Growing evidence has shown that skeletal muscle secretes several bioactive proteins from the cell into extracellular fluid. The secretion of several proteins, whose levels increase in response to exercise, can regulate the functions of several organs via autocrine, paracrine, and endocrine actions, and mediate exercise-induced benefits such as metabolic improvement, anti-inflammation, and muscle building; this is known as the myokine theory. These secretory proteins may be biomarkers that reflect muscular function and beneficial adaptation achieved by exercise training, and could estimate adequate condition of exercise to obtain its beneficial effects. Recently, we found a novel myokine, secreted protein acidic and rich in cysteine (SPARC), a secreted matricellular glycoprotein. In a colon cancer mouse model, regular exercise reduced the formation of the precursor lesions of colon adenocarcinoma in wild-type mice but not SPARC-null mice. Furthermore, regular exercise enhanced apoptosis in colon mucosal cells and increased the cleaved form of caspase in wild-type mice but not SPARC-null mice. The muscle-secreted protein SPARC can support underlying mechanisms of epidemiological studies that suggest that regular exercise prevents the incidence of colon cancer.
The purpose of this study was to examine the recruitment state of synergistic muscles in the thigh muscles in leg press exercise with and without pre-fatigue method using transverse relaxation time (T2) on muscle functional magnetic resonance imaging (MRI). Nine healthy male subjects performed the following two types of exercise trials on separate days: 1) 5 sets of a leg press exercise with pre-fatigue method, which consisted of 3 sets of knee extension exercise (LP-pre), 2) 5 sets of a leg press exercise without pre-fatigue method (LP). Both exercises were performed at a load of 80% one-repetition maximum. Before and immediately after exercise, T2-weighted MR images of right-thigh were taken to calculate T2 values of twelve-thigh muscles. The T2 values for quadriceps femoris muscle and hamstrings in LP increased significantly after the exercise, except in the adductor magnus, adductor longus, gracilis, and sartorius. In contrast, the T2 values for all of the twelve-thigh muscles in LP-pre increased significantly after the exercise. Upon comparison between the two trials, the percentage changes in T2 value for the adductor magnus, adductor longus, and sartorius in LP-pre were found to be significantly greater than those in LP. These results suggest leg press exercise with pre-fatigue method may be effective to increase activity of synergistic muscles in thigh muscles during exercise.
It is well known that decreased physical performance induces the decreased activity of daily living and increment of mortality rate in elderly subjects. On the other hand, a prolonged heart rate corrected-QT (QTc) interval is associated with an increased risk of cardiac sudden death and cardiac autonomic dysfunction. We investigated the associations between physical performance and QTc interval in elderly subjects. The subjects included 605 elderly persons (274 men and 331 women, age; 71.2±4.7 years) without a history of cardiovascular disease and taking cardioactive drugs. Resting 12-leads electrocardiography was measured after more than 5 minutes of rest. The QTc interval was calculated according to Bazett’s formula. The physical fitness test was performed to determine the physical performance (muscle strength, balance and walking abilities). The subjects were divided into four categories, which were defined as equally quantile distributions of QTc interval. The physical performance levels were significantly lower in the longest QTc interval group compared to the shortest QTc interval group in both men and women (p<0.05, respectively). Moreover, after adjusting for the age, the physical performance levels were significantly lower in the longest QTc interval group compared to the shortest QTc interval group, especially, this relationship was observed in late-stage elderly group (p<0.05, respectively). These results suggest that decreased physical performance levels were also associated with prolonged QTc interval in elderly subjects.
This study aimed to clarify the effects of a lifestyle intervention by the concurrent use of an activity monitor and Twitter on daily physical activity. Twenty-one healthy males and females (37 ± 13 yrs) were randomly assigned to Normal intervention group (N group, n = 10) or Twitter intervention group (T group, n = 11). In both groups, the intervention period was 6 weeks. Participants in N group wore an activity monitor (Lifecorder EX). Meanwhile, participants in T group were asked to tweet about their daily steps or physical activity in addition to wearing an activity monitor, and also an observer read through the tweet from each participant and commented about physical activity. There were no significant differences in daily physical activity (i.e., steps and amount of physical activity (PA)) at week 1 between both groups. In addition, no significant time-course changes in steps and amount of PA were observed in N group. In contrast, steps in T group were gradually increased from week 1 8,542 ± 3,158 steps/day to week 6 12,700 ± 3,935 steps/day (P < 0.01). Amount of PA in T group was also gradually increased from week 1 2.5 ± 1.2 METs·hour/day to week 6 4.6 ± 2.3 METs·hour/day (P < 0.01). Therefore, these findings indicate that the lifestyle intervention by the concurrent use of an activity monitor and Twitter could effectively induce an increase in daily physical activity compared with the intervention using only an activity monitor.
