Handgrip as a measure of muscle strength and its physiological dependence on therapeutic variables: A randomized case.

Clinical and medical data findings have traditionally been more representative of male than female subjects, and when combined, have not clearly differentiated between the groups. In this study there were no research questions initially contemplated, as the data were obtained from an educational setting, where participants completed tasks as part of a pedagogical program of preparation. The nature of the post-hoc analysis renders the study as a hypothesis-generating type rather than a hypothesis-testing one. It began as a cross-sectional quantitative analysis of performance on a task to explore the relationship between hand grip and three independent physiological variables. The data collected from all subjects were randomized since the total group of participants contained a disproportionate number of females as compared to males, this being a result of a demographic predominance of female students in a program of teacher preparation. Graphical analysis with the slope taken as a measure of hand grip dependence on three independent variables, and the correlation value used as a measure of association between variables yielded discernible differences. The grip strength dependence on the hand size as well as the wrist thickness show consistently significant differences for females only, with t-test of significance (p < .001), and large effect size differences based on Cohen's d values of 3.08 and 1.92, respectively. The significance of the finding that female grip strength depends the most on wrist thickness has implications for rehabilitative and therapeutic settings.

High-intensity interval training or resistance training versus usual care in men with prostate cancer on active surveillance: a 3-arm feasibility randomized controlled trial.

This study assessed the feasibility of a phase II randomized controlled trial of high-intensity interval training (HIIT), resistance training (RT), and usual care (UC) in men with prostate cancer (PCa) on active surveillance and evaluated changes in clinically relevant outcomes. Eighteen men undergoing active surveillance for PCa were randomized to HIIT (n = 5), RT (n = 7), or UC (n = 6). Exercise participants attended 2 supervised sessions weekly and were instructed to complete 1 home-based session weekly for 8 weeks. UC participants were provided with physical activity guidelines. Feasibility was met for attendance, compliance, and retention, but not recruitment. HIIT increased leg press (mean: +8.2 kg, 95% CI 1.1 to 15.3) from baseline to 8 weeks. RT increased seated row (mean: +11.7 kg, 95% CI 6.1 to 17.3), chest press (mean: +10.4 kg, 95% CI 5.3 to 15.5), leg press (mean: +13.1 kg, 95% CI 5.9 to 20.3), serum insulin-like binding protein-3 (IGFBP-3) (mean: +400.0 ng/mL, 95% CI 94.5 to 705.5), and decreased interferon-γ (mean: -3.1 pg/mL, 95% CI -5.7 to -0.4). No changes were observed in the UC group. HIIT and RT may be effective strategies for improving muscle strength; however, only RT may increase serum IGFBP-3. Strategies that can enhance recruitment in men on active surveillance are important prior to conducting a phase II trial. Trial registration number: ClinicalTrials.gov number NCT04266262. Novelty: High-intensity interval training or resistance training are feasible during active surveillance for prostate cancer. Resistance training may suppress the tumour-promoting effects of insulin-like growth factor-I (IGF-I) via increased expression of IGFBP-3.

Rest-pause and drop-set training elicit similar strength and hypertrophy adaptations compared with traditional sets in resistance-trained males.

This paper aimed to compare the effect of drop-set (DS) and rest-pause (RP) systems versus traditional resistance training (TRT) with equalized total training volume on maximum dynamic strength (1RM) and thigh muscle thickness (MT). Twenty-eight resistance-trained males were randomly assigned to either RP (n = 10), DS (n = 9) or TRT (n = 9) protocols performed twice a week for 8 weeks. 1RM and MT of the proximal, middle and distal portions of the lateral thigh were assessed at baseline and post-intervention. A significant time × group interaction was observed for 1RM (P = 0.001) in the barbell back squat after 8-weeks. Post hoc comparisons revealed that RP promoted higher 1RM than TRT (P = 0.001); no statistical differences in strength were observed between the other conditions. A significant main effect of time was revealed for MT at the proximal (P = 0.0001) and middle (P = 0.0001) aspects of the lateral thigh for all training groups; however, the distal portion did not show a time effect (P = 0.190). There were no between-group interactions for MT. Our findings suggest that RP promotes slightly superior strength-related improvements compared with TRT, but hypertrophic adaptations are similar between conditions. Novelty: Rest-pause elicited a slightly superior benefit for strength adaptations compared with traditional resistance training. Resistance training systems do not promote superior hypertrophic adaptations when total training volume is equalized. Muscle thickness in distal portion of thigh is similar to baseline. Although modest, effect sizes tended to favor rest-pause.

Contraction fatigue, strength adaptations, and discomfort during conventional versus wide-pulse, high-frequency, neuromuscular electrical stimulation: a systematic review.

