argument is often, if not acrimonious, at least heated. It gives an impression of the fluidity of opinion on many fundamental ideas under discussion and of the urgency with which cardiac cyanosis in the newborn is regarded. When Dr. William Muscott says that the earliest he has operated for pulmonary stenosis is on an infant 3 days old, and Sir Russell Brock agrees that the earlier in the first month that operation is undertaken the better, and when Dr. Varco asks Dr. Senning 'so far as I know they have never yet catheterized any child intrauterine in Sweden, but they have done it through the delivery canal sometimes-would you tell us the indications of the Scandinavian group for catheterization in the immediate newborn period?', one is indeed being kept up with the times. But that was two years ago and already some of the questions then debated have since been answered. This beautifully printed and well-illustrated stiff paperbacked volume is, and will for a few years yet remain, an invaluable companion to a full-scale textbook on congenital heart disease.

Growth at Adolescence.

The purpose of this study was to evaluate the physical demands of English Football Association (FA) Premier League soccer of three different positional classifications (defender, midfielder and striker). Computerised time-motion video-analysis using the Bloomfield Movement Classification was undertaken on the purposeful movement (PM) performed by 55 players. Recognition of PM had a good inter-tester reliability strength of agreement (κ = 0.7277). Players spent 40.6 ± 10.0% of the match performing PM. Position had a significant influence on %PM time spent sprinting, running, shuffling, skipping and standing still (p 0.05). Players spent 48.7 ± 9.2% of PM time moving in a directly forward direction, 20.6 ± 6.8% not moving in any direction and the remainder of PM time moving backward, lateral, diagonal and arced directions. The players performed the equivalent of 726 ± 203 turns during the match; 609 ± 193 of these being of 0° to 90° to the left or right. Players were involved in the equivalent of 111 ± 77 on the ball movement activities per match with no significant differences between the positions for total involvement in on the ball activity (p > 0.05). This study has provided an indication of the different physical demands of different playing positions in FA Premier League match-play through assessment of movements performed by players.

Physical demands of different positions in FA Premier League soccer

Surface electromyography (sEMG) is a popular research tool in sport and rehabilitation sciences. Common study designs include the comparison of sEMG amplitudes collected from different muscles as participants perform various exercises and techniques under different loads. Based on such comparisons, researchers attempt to draw conclusions concerning the neuro- and electrophysiological underpinning of force production and hypothesize about possible longitudinal adaptations, such as strength and hypertrophy. However, such conclusions are frequently unsubstantiated and unwarranted. Hence, the goal of this review is to discuss what can and cannot be inferred from comparative research designs as it pertains to both the acute and longitudinal outcomes. General methodological recommendations are made, gaps in the literature are identified, and lines for future research to help improve the applicability of sEMG are suggested.

/pdf/interpreting-signal-amplitudes-in-surface-electromyography-3egigoiceb.pdf

Interpreting Signal Amplitudes in Surface Electromyography Studies in Sport and Rehabilitation Sciences

In most daily activities related to work or leisure, the energy for muscle work substantially comes from oxidative metabolism. Functional limitations or impairments of this metabolism can significantly affect exercise tolerance and performance. As a method for the functional evaluation of skeletal muscle oxidative metabolism, near-infrared spectroscopy (NIRS) has important strengths but also several limitations, some of which have been overcome by recent technological developments. Skeletal muscle fractional O2 extraction, the main variable which can be noninvasively evaluated by NIRS, is the result of the dynamic balance between O2 utilization and O2 delivery; it can yield relevant information on key physiological and pathophysiological mechanisms, relevant in the evaluation of exercise performance and exercise tolerance in healthy subjects (in normal and in altered environmental conditions) and in patients. In the right hands, NIRS can offer insights into the physiological and pathophysiological adaptations to conditions of increased O2 needs that involve, in an integrated manner, different organs and systems of the body. In terms of patient evaluation, NIRS allows determination of the evolution of the functional impairments, to identify their correlations with clinical symptoms, to evaluate the effects of therapeutic or rehabilitative interventions, and to gain pathophysiological and diagnostic insights.

