RESUMEN
The purpose of this study was to investigate the characteristics of running on self-driven treadmill equipped with curve-shaped bed (TM) from kinematics and kinetics variables by comparing with those obtained on overground running (OG). Eight healthy male subjects run on TM and OG under constant speed condition of 3m/s. Thirty five reflective anatomical landmarkers were attached on the subject according to Plug-in-gait model. Kinematics and kinetics data were recorded during stance phase using VICON MX (200fps) motion capture system and Kistler force plate (1kHz). Running spatio-temporal parameters such as stride length /stride frequency, lower limb joint kinematics and ground reaction force were compared between TM and OG conditions. Significant high stride frequency on TM running was indicated compare with OG condition (P<0.05). Contact time were almost same between TM and OG, whereas in vertical ground reaction force, non-first impact force as well as lower average loading rate were indicated in TM compared to OG (P<0.05). Lower joint kinematics were significantly different between TM and OG running during first 20% stance phase of normalized stance time. Hip and knee flexion angular velocities were larger in OG than TM (P<0.05). These results suggest that TM running causes lowed intensity for lower limb joints during stance phase, which might be applicable for prevention of running injury.
RESUMEN
In order to quantify the plantar load distribution during dynamic human movement, integrated system consisted of a pressure plate, motion capture system and a force platform was constructed and examined its accuracy and validity based on foot anatomical measurement points during take-off phase in vertical jump. Foot Scan (Rs Scan,200Hz), VICON (Oxford,100Hz) and Force plate (Kistler,1KHz) were systematically synchronized as to identify each sub-area of plantar from anatomical measurement points on foot. Each five sub-area of plantar was determined by using the methods of Stebbins et al. (2005). Accuracy and validity of plantar load and the position of center of pressure (COP) were examined by % Difference and RMS error with comparison to those obtained from Force plate, Foot Scan and VICON coordinate system. Using this system, twelve subjects performed maximum counter movement vertical jump and instantaneous plantar load changes for each of five sub-area were quantified during weighing phase during take-off. % Differences in plantar load value between Force plate and Foot Scan were less than 2.3 ± 1.5 % as well as RMS errors of COP’s position were ranged from 1.5 - 8.9 mm. Medial forefoot plantar load fairly contributed to Force plate data and peak value of plantar load in each sub-area appeared as order from Heel, Lateral forefoot and Medial forefoot. This newly developed system could quantify each plantar sub-area load with both enough accuracy and validity and also demonstrate instantaneous each sub-area’s plantar load pattern during dynamic movement such as take-off phase in vertical jump.
RESUMEN
The purpose of this study was to investigate the cross-sectional development characteristics of body composition, lower-leg multi-joint power output and sprint running in non-elite junior and youth soccer players. The leg extension power, counter-movement vertical jump(CMJ), and 30m-sprint time for eighty male soccer players aged 13.8-18.1 yrs were measured. Junior and youth soccer players were compared with sedentary normal identical aged boys. Statistical analysis was used by one-way ANOVA and multiple comparisons of variance were performed on the basis of the Tukey-Kramer HSD test. Statistical significance was accepted at level of p < 0.05. Relative increases from 14 yrs to 18 yrs players were significantly (p < 0.05) indicated; body height (7.7%), leg extension power (87.8%), CMJ (35.3%), 30m-sprint (8.7%). 10m-sprint time was negatively correlated with both leg extension power (r = -0.52) and CMJ (r = -0.60). Comparison of relative values of increase from 14 to 18 yrs in junior and youth soccer players to those in sedentary normal boys were as follows; 2.3 (body height), 2.5 (leg extension power), 3.0 (CMJ), 2.1 (sprint ability). It might be suggested that consistent regular soccer training from junior and youth aged might prompt developmental gains not only largely for lower-leg multi-joint power but also not a little for sprint ability.
RESUMEN
The purpose of the present study was to determine the effect of isometric strength training in prepubescent boys and girls on muscle strength and cross-sectional area of upper arm muscle. Subjects were ninety-nine healthy elementary school children from the 1 st, 3 rd and 5th grades and who were assigned to either training (TG, n=52) or control (CG, n=47) groups. The TG participated in a strength training program for 12 weeks which consisted of three maximaly sustained isometric contractions of elbow flexion for ten sec, twice a day, three days per week, whereas the CG did not participate in a special training program during this period. The cross-sectional areas of whole tissue, muscle, fat, and bone of the upper arm were measured by ultrasonic methods. Maximum isometric and isokinetic muscle strength of elbow flexion and extension were measured by means of a Cybex II. The hand-wrist X-ray photograph was used to estimate the skeletal age (TW 2 method) . Means (SDs) of skeletal age (yrs) were 6.27 (0.98), 8.48 (0.89), and 10.77 (1.22) for 1 st, 3 rd, and 5 th graders, respectively. After the 12-week training period, the cross-sectional area of the whole tissue increased significantly in both TG (8.9%, 2.52 cm<SUP>2</SUP>) and CG (7.3%, 2.11 cm<SUP>2</SUP>) . This interment in the TG was due to the significant increases in both muscle and bone areas, while that in CG was due to the significant increase only in fat area. Mean increase in muscle area in the TG was 10.3% (1.29 cm<SUP>2</SUP>) with this increase notable in 5th graders (12.5% for males and 12.7% for females) . The increment in cross-sectional area of muscle with training significantly correlated with the skeletal age (r=0.36, p<0.01) . Maximum isometric strength in the TG increased by 5.7% (0.3kg) in flexion and 17.5% (1.2 kg) in extension and in the CG, -0.3 kg (-1.0%) in flexion and 5.7% (0.3 kg) in extension. The increases in the strength of elbow extension were statistically significant in 1st (p<0.01), 3rd (p<0.05), and 5th (p<0.05) grade males. On the other hand, maximum isokinetic strength did not change with training. Muscle strength per cross-sectional area did not show a significant increase except in the training group of 5th grade boys. It was suggested that the effects of strength training on muscle area and strength for prepubescents were similar in its direction to but different in its magnitude from those found in adults.