Junichiro Aoki

Duration of static stretching influences muscle force production in hamstring muscles.

The purpose of the present study was to investigate whether duration of static stretching could affect the maximal voluntary contraction (MVC).Volunteer male subjects (n = 10) underwent 2 different durations of static stretching of their hamstring muscles in the dominant leg: 30 and 60 seconds. No static stretching condition was used as a control condition. Before and after each stretching trial, hamstring flexibility was measured by a sit and reach test. MVC was then measured using the maximal effort of knee flexion. The hamstring flexibility was significantly increased by 30 and 60 seconds of static stretching (control: 0.5 ± 1.1 cm; 30 seconds: 2.1 ± 1.8 cm; 60 seconds: 3.0 ± 1.6 cm); however, there was no significant difference between 30 and 60 seconds of static stretching conditions. The MVC was significantly lowered with 60 seconds of static stretching compared to the control and 30 seconds of the stretching conditions (control: 287.6 ± 24.0 N; 30 seconds: 281.8 ± 24.2 N; 60 seconds: 262.4 ± 36.2 N). However, there was no significant difference between control and 30 seconds of static stretching conditions. Therefore, it was concluded that the short duration (30 seconds) of static stretching did not have a negative effect on the muscle force production.

Exercise training increases heat shock protein in skeletal muscles of old rats.

PURPOSE The effects of chronic exercise training on the expression of heat shock protein (HSP) in skeletal muscle of senescent animals are unknown. Therefore, the purpose of this study was to investigate the effects of chronic exercise training on skeletal muscle HSP expression in both young and old rats. METHODS Young adult (3 months) and old (23 months) female Fisher 344 rats were assigned to either a sedentary control or an endurance exercise trained group (N = 6 per group). Exercised animals ran (60 min.d-1, 5 d.wk-1) on a treadmill at approximately 77% VO2peak for 10 wk. After completion of the training program, the soleus (SOL), plantaris (PL), and the red (RG) and white portions (WG) of the gastrocnemius muscles were excised, and citrate synthase (CS) activity and the relative levels of HSP72 were determined. RESULTS Training resulted in increases (P < 0.05) in VO2peak in both young (67.6 +/- 3.1 vs 86.9 +/- 1.6 mL.kg-1.min-1) and old animals (54.5 +/- 1.8 vs 68.2 +/- 2.2 mL.kg-1.min-1). Training increased CS activity and the relative levels of HSP72 (P < 0.05) in all four skeletal muscles in both young and old animals. Specifically, compared with age-matched sedentary controls, exercise training resulted in increased (P < 0.05) levels of HSP72 in skeletal muscles of both young (SOL + 22%, PL +94%, RG + 44%, WG + 243%) and old animals (SOL +15%, PL +73%, RG +38%, WG +150%). CONCLUSIONS These findings reveal that the exercise-induced accumulation of HSP72 in skeletal muscle differs between fast and slow muscles. Further, these data indicate that the exercise-induced accumulation of HSP72 in highly oxidative skeletal muscles (SOL and RG) is similar between young and old animals. In contrast, aging is associated with a blunted expression of HSP72 in fast skeletal muscles (PL and WG) in response to chronic exercise.

Effect of aqua exercise on recovery of lower limb muscles after downhill running

Abstract The aim of the present study was to examine how the recovery of physiological functioning of the leg muscles after high-intensity eccentric exercise such as downhill running could be promoted by aqua exercise for a period until the damaged muscle had recovered almost completely. Ten male long-distance runners were divided equally into an aqua exercise group and a control group. From the first day (Day 0) to the fourth day (Day 3), the participants completed a questionnaire on muscle soreness, and serum creatine kinase activity, muscle power, flexibility, whole-body reaction time and muscle stiffness were measured. After measurements on Day 0, the participants performed downhill running (three 5 min runs with a 5 min rest interval at −10%, 335.7 ± 6.1 m · min−1). The aqua exercise group performed walking, jogging and jumping in water on three successive days following the downhill running on Day 0 for 30 min each day. Muscle power was reduced on Day 1 in the control group (P < 0.05). Muscle soreness in the calf on Day 3 was greater in the control group than that in the aqua exercise group (P < 0.05). In the aqua exercise group, muscle stiffness in the calf was less than that in the control group over 4 days (time main effect: P < 0.05; group × time interaction: P < 0.05). We conclude that aqua exercise promoted physiological functioning of the muscles in the legs after high-intensity downhill running for a period until the damaged muscles had recovered almost completely.