Neuromuscular electrical stimulation (NMES) can be delivered in a conventional form (CONVNMES) and using relatively wide-pulses and high-frequencies (WPHFNMES). WPHFNMES is proposed to reduce contraction fatigability and generate larger contractions with less discomfort than CONVNMES; however, there are no systematic reviews to guide the selection of NMES types. This systematic review compared the effects of CONVNMES versus WPHFNMES on contraction fatigability, strength adaptations, and perceived discomfort in clinical and non-clinical populations. Eight studies were included. When averaged across all non-clinical participants in individual short- and long-term studies, there was either no difference between CONVNMES and WPHFNMES for all outcomes or WPHFNMES produced more fatigability. In a subset of non-clinical participants ("responders"), however, WPHFNMES reduced contraction fatigability during a single session. Long-term studies found no differences between protocols for strength adaptations in non-clinical participants and those with multiple sclerosis. We concluded that WPHFNMES reduces contraction fatigability only in the short-term studies and in non-clinical responder participants and may exacerbate fatigability in non-responders. This review was registered in the prospective international registry of systematic reviews/PROSPERO (Registration Number: CRD42020153907). Novelty: WPHF NMES may reduce fatigue in some participants and exacerbate fatigue in others. There were no differences in long-term studies between WPHF and CONV NMES on strength adaptations. Future high-quality research is needed to optimize outcomes of NMES-based programs.

Effects of resistance training at different intensities of load on cross-education of muscle strength.

The objectives of this study were to 1) compare the extent of cross-transfer of muscle strength of high- versus low-load unilateral resistance training performed with external pacing of the movement (URTEP) and 2) compare the time course of the 2 approaches. Fifty subjects were randomized to 1 of the following 3 groups: G80 [2 sets at 80% and 2 sets at 40% of 1 repetition maximum (1RM), 1 concentric second and 3 eccentric seconds controlled by a metronome]; G40 (4 sets at 40% of 1RM, 1 s and 3 s controlled by a metronome); or control group. At week 1, the G80 increased the elbow flexion 1RM (P < 0.05) in contralateral arm. At week 4, both G80 and G40 increased the elbow flexion 1RM (P < 0.05) in contralateral arm. However, a greater 1RM gain was observed in the G80 than in the G40 (P < 0.05). Thus, although higher-load URTEP seems to enhance the cross-education effect when compared with lower-load URTEP, the cross-education of dynamic strength can be achieved in the 2 approaches after 4 weeks. Many patients would benefit from cross-education of muscle strength through URPEP, even those who are unable to exercise with high loads and in short periods of immobilization. Novelty: Unilateral resistance training promotes cross-education of dynamic muscle strength. However, higher-load resistance training enhances the effects of cross-education of muscle strength.

Muscle strength cut-points for metabolic syndrome detection among adults and the elderly from Brazil.

We aimed to determine cut-points for muscle strength based on metabolic syndrome diagnosis. This cross-sectional analysis comprised data from 2 cohorts in Brazil (EpiFloripa Adult, n = 626, 44.0 ± 11.1 years; EpiFloripa Aging, n = 365, 71.6 ± 6.1 years). Metabolic syndrome was assessed by relative handgrip strength (kgf/kg). Metabolic syndrome was defined as including ≥3 of the 5 metabolic abnormalities according to the Joint Interim Statement. Optimal cut-points from Receiver Operating Characteristic (ROC) curves were determined. Adjusted logistic regression was used to test the association between metabolic syndrome and the cut-points created. The cut-point identified for muscle strength was 1.07 kgf/kg (Youden index = 0.310; area under the curve (AUC)) = 0.693, 95% CI 0.614-0.764) for men and 0.73 kgf/kg (Youden index = 0.481; AUC = 0.768, 95% confidence interval (CI) = 0.709-0.821) for women (age group 25 to < 50 years). The best cut-points for men and women aged 50+ years were 0.99 kgf/kg (Youden index = 0.312; AUC = 0.651; 95% CI = 0.583-0.714) and 0.58 kgf/kg (Youden index = 0.378; AUC = 0.743; 95% CI = 0.696-0.786), respectively. Cut-points derived from ROC analysis have good discriminatory power for metabolic syndrome among adults aged 25 to <50 years but not for adults aged 50+ years. Novelty: First-line management recommendation for metabolic syndrome is lifestyle modification, including improvement of muscle strength. Cut-points for muscle strength levels according to sex and age range based on metabolic syndrome were created. Cut-points for muscle strength can assist in the identification of adults at risk for cardiometabolic disease.

Separate and combined relationships for cardiorespiratory fitness and muscular strength with visceral fat and insulin sensitivity in adolescents with obesity.

