Lateral Force and EMG Activity in Wide- and Narrow-Grip Bench Press in Various Conditions.

The purpose of this study was to investigate the lateral force and contribution of shoulder horizontal adductor and elbow extensor muscles activity during wide- and narrow-grip bench press (BP) in various conditions, such as resistance-trained/non-trained, concentric/eccentric, and muscle fatigue/non-fatigue. We measured the lateral force on the bar and the electromyographic (EMG) muscle activity of pectoralis major (PM) and triceps brachii (TB) during 10 RM BP with wide grip (81 cm) and narrow grip (40 cm) in seven resistance-trained men and seven non-trained men. The all-reps average of the lateral-to-vertical force ratio both in resistance-trained and non-trained subjects was about 30% outward for the wide grip and about 10% inward for the narrow grip. The EMG contribution ratio PM/TB shows no significant differences between narrow and wide grip in all evaluated conditions except in non-trained subjects' muscle fatigue eccentric phase. Both resistance-trained and non-trained subjects did not push the bar straight upward, and the EMG PM/TB was almost unchanged by hand width. The direction adjustment of the force on the bar that achieves almost the same muscle activity degree of the shoulder and elbow joints might be optimal BP kinetics.

Greater Hip Moments in Rear-Foot-Elevated Split Squats Than in Conventional Back Squats With the Same Relative Intensity of Loads.

ABSTRACT: Arakawa, H, Mori, M, and Tanimoto, M. Greater hip moments in rear-foot-elevated split squats than in conventional back squats with the same relative intensity of loads. J Strength Cond Res 37(5): 1009-1016, 2023-Rear-foot-elevated split squat (RFESS) is often performed as an alternative to conventional double-leg back squat (DLBS). This study aimed to compare 3-dimensional joint kinetics of DLBS and RFESS using the same relative intensity of loads. Eight male college rugby players performed 3 repetitions of DLBS and RFESS at 10-repetition-maximum (RM) loading. Before testing, both exercises were incorporated into the subjects' training program with a progressive increase in loads for 4 months. A 3-dimensional optical motion capture system and force platform were used for data collection. The 3-dimensional moments at the knee and hip joints in each of the 3 axes were calculated based on the inverse dynamic procedure. p values < 0.05 were considered statistically significant. The hip extension moment was 44% greater in the RFESS than in the DLBS at the bottom position ( p < 0.01) and 47% greater for the peak value ( p < 0.01) on harmonic averages. The hip abduction and external rotation moments at the bottom position were also greater in the RFESS than in the DLBS. The findings suggest that the magnitude of hip extension moment per leg in DLBS tends to be restricted to less than that expected from the given strength level. In conclusion, the mechanical contribution of hip extensors per leg can be greater in RFESS than in DLBS when using respective 10RM loads, even if the absolute load is smaller and the trunk is more upright in RFESS.

Effect of a 1-year intervention comprising brief counselling sessions and low-dose physical activity recommendations in Japanese adults, and retention of the effect at 2 years: a randomized trial.

