Determinants of active commuting

In this issue of Preventive Medicine Bringolf-Isler et al. (Bringolf-Isler et al., 2008) report on factors associated with active commuting to school in more than 1000 children aged 6–14 years in a German-speaking, a French-speaking, and a bilingual area in Switzerland. This study design naturally allows for separating cultural from other determinants of selftransportation. Switzerland may be a small country with a socio-economically homogenous population but it nevertheless has different language regions with subtle differences in culture. Active commuting to school of children is still the rule in Switzerland (on average 78% in this study), which is high compared to some other countries, and probably reflects a high perceived safety by parents of the way to school (63% of parents judged the way to school sufficiently safe). But, as in other countries, childhood obesity is on the rise in Switzerland and there are indications that active commuting to school is decreasing

Exercise starts and ends in the brain

Classically the limit to endurance of exercise is explained in terms of metabolic capacity. Cardio-respiratory capacity and muscle fatigue are thought to set the limit and the majority of studies on factors limiting endurance exercise discuss issues such as maximal oxygen uptake (V̇O2max), aerobic enzyme capacity, cardiac output, glycogen stores, etc. However, this paradigm does not explain the limitation to endurance exercise with large muscle groups at altitude, when at exhaustion exercise is ended without limb locomotor muscle fatigue and with sub-maximal cardiac output. A simple fact provides a basis for an explanation. Voluntary exercise starts and ends in the brain. It starts with spatial and temporal recruitment of motor units and ends with their de-recruitment. A conscious decision precedes a voluntary effort. The end of effort is again volitional and a forced conscious decision to stop precedes it, but it is unknown what forces the off-switch of recruitment at exhaustion although sensation of exertion certainly plays a role. An alternative model explaining the limitation of exercise endurance thus proposes that the central nervous system integrates input from various sources all related to the exercise and limits the intensity and duration of recruitment of limb skeletal muscle to prevent jeopardizing the integrity of the organism. This model acknowledges the cardio-respiratory and muscle metabolic capacities as prime actors on the performance scene, while crediting the central nervous system for its pivotal role as the ultimate site where exercise starts and end

Sport Tomorrow? Fewer Records, but more Science, Integrity and Ethics

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Would Relaxation of the Anti-doping Rule Lead to Red Queen Effects?

status: Published onlin

Total Energy Expenditure, Energy Intake, and Body Composition in Endurance Athletes Across the Training Season: a Systematic Review

Background: Endurance athletes perform periodized training in order to prepare for main competitions and maximize performance. However, the coupling between alterations of total energy expenditure (TEE), energy intake, and body composition during different seasonal training phases is unclear. So far, no systematic review has assessed fluctuations in TEE, energy intake, and/or body composition in endurance athletes across the training season. The purpose of this study was to (1) systematically analyze TEE, energy intake, and body composition in highly trained athletes of various endurance disciplines and of both sexes and (2) analyze fluctuations in these parameters across the training season. Methods: An electronic database search was conducted on the SPORTDiscus and MEDLINE (January 1990–31 January 2015) databases using a combination of relevant keywords. Two independent reviewers identified potentially relevant studies. Where a consensus was not reached, a third reviewer was consulted. Original research articles that examined TEE, energy intake, and/or body composition in 18–40-year-old endurance athletes and reported the seasonal training phases of data assessment were included in the review. Articles were excluded if body composition was assessed by skinfold measurements, TEE was assessed by questionnaires, or data could not be split between the sexes. Two reviewers assessed the quality of studies independently. Data on subject characteristics, TEE, energy intake, and/or body composition were extracted from the included studies. Subjects were categorized according to their sex and endurance discipline and each study allocated a weight within categories based on the number of subjects assessed. Extracted data were used to calculate weighted means and standard deviations for parameters of TEE, energy intake, and/or body composition. Results: From 3589 citations, 321 articles were identified as potentially relevant, with 82 meeting all of the inclusion criteria. TEE of endurance athletes was significantly higher during the competition phase than during the preparation phase (p < 0.001). During the competition phase, both body mass and fat-free mass were significantly higher compared to other seasonal training phases (p < 0.05). Conclusions: Limitations of the present study included insufficient data being available for all seasonal training phases and thus low explanatory power of single parameters. Additionally, the classification of the different seasonal training phases has to be discussed. Male and female endurance athletes show important training seasonal fluctuations in TEE, energy intake, and body composition. Therefore, dietary intake recommendations should take into consideration other factors including the actual training load, TEE, and body composition goals of the athlete

Exceptional Performance in Competitive Ski Mountaineering: An Inertial Sensor Case Study

