immunity ( Hagmar et al., 2008 ; Lancaster et al., 2005 ). Observational studies show that skeletal demineralization and hormonal imbalances are also prevalent among males, for example, male endurance athletes and athletes who strive for leanness ( Dolan et al., 2012 ; Guillaume et al., 2012 ; Hackney
Marc T. Hamilton, Enas Areiqat, Deborah G. Hamilton and Lionel Bey
Physical activity often declines with age because of a reduction in the spontaneous activities of daily living and because of less intense exercise. In controlled studies of young rats, it was shown that physical activities associated with walking and standing were especially important for maintaining a high level of lipoprotein lipase (LPL) activity in postural skeletal muscles (slowtwitch oxidative muscles). More intense contractions during run training were important for a high LPL activity in the fast-twitch glycolytic muscles. Aging also causes a fiber type–specific decrease of skeletal muscle LPL activity and LPL protein in weight-bearing skeletal muscles (and no aging effect in glycolytic muscles). Thus, contractile inactivity may be a significant factor causing sub-optimal triglyceride metabolism in skeletal muscles during both unloading in young animals and aging. Measurements of plasma LPL activity, plasma triglyceride (TG) clearance rates, postprandial hypertriglyceridemia after oral fat tolerance tests, and fasting TG levels were generally indicative of reduced plasma TG metabolism during middle or old age. In contrast, older endurance-trained individuals had a favorable blood lipid profile compared to age-matched or young controls, even when the controls were not overweight. Therefore, the poor TG metabolism that is frequently associated with aging may be caused by some of the same processes that lower skeletal muscle LPL activity of young sedentary individuals.
António J. Figueiredo, Manuel J. Coelho e Silva, Sean P. Cumming and Robert M. Malina
The purpose of the study was to compare the anthropometric, functional and sport-specific skill characteristics and goal orientations of male youth soccer players at the extremes of height and skeletal maturity in two competitive age groups, 11–12 and 13–14 years. The shortest and tallest players, and least and most skeletally mature players (n = 8 per group) within each age group were compared on chronological age; skeletal age (Fels method); pubertal status (pubic hair); size, proportions and adiposity; four functional capacities; four soccer-specific skills; and task and ego orientation. The tallest players were older chronologically, advanced in maturity (skeletal, pubertal) and heavier, and had relatively longer legs than the shortest players in each age group. At 11–12 years, the most mature players were chronologically younger but advanced in pubertal status, taller and heavier with more adiposity. At 13–14 years, the most mature players were taller, heavier and advanced in pubertal status but did not differ in chronological age compared with the least mature players. Players at the extremes of height and skeletal maturity differed in speed and power (tallest > shortest; most mature > lest mature), but did not differ consistently in aerobic endurance and in soccer-specific skills. Results suggested that size and strength discrepancies among youth players were not a major advantage or disadvantage to performance. By inference, coaches and sport administrators may need to provide opportunities for or perhaps protect smaller, skilled players during the adolescent years.
Pedro Gómez-Carmona, Ismael Fernández-Cuevas, Manuel Sillero-Quintana, Javier Arnaiz-Lastras and Archit Navandar
thermography has been used as a valid, 7 accurate, 8 and reliable 7 , 9 technique to use on a daily basis to detect skeletal muscle overload and fatigue in athletes. 10 Infrared thermography, a noninvasive and fast technique, applied to the skin temperature provides a detailed temperature map of the human
Bettina Mittendorfer and Samuel Klein
Endurance exercise increases the use of endogenous fuels to provide energy for working muscles. Elderly subjects oxidize more glucose and less fat during moderate intensity exercise. This shift in substrate use is presumably caused by age-related changes in skeletal muscle, including decreased skeletal muscle respiratory capacity, because adipose tissue lipolysis and plasma fatty acid availability are not rate limiting. Endurance training in elderly subjects increases muscle respiratory capacity, decreases glucose production and oxidation, and increases fat oxidation thereby correcting or compensating for the alterations in substrate oxidation associated with aging.