BACKGROUND: In an effort to increase people's adherence to active lifestyles, contemporary physical activity (PA) guidelines now include low-dose PA. METHODS: PA was evaluated in 583 participants of the Nutritional and Physical Activity Intervention Study (NEXIS) cohort (30-65 years old); 349 inactive participants (MVPA, 2.7 ± 1.0 MET-h/day) were randomly assigned to the intervention or control groups, and 235 active participants participated in follow-up visits. The intervention aimed to increase MVPA and comprised five brief counseling sessions over 1 year. The 1-year target for the participant was increasing their step-count to 10,000 steps/d or +3000 steps/d, relative to the baseline score. The counseling sessions were designed to stimulate progressive changes in physical behaviors by recommendations promoting small and/or light-intensity bouts of PA. PA was measured at baseline, the end of the intervention, and 1 year after the intervention ended. Additionally, several nutrition, health, and fitness parameters were measured. RESULTS: Participants in the intervention group significantly increased their step-count from 8415 ± 1924 at baseline to 9493 ± 2575 at the end of the 1-year period. During the same period, MVPA significantly increased by 0.9 MET-h. The daily time spent in ≥ 3, ≥ 4 and ≥ 5 MET activities increased by 11, 6, and 3 min, respectively. This increase in PA remained observable 1 year after intervention concluded. The active group maintained higher physical activity levels throughout the two years. The intervention group showed smaller energy intakes at the end of the 2-year period. Significant correlations were noted between the 1-year change in MVPA and the change in resting heart rate (r = - 0.22), and between the 2-year change in MVPA and the change in waist circumference (r = - 0.08) and peak oxygen consumption capacity (r = 0.23) in the intervention group only. CONCLUSIONS: A prolonged and progressive PA intervention promoting small bouts of light-to-moderate PA may be used in healthy, not-optimally-active people to increase PA beyond the strict period of the intervention. Further studies are necessary to understand whether low-dose PA messages can be effective in initiating a progressive increase toward larger amounts of PA. TRIAL REGISTRATION: Clinical Trials.gov, NCT00926744, retrospectively registered.

Effect of resistance training using bodyweight in the elderly: Comparison of resistance exercise movement between slow and normal speed movement.

AIM: The present study investigated whether a slow movement protocol can be applied to resistance training using bodyweight. In addition, the intervention program combined plyometric exercise with resistance exercise to improve physical function overall. METHODS: A total of 39 active elderly adults participated in a 16-week intervention. The program consisted of five resistance exercises and four plyometric exercises using their own bodyweight with a single set for each exercise. Participants were assigned to one of two experimental groups. One group carried out resistance exercise with slow movement and tonic force generation (3-s concentric, 3-s eccentric and 1-s isometric actions with no rest between each repetition). The other group as a movement comparison followed the same regimen, but at normal speed (1-s eccentric and 1-s concentric actions with 1-s rest between each repetition). Muscle size, strength and physical function were measured before and after the intervention period. RESULTS: After the intervention, strengths of upper and lower limbs, and maximum leg extensor power were significantly improved in both groups. Muscle size did not change in either group. There were no significant differences in any of the parameters between groups. CONCLUSIONS: The intervention program using only own bodyweight that comprised resistance exercise with slow movement and plyometric exercise can improve physical function in the elderly, even with single sets for each exercise. However, there was no enhanced muscle hypertrophic effect. Further attempts, such as increasing performing multiple sets, would be required to induce muscle hypertrophy. Geriatr Gerontol Int 2015; 15: 1270-1277.

Accuracy of segmental bioelectrical impedance analysis for predicting body composition in pre- and postmenopausal women.

This study aimed to compare the accuracy for predicting body composition using single-frequent segmental bioelectrical impedance analysis (BIA) between pre- and postmenopausal women. A total f 559 Japanese women aged 30-88yr were divided into 4 groups by questionnaire: natural menopause, pathological menopause, regular menstruation, or irregular menstruation. The measurement values by dual-energy X-ray absorptiometry were used as a reference of the body composition. In terms of the results, regardless of the menopausal status, BIA slightly but significantly overestimated the percentage of body fat (standard error of estimate: 5.3%-6.7%) and the leg lean soft tissue mass (LSTM; 5.1%-6.1%), and underestimated the LSTM in the whole body (6.2%-7.6%) and arm (2.8%-3.7%). The absolute values of the predictive error for leg LSTM were significantly higher in postmenopausal groups than in the premenopausal ones. The corresponding values for the whole body and arm LSTM, and the percentage of body fat were higher in premenopausal groups than in postmenopausal ones. In conclusion, the predictive accuracy of BIA for postmenopausal women is not inferior to that for premenopausal ones, unless we target the leg LSTM.

Lack of age-related increase in carotid artery wall viscosity in cardiorespiratory fit men.

