Predicting 1 Repetition Maximum Using Handheld Dynamometry

Narrative Review of Sex Differences in Muscle Strength, Endurance, Activation, Size, Fiber Type, and Strength Training Participation Rates, Preferences, Motivations, Injuries, and Neuromuscular Adaptations

ABSTRACT

Nuzzo, JL. Narrative review of sex differences in muscle strength, endurance, activation, size, fiber type, and strength training participation rates, preferences, motivations, injuries, and neuromuscular adaptations. J Strength Cond Res 37(2): 494-536, 2023-Biological sex and its relation with exercise participation and sports performance continue to be discussed. Here, the purpose was to inform such discussions by summarizing the literature on sex differences in numerous strength training-related variables and outcomes-muscle strength and endurance, muscle mass and size, muscle fiber type, muscle twitch forces, and voluntary activation; strength training participation rates, motivations, preferences, and practices; and injuries and changes in muscle size and strength with strength training. Male subjects become notably stronger than female subjects around age 15 years. In adults, sex differences in strength are more pronounced in upper-body than lower-body muscles and in concentric than eccentric contractions. Greater male than female strength is not because of higher voluntary activation but to greater muscle mass and type II fiber areas. Men participate in strength training more frequently than women. Men are motivated more by challenge, competition, social recognition, and a desire to increase muscle size and strength. Men also have greater preference for competitive, high-intensity, and upper-body exercise. Women are motivated more by improved attractiveness, muscle "toning," and body mass management. Women have greater preference for supervised and lower-body exercise. Intrasexual competition, mate selection, and the drive for muscularity are likely fundamental causes of exercise behaviors in men and women. Men and women increase muscle size and strength after weeks of strength training, but women experience greater relative strength improvements depending on age and muscle group. Men exhibit higher strength training injury rates. No sex difference exists in strength loss and muscle soreness after muscle-damaging exercise.

New perspectives for investigating muscular perfusion response after dietary supplement intake: an exploratory, randomized, double-blind, placebo-controlled crossover trial in healthy young athletes using contrast-enhanced ultrasound (CEUS)

Background

Various dietary supplements have been reported to enhance muscular perfusion in athletes practicing resistance training, especially through modulation of nitric oxide signaling.

Objectives

The aim of this study was therefore to investigate selected ‘NO-boosting’ supplements in a real-life setting i) to generate novel hypotheses and perfusion estimates for power calculation in view of a definitive trial and ii) to assess the feasibility of the study design with particular focus on the use of contrast-enhanced ultrasound (CEUS) for perfusion quantification.

Methods

Thirty young male athletes (24 ± 4 years) regularly practicing resistance training were enrolled in this three-arm, placebo(PL)-controlled crossover trial with ingestion of two commercially available supplements: an amino acid combination (AA) (containing 3 g of L-arginine-hydrochloride and 8 g of L-citrulline-malate) and 300 mg of a specific green tea extract (GTE). After intake, CEUS examinations of the dominant biceps brachii muscle were performed under resting conditions and following standardized resistance exercising. Quantitative parameters of biceps perfusion (peak enhancement, PE; wash-in perfusion index, WiPI) and caliber were derived from corresponding CEUS video files. Additionally, subjective muscle pump was determined after exercise.

Results

For PE, WiPI, and biceps caliber, the standard deviation (SD) of the within-subject differences between PL, AA, and GTE was determined, thereby allowing future sample size calculations. No significant differences between PL, AA, and GTE were observed for biceps perfusion, caliber, or muscle pump. When comparing resting with post-exercise measurements, the increase in biceps perfusion significantly correlated with the caliber increase (PE: r = 0.266, p = 0.0113; WiPI: r = 0.269, p = 0.0105). Similarly, the biceps perfusion correlated with muscle pump in the post-exercise conditions (PE: r = 0.354, p = 0.0006; WiPI: r = 0.350, p = 0.0007). A high participant adherence was achieved, and the acquisition of good quality CEUS video files was feasible. No adverse events occurred.

Conclusion

Based on our novel examination protocol, CEUS seems to be feasible following higher-load resistance exercising and may be used as a new method for high-resolution perfusion quantification to investigate the effects of pre-exercise dietary supplementation on muscle perfusion and related muscle size dynamics.

