Quantification and description of physical work performance

This article raises the question of standardization of terms and evaluation of physical performance in the scientific literature. Basic parameters of scientific research as mass, volume, force, energy, work, power are considered. In keeping with the standardization of procedures in the reporting of various types of research and the increased requirements for scientific manuscript preparation, it is vitally important that investigators conform with standard terminology. The need for standard terminology is also evident in clinical settings where different health professionals must communicate and discuss rehabilitation interventions. Strict adherence to the definitions of the international system will ensure standardization of terminology and make scientific communication more readily understandable to the worldwide scientific community

MCT1 genetic polymorphism influence in high intensity circuit training: A pilot study

Monocarboxylate Transporter 1 (MCT1) mediates the transport of the main fraction of lactate across the sarcolemma. A common polymorphic MCT1 variant has been identified, but its role in high intensity exercise performance has not been defined. We investigated the influence of MCT1 A1470T polymorphism (rs1049434) on lactate accumulation after high intensity circuit training. Ten men aged 20–26 performed three controlled circuit training (CWT) sessions at 60%, 70%, and 80% of the 15 repetition maximum (15 RM), in non-consecutive days. CWT included three sets of a circuit of eight exercises, obtaining lactate measurements immediately after each set had been completed. Two independent variables were analysed: MTC1 genotypes according to the presence or absence of the A1470T polymorphism, and the intensity of circuit training. Genotype distributions were in Hardy–Weinberg equilibrium, being 30% wild-type, 50% heterozygotes, and 20% mutated homozygotes. Mean lactate concentration at 80% of 15 RM were significantly higher than the mean lactate values at the other intensities (p < 0.01). Significant differences between genetic groups were found in the lactate accumulation slope at 80% of 15 RM (p = 0.02) and in the maximal lactate concentration reached by all subjects in the study (Lmax) (p = 0.03). The carriers of the A1470T polymorphism in the MTC1 gene seem to exhibit a worse lactate transport capability into the less active muscle cells for oxidation

Misuse of “Power” and other mechanical terms in sport and exercise science research

In spite of the Système International d’Unitès (SI) that was published in 1960, there continues to be widespread misuse of the terms and nomenclature of mechanics in descriptions of exercise performance. Misuse applies principally to failure to distinguish between mass and weight, velocity and speed, and especially the terms "work" and "power." These terms are incorrectly applied across the spectrum from high-intensity short-duration to long-duration endurance exercise. This review identifies these misapplications and proposes solutions. Solutions include adoption of the term "intensity" in descriptions and categorisations of challenge imposed on an individual as they perform exercise, followed by correct use of SI terms and units appropriate to the specific kind of exercise performed. Such adoption must occur by authors and reviewers of sport and exercise research reports to satisfy the principles and practices of science and for the field to advance

Humans Optimize Ground Contact Time and Leg Stiffness to Minimize the Metabolic Cost of Running

Trained endurance runners appear to fine-tune running mechanics to minimize metabolic cost. Referred to as self-optimization, the support for this concept has primarily been collated from only a few gait (e.g., stride frequency, length) and physiological (e.g., oxygen consumption, heart rate) characteristics. To extend our understanding, the aim of this study was to examine the effect of manipulating ground contact time on the metabolic cost of running in trained endurance runners. Additionally, the relationships between metabolic cost, and leg stiffness and perceived effort were examined. Ten participants completed 5 × 6-min treadmill running conditions. Self-selected ground contact time and step frequency were determined during habitual running, which was followed by ground contact times being increased or decreased in four subsequent conditions whilst maintaining step frequency (2.67 ± 0.15 Hz). The same self-selected running velocity was used across all conditions for each participant (12.7 ± 1.6 km · h−1). Oxygen consumption was used to compute the metabolic cost of running and ratings of perceived exertion (RPE) were recorded for each run. Ground contact time and step frequency were used to estimate leg stiffness. Identifiable minimums and a curvilinear relationship between ground contact time and metabolic cost was found for all runners (r2 = 0.84). A similar relationship was observed between leg stiffness and metabolic cost (r2 = 0.83). Most (90%) runners self-selected a ground contact time and leg stiffness that produced metabolic costs within 5% of their mathematical optimal. The majority (n = 6) of self-selected ground contact times were shorter than mathematical optimals, whilst the majority (n = 7) of self-selected leg stiffness' were higher than mathematical optimals. Metabolic cost and RPE were moderately associated (rs = 0.358 p = 0.011), but controlling for condition (habitual/manipulated) weakened this relationship (rs = 0.302, p = 0.035). Both ground contact time and leg stiffness appear to be self-optimized characteristics, as trained runners were operating at or close to their mathematical optimal. The majority of runners favored a self-selected gait that may rely on elastic energy storage and release due to shorter ground contact times and higher leg stiffness's than optimal. Using RPE as a surrogate measure of metabolic cost during manipulated running gait is not recommended