OBJECTIVES: Age-related arterial stiffening and reduction of arterial elasticity are attenuated in individuals with high levels of cardiorespiratory fitness. Viscosity is another mechanical characteristic of the arterial wall; however, the effects of age and cardiorespiratory fitness have not been determined. We examined the associations among age, cardiorespiratory fitness and carotid arterial wall viscosity. METHODS: A total of 111 healthy men, aged 25-39 years (young) and 40-64 years (middle-aged), were divided into either cardiorespiratory fit or unfit groups on the basis of peak oxygen uptake. The common carotid artery was measured noninvasively by tonometry and automatic tracking of B-mode images to obtain instantaneous pressure and diameter hysteresis loops, and we calculated the effective compliance, isobaric compliance and viscosity index. RESULTS: In the middle-aged men, the viscosity index was larger in the unfit group than in the fit group (2533 vs. 2018 mmHg·s/mm, respectively: P<0.05), but this was not the case in the young men. In addition, effective and isobaric compliance were increased, and viscosity index was increased with advancing age, but these parameters were unaffected by cardiorespiratory fitness level. CONCLUSION: These results suggest that the wall viscosity in the central artery is increased with advancing age and that the age-associated increase in wall viscosity may be attenuated in cardiorespiratory fit men.

Increased muscle size and strength from slow-movement, low-intensity resistance exercise and tonic force generation.

The authors investigated the effects of low-intensity resistance training on muscle size and strength in older men and women. Thirty-five participants (age 59-76 yr) were randomly assigned to 2 groups and performed low-intensity (50% of 1-repetition maximum) knee-extension and -flexion exercises with either slow movement and tonic force generation (LST; 3-s eccentric, 3-s concentric, and 1-s isometric actions with no rest between repetitions) or normal speed (LN; 1-s concentric and 1-s eccentric actions with 1-s rests between repetitions) twice a week for 12 wk (2-wk preparation and 10-wk intervention). The LST significantly increased thigh-muscle thickness, as well as isometric knee-extension and -flexion strength. The LN significantly improved strength, but its hypertrophic effect was limited. These results indicate that even for older individuals, the LST can be an effective method for gaining muscle mass and strength.

Effects of training volume on strength and hypertrophy in young men.

Knowledge of the effects of training volume on upper limb muscular strength and hypertrophy is rather limited. In this study, both arms of the same subject were trained in a crossover-like design with different training volumes (1 or 3 sets) to eliminate the effects of genetic variation and other individual differences. The purpose of this study was to investigate the effects of training volume on muscular strength and hypertrophy in sedentary, untrained young Japanese men. Eight subjects (age, 25.0 ± 2.1 years; body mass, 64.2 ± 7.9 kg; height, 171.7 ± 5.1 cm) were recruited. The subjects trained their elbow flexor muscles twice per week for 12 consecutive weeks using a seated dumbbell preacher curl. The arms were randomly assigned to training with 1 or 3 sets. The training weight was set at 80% of 1 repetition maximum for all sets. The 3-set protocol increased cross-sectional area significantly more than did 1 set (1 set, 8.0 ± 3.7%; 3 sets, 13.3 ± 3.6%, p < 0.05). Furthermore, gains in strength with the 3-set protocol tended to be greater than those with 1 set (1 set, 20.4 ± 21.6%; 3 sets, 31.7 ± 22.0%, p = 0.076). Based on the results, the authors recommend 3 sets for sedentary untrained individuals. However, this population should incorporate light training days of 1 set into their training program to prevent overtraining and ensure adherence. The findings are relevant for the sedentary, untrained young male population and must be interpreted within the context of this study.

Greater forearm venous compliance in resistance-trained men.