The present study aimed to investigate how the morphological and mechanical properties of Achilles tendon change in adolescent boys. Twenty-nine adolescent boys and 12 male adults participated. Ultrasonography was used to measure Achilles tendon elongation. The transition point, that is, the intersection point of the “Toe” and “Linear” regions was determined from tendon elongation-tendon force relationship, and the stiffness and Young’s modulus of the Achilles tendon were calculated from linear region. The hysteresis was calculated as the ratio of the area within the tendon elongation-tendon force loop to the area beneath the load portion of the curve. The stiffness, Young’s modulus and stress at transition point were greater in adults (544 ± 231 N/mm, 1.6 ± 0.7 GPa, 23 ± 6 MPa) than in adolescents (374 ± 177 N/mm, 1.1 ± 0.7 GPa, 19 ± 10 MPa). However, no differences were observed in the tendon length and the tendon cross-sectional area and stress at transition point between adolescents (174 ± 23 mm, 60 ± 11 mm2, 6.1 ± 2.0 %) and adults (180 ± 30 mm, 63 ± 7 mm2, 5.5 ± 2.2 %). The hysteresis in adolescents (20 ± 18 %) was greater than that of adults (12 ± 10 %). These results suggest that the morphological properties of Achilles tendon are similar between adolescents and adults, but that mechanical properties are altered with growth to become a stiffer and more spring-like structure.
This study aimed to develop a new method of increasing water content in the cutaneous stratum corneum under a dry skin condition. For this purpose, the experiments were performed using 10 healthy women (age: 20 ± 5 years, height: 158 ± 4 cm, weight: 50 ± 6 kg) in winter to ensure the dry condition. The subjects immersed the right hand into a 42˚C bath for 10 min. Skin surface temperature and water content in the stratum corneum of the left forearm were simultaneously measured during and for 1 h after the hand warming. The skin surface temperature began to increase (P<0.05) 15 min after the hand warming and thereafter remained increased for 1 h. Similarly, the water content in the stratum corneum began to increase immediately after the hand warming and remained increased throughout the experiment. The present results suggest that warming of one hand is effective in enhancing skin moisture in the other forearm and thereby maintaining barrier function of the skin.
This study aimed to examine the association between body mass index (BMI) and muscle strength, and mobility limitation (ML). A cross-sectional analysis was conducted on data from 570 community-dwelling older Japanese women aged 65-91 years [mean age, 73.9 ± 5.8 (SD) years]. Muscle strength was assessed by hand-grip strength (HGS). ML was assessed using self-reported difficulty level in walking 400 m and ascending 10 steps without resting. BMI and muscle strength were divided into tertiles (high: BMI ≧ 25.1 kg/m2, HGS ≧ 22.5 kg; middle: BMI 22.4-25.0 kg/m2, HGS 18.8-22.4 kg; low: BMI ≦ 22.3 kg/m2, HGS ≦ 18.7 kg) respectively, and logistic regression analysis was used to determine the association between BMI and muscle strength with ML. 256 participants (44.9%) were identified as having ML. Adjusted odds ratios of BMI for ML were 1.64 (95% confidence interval (CI): 1.00-2.68) in the middle group and 1.89 (95% CI: 1.15-3.12) in the high group when compared to the low group. Adjusted odds ratios of muscle strength for ML were 1.25 (95% CI: 0.77-2.04) in the middle group and 1.85 (95% CI: 1.11-3.09) in the low group when compared to the high group. Compared to the low BMI plus high muscle strength group, adjusted odds ratio for ML was significantly higher in the high BMI plus low muscle strength group (2.65, 95% CI: 1.02-6.87) and the high BMI plus middle muscle strength group (3.09, 95% CI: 1.25-7.61). Our findings indicate that the combination of overweight plus muscle weakness is more predictive for having ML than overweight or muscle weakness alone.
This study evaluated the exercise profile (heart rate, cycling speed and pedal cadence) during 25-30 km cycling and fitness and health level for adults (11 males: 69.6 ± 4.7 yrs; 6 females: 66.3 ± 4.9 yrs) with a recreational cycling habit (27.6 ± 14.8 km/week). Exercise intensity at a constant speed on a flat road during male and female cycling was 71.2 ± 11.5 and 66.8 ± 11.4% heart rate reserved (HRR), respectively. Exercise intensity over 60% HRR occupied 72% of cycling time. Peak intensity during male and female cycling was 89.2 ± 8.9 and 93.1 ± 6.1% HRR, respectively. VO2max and CS (chair stand)-30 test for male and female were 40.3 ± 4.3 and 37.7 ± 2.4 ml/kg/min, and 30.8 ± 3.1 and 30.1 ± 3.2 times, respectively. The muscle cross-sectional area of thigh extensor and flexor measured by MRI were 55.4 ± 6.5 and 58.3 ± 13.3 cm2 for male, and 45.5 ± 6.4 and 50.2 ± 5.7 cm2 for female, respectively. Blood profile for HDL-C (cholesterol), LDL-C and HbA1c (JDS) for male and female were 65.9 ± 8.2 and 67.9 ± 10.6 mg/dl, 112.3 ± 32.0 and 130.6 ± 12.3 mg/dl, and 4.8 ± 0.4 and 4.7 ± 0.1%, respectively. Fitness level and blood profile results were superior to those of the same aged adults. We concluded that the exercise intensity of cycling by middle and older adults with a recreational cycling habit is high and their fitness and health level are higher than average adults.