Maximal Voluntary Muscle Strength Research Articles

Can phase angle from bioelectrical impedance analysis associate with neuromuscular properties of the knee extensors?

Maintenance and improvement of neuromuscular functions is crucial for everyone regardless of age. An easy way to assess neuromuscular properties without muscle contraction is useful especially for those who cannot perform strenuous muscular force production, such as older adults and patients with orthopedic or cognitive disorders. Bioelectrical impedance analysis (BIA) can assess body electrical properties e.g., phase angle (PhA) which is regarded as muscle quantity/quality index. The purpose of this study was to investigate associations of PhA with neuromuscular properties of the knee extensors in 55 young (n = 23) and older (n = 32) adults. The values of PhA of the right thigh and whole-body were determined with BIA at 50 kHz. The participants performed 4-s maximal voluntary isometric contraction (MVIC) to measure peak torque (PTMVIC), and 1-s brief MVIC to assess rate of torque development (RTD) over the time interval of 0–200 ms. As markers of physiological mechanisms of muscle force production, twitch contractile properties (peak twitch torque, rate of twitch torque development, and time-to-peak twitch torque) of the knee extensors obtained by femoral nerve electrical stimulation, and muscle activity assessed as root mean square values of electromyographic activity (EMG-RMS) during PTMVIC and RTD measurements were measured. Thigh and whole-body PhA significantly correlated with PTMVIC (r ≥ 0.555, p < 0.001) and electrically evoked twitch parameters (peak twitch torque, rate of twitch torque development, and time-to-peak twitch torque; |r| ≥ 0.420, p ≤ 0.001), but not RTD (r ≤ 0.237, p ≥ 0.081) or EMG-RMSs (|r| ≤ 0.214, p ≥ 0.117). Stepwise multiple linear regression analysis revealed that thigh PhA was selected as a significant variable to predict PTMVIC but not RTD. Whole-body PhA was not selected as a significant variable to predict PTMVIC or RTD. In conclusion, both thigh and whole-body PhA can associate with maximal voluntary muscle strength of the knee extensors, and this association may be due to intrinsic contractile properties but not neural aspects. Regarding prediction of the knee extensor strength, thigh PhA is preferable as the predictor rather than whole-body PhA which is used as a widely acknowledged indicator of sarcopenia.

Effect of blood-flow restricted vs heavy-load strength training on muscle strength: Systematic review and meta-analysis.

Heavy-load strength training (HLT) is generally considered the Gold Standard exercise modality for inducing gains in skeletal muscle strength. However, use of heavy external exercise loads may be contraindicative in frail individuals. Low-load resistance exercise combined with partial blood-flow restriction (LL-BFR exercise) may offer an effective alternative for increasing mechanical muscle strength and size. The aim of this study was to compare the effect of LL-BFR training to HLT on maximal muscle strength gains. Prospero registration-id (CRD42014013382). A systematic search in six healthcare science databases and reference lists was conducted. Data selected for primary analysis consisted of post-intervention changes in maximal muscle strength. A random-effects meta-analysis with standardized mean differences (SMD) was used. Of 1413 papers identified through systematic search routines, sixteen papers fulfilled the inclusion criteria, totalling 153 participants completing HLT and 157 completing LL-BFR training. The magnitude of training-induced gains in maximal muscle strength did not differ between LL-BFR training and HLT (SMD of -0.17 (95% CI: -0.40; 0.05)). Low between-study heterogeneity was noted (I2 =0.0%, Chi2 P=9.65). Low-load blood-flow-restricted training appears equally effective of producing gains in maximal voluntary muscle strength compared to HLT in 20- to 80-year-old healthy and habitually active adults.

Wearable electromyography recordings during daily life activities in children with cerebral palsy.