Greater venous compliance is associated with attenuation of the tolerance response to orthostatic stress and reduced incidence of venous diseases. Resistance training induces tolerance to orthostatic challenge and the growth of capillaries, which may lead to negative and positive effects on venous compliance, respectively. It has not been confirmed, however, whether habitual resistance training positively or negatively affects venous compliance. We compared the forearm venous compliance in resistance-trained men with age-matched controls. Eleven resistance-trained middle-aged men (37.7 ± 1.5 years) and 12 age-matched sedentary controls (36.7 ± 1.6 years) were studied. Forearm venous compliance was measured in subjects in the supine position by inflating a venous collecting cuff placed around the upper arm to 60 mmHg for 8 min and then decreasing cuff pressure to 0 mmHg at a rate of 1 mmHg/s. Forearm venous compliance was determined using the first derivative of the pressure-volume relation during cuff pressure reduction (compliance = ß(1) + 2ß(2) × cuff pressure). Forearm venous compliance at 20 mmHg cuff pressure was 16% greater in the resistance-trained group than in the age-matched sedentary controls (0.097 ± 0.005 vs. 0.083 ± 0.004 ml/dl/mmHg, P < 0.05). Forearm venous compliance was positively related to forearm venous volume (r = 0.643, P = 0.0009), but not forearm muscle mass (r = 0.391, P = 0.0648). In conclusion, the present study suggests that (1) the resistance-trained men have greater forearm venous compliance than age-matched controls, and (2) the higher forearm venous compliance in the resistance-trained men may be explained by greater forearm venous capacitance.

Changes in muscle activation and force generation patterns during cycling movements because of low-intensity squat training with slow movement and tonic force generation.

Our previous studies showed that relatively low-load (approximately 50-60% 1 repetition maximum [1RM]) resistance training with slow movement and tonic force generation (LST) significantly increased muscle size and strength. However, LST is a very specific movement that differs from natural movements associated with sport activities and activities of daily life, and therefore, it might have some unfavorable effects on dynamic sport movement. We investigated the effects of LST on muscle activity and force generation patterns during cycling movement as a representative dynamic sports movement. Twenty-four healthy young men who were not in the habit of bicycle riding and did not have a history of regular resistance training were randomly assigned to the LST (approximately 60% 1RM load, 3-second lifting, and 3-second lowering movement without a relaxing phase: n = 8), a high-intensity exercise at normal speed (HM) group (85% 1RM load, 1-second lifting, 1-second lowering, and 1-second relaxed movement: n = 8), or sedentary control (CON, n = 8) group. Subjects in the training groups performed vertical squats by the assigned method. Exercise sessions consisted of 3 sets and were performed twice a week for 13 weeks. Pre- and posttraining muscle activation and force generation patterns during the cycling movements were evaluated by the coefficient of variation (CV) of the rectified electromyographic (EMG) wave from the vastus lateralis and CV of pedaling force. Both the CV of the rectified EMG and of pedaling force decreased significantly in the LST group (-21 and -18%, p < 0.05, respectively), whereas there were no significant changes in either the HN or the CON group. This decrease in CV in the LST group could mean that muscle activity and force generation during cycling movement have become more tonic. This result following LST may have an unfavorable effect on cycling movement and other dynamic sports movements.

Poor trunk flexibility is associated with arterial stiffening.

Flexibility is one of the components of physical fitness as well as cardiorespiratory fitness and muscular strength and endurance. Flexibility has long been considered a major component in the preventive treatment of musculotendinous strains. The present study investigated a new aspect of flexibility. Using a cross-sectional study design, we tested the hypothesis that a less flexible body would have arterial stiffening. A total of 526 adults, 20 to 39 yr of age (young), 40 to 59 yr of age (middle-aged), and 60 to 83 yr of age (older), participated in this study. Subjects in each age category were divided into either poor- or high-flexibility groups on the basis of a sit-and-reach test. Arterial stiffness was assessed by brachial-ankle pulse wave velocity (baPWV). Two-way ANOVA indicated a significant interaction between age and flexibility in determining baPWV (P < 0.01). In middle-aged and older subjects, baPWV was higher in poor-flexibility than in high-flexibility groups (middle-aged, 1,260 +/- 141 vs. 1,200 +/- 124 cm/s, P < 0.01; and older, 1,485 +/- 224 vs. 1,384 +/- 199 cm/s, P < 0.01). In young subjects, there was no significant difference between the two flexibility groups. A stepwise multiple-regression analysis (n = 316) revealed that among the components of fitness (cardiorespiratory fitness, muscular strength, and flexibility) and age, all components and age were independent correlates of baPWV. These findings suggest that flexibility may be a predictor of arterial stiffening, independent of other components of fitness.

