Aerobic fitness and physical activity are inversely associated with body fat,dyslipidemia and inflammatory mediators in children and adolescents living with HIV

This study aimed to investigate if moderate to vigorous physical activity (MVPA) and aerobic fitness are associated with cardiovascular risk factors in HIV+ children and adolescents. Sixty-five children and adolescents (8 to 15 years) provided minutes of MVPA measured by accelerometers and peak oxygen uptake (peak VO₂) by breath-by-breath respiratory exchange. Cardiovascular risk factors were characterized by body fat, blood pressure, total cholesterol, HDL-c, LDL-c, triglycerides, glucose, insulin, C-reactive protein (CRP), interleukin (IL)-6, tumor necrosis factor-alpha (TNF-α) and carotid intima-media thickness. Results indicated that higher MVPA was associated with lower values of total (β = ?3.566) and trunk body fat (β = ?3.495), total cholesterol (β = ?0.112) and LDL-c (β = ?0.830). Likewise, higher peak VO₂ was associated with lower total (β = ?0.629) and trunk body fat values (β = ?0.592) and levels of CRP (β = ?0.059). The physically active participants had lower total cholesterol (?24.4 mg.dL^?1) and LDL-c (?20.1 mg.dL^?1) compared to participants judged to be insufficiently active. Moreover, participants with satisfactory peak VO? showed lower total (?4.1%) and trunk (?4.3%) body fat, CRP (?2.3 mg.L^?1), IL-6 (?2.4 pg.mL^?1) and TNF-α (?1.0 pg.mL^?1) compared to low peak VO₂ peers. High levels of MVPA and aerobic fitness may prevent developing of cardiovascular risk factors in children and adolescents HIV+.     

A mathematical model for decision-making in the classification of para-footballers with different severity of coordination impairments

Classification is a defining feature of Para-sport, and sports-specific classification systems determined through multidisciplinary scientific research are required, i.e., evidence-based and focused on the relationship between the impairment and the key performance determinants. Data envelopment analysis (DEA) was applied as a classification tool using a directional distance function (DDF) model. The aim of the study was to test the DEA as a possible classification tool in cerebral palsy football. We analyse the performance of 56 international para-footballers with hypertonia, ataxia or athetosis, who completed a 20-test battery with DEA models. Five of the tests are included in the model (change of direction: Illinois agility test; jumping: standing broad jump, four bounds for distance, and triple hop with the non-dominant leg; 10-m sprint/acceleration; and ball dribbling, both in a straight line and following a trajectory), showing that players with less impairment exhibit the highest efficiency. This outcome suggests that DEA models might be feasible for detecting and discriminating the performance and magnitude of impairment in cerebral palsy football, with an objective ranking of the athletes in relation to different physical performance tests. This study also provides reference scores for decision-making during classification and guidance for further research in team Paralympic sports.     

David Foster Wallace on dumb jocks and athletic genius

David Foster Wallace was genuinely troubled by what he perceived to be a serious incongruity in the mental lives of elite athletes. To perform with grace and beauty, elite athletes must be ‘geniuses,’ yet in conversation and prose these same athletes often exhibit such vapidity and banality that he was tempted to simply write them off as unintelligent or worse. In response to this puzzle, Wallace developed different philosophical conceptions of the elite athlete aimed at bridging the gap between genius and dumb jock. For Wallace, this was an exercise designed to help him live a more compassionate life.     

Designing,building, measuring,and testing a constant equivalent fall height terrain park jump

Previous work has presented both a theoretical foundation for designing terrain park jumps that control landing impact and computer software to accomplish this task. US ski resorts have been reluctant to adopt this more engineered approach to jump design, in part due to questions of feasibility. The present study demonstrates this feasibility. It describes the design, construction, measurement, and experimental testing of such a jump. It improves on the previous efforts with more complete instrumentation, a larger range of jump distances, and a new method for combining jumper- and board-mounted accelerometer data to estimate equivalent fall height, a measure of impact severity. It unequivocally demonstrates the efficacy of the engineering design approach, namely that it is possible and practical to design and build free style terrain park jumps with landing surface shapes that control for landing impact as predicted by the theory.     

The effects of short versus long inter-set rest intervals in resistance training on measures of muscle hypertrophy: A systematic review

Although the effects of short versus long inter-set rest intervals in resistance training on measures of muscle hypertrophy have been investigated in several studies, the findings are equivocal and the practical implications remain unclear. In an attempt to provide clarity on the topic, we performed a systematic literature search of PubMed/MEDLINE, Scopus, Web of Science, Cochrane Library, and Physiotherapy Evidence Database (PEDro) electronic databases. Six studies were found to have met the inclusion criteria: (a) an experimental trial published in an English-language peer-reviewed journal; (b) the study compared the use of short (≤60?s) to long (>60?s) inter-set rest intervals in a traditional dynamic resistance exercise using both concentric and eccentric muscle actions, with the only difference in resistance training among groups being the inter-set rest interval duration; (c) at least one method of measuring changes in muscle mass was used in the study; (d) the study lasted for a minimum of four weeks, employed a training frequency of ≥2 resistance training days per week, and (e) used human participants without known chronic disease or injury. Current evidence indicates that both short and long inter-set rest intervals may be useful when training for achieving gains in muscle hypertrophy. Novel findings involving trained participants using measures sensitive to detect changes in muscle hypertrophy suggest a possible advantage for the use of long rest intervals to elicit hypertrophic effects. However, due to the paucity of studies with similar designs, further research is needed to provide a clear differentiation between these two approaches.     