Comparison of interdevice measurement difference of pedometers in younger and older adults

Objectives In this study, the relationship between inter-instrument differences in regard to the daily number of steps with the intensity distribution of daily physical activity in younger and older adults was examined. Methods 17 younger individuals and 28 older individuals wore two pedometers (Lifecorder (LC) and EC-200 (YM)) simultaneously for 7 days, in order to determine the number of steps each took. Furthermore, LC determined the time spent in light, moderate and vigorous physical activity, corresponding to <3 metabolic equivalent (METs), 3 to 6 METs and >6 METs, respectively. Results The LC detected a significantly larger number of steps than YM (p<0.001), yet there was a strong relationship between the two measurements (r = 0.962, p<0.001). The interdevice difference with the number of steps significantly decreased in inactive older individuals compared with the active older and younger individuals, and it was also significantly negatively correlated with the time spent in light-intensity physical activity (LPA) (r = 0.523, p<0.01). Conclusion This study showed that the interdevice difference with the number of steps significantly increased in older participants due to the greater length of time spent in LPAs.

Six-year prospective study of physical fitness and incidence of disability among community-dwelling Japanese elderly women

Aim:  To identify physical fitness factors associated with occurrence of disability requiring long‐term care and reviewing physical fitness factors to identify threshold values at which future care risk is expected to rise rapidly.

Effects of proprioceptive neuromuscular facilitation stretching and static stretching on maximal voluntary contraction.

Abstract Miyahara, Y, Naito, H, Ogura, Y, Katamoto, S, and Aoki, J. Effects of proprioceptive neuromuscular facilitation stretching and static stretching on maximal voluntary contraction. J Strength Cond Res 27(1): 195–201, 2013—This study was undertaken to investigate and compare the effects of proprioceptive neuromuscular facilitation (PNF) stretching and static stretching on maximal voluntary contraction (MVC). Thirteen male university students (age, 20 ± 1 years; height, 172.2 ± 4.6 cm; weight, 68.4 ± 6.7 kg; mean ± SD) completed 3 different conditions on 3 nonconsecutive days in randomized order: static stretching (SS), PNF stretching (PNF), and no stretching (control, CON). Each condition consisted of a 5-minute rest accompanied by one of the following activities: (a) control, (b) SS, or (c) PNF stretching. The hip flexion range of motion (ROM) was evaluated immediately before and after the activity. The MVC of knee flexion was then measured. Surface electromyography was recorded from the biceps femoris and vastus lateralis muscles during MVC tests and stretching. Although increases in ROM were significantly greater after PNF than after SS (p < 0.01), the decreases in MVC were similar between the 2 treatments. These results suggest that, although PNF stretching increases ROM more than SS, PNF stretching and SS is detrimental to isometric maximal strength.

Self-monitoring moderate-vigorous physical activity versus steps/day is more effective in chronic disease exercise programs.

PURPOSE The effects of self-monitoring number of steps/day versus minutes of moderate to vigorous-intensity physical activity (MVPA/day) were compared to determine which is more effective for increasing physical activity levels. METHODS A total of 18 participants of a university-based chronic disease prevention program (age 61 ± 12 years) were enrolled in the 3-week intervention. Subjects were randomly assigned to a group (n = 8) that wore a New Lifestyles accelerometer (NL-1000) and were instructed to increase minutes of MVPA to 30 min/d or more (MIN) or to a group (n = 10) that wore a New Lifestyles pedometer (NL-800) and were instructed to increase the number of steps/day to 10,000 or more (STE). To objectively assess changes in physical activity levels, subjects in both groups simultaneously wore a Lifecorder-EX accelerometer (with display blank) during the intervention. RESULTS The number of steps increased significantly in the MIN (10,810 ±3,211 to 13,355 ± 3,498 steps/day) and STE (11,517 ± 3,383 to 12,809 ±2,479 steps/day) from the first to fourth weeks, respectively. However, the time spent in MVPA increased significantly only in MIN group (36 ± 11 to 52 ± 15 min/d) but not in the STE group (32 ± 7 to 37 ± 11 min/d) from the first to fourth weeks, respectively. CONCLUSION Data suggest that individuals with chronic disease conditions can more effectively increase levels of physical activity, expressed as both MVPA/day and steps/day, by self-monitoring MIN rather than STE. The effect of self-monitoring physical activity levels for longer periods and/or the effect of increasing minutes of MVPA/day versus steps/day on specific health outcomes have not yet been examined.