We examined the separate and combined associations for cardiorespiratory fitness (CRF) and muscular strength (MS) with total and regional fat, and insulin sensitivity (IS) in 204 adolescents (BMI ≥85th percentile, 12-18 years) at UPMC Children's Hospital of Pittsburgh. CRF was measured by maximum oxygen consumption during a graded treadmill test. MS was quantified by combining 1-repetition maximum test for the leg and bench press. Participants were stratified as having either high or low CRF and MS based on sex-specific median split. Both high CRF and high MS groups had lower (P < 0.05) total fat after adjustment for sex, Tanner stage and ethnicity than the low CRF and MS groups (Difference: 6.6, 2.6-9.6% and 5.4, 2.4-8.3%, respectively). High CRF, but not high MS, had lower visceral (67.5 versus 77.9 cm2, P < 0.01) and intermuscular fat (3.6 versus 4.0 kg, P = 0.01) than the low CRF groups. Differences by CRF remained significant after adjustment for MS. High CRF, but not high MS, was associated (P < 0.05) with lower fasting glucose and higher IS after accounting for sex, Tanner stage and ethnicity than the low CRF group, and high CRF remained associated with these markers after adjustment for MS. High CRF is associated with lower total and regional fat, and higher IS after adjustment for MS. Novelty: CRF is associated with lower total fat, visceral and intermuscular fat, and higher insulin sensitivity adjusting for muscular strength. Muscular strength is not associated with regional body fat and insulin sensitivity after accounting for CRF.

Determinants of High-Dose Insulin Usage and Upper Extremity Muscle Strength in Adult Patients With Type 2 Diabetes.

OBJECTIVES: In this study, we aimed to determine the association between upper extremity muscle strength and insulin dose in patients with type 2 diabetes. METHODS: A total of 236 patients with type 2 diabetes under insulin treatment for at least 1 year were included in this cross-sectional study. Patients were divided into 3 groups based on their total daily insulin dose (TDID): group 1, TDID >2 U/kg/day or >200 units/day; group 2, TDID 1 to 2 U/kg/day or 51 to 199 U/day; and group 3, TDID <0.5 U/kg/day or 50 U/day. High-dose insulin use was defined as total daily insulin dose >2 U/kg or >200 U/day. Muscle strength was measured using a handgrip dynamometer. RESULTS: High-dose insulin users were younger and had higher measures of generalized and central obesity and glycated hemoglobin. There was no significant difference in muscle strength between the groups. Low muscle strength was seen in 26.7% of all patients. Patients with low muscle strength were older, had lower insulin dose treatment and had better glycemic control than patients with normal muscle strength. Handgrip strength was inversely correlated with age, body mass index and duration of diabetes, but not with TDID. CONCLUSIONS: Patients with type 2 diabetes with high-dose insulin use had similar upper extremity muscle strength measurements with standard-dose insulin users. Studies with more patients are needed to determine the relationship between muscle mass, muscle strength and high-dose insulin use.

Effects of resistance exercise and dance in the functionality of lower limbs in the older adult of INAPAM´s senior clubs / Efectos del ejercicio de resistencia y baile en la funcionalidad de miembros inferiores en el adulto mayor de clubes de ancianos INAPAM / Efeitos do exercício físico e da dança a funcionalidade dos membros inferiores em idosos dos clubes seniores do INAPAM / Effets de la résistance et exercice de danse dans la fonctionnalité des membres inférieurs chez les personnes âgées,des clubs seniors de l'INAPAM

Abstract Objective To determine the effect of resistance exercise routine and dancing in the lower limbs of no institutionalized elderly, cognitively intact, functional for basic activities of daily living without falling risks. Material and Methods A quasi-experimental study, the effect of an intervention on a single group, consisting of 26 persons aged 60 AM considering criteria of inclusion and non-inclusion was determined. The Short Portable Mental Status Questionnaire was used; Katz Scale and the Scale of Tinetti. The information obtained was analyzed in two stages, descriptive and inferential. In the first phase, frequency distribution tables and measures of central tendency and dispersion for all variables were obtained, as discussed in qualitative or quantitative variables, respectively. In the second phase, the effect of the intervention trophism comparing averages, muscle strength and arcs of movement group and individual pre- and post-intervention was evaluated. Results There was a trend for improvement in the flexibility of the hip, knee and ankle mostly knee extension remained the same, 84.61% and 80.76% right left. Left hip extension remains the same at 50% and 53.84%, the right side. Muscle strength increased overall in all muscle groups of both lower extremities. Trophism increased in diameter thighs, calves by 46% and over 50% were similar diameters, some of the older adults lost weight so their diameter decreased. Conclusions This program showed significant changes in muscle strength and range of motion in the study participants could see the significant association between dancing Zumba Gold and resistance exercises to increase muscle strength, flexibility lower extremities and increased level of activity in older adults. Exercise and physical activity are important for the positive effects that cause health and improvements in the diameter of the thighs and increased functionality of the elderly.