The use of player physical and technical skill match activity profiles to predict position in the Australian Football League draft

This study investigated the extent to which position in the Australian Football League (AFL) national draft is associated with individual game performance metrics. Physical/technical skill performance metrics were collated from all participants in the 2014 national under 18 (U18) championships (18 games) drafted into the AFL (n = 65; 17.8 ± 0.5 y); 232 observations. Players were subdivided into draft position (ranked 1–65) and then draft round (1–4). Here, earlier draft selection (i.e., closer to 1) reflects a more desirable player. Microtechnology and a commercial provider facilitated the quantification of individual game performance metrics (n = 16). Linear mixed models were fitted to data, modelling the extent to which draft position was associated with these metrics. Draft position in the first/second round was negatively associated with “contested possessions” and “contested marks”, respectively. Physical performance metrics were positively associated with draft position in these rounds. Correlations weakened for the third/fourth rounds. Contested possessions/marks were associated with an earlier draft selection. Physical performance metrics were associated with a later draft selection. Recruiters change the type of U18 player they draft as the selection pool reduces. juniors with contested skill appear prioritised.     

Changes in kinematics and arm–leg coordination during a 100-m breaststroke swim

The purpose of this study was to compare arm–leg coordination and kinematics during 100 m breaststroke in 26 (8 female; 18 male) specialist breaststroke swimmers. Laps were recorded using three 50-Hz underwater cameras. Heart rate and blood lactate were measured pre- and post-swim. Arm–leg coordination was defined using coordination phases describing continuity between recovery and propulsive phases of upper and lower limbs: coordination phase 1 (time between end of leg kick and start of the arm pull phases); and coordination phase 2 (time between end of arm pull and start of leg kick phases). Duration of stroke phases, coordination phases, swim velocity, stroke length (SL), stroke rate (SR) and stroke index (SI) were analysed during the last three strokes of each lap that were unaffected by turning or finishing. Significant changes in velocity, SI and SL (P < 0.05) were found between laps. Both sexes showed significant increase (P < 0.05) in heart rate and blood lactate pre- to post-swim. Males had significantly (P < 0.01) faster swim velocities resulting from longer SLs (P = 0.016) with no difference in SR (P = 0.064). Sex differences in kinematic parameters can be explained by anthropometric differences providing males with increased propelling efficiency.     

Metabolic cost of running is greater on a treadmill with a stiffer running platform

Exercise testing on motorised treadmills provides valuable information about running performance and metabolism; however, the impact of treadmill type on these tests has not been investigated. This study compared the energy demand of running on two laboratory treadmills: an HP Cosmos (C) and a Quinton (Q) model, with the latter having a 4.5 times stiffer running platform. Twelve experienced runners ran identical bouts on these treadmills at a range of four submaximal velocities (reported data is for the velocity that approximated 75–81% VO_2max). The stiffer treadmill elicited higher oxygen consumption (C: 46.7 ± 3.8; Q: 50.1 ± 4.3 ml·kg^?1 · min^?1), energy expenditure (C: 16.0 ± 2.5; Q: 17.7 ± 2.9 kcal · min^?1), carbohydrate oxidation (C: 9.6 ± 3.1; Q: 13.0 ± 3.9 kcal · min^?1), heart rate (C: 155 ± 16; Q: 163 ± 16 beats · min^?1) and rating of perceived exertion (C: 13.8 ± 1.2; Q: 14.7 ± 1.2), but lower fat oxidation (C: 6.4 ± 2.3; Q: 4.6 ± 2.5 kcal · min^?1) (all analysis of variance treadmill comparisons P < 0.01). This study confirms that caution is required when comparing performance and metabolic results between different treadmills and suggests that treadmills will vary in their comparability to over-ground running depending on the running platform stiffness.     

Short-term heat acclimation prior to a multi-day desert ultra-marathon improves physiological and psychological responses without compromising immune status

Multistage, ultra-endurance events in hot, humid conditions necessitate thermal adaptation, often achieved through short term heat acclimation (STHA), to improve performance by reducing thermoregulatory strain and perceptions of heat stress. This study investigated the physiological, perceptual and immunological responses to STHA prior to the Marathon des Sables. Eight athletes (age 42 ± 4 years and body mass 81.9 ± 15.0 kg) completed 4 days of controlled hyperthermia STHA (60 min·day^?1, 45°C and 30% relative humidity). Pre, during and post sessions, physiological and perceptual measures were recorded. Immunological measures were recorded pre-post sessions 1 and 4. STHA improved thermal comfort (P = 0.02), sensation (P = 0.03) and perceived exertion (P = 0.04). A dissociated relationship between perceptual fatigue and T_re was evident after STHA, with reductions in perceived Physical (P = 0.04) and General (P = 0.04) fatigue. Exercising T_re and HR did not change (P > 0.05) however, sweat rate increased 14% (P = 0.02). No changes were found in white blood cell counts or content (P > 0.05). Four days of STHA facilitates effective perceptual adaptations, without compromising immune status prior to an ultra-endurance race in heat stress. A greater physiological strain is required to confer optimal physiological adaptations.