Acute endocrine responses to plyometrics versus resistance exercise in children

The purpose of this study was to examine the acute hormonal responses to a bout of resistance versus plyometric exercise in young male athletes. Specifically, changes in salivary cortisol, testosterone and testosterone-to-cortisol ratio from pre- to post-exercise between the two different exercise protocols were examined. Twenty-six peri-pubertal active boys participated in this cross-over study, completing two exercise sessions. During each session, participants first completed a 30 min control period, which did not include any exercise, and then was randomly assigned to perform a 45 min of either a resistance exercise or a plyometric exercise protocol. All participants crossed over to perform the other exercise protocol during their second exercise session, a week later. Four saliva samples during each protocol were taken at: baseline, pre-exercise, 5 min post-exercise and 30 min post-exercise. Significant increases in testosterone values were reported 5 min post-exercise following the resistance protocol, but not the plyometric protocol. Both exercise protocols resulted in significant cortisol decreases overtime, as well as significant testosterone-to-cortisol ratio increases. The post-exercise increases in salivary testosterone and testosterone-to-cortisol ratio followed the typical exercise induced anabolic response seen in adults. However, the post-exercise decrease in salivary cortisol was different than the typical adult response indicating an insufficient stimulus for this age group maybe due to their stage of the biological development. Thus, in the adolescent boys, exercise appears to change the anabolic to catabolic balance in favor of anabolism.

The electromyographic threshold in boys and men

Abstract Background Children have been shown to have higher lactate (LaTh) and ventilatory (VeTh) thresholds than adults, which might be explained by lower levels of type-II motor-unit (MU) recruitment. However, the electromyographic threshold (EMGTh), regarded as indicating the onset of accelerated type-II MU recruitment, has been investigated only in adults. Purpose To compare the relative exercise intensity at which the EMGTh occurs in boys versus men. Methods Participants were 21 men (23.4 ± 4.1 years) and 23 boys (11.1 ± 1.1 years), with similar habitual physical activity and peak oxygen consumption (VO2pk) (49.7 ± 5.5 vs. 50.1 ± 7.4 ml kg−1 min−1, respectively). Ramped cycle ergometry was conducted to volitional exhaustion with surface EMG recorded from the right and left vastus lateralis muscles throughout the test (~10 min). The composite right–left EMG root mean square (EMGRMS) was then calculated per pedal revolution. The EMGTh was then determined as the exercise intensity at the point of least residual sum of squares for any two regression line divisions of the EMGRMS plot. Results EMGTh was detected in 20/21 of the men (95.2 %) and only in 18/23 of the boys (78.3 %). The boys’ EMGTh was significantly higher than the men’s (86.4 ± 9.6 vs. 79.7 ± 10.0 % of peak power output at exhaustion; p < 0.05). The pattern was similar when EMGTh was expressed as percentage of VO2pk. Conclusions The boys’ higher EMGTh suggests delayed and hence lesser utilization of type-II MUs in progressive exercise, compared with men. The boys–men EMGTh differences were of similar magnitude as those shown for LaTh and VeTh, further suggesting a common underlying factor.

The Clinical Translation Gap in Child Health Exercise Research: A Call for Disruptive Innovation

In children, levels of play, physical activity, and fitness are key indicators of health and disease and closely tied to optimal growth and development. Cardiopulmonary exercise testing (CPET) provides clinicians with biomarkers of disease and effectiveness of therapy, and researchers with novel insights into fundamental biological mechanisms reflecting an integrated physiological response that is hidden when the child is at rest. Yet the growth of clinical trials utilizing CPET in pediatrics remains stunted despite the current emphasis on preventative medicine and the growing recognition that therapies used in children should be clinically tested in children. There exists a translational gap between basic discovery and clinical application in this essential component of child health. To address this gap, the NIH provided funding through the Clinical and Translational Science Award (CTSA) program to convene a panel of experts. This report summarizes our major findings and outlines next steps necessary to enhance child health exercise medicine translational research. We present specific plans to bolster data interoperability, improve child health CPET reference values, stimulate formal training in exercise medicine for child health care professionals, and outline innovative approaches through which exercise medicine can become more accessible and advance therapeutics across the child health spectrum.