To test whether wearable textile electromyography (EMG) recording systems may detect differences in muscle activity levels during daily activities between children with cerebral palsy (CP) and age-matched typically developing children. Wearable textile EMG recording systems were used to obtain leg muscle activity in 10 children with spastic CP (four females, six males; mean age 9y 6mo, standard deviation [SD] 2y 4mo, range: 6-13y; Gross Motor Function Classification System [GMFCS] level I and II) and 11 typically developing children (four females, seven males; mean age 9y 9mo, SD 1y 11mo, 7-12y) at rest and while performing seven daily activities. Children with CP showed significantly lower absolute EMG levels during maximal voluntary contractions (MVCs) of muscles on the most affected side as compared to the least affected side and to typically developing children. None of the typically developing children or children with CP showed detectable EMG activity in resting situations. EMG activity relative to MVC was greater in children with CP during walking, jumping, and kicking on the most affected side as compared to the least affected side and to typically developing children. Wearable textile EMG recording systems may be used to determine differences in muscle activity during daily activities in children with CP. Children with CP showed reduced muscle activity during daily activities compared to their peers, but used a significantly larger part of their maximal voluntary muscle strength to perform these activities. Wearable textile electromyography (EMG) systems are feasible for measurement of daily muscle activity in children with cerebral palsy (CP). Children with CP showed reduced EMG levels during maximal voluntary contractions. Neither typically developing childrenor children with CP showed EMG activity in resting situations. Children with CP used a larger part of their voluntary muscle strength during daily activities.

High Resistance-Training Volume Enhances Muscle Thickness in Resistance-Trained Men.

Brigatto, FA, Lima, LEdM, Germano, MD, Aoki, MS, Braz, TV, and Lopes, CR. High resistance-training volume enhances muscle thickness in resistance-trained men. J Strength Cond Res 36(1): 22-30, 2022-This study investigated the effects of different volumes of resistance training (RT) (8 weeks of 16, 24, and 32 weekly sets per muscle group) on muscular strength and hypertrophy. Subjects were pair-matched according to baseline strength and then randomly assigned to 1 of 3 experimental groups: 16 weekly sets per muscle group (G16, n = 9), 24 weekly sets per muscle group (G24, n = 9), or 32 weekly sets per muscle group (G32, n = 9). All other RT variables (e.g., exercise performed, exercise order, weekly frequency, range of repetitions, rest interval between sets and exercises, etc.) were maintained constant. The total load lifted was calculated for every RT session to compare the accumulated external training load among experimental groups across the intervention period. Testing was conducted before intervention (pre) and after 8-week (post-8) periods for maximal voluntary muscle strength (1 repetition maximum [1RM] test for bench press and parallel back squat exercises) and muscle thickness (MT) of the biceps brachii, triceps brachii, and vastus lateralis. The major findings were as follows: (a) all RT volumes increased bench press and parallel back squat 1RM and (b) all RT volumes increased the biceps brachii, triceps brachii, and vastus lateralis MT. The magnitude of increase in 1RM and MT of the lower body when training with 32 weekly sets per muscle group was higher than for 16 weekly sets per muscle group. The magnitude of the increase in MTTB was higher when training with 32 weekly sets than for 16 weekly sets.

Impaired muscle strength may contribute to fatigue in patients with aneurysmal subarachnoid hemorrhage.

Patients with aneurysmal subarachnoid hemorrhage (a-SAH) show long-term fatigue and face difficulties in resuming daily physical activities. Impaired muscle strength, especially of the lower extremity, impacts the performance of daily activities and may trigger the onset of fatigue complaints. The present study evaluated knee muscle strength and fatigue in patients with a-SAH. This study included 33 patients, 6 months after a-SAH, and 33 sex-matched and age-matched healthy controls. Isokinetic muscle strength of the knee extensors and flexors was measured at 60 and 180°/s. Maximal voluntary muscle strength was defined as peak torque and measured in Newton-meter. Fatigue was examined using the Fatigue Severity Scale. In patients with a-SAH, the maximal knee extension was 22% (60°/s) and 25% (180°/s) lower and maximal knee flexion was 33% (60°/s) and 36% (180°/s) lower compared with that of matched controls (P≤0.001). The Fatigue Severity Scale score was related to maximal knee extension (60°/s: r=-0.426, P=0.015; 180°/s: r=-0.376, P=0.034) and flexion (60°/s: r=-0.482, P=0.005; 180°/s: r=-0.344, P=0.083). The knee muscle strength was 28-47% lower in fatigued (n=13) and 11-32% lower in nonfatigued (n=20) patients; deficits were larger in fatigued patients (P<0.05), particularly when the muscle strength (peak torque) was measured at 60°/s. The present results indicate that patients with a-SAH have considerably impaired knee muscle strength, which is related to more severe fatigue. The present findings are exploratory, but showed that knee muscle strength may play a role in the severity of fatigue complaints, or vice versa. Interventions targeting fatigue after a-SAH seem necessary and may consider strengthening exercise training in order to treat a debilitating condition.