Resumen Objetivo Determinar el efecto de una rutina de ejercicios de resistencia y baile en miembros inferiores de adultos mayores no institucionalizados, cognitivamente íntegros, funcionales para actividades básicas de la vida diaria, sin riesgo de caídas. Material y métodos Estudio cuasi-experimental, se determinó el efecto de una intervención sobre un grupo único, constituido por 26 personas AM de 60 años considerando criterios de inclusión y de no inclusión. Se utilizó el Short Portable Mental Status Questionnaire; la Escala de Katz y la Escala de Tinetti. La información obtenida fue analizada en dos fases, descriptiva e inferencial. En la primera fase, se obtuvieron tablas de distribución de frecuencias así como medidas de tendencia central y de dispersión para todas las variables, según se trató de variables cualitativas o cuantitativas, respectivamente. En la segunda fase, se evaluó el efecto de la intervención comparando los promedios de trofismo, fuerza muscular y de arcos de movimientos, individuales y grupales pre- y post intervención. Resultados Hubo tendencia a la mejoría en la flexibilidad en cadera, rodilla y tobillo en su mayoría, la extensión de rodilla se mantuvo igual, 84.61% derecha y 80.76% izquierda. La extensión de cadera izquierda permanece igual en un 50% y 53.84%, del lado derecho. La fuerza muscular incrementó en general en todos los grupos musculares de ambas extremidades inferiores. El trofismo de muslos aumentó en su diámetro, las pantorrillas en un 46% y más del 50% mantuvieron diámetros similares Algunos de los AM bajaron de peso, por lo tanto sus diámetros disminuyeron. Conclusiones Este programa mostró modificaciones significativas en la fuerza muscular y rangos de movimientos en los participantes del estudio, se pudo ver la asociación importante que existe entre el baile de Zumba Gold y Ejercicios de Resistencia con el incremento de la fuerza muscular, flexibilidad de las extremidades inferiores y el incremento en el nivel de la actividad en los adultos mayores. El ejercicio y la actividad física son importantes, por los efectos positivos que causan sobre la salud y la mejoría en el diámetro de los muslos y el aumento en la funcionalidad del adulto mayor.

Resumo Objetivo Para determinar o efeito de uma rotina de exercícios de resistência e dança nos membros inferiores de idosos não institucionalizados, cognitivamente íntegros e funcionais para atividades básicas da vida diária, sem risco de queda. Material e métodos Estudo quase experimental, determinou-se o efeito de uma intervenção sobre um único grupo, constituído por 26 pessoas AM de 60 anos considerando critérios de inclusão e não-inclusão. Utilizou-se o Short Portable Mental Status Questionnaire; a escala Katz e a escala de Tinetti. A informação obtida foi analisada em duas fases, descritiva e inferencial. Na primeira fase, foram obtidos tabelas de distribuição de frequência assim como medidas de tendência central e de dispersão para todas as variáveis, segundo se tratou de variáveis qualitativas ou quantitativas, respectivamente. Na segunda fase, avaliou-se o efeito da intervenção através da comparação da média de trofismo, força muscular e arcos de movimentos, individual, em grupo pré- e pós-intervenção. Resultados Houve uma tendência de melhora na flexibilidade do quadril, joelho e tornozelo principalmente, a extensão do joelho permaneceu a mesma, 84,61% direita e 80,76% para a esquerda. A extensão do quadril esquerdo permanece igual em um 50% e 53,84%, no lado direito. A força muscular aumentou geralmente em todos os grupos musculares de ambas as extremidades inferiores. O trofismo de coxas aumentou em diâmetro, pantorilha em um 46% e mais do 50% mantiveram diâmetros semelhantes. Alguns dos AM perderam peso, pelo que os seus diâmetros diminuíram. Conclusões Este programa mostrou mudanças significativas na força muscular e amplitude de movimento nas participantes do estudo, pôde-se ver a associação significativa que existe entre a dança Zumba Ouro e Exercícios de Resistência com o aumento da força muscular, flexibilidade das extremidades inferiores e o aumento no nível da atividade em adultos mais velhos. O exercício e a atividade física são importantes, pelos efeitos positivos que causam sobre a saúde e a melhoria do diâmetro das coxas e do aumento da funcionalidade do idoso.

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Velocity-based resistance training: impact of velocity loss in the set on neuromuscular performance and hormonal response.

