This study aims to clarify oxygen uptake (VO₂) and heart rate (HR) kinetics of body mass-based squat exercise (SQ_BM) with relation to age. Fourteen healthy adults and 19 healthy children performed SQ_BM 200 times as well as an incremental loaded bicycle test to determine maximal VO₂ and HR. The VO₂ and HR during SQ_BM were normalized to maximal VO₂ (%VO₂peak) and HR (%HRmax), respectively. Electromyograms (EMGs) were recorded from the vastus lateralis, rectus femoris, vastus medialis and biceps femoris muscles from the right leg. In the VO₂ and HR during SQ_BM, the time constant in children was faster than adults, whereas the physiological load (%VO₂peak and %HRmax) was almost the same between children and adults. In both groups, %VO₂peak was significantly related to %HRmax during SQ_BM. The slope of the %VO₂peak-%HRmax relationship was 0.92 for children, and 0.73 for adults. The current results demonstrate that, compared to adults, the rise in VO₂ and HR after initiation of SQ_BM is faster in children, and the physiological load during SQ_BM partially depends on individual maximal aerobic capacity.

This study aimed to investigate the effect of incline on neuromuscular mechanisms in uphill sprint running. Nine male college sprinters performed 5-sec constant speed running trials on a motorized treadmill at 7.5 m/s. Each trial was conducted under different inclined conditions (level and 5.0% grade). Surface electromyography (EMG) was recorded from 6 muscles of the lower limbs, including gluteus maximus, gluteus medius, rectus femoris, vastus lateralis, biceps femoris, and lateral gastrocnemius lateralis. We found higher muscle activity in all muscles during the stance phase in uphill sprinting except for rectus femoris and vastus lateralis. Higher muscle activation during the recovery phase was found in the rectus femoris muscle in uphill sprinting. These muscle activity adaptations in uphill sprinting were paralleled by higher step frequency and shorter step length. Our results suggest that lower limb muscle activity can meaningfully adapt to sprint-specific demand in uphill running.

Assessment of the total weight-bearing response of the navicular and talus bones is essential for evaluating the load absorption function. Although the weight-bearing response of the hindfoot valgus is likely related to the total weight-bearing response of the navicular and talus bones, this relationship is not well-understood. We evaluated the relationship between the total weight-bearing response of the navicular and talus bones and the weight-bearing response of the hindfoot valgus in the normal foot arch. Twenty-three males with normal foot arches were analyzed. We scanned the right foot of each participant under both non-loading and full weight-bearing conditions, using positional magnetic resonance imaging (pMRI). We measured the vertical and medial positions of the navicular and talus bones. The total positional changes of the navicular and talus bones (ΔTPCN and ΔTPCT, respectively) were calculated from the vertical and medial displacement values, using the Pythagorean theorem. To evaluate the weight-bearing response of the hindfoot valgus, the hindfoot alignment view (HAV) was measured. The difference in HAV (ΔHAV) between non-loading and full weight-bearing conditions was considered the weight-bearing response of the hindfoot valgus. Correlations between ΔTPCN, ΔTPCT, and ΔHAV were assessed using the Pearson correlation coefficient, and ΔTPCN and ΔTPCT were found to be moderately correlated with ΔHAV. Our study indicated that the total weight-bearing response of the navicular and talus bones correlated with the weight-bearing response of the hindfoot valgus in healthy adult males with normal foot arch.

Diabetes mellitus, a life-threatening non-communicable disease, is now an epidemic-level problem in developed countries, and also prevalent in developing countries, including Bangladesh. Bangladesh has been facing a significant and growing burden of diabetes mellitus handling in recent decades. In the present study, we investigated whether a daily walking intervention could improve the fasting blood sugar level in newly diagnosed diabetes mellitus participants in rural Bangladesh who were not on medication. A rural population of 1,045 people in Bangladesh were screened for diabetes mellitus. One hundred fifty-six people, including 87 diabetes mellitus participants, went through a 5-month daily walking program (twice daily, 1.5 km walking each time). In our initial screening, the prevalence of newly diagnosed diabetes mellitus cases was 8.5% in the rural population. Mean fasting blood sugar level in these new diabetes mellitus cases was 10.0 ± 0.33 mmol/L. After five months of exercise, both the fasting blood sugar and 2h OGTT sugar levels were significantly improved, and no DM (diabetes mellitus) cases were on medication. The current research findings show that a walking program can be a potential lifestyle intervention to combat the diabetes mellitus epidemic in a poor rural context in Bangladesh.