Canadian Society for Exercise Physiology Position Paper: Resistance Training in Children and Adolescents

Many position stands and review papers have refuted the myths associated with resistance training (RT) in children and adolescents. With proper training methods, RT for children and adolescents can be relatively safe and improve overall health. The objective of this position paper and review is to highlight research and provide recommendations in aspects of RT that have not been extensively reported in the pediatric literature. In addition to the well-documented increases in muscular strength and endurance, RT has been used to improve function in pediatric patients with cystic fibrosis, cerebral palsy and burn victims. Increases in children’s muscular strength have been attributed primarily to neurological adaptations due to the disproportionately higher increase in muscle strength than in muscle size. Although most studies using anthropometric measures have not shown significant muscle hypertrophy in children, more sensitive measures such as magnetic resonance imaging and ultrasound have suggested hypertrophy may occur. There is no minimum age for RT for children. However the training and instruction must be appropriate for children and adolescents involving a proper warm-up, cool-down and an appropriate choice of exercises. It is recommended that low-to-moderate intensity resistance should be utilized 2-3 times per week on non-consecutive days, with 1-2 sets initially, progressing to 4 sets of 8-15 repetitions for 8-12 exercises. These exercises can include more advanced movements such as Olympic style lifting, plyometrics and balance training, which can enhance strength, power, co-ordination and balance. However specific guidelines for these more advanced techniques need to be established for youth. In conclusion, a RT program that is within a child’s or adolescent’s capacity, involves gradual progression under qualified instruction and supervision with appropriately sized equipment can involve more advanced or intense RT exercises which can lead to functional (i.e. muscular strength, endurance, power, balance and co-ordination) and health benefits.

The Impact of Directed Mirror Focus and Technique Cues on Psychological, Cognitive and Emotional Exercise Correlates in an Introductory Weight Training Orientation

The purpose of the study was to investigate whether teaching inactive and low active women to use mirrors for form and technique purposes could lessen the negative impact of mirrors on self-presentational concerns, affect, and self-efficacy. Eligible women (N = 82) underwent a one-on-one weight training orientation with a personal trainer. Participants were randomized into one of four experimental groups, each unique in the type of feedback (general or technique-specific) and the degree of focus on the mirror for technique reinforcement. Questionnaires assessed study outcomes pre- and post-orientation. Results indicated groups did not significantly differ on any post-condition variables, when controlling for pre-condition values (all p’s >.05). All groups showed outcome improvements following the orientation. This suggests that during a complex task, a personal trainer who emphasizes form and technique can facilitate improvements to psychological outcomes in novice exercisers, independent of the presence of mirrors or directional cues provided.

License no. 144 of season 1872/73 made out to S.D. Woodruff for 36 square miles in berth no. 192

License no. 144 of season 1872/73 made out to S.D. Woodruff for 36 square miles in berth no. 192. This document is slightly torn and stained along the right hand side. This does not affect the text, April 7, 1873.

License no. 145 of season 1872/73 made out to S.D. Woodruff for 35 ¾ square miles in berth no. 198

License no. 145 of season 1872/73 made out to S.D. Woodruff for 35 ¾ square miles in berth no. 198, April 7, 1873.

License no. 67 of season 1873/74 made out to S.D. Woodruff for 36 square miles in berth no. 192

License no. 67 of season 1873/74 made out to S.D. Woodruff for 36 square miles in berth no. 192, June 13, 1873

License no. 68 of season 1873/74 made out to S.D. Woodruff for 35 ¾ square miles in berth no. 198

License no. 68 of season 1873/74 made out to S.D. Woodruff for 35 ¾ square miles in berth no. 198, June 13, 1873.

License no. 11 of season 1874/75 made out to S.D. Woodruff for 35 ¾ square miles in berth no. 198

License no. 11 of season 1874/75 made out to S.D. Woodruff for 35 ¾ square miles in berth no. 198, May 20, 1874.

License no. 5 of season 1875/76 made out to S.D. Woodruff for 36 square miles in berth no. 192

License no. 5 of season 1875/76 made out to S.D. Woodruff for 36 square miles in berth no. 192, June 1, 1875.

License no. 2 of season 1886/87 made out to S.D. Woodruff for 36 square miles in berth no. 192

License no. 2 of season 1886/87 made out to S.D. Woodruff for 36 square miles in berth no. 192, May 15, 1876.

License no. 3 of season 1886/87 made out to S.D. Woodruff for 35 ¾ square miles in berth no. 198

License no. 3 of season 1886/87 made out to S.D. Woodruff for 35 ¾ square miles in berth no. 198, May 15, 1876

License no. 7 of season 1877/78 made out to S.D. Woodruff for 35 ¾ square miles in berth no. 198

License no. 7 of season 1877/78 made out to S.D. Woodruff for 35 ¾ square miles in berth no. 198, May 31, 1877.

License no. 6 of season 1877/78 made out to S.D. Woodruff for 36 square miles in berth no.192

License no. 6 of season 1877/78 made out to S.D. Woodruff for 36 square miles in berth no.192, May 31, 1877.