Low-intensity resistance training with slow movement and tonic force generation increases basal limb blood flow.

Metabolic syndrome is associated with reductions in basal limb blood flow. Resistance training increasing muscle mass and strength increases basal limb blood flow. Low-intensity resistance exercise with slow movement and tonic force generation (LST) has been proposed as one of the effective methods of resistance training increasing muscle mass and strength. The hypothesis that LST training increases basal femoral blood flow as well as traditional high-intensity resistance training at normal speed (HN) was examined. Thirty-six healthy young men without a history of regular resistance training were randomly assigned to the LST [approximately 55-60% one repetition maximum (1RM) load, 3 s lifting and 3 s lowering with no relaxation phase, n = 12], HN (approximately 85-90% 1RM, 1 s lifting and 1 s lowering with 1 s relaxation, n = 12) or sedentary control (CON, n = 12) groups. Participants in the training groups underwent two whole-body training sessions per week for 13 weeks. Basal femoral blood flow increased significantly by +18% in LST and +35% in HN (both P<0.05), while there was no such change in CON. There were no significant differences between these increases induced by LST and HN, although the increase in LST corresponded to about half that in HN. In conclusion, not only resistance training in HN but in LST as well, were effective for increasing basal limb blood flow, and that this effect was evident even in healthy young men.

Effects of whole-body low-intensity resistance training with slow movement and tonic force generation on muscular size and strength in young men.

Our previous study showed that relatively low-intensity (approximately 50% one-repetition maximum [1RM]) resistance training (knee extension) with slow movement and tonic force generation (LST) caused as significant an increase in muscular size and strength as high-intensity (approximately 80% 1RM) resistance training with normal speed (HN). However, that study examined only local effects of one type of exercise (knee extension) on knee extensor muscles. The present study was performed to examine whether a whole-body LST resistance training regimen is as effective on muscular hypertrophy and strength gain as HN resistance training. Thirty-six healthy young men without experience of regular resistance training were assigned into three groups (each n = 12) and performed whole-body resistance training regimens comprising five types of exercise (vertical squat, chest press, latissimus dorsi pull-down, abdominal bend, and back extension: three sets each) with LST (approximately 55-60% 1RM, 3 seconds for eccentric and concentric actions, and no relaxing phase); HN (approximately 80-90% 1RM, 1 second for concentric and eccentric actions, 1 second for relaxing); and a sedentary control group (CON). The mean repetition maximum was eight-repetition maximum in LST and HN. The training session was performed twice a week for 13 weeks. The LST training caused significant (p < 0.05) increases in whole-body muscle thickness (6.8 +/- 3.4% in a sum of six sites) and 1RM strength (33.0 +/- 8.8% in a sum of five exercises) comparable with those induced by HN training (9.1 +/- 4.2%, 41.2 +/- 7.6% in each measurement item). There were no such changes in the CON group. The results suggest that a whole-body LST resistance training regimen is as effective for muscular hypertrophy and strength gain as HN resistance training.

Required muscle mass for preventing lifestyle-related diseases in Japanese women.

BACKGROUND: Since it is essential to maintain a high level of cardiorespiratory fitness to prevent life-style related disease, the Ministry of Health, Labour and Welfare of Japan in 2006 proposed to determine the maximal oxygen uptake (Vo2max: mL.kg-1.min-1) reference values to prevent life-style related diseases (LSRD). Since muscle mass is one of the determinant factors of Vo2max, it could be used as the reference parameter for preventing LSRD. The aim of this study was to determine and quantify the muscle mass required to maintain the Vo2max reference values in Japanese women. METHODS: A total of 403 Japanese women aged 20-69 years were randomly allocated to either a validation or a cross-validation group. In the validation group, a multiple regression equation, which used a set of age and the percentage of muscle mass (%MM, percentage of appendicular lean soft tissue mass to body weight), as independent variables, was derived to estimate the Vo2max. After the equation was cross-validated, data from the two groups were pooled together to establish the final equation. The required %MM for each subject was recalculated by substituting the Vo2max reference values and her age in the final equation. RESULTS: The mean value of required %MM was identified as (28.5 +/- 0.35%). Thus, the present study proposed the required muscle mass (28.5% per body weight) in Japanese women to maintain the Vo2max reference values determined by the Japanese Ministry of Health Labour and Welfare. CONCLUSION: The estimated required %MM (28.5% per body weight) can be used as one of the reference parameters of fitness level in Japanese women.