This study aimed to compare the effects of 2 resistance training (RT) programs with different velocity losses (VLs) allowed in each set: 10% (VL10%) versus 30% (VL30%) on neuromuscular performance and hormonal response. Twenty-five young healthy males were randomly assigned into 2 groups: VL10% (n = 12) or VL30% (n = 13). Subjects followed a velocity-based RT program for 8 weeks (2 sessions per week) using only the full-squat (SQ) exercise at 70%-85% 1-repetition maximum (1RM). Repetition velocity was recorded in all training sessions. A 20-m running sprint, countermovement jump (CMJ), 1RM, muscle endurance, and electromyogram (EMG) during SQ exercise and resting hormonal concentrations were assessed before and after the RT program. Both groups showed similar improvements in muscle strength and endurance variables (VL10%: 7.0%-74.8%; VL30%: 4.2%-73.2%). The VL10% resulted in greater percentage increments in CMJ (9.2% vs. 5.4%) and sprint performance (-1.5% vs. 0.4%) than VL30%, despite VL10% performing less than half of the repetitions than VL30% during RT. In addition, only VL10% showed slight increments in EMG variables, whereas no significant changes in resting hormonal concentrations were observed. Therefore, our results suggest that velocity losses in the set as low as 10% are enough to achieve significant improvements in neuromuscular performance, which means greater efficiency during RT. Novelty The VL10% group showed similar or even greater percentage of changes in physical performance compared with VL30%. No significant changes in resting hormonal concentrations were observed for any training group. Curvilinear relationships between percentage VL in the set and changes in strength and CMJ performance were observed.

Detrimental association between quadriceps strength and exposure to polycyclic aromatic hydrocarbons in elderly adults.

Polycyclic aromatic hydrocarbons (PAHs) are environmental pollutants primarily from the incomplete combustion of organic materials. Myriads of studies have reported the associations between PAH exposure with several adverse health outcomes. However, no previous study had explored the relationship between PAH exposure with muscle strength in the elderly population. In the present study, we included 473 elderly adults who were obtained from the US National Health and Nutrition Examination Survey (NHANES) (2001-2006). PAH metabolites were measured in urine samples. Muscle strength was determined as the isokinetic strength of the quadriceps. Pertinent variables were analyzed by various standard measurements. The association between PAH exposure and muscle strength was examined using multivariable linear regression models. After fully adjusting for covariables, PAH metabolites had a negative relationship with muscle strength, especially 3-fluorene (ß = -0.021, 95% CI: -0.042, 0.000) and 2-fluorene (ß = -0.020, 95% CI: -0.034, -0.005). Notably, the relationship remained significant in males, but not in females. PAH exposure is associated with decreased muscle strength in the US elderly population. Further studies are needed to bring to light the underlying mechanisms for these findings. In addition, it is important to provide interventions and determine strategies for treating the adverse impact of PAH exposure on dynapenia. Novelty PAH exposure is associated with decreased muscle strength in elderly adults. The adverse impact remains in males.

Healthy lifestyle moderates the relationship between cardiovascular disease with blood pressure, body composition, carotid intima-media thickness, and glycated hemoglobin among adults.

We investigate whether the adherence to healthy lifestyle recommendations (regular physical activity, healthy diet, reduced alcohol consumption, nonsmoking) moderates the relationship between cardiovascular disease (CVD) and its risk factors (obesity, diabetes, dyslipidemia, and hypertension) with clinical variables among adults. This cross-sectional population-based study comprised 862 adults (39.3 ± 11.4 years, 46.4% men) from Florianópolis, Brazil. Clinical variables were systolic (SBP) and diastolic blood pressure, waist circumference, body mass index (BMI), percentage of body fat, muscular strength, carotid intima-media thickness (IMT), high sensitive C-reactive protein, and lipid and glucose metabolism markers. Multiple linear regression adjusted for confounding factors was used. Reduced IMT and HbA1c were observed in males with CVD or its risk factors who adopted healthy lifestyle recommendations (p < 0.001), and lower SBP levels were observed in females without CVD or its risk factors (p = 0.034). Females with CVD or its risk factors who followed healthy lifestyle recommendations showed higher BMI (p = 0.035). Adherence to number of healthy lifestyle recommendations moderated cardiovascular health in adults with CVD and without CVD. Novelty The adherence to healthy lifestyle recommendations moderated the relationship between IMT and HbA1c with CVD or its risk factors among males. The lower values of SBP among females without CVD or its risk factors were moderated by the adherence to healthy lifestyle recommendations.

Effects of combined supervised intermittent aerobic, muscle strength and home-based walking training programs on cardiorespiratory responses in women with breast cancer.

