of the rectus femoris using TMG according to sex among healthy college students and its relationship with muscle function evaluation, such as lower limb muscle mass and muscle strength.

Methods

This cross-sectional study included 91 healthy university students (18-24 years). Five tools were used: TMG, lower-limb muscle mass, rectus femoris thickness, isometric knee joint extension torque, and thigh circumference. Each parameter was compared by the generalized linear mixed model (GLMM) and Bonferroni's multiple comparison test, with sex as the without-subject factor and dominant/non-dominant foot as the within-subject factor. The correlation between the TMG parameters and other parameters was examined using Pearson's correlation coefficient for both males and females.

Results

The results of the GLMM, in terms of the TMG parameters, an interaction was observed for maximum displacement (Dm); in the results of the multiple comparison test, Dm for the non-dominant leg was significantly lower in females than in males. A main effect and interaction were not observed for delay time (Td) and contraction time (Tc) by sex, dominant foot, or non-dominant foot. There was a main effect of sex on muscle function evaluation parameters (ρ ≤ 0.05). The correlation between TMG parameters for males and females and lower limb muscle mass, muscle thickness, joint torque, and thigh circumference were significantly correlated with some TMG parameters, lower limb muscle mass and muscle thickness (ρ ≤ 0.05). The absolute value of the correlation coefficient was low overall (0.20-0.38).

Conclusion

In healthy college students, TMG parameters for the rectus femoris showed sex differences in Dm, and there was a weak correlation between TMG parameters and lower limb muscle mass. TMG parameter evaluation may indicate a different function compared to the traditional muscle function assessment used in clinical practice. When using the Dm of the TMG as an evaluation battery for the rectus femoris muscle, it is important to consider sex-related differences.

One-repetition maximum can be estimated with a handheld dynamometer and circumference in community-dwelling older adults

[Purpose] One-repetition maximum is an essential statistic for physical therapists and coaches in rehabilitation and athletic settings. In a previous study, we showed that one-repetition maximum of the knee extensor could be predicted more accurately with the combination of maximal voluntary isometric contraction strength, as measured by a handheld dynamometer, muscle thickness, and thigh circumference, in young adults. However, there has been no study in older adults investigating the relationship between one-repetition maximum and maximal voluntary isometric contraction strength, or muscle thickness, and thigh circumference. Therefore, the aim of this study was to investigate the relationship between one-repetition maximum and maximal voluntary isometric contraction strength, or muscle thickness, and thigh circumference in older adults. [Participants and Methods] Twenty-eight older community-dwelling adults (18 males and 10 females) participated in this study. Muscle strength of the knee extensor was measured using one-repetition maximum and maximal voluntary isometric contraction strength. In addition, muscle thicknesses of the refutes femoris and the vastus intermedius, and thigh circumference were measured using ultrasonography and measuring tape, respectively. [Results] Stepwise regression analysis revealed that body mass, gender, thigh circumference at 15 cm above the patella, and maximal voluntary isometric contraction strength were significant and independent determinants (R²=0.868). [Conclusion] One-repetition maximum could be predicted more accurately using a combination of maximal voluntary isometric contraction strength, as measured with a handheld dynamometer, and thigh circumference in older adults.