https://www.spiedigitallibrary.org/journals/journal-of-biomedical-optics/volume-21/issue-9/091313/Near-infrared-spectroscopy-and-skeletal-muscle-oxidative-function-in-vivo/10.1117/1.JBO.21.9.091313.pdf

Near-infrared spectroscopy and skeletal muscle oxidative function in vivo in health and disease: a review from an exercise physiology perspective

Walking for Health

It has been reported that exercise under hypoxic conditions elevates acute growth hormone secretion after exercise compared with that under normoxic conditions. This study examined the influence of resistance training under moderate hypoxic conditions on muscle thickness, strength and hormonal responses. Thirteen healthy men were assigned into two groups matched for physical fitness level and then randomized into two groups that performed exercise under normoxic (FiO2 = 20·9%) or hypoxic (FiO2 = 12·7%) conditions. Three sets of elbow extensions with unilateral arm were performed to exhaustion at a workload of a 10 repetition maximum with 1-minute intervals for 3 days per week for 8 weeks. The thickness of the biceps and triceps brachii was determined using B-mode ultrasound before and after training. Blood sampling was carried out before and after exercise, as well as during the first and last training sessions. Increase in the thickness of the triceps brachii in trained arm was significantly greater in the hypoxic group than in the normoxic group. The 10 repetition maximum was significantly increased not only in the trained arm but also in the untrained arm in both groups. Serum growth hormone concentrations after exercise were significantly higher in the hypoxic group than in the normoxic group on both the first and last training sessions. These findings suggest that hypoxic resistance training elicits more muscle hypertrophy associated with a higher growth hormone secretion, but that the greater muscle hypertrophy did not necessarily contribute a greater gain of muscle strength.

/pdf/effects-of-resistance-training-under-hypoxic-conditions-on-495ssbp3t1.pdf

Effects of resistance training under hypoxic conditions on muscle hypertrophy and strength.

Purpose:The aim of this study was to investigate the relationship between the attenuation point of muscle deoxygenation (APMD) and the EMG threshold (EMGT) during incremental cycling exercise under different fractions of inspired O2 (FIO2).Methods:Nine male subjects performed ramp cycling ex

Attenuation of muscle deoxygenation precedes EMG threshold in normoxia and hypoxia.

This study was conducted to obtain useful information for developing training techniques for the running 1-legged vertical jump in basketball (lay-up shot jump). The ability to perform the lay-up shot jump and various basic jumps was measured by testing 19 male basketball players. The basic jumps consisted of the 1-legged repeated rebound jump, the 2-legged repeated rebound jump, and the countermovement jump. Jumping height, contact time, and jumping index (jumping height/contact time) were measured and calculated using a contact mat/computer system that recorded the contact and air times. The jumping index indicates power. No significant correlation existed between the jumping height and contact time of the lay-up shot jump, the 2 components of the lay-up shot jump index. As a result, jumping height and contact time were found to be mutually independent abilities. The relationships in contact time between the lay-up shot jump to the 1-legged repeated rebound jump and the 2-legged repeated rebound jump were correlated on the same significance levels (p < 0.05). A significant correlation for jumping height existed between the 1-legged repeated rebound jump and the lay-up shot jump (p < 0.05), although none existed for jumping height between the lay-up shot jump and both the 2-legged repeated rebound jump and countermovement jump. The lay-up shot index correlated more strongly to the 1-legged repeated rebound jump index (p < 0.01) when compared to the 2-legged repeated rebound jump index (p < 0.05). These results suggest that the 1-legged repeated rebound jump is effective in improving both contact time and jumping height in the lay-up shot jump.

Determinants of the abilities to jump higher and shorten the contact time in a running 1-legged vertical jump in basketball.