Organized biannually in the Swiss Alps since 1984, the “Patrouille des Glaciers” (PDG) is one of the most challenging long-distance ski mountaineering (skimo) team competitions in the world. The race begins in Zermatt (1,616 m) and ends in Verbier (1,520 m), covering a total distance of 53 km with a cumulated 4,386 m of ascent and 4,482 m of descent. About 4,800 athletes take part in this competition, in teams of three. We hereby present the performance analysis of the uphill parts of this race of a member (#1) of the winning team in 2018, setting a new race record at 5 h and 35 min, in comparison with two amateur athletes. The athletes were equipped with the Global Navigation Satellite System (GNSS) antenna, a heart rate monitor, and a dedicated multisensor inertial measurement unit (IMU) attached to a ski, which recorded spatial-temporal gait parameters and transition events. The athletes' GNSS and heart rate data were synchronized with the IMU data. Athlete #1 had a baseline VO2 max of 80 ml/min/kg, a maximum heart rate of 205 bpm, weighed 69 kg, and had a body mass index (BMI) of 21.3 kg/m2. During the race, he carried 6 kg of gear and kept his heart rate constant around 85% of max. Spatiotemporal parameters analysis highlighted his ability to sustain higher power, higher pace, and, thus, higher vertical velocity than the other athletes. He made longer steps by gliding longer at each step and performed less kick turns in a shorter time. He spent only a cumulative 5 min and 30 s during skins on and off transitions. Skimo performance, thus, requires a high aerobic power of which a high fraction can be maintained for a prolonged time. Our results further confirm earlier observations that speed of ascent during endurance skimo competitions is a function of body weight and race gear and vertical energy cost of locomotion, with the latter function of climbing gradient. It is also the first study to provide some reference benchmarks for spatiotemporal parameters of elite and amateur skimo athletes during climbing using real-world data

Task failure from inspiratory resistive loaded breathing: a role for inspiratory muscle fatigue?

The use of non-invasive resistive breathing to task failure to assess inspiratory muscle performance remains a matter of debate. CO2 retention rather than diaphragmatic fatigue was suggested to limit endurance during inspiratory resistive breathing. Cervical magnetic stimulation (CMS) allows discrimination between diaphragmatic and rib cage muscle fatigue. We tested a new protocol with respect to the extent and the partitioning of inspiratory muscle fatigue at task failure. Nine healthy subjects performed two runs of inspiratory resistive breathing at 67 (12)% of their maximal inspiratory mouth pressure, respiratory rate ( f R), paced at 18min-1, with a 15-min pause between runs. Diaphragm and rib cage muscle contractility were assessed from CMS-induced esophageal (P es,tw), gastric (P ga,tw), and transdiaphragmatic (P di,tw) twitch pressures. Average endurance times of the first and second runs were similar [9.1 (6.7)and 8.4 (3.5)min]. P di,tw significantly decreased from 33.1 to 25.9cmH2O in the first run, partially recovered (27.6cmH2O), and decreased further in the second run (23.4cmH2O). P es,tw also decreased significantly (-5.1 and -2.4cmH2O), while P ga,tw did not change significantly (-2.0 and -1.9cmH2O), indicating more pronounced rib cage rather than diaphragmatic fatigue. End-tidal partial pressure of CO2 (P ETCO2) rose from 37.2 to 44.0 and 45.3mmHg, and arterial oxygen saturation (S aO2) decreased in both runs from 98% to 94%. Thus, task failure in mouth-pressure-targeted, inspiratory resistive breathing is associated with both diaphragmatic and rib cage muscle fatigue. Similar endurance times despite different degrees of muscle fatigue at the start of the runs indicate that other factors, e.g. increases in P ETCO2, and/or decreases in S aO2, probably contributed to task-failur

Nutrient intake and performance during a mountain marathon: an observational study

In order to study nutrient intake of amateur runners during a mountain marathon, compliance with recommendations, and association with performance, an intake of 42 participants in a Swiss mountain marathon was assessed by direct observation. Data on demographics, dietary preparation and race experience were obtained by questionnaires. Anthropometrical measures were performed before and after the race. Mean hourly intakes (SD) of fluid, carbohydrate, energy and sodium were 545 (158)ml, 31 (14)g, 141 (63)kcal [or 590 (264)kJ], and 150 (203)mg respectively. A third of the runners drank 600mlh−1 or more, 52% consumed less than 30gh−1 carbohydrates, 95% consumed less than 500mgh−1 sodium. Mean weight loss was 4 (1.5)kg; 30 runners (71%) lost over 3% body mass. Mean running time was 7h 3min (1h17min). Most participants failed to meet nutritional recommendations. None were at risk of overhydration. Body composition and race experience were correlated with performance, but not nutrient intake. Because experienced runners are well trained, fitter, and know better their personal needs during such a race, it is difficult to disentangle these associations. As causal relationship cannot be proven with this cross-sectional design, non-compliance with intake recommendations requires additional experimental research on the impact of nutrient intake on field performanc