Takayuki Inami

Difference in fascicle behaviors between superficial and deep quadriceps muscles during isometric contractions

In this study we examined changes in fascicle length and pennation of vastus intermedius (VI) and vastus lateralis (VL) from rest to isometric contraction.

Unstable rocker shoes promote recovery from marathon-induced muscle damage in novice runners

We recently reported that wearing unstable rocker shoes (Masai Barefoot Technology: MBT) may enhance recovery from marathon race‐induced fatigue. However, this earlier study only utilized a questionnaire. In this study, we evaluated MBT utilizing objective physiological measures of recovery from marathon‐induced muscle damages. Twenty‐five university student novice runners were divided into two groups. After running a full marathon, one group wore MBT shoes (MBT group), and the control group (CON) wore ordinary shoes daily for 1 week following the race. We measured maximal isometric joint torque, muscle hardness (real time tissue elastography of the strain ratio) in the lower limb muscles before, immediately after, and 1, 3, and 8 days following the marathon. We calculated the magnitude of recovery by observing the difference in each value between the first measurement and the latter measurements. Results showed that isometric torques in knee flexion recovered at the first day after the race in the MBT group while it did not recover even at the eighth day in the CON group. Muscle hardness in the gastrocnemius and vastus lateralis showed enhanced recovery in the MBT group in comparison with the CON group. Also for muscle hardness in the tibialis anterior and biceps femoris, the timing of recovery was delayed in the CON group. In conclusion, wearing MBT shoes enhanced recovery in lower leg and thigh muscles from muscle damage induced by marathon running.

Acute Changes in Peripheral Vascular Tonus and Systemic Circulation during Static Stretching

This study aimed to investigate the acute effect of static stretching (SS) on peripheral vascular tonus and to clarify the effect of SS on systemic circulation. Twenty healthy young male volunteers performed a 1-min SS motion of the right triceps surae muscle, repeated five times. The peripheral vascular tonus (|d/a| ratio) was obtained using second derivatives of the photoplethysmogram readings before, during, and after SS. Heart rate and blood pressure (BP) were also measured. The |d/a| ratio and BP were transiently, but significantly, elevated during SS and returned to baseline immediately after SS. Furthermore, we observed a significant correlation between the amount of change in the |d/a| ratio and the ankle range of motion during SS (r = 0.793 to 0.832, P = 0.01). These responses may be caused by mechanical stress during SS.

Stretching combined with repetitive small length changes of the plantar flexor muscles enhances their passive extensibility for longer duration than conventional static stretching, while not compromising strength

Static stretching increases flexibility but can decrease muscle strength, and the method to avoid the latter has been longed for. In this study, a novel stretching modality was developed that provides repetitive small length changes to the plantar flexor muscles undergoing passive static stretching (“local vibration stretching,”). We investigated the effects of local vibration stretching on muscle strength, flexibility and its persistence. Plantar flexion strength and maximal ankle joint dorsiflexion angle (dorsiflexion range of motion) were measured for 10 healthy young males before (pre) and immediately after (post) three types of stretching: static stretching, local vibration stretching at 15 Hz, and no intervention (control). The dorsiflexion range of motion was measured also at 15, 30, and 60 min post-stretching. Elongation of the medial gastrocnemius and Achilles tendon was determined by ultrasonography. Plantar flexion strength significantly decreased by 4.3 ± 3.5 % in static stretching but not in local vibration stretching. The dorsiflexion range of motion significantly increased both in static stretching (7.2 ± 8.1 %) and local vibration stretching (11.2 ± 14.6 %) which was accompanied by a significantly larger muscle elongation but not tendon elongation. Elevated dorsiflexion range of motion was maintained until 30 min after the local vibration stretching while it returned to baseline level (pre-intervention) in 15 min after the static stretching. All variables remained unchanged in the control condition. In conclusion, local vibration stretching improves extensibility of the muscle belly without decreasing strength, and the increased flexibility is retained longer than static stretching.

Differences in autonomic neural activity during exercise between the second and third trimesters of pregnancy

To test the hypothesis that autonomic neural activity in pregnant women during exercise varies according to gestational age.

Long-term Stretching Program in Older Active Adults Increases Muscle Strength

The purpose of this study was to evaluate the long-term and repeated bout effects of static stretching (SS) program in older active adults, and to clarify the effects of flexibility on muscle strength of knee and trunk. The subjects were healthy active adults (aged 67–80 years). The intervention group (n = 7) performed the SS program for 1 year and an additional period of 2 years. The SS program was configured to target the body’s major muscle groups, and the exercises were performed five times a week. The peak torques in extension and flexion of knee and trunk (isokinetic contraction 60°/ sec) were obtained from isokinetic dynamometer, and sit and reach test was assessed yearly. As a result, flexibility was increased by 31% during the first SS intervention (period of 1 year), and muscle strength were also increased by about 10% to 17%. Additionally, a higher effect was obtained by the second SS intervention (period of 2 years). We found a significant correlation between the magnitude of changes in flexibility and muscle strength. Therefore, the repetition of an SS program is important for improving or maintaining flexibility and muscle strength in older active adults.