Inclusion body myositis: clinical, morphological, physiological and laboratory findings in 18 cases.

Eighteen consecutive patients with inclusion body myositis (IBM) were studied. The mean age of onset of symptoms was 60 years. A typical clinical pattern with insidious onset of muscle weakness in knee extensors and finger flexors combined with dysphagia was observed. Serial measurements of the maximal voluntary muscle strength revealed a mean loss of muscle strength of 1.4% per month. Two of the cases had common variable immunodeficiency, and three cases had reduced levels of the IgG3 subclass. Treatment with prednisone resulted in a temporary improvement of muscle function in three patients. No positive effect of azathioprine or cyclosporine A could be documented. The results show that IBM may be associated with immunodeficiency, and that prednisone treatment may temporarily improve the clinical signs. The results from our studies on the progression of the muscle weakness may provide basis for future studies on treatment of IBM.

Neurofibromatose tipo 1: mais comum e grave do que se imagina

To study prevalence of clinical features among Brazilian patients diagnosed with neurofibromatosis type 1(NF1), comparing these features with international data to evaluate the severity and visibility of the disease and quantify less frequent manifestations such as short stature, macrocephaly, muscle strength, voice abnormalities and oral motor disorders. 183 patients diagnosed with NF1, attended at the Neurofibromatosis Outpatient Reference Center, were evaluated for clinical manifestations and complications of NF1. Severity and visibility were verified using the Riccardi and Ablon scales respectively. Voice abnormalities and oral motor disorders were quantified using the Vox-Metria software and maximal voluntary muscle strength (MVMS) was quantified using a handgrip dynamometer. Clinical manifestations of NF1 observed were comparable to those described in literature. However, more then 50% of patients presented severity and visibility classified as moderate and severe. The incidence of macrocephaly and short stature was higher among the Brazilian patients. Voice abnormalities and oral motor disorders were quantified for the first time, with hoarseness and oral motor disorders observed in more then 60% the patients. Maximal voluntary muscle strength was found to be reduced in 67% of patients. The main clinical features of these patients are similar to those reported in previous studies. More then one-half of the patients presented moderate and severe levels of NF1 (severity and visibility), including short stature, macrocephaly, voice abnormalities and oral motor disorders and decreased muscle strength. These results are in disagreement with the traditional concept that NF1 is a benign disease and also disclosed some clinical aspects not previously reported.

Effects of testosterone therapy on muscle performance and physical function in older men with mobility limitations (The TOM Trial): Design and methods

The TOM study is the first, single-site, placebo-controlled, randomized clinical trial designed to comprehensively determine the effects of testosterone administration on muscle strength and physical function in older men with mobility limitations. A total of 252 community dwelling individuals aged 65 and older with low testosterone levels and self-reported limitations in mobility and short physical performance battery (SPPB) scores between 4 and 9 will be randomized to receive either placebo or testosterone therapy for 6 months. The primary objective is to determine whether testosterone therapy improves maximal voluntary muscle strength as quantified by the one repetition maximum. Secondary outcomes will include measures of physical function (walking, stair climbing and a lifting and lowering task), habitual physical activity and self-reported disability. The effects of testosterone on affect, fatigue and sense of well being will also be assessed. Unique aspects of the TOM Trial include selection of men with self-reported as well as objectively demonstrable functional limitations, community-based screening and recruitment, adjustment of testosterone dose to ensure serum testosterone levels in the target range while maintaining blinding, and inclusion of a range of self-reported and performance-based physical function measures as outcomes. Clinicaltrials.gov identifier: NCT00240981.

