ECSS Paris 2023: CP-PN10
INTRODUCTION: Toe grasp strength is crucial for maintaining stable standing posture in humans, involving complex movements facilitated by muscles such as the flexor digitorum brevis, flexor digitorum longus, and others. Toe grasping force, essential for balance and physical performance, varies with factors like heredity and environment. Therefore, it is assumed that Nepal’s diverse geography. This study investigates the growth characteristics of toe grip strength among Nepalese children, hypothesizing that the unique hill and mountain terrains influence developmental patterns. METHODS: This study analyzed 1,193 healthy children (628 boys and 565 girls) aged 10-16 from schools in and around Pokhara Valley and the Lumbini lowlands, Nepal. The data was collected in Dec, 2023. We measured toe grip strength using a T.K.K.3362 toe-grip dynamometer (Takei Scientific Instruments Co.,Ltd, Japan), with the maximum strength of two trials recorded. Height and weight were also measured, and descriptive statistics were calculated by age and sex to compare differences. RESULTS: The study found significant growth patterns in height, weight, and toe grip strength among Nepalese children aged 10-16. The mean height of Nepalese children aged 10 -16 years ranged from 134.7-167.0 cm for boys and 138.9-154.1 cm for girls. The mean weight of children ranged from 31.8-57.9 kg for boys and 32.3-49.2 kg for girls. The mean toe grip strength of children ranged from 12.2-27.6 kg for boys and 10.8-49.2 kg for girls. Girls exhibited greater height and weight until age 12, after which boys surpassed them. Toe grip strength increased with age, showing a plateau after age 13 in girls but continuing to rise in boys until age 16. In terms of the mode of transportation used to get to school (walking, bicycle, motorcycle, school bus, or public bus), 35.5% of the children walked in Pokhara, and in Lumbini it was 66.7%, with Lumbini children walking a higher percentage of the time. The mean toe grip strength of Lumbini girls was higher than Pokhara girls. It potentially reflecting differences in daily physical activity, such as walking to school. Compared to Japanese children, Nepalese children showed superior toe grip strength. CONCLUSION: The study concludes that geographical and environmental factors, alongside gender, significantly affect the growth patterns of toe grip strength in Nepalese children. The findings highlight the importance of considering local environmental contexts in studies of physical development and suggest avenues for further research into the impact of daily activities on physical health.
Read CV Keiko UedaECSS Paris 2023: CP-PN10
INTRODUCTION: The acute application of local vibration (LV) leads to the projection of Ia afferents to the alpha motor neurons pool and sensorimotor areas of the cortex. Depending on the conditions under which the LV is applied, two phenomena may occur: the tonic vibratory reflex (TVR) and the illusion of movement (1, 2). This study aimed to understand the role of these two phenomena, whose presence is rarely controlled in studies, on the ability to produce maximum voluntary isometric contraction (MVIC). METHODS: The LV was applied to the flexor carpi radialis muscle (FCR) of 16 participants (6 minutes, continuous, 80 Hz, 2mm amplitude) in two separate sessions to test both conditions: one favoring the presence of TVR (visual attention focused on the vibrating wrist, no electromyographic muscle feedback), the other favoring ILLUSION (hand hidden, focus on kinesthetic feedback, electromyographic feedback from the FCR muscle). Illusion perception was measured subjectively, and electromyographic activity (EMGa) of the FCR muscle and the extensor carpi radialis (ECR) antagonist muscle recorded during LV was compared with EMGa recorded at rest. MVIC with superimposed and potentiated doublet electrical stimulations at 100Hz were performed in isometric flexion and extension. Assessments were performed 10 minutes before (PR1), and just before (PR2) the LV protocol, and then 0 (P0) and 30 minutes (P30) after the end of the protocol. In addition, voluntary activation level (VAL) and maximal EMGa of the FCR and ECR muscles during MVIC were studied. RESULTS: Compared to rest, EMGa increased during LV for vibrated muscle only in TVR condition (P < 0.001). The illusion of movement was greater in the ILLUSION condition than in the TVR condition (P < 0.001). The repeated measures ANOVA showed an interaction only for MVIC performed in flexion. While the ILLUSION condition showed no change (P > 0.472), MVIC in the TVR condition was lower at P0 (P < 0.027) and P30 (P < 0.034) compared with PR1 and PR2. In addition, the MVIC at P0 was lower than that observed in the ILLUSION condition (P = 0.001). Moreover, the amount of TVR was negatively correlated with the decrease in MVIC. Other variables remained unchanged. CONCLUSION: The ability to produce maximal force is reduced only when the six minutes of LV induces TVR, and the amount of TVR recorded on the vibrated muscle is negatively correlated with force loss. Consequently, the conditions under which LV is applied (i.e., EMGa of the vibrated and antagonist muscle and the presence of illusion) should be better controlled to ensure reproducibility of results accros studies. References: 1. Burke D, et al., J Physiol, 1976. doi: 10.1113/jphysiol.1976.sp011580. 2. Taylor MW, et al., Multisens Res, 2017. doi: 10.1163/22134808-00002544.
Read CV Nicolas AmiezECSS Paris 2023: CP-PN10
INTRODUCTION: Photobiomodulation (PBM), sometimes referred to as low-level laser therapy, has been shown to improve aerobic endurance performance, along with muscular endurance during single joint resistance exercises targeting smaller muscles. It is unclear whether this benefit extends to compound exercises targeting larger muscles, such as the barbell bench press. METHODS: In a within-group design, 10 collegiate athletes (mean±sd; age 20.1±1.1 yrs; BMI 25.3±3.9 kg.m-2) received PBM or a sham treatment both six hours prior and then immediately preceding a bench press protocol. Photobiomodulation dosage was 30 Joules per site using an 850 nm wavelength nine diode cluster applicator with five infrared laser diodes (6 J/diode) at 200 milliwatts each and four 650 nm wavelength LED diodes at 10 milliwatts each. Two treatment sites each on the pectoralis major, triceps, and deltoids were irradiated. Bench press one repetition maximum (1RM), volume load (VL) lifted during five sets to failure at 60% 1RM, and soreness immediately after and in the three days following were compared between PBM and sham conditions. Testing was conducted over three sessions separated by a week each, with a baseline testing day occurring first, and the PBM and sham condition testing days following in a counterbalanced fashion to control for order effects. Two-tailed paired t-tests were used to compare the change from baseline between conditions (alpha level = 0.05). Cohen’s d was used to calculate effect size. RESULTS: No significant differences were observed between groups for bench press 1RM (p=0.48), VL (p=0.19), or soreness (p=0.90). No effect was observed for 1RM (d=.18) or soreness (d=.08). A moderate effect (d=.50) was observed for VL, where sham condition change from baseline was 710±518 lbs versus 459±484 lbs in the PBM condition. CONCLUSION: These findings suggest that muscular performance during compound, large muscle group exercises such as the bench press may not benefit from PBM at moderate loads relative to 1RM. Photobiomodulation is thought to exert its effects via mitrochondrial biogenesis and increased electron transport chain activity; therefore, ergogenic benefits may be limited to longer-duration exercise. Further, while a significant result was not observed, the moderate effect observed in the volume load assessment, where more weight was lifted over five sets in athletes in the placebo condition versus the PBM condition, suggests that the specific treatment used in this study may have inhibited performance. It is unclear whether there is an upper limit at which point PBM becomes ergolytic, but the findings of this study may indicate that such a threshold exists.
Read CV Anthony DamicoECSS Paris 2023: CP-PN10