The purpose of this study was to determine the effects of body mass-based squat training on body composition, muscular strength and motor fitness in adolescent boys. Ninety-four boys (13.7 ± 0.6 yrs, 1.60 ± 0.09 m, 50.2 ± 9.6 kg) participated in this study and were randomly assigned to training (n = 36) or control (n = 58) groups. The training group completed body mass-based squat exercise training (100 reps/day, 45 sessions) for 8 weeks. Body composition and muscle thickness at the thigh anterior were determined by a bioelectrical impedance analyzer and ultrasound apparatus, respectively. Maximal voluntary knee extension strength and sprint velocity were measured using static myometer and non-motorized treadmill, respectively. Jump height was calculated using flight time during jumping, which was measured by a matswitch system. The 8-wk body mass-based squat training significantly decreased percent body fat (4.2%) and significantly increased the lean body mass (2.7%), muscle thickness (3.2%) and strength of the knee extensors (16.0%), compared to control group. The vertical jump height was also significantly improved by 3.4% through the intervention. The current results indicate that body mass-based squat training for 8 weeks is a feasible and effective method for improving body composition and muscular strength of the knee extensors, and jump performance in adolescent boys. Key pointsAn 8-wk body mass-based squat exercise training decreased percent body fat in adolescent boys.The body mass-based squat exercise training increased muscle size and strength capability of the knee extensors in adolescent boys.The squat exercise training improves vertical jump height in adolescent boys.

https://www.jssm.org/hfpdf.php?volume=12&issue=1&page=60

Effects of body mass-based squat training in adolescent boys

Purpose 
Mountain trekking involves level, uphill, and downhill walking (DW). Prolonged DW induces damage to leg muscles, reducing force generating ability and muscle coordination. These increase risks for more serious injuries and accidents in mountain trekking, thus a strategy to minimize muscle damage is warranted. It has been shown that low-intensity eccentric contractions confer protective effect on muscle damage induced by high-intensity eccentric contractions. This study tested the hypothesis that 5-min non-damaging DW would attenuate muscle damage induced by 40-min DW, but 5-min level walking (LW) would not.


Methods 
Untrained young men were allocated (n = 12/group) to either a control or one of the two preconditioning groups (PRE-DW or PRE-LW). The PRE-DW and PRE-LW groups performed 5-min DW (-28%) and 5-min LW, respectively, at 5 km/h with a load of 10% body mass, 1 week before 40-min DW (-28%, 5 km/h, 10% load). The control group performed 40-min DW only. Maximal knee extension strength, plasma creatine kinase (CK) activity, and muscle soreness (0–100 mm visual analogue scale) were measured before and 24 h after 5-min DW and 5-min LW, and before and 24, 48, and 72 h after 40-min DW.


Results 
No significant changes in any variables were evident after 5-min DW and 5-min LW. After 40-min DW, the control and PRE-LW groups showed significant (P<0.05) changes in the variables without significant differences between groups (control vs. PRE-LW; peak strength reduction: -19.2 ± 6.9% vs. -18.7 ± 11.0%, peak CK: 635.5 ± 306.0 vs. 639.6 ± 405.4 U/L, peak soreness: 81.4 ± 14.8 vs. 72.0 ± 29.2 mm). These changes were significantly (P<0.05) attenuated (47–64%) for the PRE-DW group (-9.9 ± 9.6%, 339.3 ± 148.4 U/L, 27.8 ± 16.8 mm).


Conclusions 
The results supported the hypothesis and suggest that performing small volume of downhill walking is crucial in preparation for trekking.

/pdf/prevention-of-downhill-walking-induced-muscle-damage-by-non-5d1ehy1b00.pdf

Masayoshi Yamamoto

Papers

Effects of resistance training under hypoxic conditions on muscle hypertrophy and strength.

Attenuation of muscle deoxygenation precedes EMG threshold in normoxia and hypoxia.

Determinants of the abilities to jump higher and shorten the contact time in a running 1-legged vertical jump in basketball.

Effects of body mass-based squat training in adolescent boys

Prevention of downhill walking-induced muscle damage by non-damaging downhill walking.