Reliability of Maximal Voluntary Muscle Strength and Power Testing in Older Men

Maximal voluntary muscle strength (MVMS) and leg power are important measures of physical function in older adults. We hypothesized that performing these measures twice within 7-10 days would demonstrate a >5% increase due to learning and familiarization of the testing procedures. Data were collected from three studies in older adult men (60-87 years) and were divided into two cohorts defined by study site and type of exercise equipment. MVMS was assessed in 116 participants using the one-repetition maximum method at two separate study visits for the chest press, latissimus pull-down, leg press, leg flexion, and leg extension exercises along with unilateral leg extension power. Test-retest scores were not different and did not exceed 0.8 +/- 9.0% in Cohort 1 or 2.3 +/- 9.8% in Cohort 2, except for leg extension, which improved by 6.6 +/- 14.4% (p <.009) and 3.4 +/- 6.8% (p <.016), respectively. Repeat tests were closely correlated with initial tests (all p <.001). Pearson correlation coefficients ranged from 0.74 for leg extension power to 0.96 for leg press. Coefficients of variation were <10% (4.2%-9.0%) for all exercises except for leg extension power, which was 15.5%. Our findings demonstrated that test-retest measures of MVMS and power in older adult men do not differ by more than 2.3% except for leg extension, and have relatively low coefficients of variation using data collected from three studies. Moreover, these findings were similar between two study sites using different equipment, which further supports the reliability of MVMS and power testing in older adult men.

Circamensal Rhythmicity and Muscle Function: The Role of Reproductive Hormones in the Regulation of Strength

The human female menstrual cycle is characterised by fluctuations in reproductive and pituitary hormones which regulate the monthly release of an ovum for fertilisation. The circamensal changes in the hormonal milieu may influence exercise performance. The generation of maximal voluntary muscle strength, mediated by changes in the steroid hormones, has been the focus of recent research, particularly ergogenic effects of oestrogen. Peak force of the adductor pollicis, normalised for muscle size, has been reported mid-cycle in concert with the rise in oestrogen. The removal of an oestrogen and progesterone environment results in muscle weakness in humans and animals. These hormones decline concomitantly following natural ovarian failure (i.e., the menopause) and surgical extraction of the ovaries (i.e., bilateral oophorectomy). To overcome the problem of controlling for rapid cyclical changes in reproductive hormones across the menstrual cycle, and to isolate the effects of oestrogen when measuring strength, other models have been adopted. Treatment of in vitro fertilisation patients involves, in part, the down-regulation of gonadotropin releasing hormone receptors followed by up-regulation with exogenous pituitary hormones. This presents a very low and very high oestrogenic milieu while progesterone remains rel atively stable. Under these conditions, maximal strength of the first dorsal interosseus muscle has been unchanged. The rapid loss in strength observed post-menopause is preserved, and possibly restored, in women taking hormone replacement therapy. These findings are significant for the preservation of skeletal and muscular health of post-menopausal women. There is increasing evidence to support the role of reproductive hormones in the regulation of muscle strength. Since the link between the hormone milieu during the menstrual cycle and strength changes is weak, other models must be employed. Strength declines rapidly at the menopause, and offsetting muscle weakness in post-menopausal women has implications in reducing the risk of muscloskeletal injury. Female athletes who are prone to amenorrhoea constitute another target group. A hormone-deficient state may not be beneficial to performance, but may compromise muscle function.

Muscle performance in fibromyalgia syndrome.

The objective of the study was to examine the muscle performance, isokinetic muscle strength, muscle endurance ratio, and submaximal aerobic performance in fibromyalgia syndrome (FMS) patients, to evaluate the relation between muscle performance, pain severity, clinical findings, and physical activity level, and to compare the results with healthy control subjects. Twenty-four FMS patients and 15 control subjects participated in this study. Data were obtained about the symptoms, location and onset of pain, treatment, and associated symptoms. Patients and controls underwent an examination of isokinetic muscle strength of right quadriceps on a Cybex dynamometer, and submaximal aerobic performance tests (PWC-170) were done for all subjects. Maximal voluntary muscle strength of the quadriceps was significantly lower in patients compared with the control group. Endurance ratios showing the work capacity were not statistically different between two groups. Submaximal aerobic performance scores were higher in the control group. There was not a relation between the decreased muscle performance and clinical findings, including pain severity, number of tender points, and duration of the symptoms of FMS patients. We found a reduced quadriceps muscle strength and submaximal aerobic performance in patients with FMS, indicating that patients have impaired muscle function.