BACKGROUND: The aim of this investigation was to study the effects of supervised combined intermittent aerobic, muscle strength and home-based walking training programs on cardiorespiratory fitness in women with breast cancer during adjuvant chemotherapy treatment. METHODS: Thirty-two women with breast cancer undertaking adjuvant chemotherapy participated in the study (trained group n=20 and control group n=12). The trained group carried out 6weeks of supervised intermittent cycling aerobic, muscle strength and home-based walking training programs. The self-selected walking speed (WS), walking distance covered (WD), heart rate (rHR), blood lactate ([La]b) concentration and rating of perceived exertion (RPE) were assessed in the two groups during the 6-min walking test before and after the training period. RESULTS: Compared to controls, a significant increase in the WS (P<0.01) and the WD (P<0.01) accompanied by a significant decrease in resting rHR (P<0.01), exercising HR6' (P<0.01), [La]b (P<0.05), HR6'/WS (P<0.01) and [La]b/WS ratios (P<0.01) was reported in the trained group. However, a significant decrease both in WD (P<0.01) and WS (P<0.01) has been observed in the controls. No significant difference was observed in resting HR, exercising HR6', [La]b, HR6'/WS, and [La]b/WS ratios were observed in the control group. A significant improvement was observed for RPE in training group (P<0.05). However, no difference was shown in controls. CONCLUSION: Combined training based on intermittent aerobic exercise, muscle strength and walking improve cardiorespiratory responses and reduce the perception of fatigue in women with breast cancer.

Association of Modifiable Risk Factors with Bone Mineral Density among People with Distal Radius Fracture: A Cross-Sectional Study.

Purpose: This study determined the extent to which modifiable risk factors (balance, muscle strength, and physical activity [PA]) explained variability in bone mineral density (BMD) among people with a recent distal radius fracture (DRF). Method: This cross-sectional study included 190 patients, aged 50-80 years, with a DRF. Participants were assessed for balance, muscle strength, PA, fracture-specific pain, and disability. Areal BMD at the femoral neck (BMD-FN) and total hip (BMD-TH) was assessed. Correlation and multiple linear regression was used to determine the contribution of modifiable risk factors to BMD. Results: Balance, handgrip strength, knee extension strength, and plantar-flexion strength had significant bivariate associations with BMD-FN. There was a weak to moderate correlation (r = 0.25-0.40; p < 0.05) of balance and grip strength with BMD. Grip strength independently (p < 0.05) explained 17% and 12% of the variability in BMD-FN (n = 81) and BMD-TH (n = 82), respectively. Stratified by age, balance (R 2 = 0.10; p = 0.04) and grip strength (R 2 = 0.32; p = 0.003) were independent significant predictors of BMD-FN among women aged 50-64 years and 65-80 years, respectively. Conclusions: Grip strength of the unaffected hand is independently associated with BMD-FN and BMD-TH in people with recent DRF. It may act as a surrogate for general bone health, frailty, or overall muscle strength rather than as a direct target for intervention.

Objectif : déterminer dans quelle mesure les facteurs de risque modifiables (équilibre, force musculaire et activité physique [AP]) expliquait la variabilité de l'ostéodensitométrie, ou densité minérale osseuse (DMO), chez les personnes victimes d'une récente fracture du radius distal (FRD). Méthodologie : la présente étude transversale incluait 190 patients de 50 à 80 ans victimes d'une FRD. Les chercheurs ont évalué l'équilibre, la force musculaire, l'AP, la douleur propre à la fracture et l'incapacité des participants. Ils ont évalué la DMO surfacique du col du fémur (DMO-CF) et de la hanche totale (DMO-HT). Ils ont utilisé la corrélation et la régression linéaire multiple pour déterminer l'apport des facteurs de risque modifiables à la DMO. Résultats : l'équilibre, la force de préhension de la main, la force d'extension du genou et la force de flexion plantaire avaient des associations bivariées significatives avec la DMO-CF. On constatait une corrélation faible à modérée (r = 0,25 à 0,40; p < 0,05) de l'équilibre et de la force de préhension avec la DMO. La force de préhension seule (p < 0,05) expliquait 17 % de la variabilité de la DMO-CF (n = 81) et 12 % de la DMO-HT (n = 82). Stratifiées en fonction de l'âge, l'équilibre (R 2 = 0,10; p = 0,04) et la force de préhension (R 2 = 0,32; p = 0,003) étaient des prédicteurs indépendants importants de DMO-CF chez les femmes de 50 à 64 ans et de 65 à 80 ans, respectivement. Conclusion : la force de préhension de la main non atteinte s'associe de manière indépendante à la DMO-CF et à la DMO-HT chez les personnes victimes d'une récente FRD. Elle peut remplacer l'évaluation de la santé osseuse générale, de la fragilité ou de la santé musculaire globale plutôt que d'être une cible directe d'intervention.

Maintenance of skeletal muscle function following reduced daily physical activity in healthy older adults: a pilot trial.

