How a young child learns how to take part in mealtimes in a Japanese day-care center: a longitudinal case study

This research is a longitudinal, ethnographic study that focuses on mealtimes with one boy from 9 to 78 months of age in a day-care center in Japan. It looks at routine interactions between a child, his nursery teachers, and the environment, which is a shared and mutually available communicative space between participants in collaboration. The aim of this study is to clarify how the meal as a learning problem is “solved,” especially with young children whom the teacher cannot instruct verbally, and how the environment in which this takes place affects the process and is used in collaboration. The first part, a diachronic illustration of the child’s environment, in which all materials are organized as a total system to constrain his action, demonstrates the dynamic relation between his actions, the nursery teachers’ actions, and the environment. The second part presents the findings of a microanalysis of the interaction between a nursery teacher and the boy at 15 months, which is a critical transitional time from other-assisted to self-organized eating. It shows the close interdependence between the child’s environment and the teacher’s way of caring for him. The teachers generally used environmental modifications to assist his eating and to channel his actions toward their preferences. This study has demonstrated that children can learn much through an intentional arrangement of an artificial environment.     

Separation of serum LD isoenzymes by capillary electrophoresis

Separation and quantitative estimation of the isoenzymes of lactate dehydrogenase(LD) in serum were accomplished with capillary electrophoresis system. An uncoated fused silica capillary column 50 cm long, 75μm I.D. and substrate containing running buffer including L-lactic acid and NAD⁺ were used for the separation of serum LD isoenzymes. The resulting product of “NADH” was detected at 340 nm. Injection of 10 nL of five fold diluted serum sample were performed by pressure injection within 2 seconds. The isoenzymes were separated at 10 kV of voltage for 5 min, by turning off the voltage applied for 30 min incubation at 24°C for reaction between substrate and isoenzymes, and applying voltage of 30 min. Under these conditions, the isoenzymes of LD were detected by a NADH generated as isoenzyme of LD-5 emerged at 20 min, LD-1 peak at 23.5 min with close to baseline separation of the other isoenzymes which emerge between LD-5 to LD-1, after the emergence to LD-1 peak, followed another peak, termed “sample shock”: The results obtained by the proposed method correlated well with those by gel electrophoresis systemes (r=0.92∼0.98) for each five LD isoenzymes, respectively. Within-run precision CVs for 5 replicate analysis were 3.01 (LD-3, mean 14.6%)%∼7.82% (LD-4, mean 4.22%.), respectively.     

Effects of series elasticity on the human knee extension torque-angle relationship in vivo

The purpose of this study was to investigate the effects of series elasticity on the torque-angle relationship of the knee extensors in vivo. Forty-two men volunteered to take part in the present study. The participants performed maximal voluntary isometric contractions at eight knee-joint angles (40, 50, 60, 70, 80, 90, 100, 110 degrees). The elongation of the tendon and aponeurosis of the vastus lateralis muscle was directly measured by ultrasonography, while the participants performed ramp isometric knee extensions to the voluntary maximum at 800 of knee angle. There was no significant difference in the torque value between 50 degrees and 100 degrees, although there was variation in the shape of the "torque-angle" relationship. The variability in the torque-angle curve was not affected by the activation level of agonist and antagonist muscles and the moment arm length. The ratio of torque at 1000 compared to that at 50 degrees was significantly (r(2) = 18-23 %) correlated to the maximal elongation and strain (to initial length) of the tendon structures. These results suggest that increased compliance of tendon structures of the knee extensors may contribute to variations in the torque-angle curves of the knee extensors.     

Intensity-level assessment of lower body plyometric exercises based on mechanical output of lower limb joints

Abstract

The present study aimed to quantify the intensity of lower extremity plyometric exercises by determining joint mechanical output. Ten men (age, 27.3 ± 4.1 years; height, 173.6 ± 5.4 cm; weight, 69.4 ± 6.0 kg; 1-repetition maximum [1RM] load in back squat 118.5 ± 12.0 kg) performed the following seven plyometric exercises: two-foot ankle hop, repeated squat jump, double-leg hop, depth jumps from 30 and 60 cm, and single-leg and double-leg tuck jumps. Mechanical output variables (torque, angular impulse, power, and work) at the lower limb joints were determined using inverse-dynamics analysis. For all measured variables, ANOVA revealed significant main effects of exercise type for all joints (P < 0.05) along with significant interactions between joint and exercise (P < 0.01), indicating that the influence of exercise type on mechanical output varied among joints. Paired comparisons revealed that there were marked differences in mechanical output at the ankle and hip joints; most of the variables at the ankle joint were greatest for two-foot ankle hop and tuck jumps, while most hip joint variables were greatest for repeated squat jump or double-leg hop. The present results indicate the necessity for determining mechanical output for each joint when evaluating the intensity of plyometric exercises.     

Differences in take-off leg kinetics between horizontal and vertical single-leg rebound jumps

This study aimed to clarify the differences between the horizontal single-leg rebound jump (HJ) and vertical single-leg rebound jump (VJ) in terms of three-dimensional joint kinetics for the take-off leg, while focusing on frontal and transverse plane movements. Eleven male track and field athletes performed HJ and VJ. Kinematic and kinetic data were calculated using data recorded with a motion capture system and force platforms. The hip abduction torque, trunk lateral flexion torque (flexion for the swing-leg side), hip external and internal torque, trunk rotational torque, and the powers associated with these torques were larger when performing HJ because of resistance to the impact ground reaction force and because of pelvic and posture control. Pelvic rotation was noted in HJ, and this was controlled not only by the hip and trunk joint torque from the transverse plane but also by the hip abduction torque. Therefore, hip and trunk joint kinetics in the frontal and transverse plane play an important role in a single-leg jump, regardless of the jumping direction, and may also play a more important role in HJ than in VJ.