The efficacy of resistance training in addition to usual care for adults with acute burn injury: A randomised controlled trial

Resistance training immediately after a burn injury has not been investigated previously. This randomised, controlled trial assessed the impact of resistance training on quality of life plus a number of physical, functional and safety outcomes in adults with a burn injury. Patients were randomly assigned to receive, in addition to standard physiotherapy, four weeks of high intensity resistance training (RTG) or sham resistance training (CG) three days per week, commenced within 72h of the burn injury. Outcome data was collected at six weeks, three and six months after burn injury. Quality of life at 6 months was the primary endpoint. Data analysis was an available cases analysis with no data imputed. Regression analyses were used for all longitudinal outcome data and between-group comparisons were used for descriptive analyses. Forty-eight patients were randomised resistance training (RTG) (n=23) or control group (CG) (n=25). The RTG demonstrated improved outcomes for the functional domain of the Burn Specific Health Scale-Brief (p=0.017) and the Quick Disability of Arm Shoulder and Hand (p<0.001). Between group differences were seen for C-reactive protein and retinol binding protein (p=0.001). Total quality of life scores, lower limb disability, muscle strength and volume were not seen to be different between groups (p>0.05). Resistance training in addition to usual rehabilitation therapy showed evidence of improving functional outcomes, particularly in upper limb burn injuries. Additionally, resistance training commenced acutely after a burn injury was not seen to be harmful to patients.

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.

Quadriceps Strength and Mortality in Older Patients With Heart Failure

BACKGROUND

This study was performed to test the hypothesis that low quadriceps isometric strength (QIS) is associated with greater risk of mortality and has the additive prognostic significance to the severity of heart failure (HF) and gait speed in older patients with HF.

METHODS

A retrospective cohort study was performed in 1273 patients ≥ 60 years of age with HF (mean age 75 ± 8 years, 59.1% men); all of whom were evaluated during hospitalization for usual gait speed and maximal QIS. The QIS was expressed relative to body mass (% BM). The endpoint was all-cause mortality.

RESULTS

Over a median follow-up period of 1.59 years (interquartile range, 0.58 to 3.42 years), 224 patients died. The cutoff value based on the Youden index for the QIS discriminating those at high risk of mortality was 36.2% BM for overall, and we defined less than this cutoff point of QIS as low QIS. After adjustment for the HF risk score, the hazard ratio in low QIS was 1.55 for overall (95% confidence interval [CI], 1.17-2.06). The addition of low QIS to the HF risk score and gait speed was associated with significant increases in both net reclassification improvement (NRI, 0.239 for overall; 95% CI, 0.096-0.381) and integrated discrimination improvement (IDI, 0.004 for overall; 95% CI, 0.001-0.009) for all-cause mortality.

CONCLUSION

Low QIS was strongly associated with poor prognosis and showed complementary prognostic predictive capability to the HF risk score and gait speed in older patients with HF.

Game-based hand resistance exercise versus traditional manual hand exercises for improving hand strength, motor function, and compliance in stroke patients: A multi-center randomized controlled study

BACKGROUND

Game-based exercise is effective for improving strength and motor function in stroke patients undergoing rehabilitation, and it creates fun and motivation for exercise.

OBJECTIVE

We investigated the effect of game-based exercise on hand strength, motor function, and compliance in stroke patients.

METHODS

Fifty stroke patients were randomly divided into experimental and control groups. The experimental group performed a game-based hand resistance exercise. This exercise was divided into isotonic and isometric types and was performed 30 min/day, 5 days/week, for 6 weeks with 70% of the 1-repetition maximum. In contrast, the control group was given a traditional manual exercise by the occupational therapist, and the type of exercise and time involved were the same as those in the experimental group. The primary outcome measure was hand strength test measured using a dynamometer. Secondary outcome measures were manual function tests (MFT) and hand function tests using box and block test (BBT). Subject-based reports of motivation, fun, pain/fatigue evaluated on 0 to 10 numeric rating scales were compared between groups.

RESULTS

After training, hand strength, MFT and BBT was improved in the experimental group compared to the control group (P < 0.001, both). Subject-based reports of motivation and fun was significantly greater in the experimental group than the control group (P < 0.001, both), except to pain/fatigue (P = 0.728).

CONCLUSIONS

In conclusion, we demonstrated that game-based exercise is more effective than manual exercise in improving muscle strength, motor function, and compliance in stroke patients.

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

[Purpose] It is important to accurately measure one-repetition maximum to determine the training load and number of repetitions. However, huge and expensive equipment, such as a torque machine and/or dynamometer, is needed to measure one-repetition maximum. Therefore, a more accessible and affordable method has been developed to predict one-repetition maximum. In this study, we aimed to investigate whether one-repetition maximum of the knee extensor could be predicted more accurately with a combination of muscle strength, measured using a handheld dynamometer, muscle thickness, and thigh circumference. [Participants and Methods] Participants were sixty-four non-athletic healthy adult volunteers (33 males and 31 females). Muscle strength of the knee extensor measured using one-repetition maximum, maximal voluntary isometric contraction measured using a handheld dynamometer, muscle thickness of the quadriceps and/or thigh circumference measured on ultrasonography. [Results] The stepwise regression analysis revealed that body mass, gender, muscle thickness at 15 cm above the patella, and maximal voluntary isometric contraction were the significant and independent determinants (R²=0.813). [Conclusion] One-repetition maximum could be predicted more accurately with a combination of maximal voluntary isometric contraction measured using a handheld dynamometer and muscle thickness.