Minute-by-minute stepping rate of daily physical activity in normal and overweight/obese adults

SUMMARY The relationship between minute-by-minute stepping rate under free-living and obesity remains unclear. The purpose of the present investigation was to compare the levels of physical activity (PA) based on the minute-by-minute stepping rate under free-living conditions between normal weight (NW) and overweight and obese (OV) individuals. A total 40 volunteers participated in the present investigation. These participants were divided into NW or OV according to the body mass index (<25 kg m(-2) or 25 kg m(-2)). All participants wore a pedometer with a uni-axial accelerometer (Lifecorder-EX 4sec, Kenz, Japan) for 7 days continuously. The Lifecorder determined the number of steps and time spent in PA at <100, 100-129, 130 steps min(-1) according to the minute-by-minute stepping rate. The OV group took a significantly fewer number of steps per day in comparison to that in the NW group (p < 0.05). The average daily stepping rate was significantly lower in the OV group in comparison to that in the NW group (p = 0.01). Furthermore, the OV group spent a significantly shorter time in PA at a 100 steps min(-1) of the stepping rate compared with that in the NW group (p < 0.05). These results indicate that obese individuals spent significantly shorter time in PA at 100 steps min(-1) of stepping rate in comparison to the NW individuals.:

Assessment of minute-by-minute stepping rate of physical activity under free-living conditions in female adults

BACKGROUND The minute-by-minute stepping rate (MMSR) is a unique index of the walking speed. The MMSR under free-living conditions remains unclear. PURPOSE The purpose of the present investigation was to clarify the physical activity (PA) levels based on MMSR under free-living conditions. METHODS A total of 85 female volunteers, age from 21 to 91 year, wore a pedometer with a uni-axial accelerometer (Lifecorder, Kenz, Japan) for 7 days consecutively in order to determine the number of steps, the intensity of PA (light intensity PA; LPA, moderate intensity PA; MPA, and vigorous intensity PA; VPA), and the MMSR. Thereafter, the daily time spent in PA at <100, 100 to 129, and 130 steps min(-1) (min day(-1)) was calculated. All experiments were conducted in March 2007. RESULTS The number of steps, the time spent in LPA, MPA, VPA, PA at <100, 100 to 129, and 130 steps min(-1) were 9275±3453 steps day(-1), 71±25 min day(-1), 34±22 min day(-1), 4±6 min day(-1), 295±88 min day(-1), 16±12 min day(-1), and 4±6 min day(-1). The time spent in PA at <100 steps min(-1) positively associated with age (p<0.05). The time spent in PA at 100 to 129 steps min(-1) negatively associated with age (p<0.01). CONCLUSION The time spent in PA at <130 of steps min(-1) MMSR differs across different age-groups under free-living conditions in female adults. The clinical significance with regards to the age-associated changes in MMSR remains unclear.

Different adaptations of alpha-actinin isoforms to exercise training in rat skeletal muscles

Aim:  Alpha (α)‐actinins are located in the skeletal muscle Z‐line and form actin–actin cross‐links. Mammalian skeletal muscle has two isoforms: α‐actinin‐2 and α‐actinin‐3. However, the response of α‐actinin to exercise training is little understood. Therefore, the current study examined the effects of exercise training on the expression level of two α‐actinin isoforms in skeletal muscles.