Older adults can experience periods of inactivity related to disease or illness, which can hasten the development of physical disability, in part, through reductions in skeletal muscle strength and power. To date no study has characterized adaptations in skeletal muscle physical function in response to reduced daily physical activity. Participants (15 men, aged 69 ± 2 years; 15 women, aged 68 ± 4 years) restricted their daily steps (<750 steps/day) while being energy restricted (-500 kcal/day) for 2 weeks before returning to normal activity levels during recovery (RC; 1 week). Before and after each phase, measures of knee extensor isometric maximum voluntary contraction (MVC), time-to-peak torque, and physical function were performed and muscle biopsies were taken from a subset of participants. Following the energy restriction and step-reduction phase (ER+SR), MVC was reduced by 9.1 and 6.1 Nm in men and women, respectively (p = 0.02), which returned to baseline after RC in men, but not women (p = 0.046). Maximum isometric tension in MHC IIA fibres (p < 0.01) and maximum power production in MHC I and IIA (p = 0.05) were increased by 14%, 25%, and 10%, respectively, following ER+SR. Reductions in muscle strength could not be explained by changes in single muscle fibre function in a subsample (n = 9 men) of volunteers. These data highlight the resilience of physical function in healthy older men in the face of an acute period of ER+SR and demonstrate sex-based differences in the ability to recover muscle strength upon resumption of physical activity.

Effect of strength training combined with antioxidant supplementation on muscular performance.

This was a placebo-controlled randomized study that aimed to investigate the effects of strength training (ST) combined with antioxidant supplementation on muscle performance and thickness. Forty-two women (age, 23.8 ± 2.7 years; body mass, 58.7 ± 11.0 kg; height, 1.63 ± 0.1 m) were allocated into 3 groups: vitamins (n = 15), placebo (n = 12), or control (n = 15). The vitamins and placebo groups underwent an ST program, twice a week, for 10 weeks. The vitamins group was supplemented with vitamins C (1 g/day) and E (400 IU/day) during the ST period. Before and after training, peak torque (PT) and total work (TW) were measured on an isokinetic dynamometer, and quadriceps muscle thickness (MT) was assessed by ultrasound. Mixed-factor ANOVA was used to analyze data and showed a significant group × time interaction for PT and TW. Both the vitamins (37.2 ± 5.4 to 40.3 ± 5.6 mm) and placebo (39.7 ± 5.2 to 42.5 ± 5.6 mm) groups increased MT after the intervention (P < 0.05) with no difference between them. The vitamins (146.0 ± 29.1 to 170.1 ± 30.3 N·m) and placebo (158.9 ± 22.4 to 182.7 ± 23.2 N·m) groups increased PT after training (P < 0.05) and PT was higher in the placebo compared with the control group (P = 0.01). The vitamins (2068.3 ± 401.2 to 2295.5 ± 426.8 J) and placebo (2165.1 ± 369.5 to 2480.8 ± 241.3 J) groups increased TW after training (P < 0.05) and TW was higher in the placebo compared with the control group (P = 0.01). Thus, chronic antioxidant supplementation may attenuate peak torque and total work improvement in young women after 10 weeks of ST.

The effects of priming exercise on the V̇O2 slow component and the time-course of muscle fatigue during very-heavy-intensity exercise in humans.

We hypothesized that prior exercise would attenuate the muscle fatigue accompanied by oxygen uptake slow-component (V̇O2SC) behavior during a subsequent very-heavy (VH)-intensity cycling exercise. Thirteen healthy male subjects performed tests to determine the critical power (CP) and the fixed amount of work above CP ([Formula: see text]) and performed 6 square-wave bouts until 3 or 8 min, each at a work rate set to deplete 70% [Formula: see text] in 8 min, with a maximal isokinetic effort before and after the conditions without (VHCON) and with prior exercise (VHEXP), to measure the cycling peak torque decrement. The V̇O2SC magnitude at 3 min (VHCON = 0.280 ± 0.234, VHEXP = 0.116 ± 0.109 L·min-1; p = 0.04) and the V̇O2SC trajectory were significantly lower for VHEXP (VHCON = 0.108 ± 0.042, VHEXP = 0.063 ± 0.031 L·min-2; p < 0.01), leading to a V̇O2SC magnitude at the eighth minute that was significantly lower than VHCON (VHCON = 0.626 ± 0.296 L·min-1, VHEXP = 0.337 ± 0.179; p < 0.01). Conversely, peak torque progressively decreased from pre-exercise to 3 min (Δtorque = 21.5 ± 7.7 vs. 19.6 ± 9.2 Nm) and to 8 min (Δtorque = 29.4 ± 15.8 vs. 27.5 ± 12.0 Nm) at VHCON and VHEXP, respectively, without significant differences between conditions. Regardless of the condition, there was a significant relationship between Δtorque and the V̇O2SC (R2: VHCON = 0.23, VHEXP = 0.25; p = 0.01). Considering that "priming" effects on the V̇O2SC were not accompanied by the muscle force behavior, these findings do not support the hypothesis of a "causal" relationship between the time-course of muscle fatigue and V̇O2SC.

