This study aimed to elucidate how body composition, force-generating capacity and jump performances are associated with 50-m sprint velocity in circumpubertal boys, in relation to sprint phases and maturation. One hundred thirty four circumpubertal boys were allocated to preadolescent or adolescent group on basis of the height at the peak height velocity of Japanese boys (154 cm) reported in literature: those with body heights over 154 cm as adolescent group and others as preadolescent group. Body composition was determined by bioelectrical impedance analysis. In addition to maximal voluntary isometric knee extension torque, the performances of counter movement jump (CMJ), rebound jump (RJ), standing long jump (SLJ) and standing 5-step jump (SFJ) were also measured. RJ-index was calculated by dividing height by contact time. The time of 50-m sprint was determined at 10-m intervals. Multiple regression analysis showed that in preadolescent boys, SFJ become a predictor for the sprint speed during acceleration phases, and SFJ, RJ-index and CMJ as predictors for the sprint speeds during maximal speed and deceleration phases. In the adolescent boys, age, CMJ, SLJ, and SFJ become a predictor for the sprint speed during acceleration phases, and torque relative to body mass, CMJ and SFJ were selected as predictors for the sprint speeds during maximal speed and deceleration phases. Thus, the current results indicate that force-generating capacity and jumping ability are determinants for sprint performance in circumpubertal boys, but the relative contribution of each of the two factors differs between preadolescent and adolescent stages and among the sprint phases.

This study aimed to determine the relationships between the torque generating capacity of the lower extremity muscles and either running or jump performance in primary and junior high school boys. A total of 102 primary and junior high school boys participated in this study. Muscle thicknesses (MTs) of the knee extensors and plantar flexors were determined using ultrasonography. Muscle volumes (MVs) of the knee extensors and plantar flexors were estimated using MTs and limb lengths. The isometric joint torques (TQs) for knee extensors and ankle plantar flexors were measured using myometer. MV and TQ were divided by body mass (MV/BM and TQ/BM, respectively). Running velocity was measured using a non-motorized treadmill. The counter movement jump (CMJ) and squat jump (SJ) were performed on a matswitch system. The flight time was measured and used to calculate the heights of CMJ and SJ using the following equation; height (cm) = g × (flight time)² /8/10. As the result of multiple regression analysis, age, MV/BM and TQ/BM were selected as predictors of running velocity in the primary school boys, whereas TQ and lean body mass in junior high school boys. In the primary school boys, TQ/BM and body fat mass was selected as significant contributors for SJ and CMJ performances, whereas, in the junior high school boys, TQ and the percent of body fat for SJ performance and MV/BM and TQ for CMJ performance. Thus, the present results indicate that the relationships between torque generating capacity of the lower extremity muscles and either running or jump performance differ between primary and junior high school boys. It may be assumed that, for running and jump performances, muscle mass and strength become determinant factors in junior high school boys, whereas their values relative to body mass in primary school boys.

Purpose: Re-irradiation is a treatment option for recurrent esophageal cancer patients with a history of radiotherapy, but there is a risk of severe late adverse effects. This study focused on the efficacy and safety of re-irradiation using hyperfractionated radiotherapy. Materials and Methods: Twenty-six patients who underwent re-irradiation by the hyperfraction technique using twice-daily irradiation of 1.2 Gy per fraction for recurrent esophageal cancer were retrospectively included in this study. The overall survival period after the start of secondary radiotherapy and the occurrence of late adverse effects were investigated. Results: Of 26 patients, 21 (81%) received re-irradiation with definitive intention and 21 (81%) underwent concurrent chemotherapy. The median re-irradiation dose was 60 Gy in 50 fractions in 25 treatment days, and the median accumulated irradiation dose in equivalent dose in 2 Gy per fraction was 85.4 Gy with an α/β value of 3. The median interval between two courses of radiotherapy was 21.0 months. The median overall survival period was 15.8 months and the 1-year and 3-year overall survival rates were 64.3% and 28.3%, respectively. Higher dose of re-irradiation and concurrent chemotherapy significantly improved survival (p < 0.001 and p = 0.019, respectively). Severe late adverse effects with the Common Terminology Criteria for Adverse Events grade 3 or higher were observed in 5 (19.2%) patients, and 2 (7.7%) of them developed a grade 5 late adverse effect. Conclusion High-dose re-irradiation using a hyperfractionated schedule with concurrent chemotherapy might be related to good prognosis, while the rate of late severe adverse effects is not high compared with the rates in past reports.