The aim of this study was to examine the validity of a Japanese version of the physical activity (PA) question of the Patient-Centered Assessment and Counseling for Exercise Plus Nutrition (PACE+), which is globally used to assess compliance with the WHO PA recommendation for youth. Analyses included 80 Japanese upper elementary students and 44 Japanese junior high students. Consistency of the classification of achieving/not achieving the PA recommendation between the two methods (PACE+ and ActiGraph accelerometry) was assessed by calculating percentage agreement rate, sensitivity, and specificity. Spearman rank correlation (𝜌) was applied to assess the correlation between the two methods. The percentage agreement in upper elementary students and junior high students was 83.8% and 65.9%, respectively. While the sensitivity and specificity of the scale in assessing the compliance of upper elementary students with PA recommendation were 8.3% and 97.1%, respectively, and for junior high school students 42.9% and 76.7%, respectively. The correlation coefficients between PACE+ and accelerometry for elementary and junior high school students were 0.13 and 0.50, respectively. The validity of PACE+ among Japanese adolescents was confirmed similarly to previous studies conducted in other countries. However, it should be viewed with caution that PACE+ may underestimate the proportion of children achieving PA recommendations.

A set of mathematical models for resistance training (RT model) with repeated dynamic and voluntary activations of knee extensor muscles was proposed and validated. RT model predicts muscle activity, fatigue and recovery, and can be used to predict the mechanical impulses identified in different muscle fiber types. Several resistance training program variables (e.g. load, velocity, number of sets, and duration of rest intervals) were addressed in this study. Experimental data from six subjects were taken under several different training protocols. For the protocols studied, the model precisely predicted the maximum number of repetitions during knee extension resistance exercise (R² = 0.87). This study demonstrates the applicability of the first simple mathematical model for voluntary dynamic exercise of knee extensor muscles. The developed model calculates the mechanical impulse of fast twitch fiber for the selected protocols. For instance, the model shows high intensity training tends to induce more fast-twitch fiber recruitment than that in low intensity training in the case of non-failure. This model is expected to help in understanding how impulses of different fiber types contribute and affect training.

Several recent studies reported that a lack of moderate to vigorous physical activity (MVPA) in combination with a high degree of sedentary behavior (SB) is associated with health problems including overweight and obesity in children, as well as psychosocial stress. Therefore, it is important that methods are developed to objectively evaluate both MVPA and SB. The aim of this study was to redevelop the existing equation for estimating SB to improve its accuracy. Healthy boys (n = 42) and girls (n = 26) attending primary school were invited to participate in this study. Participants were asked to perform 2 SB tasks, which were desk work and Nintendo DS, 2 light intensity activities such as sweeping up and clearing away, and higher intensity activities such as sweeping up and throwing a ball, with a few minutes of recovery time between tasks. The tasks and activities were performed in order of PA intensity (lower to higher). All participants wore a triaxial accelerometer on their waist. In addition, they wore a facemask connected to a Douglas bag to gather respiratory gas samples while performing each activity. First, we proposed the two linear regression equations (TL), including an equation for SB, and another equation for light or higher intensity activities with a fixed intercept of 0.9. Moreover, we redeveloped a quadratic polynomial (QP) equation that takes into account all activities. Both models were demonstrated to improve the accuracy of estimations of PA (about 0.2 to 0.3 METs), including SB (about 1.0 METs) other than sweeping up and wiping floor, compared to the existing model.