Separate and combined effects of time of day and verbal instruction on knee extensor neuromuscular adjustments.

We examined the effects of time of day and verbal instruction, separately and combined, on knee extensor neuromuscular adjustments, with special reference to rapid muscle force production capacity. Ten healthy male participants performed 4 experimental trials in counterbalanced order: morning "hard-and-fast" instruction, evening hard-and-fast instruction, morning "fast" instruction, and evening fast instruction. During each experimental trial, neuromuscular performance was assessed from the completion of 6 maximal isometric voluntary contractions (rest = 2 min) of the knee extensors with concomitant quadriceps surface electromyography recordings. For each contraction, we determined maximal voluntary force (Fmax), maximal rate of force development (RFDmax) and associated maximal electromechanical delay (EMDmax), and maximal rate of muscle activation (RMAmax). Globally, oral temperature (+2.2%), Fmax (+4.9%) and accompanying median frequency (+6.6%)/mean power frequency (+6.0%) as well as RFDmax (+13.5%) and RMAmax (+15.5%) were significantly higher in the evening than morning (p < 0.05). Conversely, evening in reference to morning values were lower for EMDmax (-4.3%, p < 0.05). Compared with a hard-and-fast instruction, RFDmax (+30.6%) and corresponding root mean square activity (+18.6%) were globally higher using a fast instruction (p < 0.05), irrespectively of the time of day. There was no significant interaction effect of time of day and verbal instruction on any parameter, except for EMDmax (p = 0.028). Despite diurnal variation in maximal or explosive force production of knee extensors and associated neuromuscular parameters, these adjustments occurred essentially independently of the verbal instruction provided.

Mechanical, biochemical, and dietary determinants of the functional model of bone development of the radius in children and adolescents.

This study examined the degree to which various mechanical, biochemical, and dietary factors are related to nonweight bearing bone properties in 172 healthy peri-pubertal children (age, 11.7 ± 2.0 years). Dominant radial speed of sound (rSOS) was measured by transaxial quantitative ultrasound at distal radius. Potential modulating factors included somatic maturity offset (years from age of peak height velocity), grip strength, forearm lean cross-sectional area (CSA), physical activity, nutritional intake, and amino-terminal cross-linking propeptide (NTx), reflecting bone resorption. In a hierarchical regression, grip strength adjusted for CSA was the second most important predictor of rSOS after the maturity offset (ß = 0.22 and ß = 0.33, respectively; R2 = 0.16). When relative grip strength was added to the model the contribution of sex was no longer significant. Calcium intake was a significant predictor of rSOS only after NTx was accounted for in the model (ß = 0.17, R2 = 0.21). This may suggest that calcium's effects on the muscle-bone unit may be modulated through bone resorption. In the final model, relative grip strength together with maturity offset, dietary calcium, and NTx explained up to 21% of the variance in rSOS in this cohort of children. Therefore, during the peri-pubertal stage, size-adjusted forearm muscle strength is related to radial bone strength after controlling for maturity, with calcium intake having a potential indirect association through NTx.

Association of plasma 25-hydroxyvitamin D with physical performance in physically active children.

Vitamin D is thought to regulate skeletal muscle function and boost physical performance. The aim of this study was to assess the relationship between vitamin D and physical performance in physically active children. This cross-sectional study included 125 children who practice football as a leisure activity. Plasma 25-hydroxyvitamin D (25-OHD) was assessed using a chemiluminescence immunoassay method. Vitamin D inadequacy was defined as 25-OHD < 20 ng/mL. Physical performance testing included measurements of muscle strength (maximal isometric contraction), jumping ability (vertical jump, standing broad jump, triple hop test), linear sprint (10 m and 20 m), and agility (9 × 4-m shuttle run). Plasma 25-OHD concentrations were positively correlated with muscle strength (r = 0.539; p < 0.001), vertical jump (r = 0.528; p < 0.001), and standing broad jump (r = 0.492; p < 0.001) but inversely correlated with sprint performance (r = -0.539; p < 0.001). In multivariate analysis models, plasma 25-OHD concentrations were associated with each physical performance parameter independently of age, maturity status, body mass index, fat mass, and protein and calcium intakes. In conclusion, a low plasma 25-OHD level was associated with decreased muscle strength, agility, and jumping and sprinting abilities in physically active children. Vitamin D inadequacy may limit exercise performance. Further research should verify whether correction of vitamin D deficiency enhances physical performance.