Balance in single-limb stance in healthy subjects – reliability of testing procedure and the effect of short-duration sub-maximal cycling

BACKGROUND: To assess balance in single-limb stance, center of pressure movements can be registered by stabilometry with force platforms. This can be used for evaluation of injuries to the lower extremities. It is important to ensure that the assessment tools we use in the clinical setting and in research have minimal measurement error. Previous studies have shown that the ability to maintain standing balance is decreased by fatiguing exercise. There is, however, a need for further studies regarding possible effects of general exercise on balance in single-limb stance. The aims of this study were: 1) to assess the test-retest reliability of balance variables measured in single-limb stance on a force platform, and 2) to study the effect of exercise on balance in single-limb stance, in healthy subjects. METHODS: Forty-two individuals were examined for test-retest reliability, and 24 individuals were tested before (pre-exercise) and after (post-exercise) short-duration, sub-maximal cycling. Amplitude and average speed of center of pressure movements were registered in the frontal and sagittal planes. Mean difference between test and retest with 95% confidence interval, the intraclass correlation coefficient, and the Bland and Altman graphs with limits of agreement, were used as statistical methods for assessing test-retest reliability. The paired t-test was used for comparisons between pre- and post-exercise measurements. RESULTS: No difference was found between test and retest. The intraclass correlation coefficients ranged from 0.79 to 0.95 in all stabilometric variables except one. The limits of agreement revealed that small changes in an individual's performance cannot be detected. Higher values were found after cycling in three of the eight stabilometric variables. CONCLUSIONS: The absence of systematic variation and the high ICC values, indicate that the test is reliable for distinguishing among groups of subjects. However, relatively large differences in an individual's balance performance would be required to confidently state that a change is real. The higher values found after cycling, indicate compensatory mechanisms intended to maintain balance, or a decreased ability to maintain balance. It is recommended that average speed and DEV 10; the variables showing the best reliability and effects of exercise, be used in future studies

Relação dos saltos vertical, horizontal e sêxtuplo com a agilidade e velocidade em crianças

The aim of the present study were: 1) To verify the relationship of vertical, horizontal and sextuple jumps with agility and velocity of 5, 10 and 25 m; 2) To verify the capacity of these jumps to predict the agility and 5, 10 and 25 m velocity performance in children. Twenty eight boys (9.47 ± 0.64 years) and thirty girls (9.69 ± 0.70 years) were evaluated. The correlation values between agility and velocity on 5, 10 and 25 m velocity were, respectively, r = 0.63, 0.51, 0.44 and 0.64 with vertical jump, r = 0.68, 0.62, 0.28 and 0.62 with sextuple jump, and r = 0.60, 0.50, 0.26 and 0.57 with horizontal jump. The vertical and sextuple jumps were able to predict the agility and 25 m velocity performance (p < 0.05). Furthermore, they demonstrated capacity to predict 5 and 10 m velocity, respectively (p < 0.05). The vertical and sextuple jump tests may be used for assessment and control of training with children practicing activities that require agility and velocity, since both jumps predicted the agility and velocity performance, which did not occur with the horizontal jump.Os objetivos do presente estudo foram: 1) verifi car a relação dos saltos vertical, horizontal e sêxtuplo com a agilidade e velocidade de 5, 10 e 25 m; 2) verifi car a capacidade desses saltos em predizer o desempenho da agilidade e velocidade de 5, 10 e 25 m em crianças. Vinte e oito meninos (9,47 ± 0,64 anos) e 30 meninas (9,69 ± 0,70 anos) foram avaliados. Os valores de correlação entre a agilidade, velocidade de 5, 10 e 25 m foram, respectivamente, r = 0,63, 0,51, 0,44 e 0,64 com o salto vertical, r = 0,68, 0,62, 0,28 e 0,62 com o salto sêxtuplo, e r = 0,60, 0,50, 0,26 e 0,57 com o salto horizontal. O salto vertical e o salto sêxtuplo foram capazes de predizer o desempenho da agilidade e da velocidade de 25 m (p < 0,05). Além disso, demonstraram capacidade de predizer a velocidade de 5 e 10 m, respectivamente (p < 0,05). Os testes de salto vertical e sêxtuplo podem ser utilizados para avaliação e controle do treinamento com crianças praticantes de atividades que demandam agilidade e velocidade, uma vez que ambos os saltos predisseram o desempenho da agilidade e velocidade, o que não ocorreu com o salto horizontal