Karinna Sonálya Aires da Costa, Daniel Tezoni Borges, Liane de Brito Macedo, Caio Alano de Almeida Lins and Jamilson Simões Brasileiro
, such as frequency, amplitude, position, and exposure time. 15 Therefore, despite being a widely used resource in rehabilitation, there is still a lack of consensus in the literature regarding neurophysiological responses in the skeletal muscle immediately after the use of WBV, 15 specifically in
Michael Svensson, Christer Malm, Michail Tonkonogi, Bjǒrn Ekblom, Bertil Sjödin and Kent Sahlin
The aim of the present study was to investigate the concentration of ubiquinone-10 (Q10), at rest, in human skeletal muscle and blood plasma before and after a period of high-intensity training with or without Q10 supplementation. Another aim was to explore whether adenine nucleotide catabolism, lipid peroxidation, and mitochondrial function were affected by Q10 treatment. Seventeen young healthy men were assigned to either a control (placebo) or a Q10-supplementation (120 mg/day) group. Q10 supplementation resulted in a significantly higher plasma Q10/lotal cholesterol level on Days 11 and20compared with Day 1. There was no significant change in the concentration of Q10 in skeletal muscle or in isolated skeletal muscle mitochondria in either group. Plasma hypoxanthine and uric acid concentrations increased markedly after each exercise test session in both groups. After the training period, the postexercise increase in plasma hypoxanthine was markedly reduced in both groups, but the response was partially reversed after the recovery period. It was concluded that Q10 supplementation increases the concentration of Q1O in plasma but not in skeletal muscle.
Thomas Dos’Santos, Paul A. Jones, Jonathan Kelly, John J. McMahon, Paul Comfort and Christopher Thomas
Skeletal-muscle function can be evaluated using force-time curves generated during dynamic and isometric activities. Peak force (PF) and peak rate of force development (RFD) are commonly assessed 1 – 5 and have been reported to relate to various athletic performance tasks including baseball
William J. Evans
Most exercise results in some skeletal muscle damage. However, unaccustomed exercise andlor eccentric exercise can cause extensive damage. This exercise-induced muscle damage causes a response that can be characterized by a cascade of metabolic events. Within 24 to 48 hours, delayed onset muscle soreness and weakness, the most obvious manifestations of the damage, peak. Increased circulating neutrophils and interleukin-1 occurs within 24 hours after the exercise, with skeletal muscle levels remaining elevated for a much longer time. There is a prolonged increase in ultrastructural damage and muscle protein degradation as well as a depletion of muscle glycogen stores. These metabolic alterations may result in the increased need for dietary protein, particularly at the beginning of a training program that has a high eccentric component such as strength training. The delay in muscle repair and glycogen repletion following damaging exercise should cause coaches and athletes to allow an adequate period of time between competition for complete recovery.
Jennifer M. Dent, Cameron J.R. Blimkie, Colin E. Webber, Angus B. McMillan and Rhona M. Hanning
Absolute total body (TB) and regional spine (RS) bone mineral content (BMC) measured by dual photon absorptiometry were lower (p < .05) in Turner syndrome (TS) girls compared to a cohort of younger (by 2 years) but taller and heavier prepubertal girls. Maximal voluntary strength (MVC) of the elbow flexors, knee extensors, and plantar flexors were also consistently and, in most cases, significantly lower in TS girls. Differences between groups in absolute bone mineral and muscle strength disappeared, however, when normalized for skeletal cross-sectional area (areal density) and for the product of muscle cross-sectional area and estimated moment arm, respectively. Maximal voluntary strength and body mass correlated moderately strongly with the bone mineral measures, but only body mass contributed significantly to the variance in total body and regional spine bone mineral measures. Bone mineral and muscle strength appear appropriate for body size and for skeletal and muscle morphology in young TS girls.