Resistance training in men is associated with increased arterial stiffness and blood pressure but does not adversely affect endothelial function as measured by arterial reactivity to the cold pressor test.

Resistance training is a popular mode of exercise, but may result in stiffening of the central arteries. Changes in carotid artery diameter were determined using the cold pressor test (CPT), which results in production of nitric oxide via sympathetic activation and is one of the novel methods available for assessing endothelial function in the carotid artery. To investigate the effect of resistance training on endothelial function, we designed a cross-sectional study of carotid arterial vasoreactivity to CPT in men participating in regular resistance training with increased carotid arterial stiffness compared with age-matched control subjects. Twelve resistance-trained middle-aged men (age 38.7 +/- 1.7 years) and 17 age-matched control subjects (age 36.8 +/- 1.2 years) were studied. The direction and magnitude of changes in carotid artery diameter were measured by B-mode ultrasonography during sympathetic stress induced by submersion of the foot in ice slush for 90 s. Carotid arterial beta-stiffness index, and systolic and mean arterial blood pressure were higher (7.7 +/- 0.7 versus 6.0 +/- 0.4 arbitrary units, 116 +/- 2 versus 131 +/- 4 mmHg and 86 +/- 2 versus 95 +/- 2 mmHg, respectively, all P < 0.05) in the resistance training group compared with control subjects. There were, however, no significant differences in the amount or percentage change in carotid artery diameter in CPT between the two groups (resistance training group, 0.33 +/- 0.07 mm and 5.2 +/- 1.1%; control group, 0.37 +/- 0.06 mm and 5.8 +/- 0.9%, respectively). These findings suggest that while carotid arterial stiffening and higher blood pressure are observed in regular resistance-trained men, these are not associated with abnormalities in carotid arterial vasoreactivity to sympathetic stimulus, which implies intact endothelial function.

Effects of low-intensity resistance exercise with slow movement and tonic force generation on muscular function in young men.

We investigated the acute and long-term effects of low-intensity resistance exercise (knee extension) with slow movement and tonic force generation on muscular size and strength. This type of exercise was expected to enhance the intramuscular hypoxic environment that might be a factor for muscular hypertrophy. Twenty-four healthy young men without experience of regular exercise training were assigned into three groups (n = 8 for each) and performed the following resistance exercise regimens: low-intensity [ approximately 50% of one-repetition maximum (1RM)] with slow movement and tonic force generation (3 s for eccentric and concentric actions, 1-s pause, and no relaxing phase; LST); high-intensity ( approximately 80% 1RM) with normal speed (1 s for concentric and eccentric actions, 1 s for relaxing; HN); low-intensity with normal speed (same intensity as for LST and same speed as for HN; LN). In LST and HN, the mean repetition maximum was 8RM. In LN, both intensity and amount of work were matched with those for LST. Each exercise session consisting of three sets was performed three times a week for 12 wk. In LST and HN, exercise training caused significant (P < 0.05) increases in cross-sectional area determined with MRI and isometric strength (maximal voluntary contraction) of the knee extensors, whereas no significant changes were seen in LN. Electromyographic and near-infrared spectroscopic analyses showed that one bout of LST causes sustained muscular activity and the largest muscle deoxygenation among the three types of exercise. The results suggest that intramuscular oxygen environment is important for exercise-induced muscular hypertrophy.