The point of maximum curvature as a marker for physiological time series

We present a geometric analysis of the model of Stirling. In particular we analyze the curvature of a heart rate time series in response to a step like increment in the exercise intensity. We present solutions for the point of maximum curvature which can be used as a marker of physiological interest. This marker defines the point after which the heart rate no longer continues to rapidly rise and instead follows either a steady state or slow rise. These methods are then applied to find analytic solutions for a mono exponential model which is commonly used in the literature to model the response to a moderate exercise intensity. Numerical solutions are then found for the full model and parameter values presented in Stirling

Even Between-Lap Pacing Despite High Within-Lap Variation During Mountain Biking

Purpose: Given the paucity of research on pacing strategies during competitive events, this study examined changes in dynamic high-resolution performance parameters to analyze pacing profiles during a multiple-lap mountain-bike race over variable terrain. Methods: A global-positioning-system (GPS) unit (Garmin, Edge 305, USA) recorded velocity (m/s), distance (m), elevation (m), and heart rate at 1 Hz from 6 mountain-bike riders (mean ± SD age = 27.2 ± 5.0 y, stature = 176.8 ± 8.1 cm, mass = 76.3 ± 11.7 kg, VO2max = 55.1 ± 6.0 mL · kg–1 . min–1) competing in a multilap race. Lap-by-lap (interlap) pacing was analyzed using a 1-way ANOVA for mean time and mean velocity. Velocity data were averaged every 100 m and plotted against race distance and elevation to observe the presence of intralap variation. Results: There was no significant difference in lap times (P = .99) or lap velocity (P = .65) across the 5 laps. Within each lap, a high degree of oscillation in velocity was observed, which broadly reflected changes in terrain, but high-resolution data demonstrated additional nonmonotonic variation not related to terrain. Conclusion: Participants adopted an even pace strategy across the 5 laps despite rapid adjustments in velocity during each lap. While topographical and technical variations of the course accounted for some of the variability in velocity, the additional rapid adjustments in velocity may be associated with dynamic regulation of self-paced exercise

Age differences in physiological responses to self-paced and incremental V˙O2max\dot V O_{2max} testing

Purpose: A self-paced maximal exercise protocol has demonstrated higher $\dot V O_{2max}$ values when compared against traditional tests. The aim was to compare physiological responses to this self-paced $\dot V O_{2max}$ protocol (SPV) in comparison to a traditional ramp $\dot V O_{2max}$ (RAMP) protocol in young (18–30 years) and old (50–75 years) participants. Methods: Forty-four participants (22 young; 22 old) completed both protocols in a randomised, counter-balanced, crossover design. The SPV included 5 × 2 min stages, participants were able to self-regulate their power output (PO) by using incremental ‘clamps’ in ratings of perceived exertion. The RAMP consisted of either 15 or 20 W min$^{−1}$. Results: Expired gases, cardiac output (Q), stroke volume (SV), muscular deoxyhaemoglobin (deoxyHb) and electromyography (EMG) at the vastus lateralis were recorded throughout. Results demonstrated significantly higher $\dot V O_{2max}$ in the SPV (49.68 ± 10.26 ml kg$^{−1}$ min$^{−1}$) vs. the RAMP (47.70 ± 9.98 ml kg$^{−1}$ min$^{−1}$) in the young, but not in the old group (>0.05). Q and SV were significantly higher in the SPV vs. the RAMP in the young (0.05). No differences seen in deoxyHb and EMG for either age groups (>0.05). Peak PO was significantly higher in the SPV vs. the RAMP in both age groups (<0.05). Conclusion: Findings demonstrate that the SPV produces higher $\dot V O_{2max}$, peak Q and SV values in the young group. However, older participants achieved similar $\dot V O_{2max}$ values in both protocols, mostly likely due to age-related differences in cardiovascular responses to incremental exercise, despite them achieving a higher physiological workload in the SPV

Pulmonary oxygen uptake and muscle deoxygenation kinetics during recovery in trained and untrained male adolescents

Previous studies have demonstrated faster pulmonary oxygen uptake ( V ˙ O 2 ) kinetics in the trained state during the transition to and from moderate-intensity exercise in adults. Whilst a similar effect of training status has previously been observed during the on-transition in adolescents, whether this is also observed during recovery from exercise is presently unknown. The aim of the present study was therefore to examine V ˙ O 2 kinetics in trained and untrained male adolescents during recovery from moderate-intensity exercise. 15 trained (15 ± 0.8 years, V ˙ O 2max 54.9 ± 6.4 mL kg−1 min−1) and 8 untrained (15 ± 0.5 years, V ˙ O 2max 44.0 ± 4.6 mL kg−1 min−1) male adolescents performed two 6-min exercise off-transitions to 10 W from a preceding “baseline” of exercise at a workload equivalent to 80% lactate threshold; V ˙ O 2 (breath-by-breath) and muscle deoxyhaemoglobin (near-infrared spectroscopy) were measured continuously. The time constant of the fundamental phase of V ˙ O 2 off-kinetics was not different between trained and untrained (trained 27.8 ± 5.9 s vs. untrained 28.9 ± 7.6 s, P = 0.71). However, the time constant (trained 17.0 ± 7.5 s vs. untrained 32 ± 11 s, P < 0.01) and mean response time (trained 24.2 ± 9.2 s vs. untrained 34 ± 13 s, P = 0.05) of muscle deoxyhaemoglobin off-kinetics was faster in the trained subjects compared to the untrained subjects. V ˙ O 2 kinetics was unaffected by training status; the faster muscle deoxyhaemoglobin kinetics in the trained subjects thus indicates slower blood flow kinetics during recovery from exercise compared to the untrained subjects

Vers la détermination d'un profil d'humidité dans des matériaux biopolymères en utilisant une méthode de séparation de sources

Le but de ce travail est de déterminer de manière non destructive un profil d'humidité dans des matériaux biopolymères. Son originalité réside dans l'utilisation de deux capteurs pyroélectriques sans contact direct avec l'échantillon. Le capteur en face avant est transparent à la longueur d'onde utilisée. C'est le traitement du signal réalisé par une méthode de séparation de sources qui permet d'exploiter les possibilités de ce nouveau montage expérimental. La mise en oeuvre d'un tel dispositif n'a jamais été faite tant du point de vue expérimental que du point de vue traitement de l'information

Time Limit at vV02max and V02max Slow Component in Swimming: a pilot study of University Students

The aim oftms study was to measure in swimming-pool conditions, the time to exhaustion at the minimum velocity that elicits maximal oxygen consumption (TLim-vV02max) and to verify the existence of an oxygen uptake slow component (02SC) in freestyle swimming. Ten university students performed a continuous incremental protocol for vV02max assessment. Forty-eight hours later, they swam to exhaustion at vV02max to assess TLim-vV02max and 02SC. V02 was directly measured and swimming velocity was controlled by a visual pacer. Blood lactate concentrations ([La-]) and heart rate (HR) values were also measured. Mean V02max for the incremental test was 54.2±8.2 m1.kg'l.min'l, and the correspondent vV02max was 1.19±O.08 m.S,l The mean duration ofthe TLim-vV02max test was 325±76.5 s. 02SC appeared in the allout swim at VV02max (279.0±195.2 ml.min'l) and it was found to significant1y correlate with the TLim-vV02max (r = .74, p< .05). These results demonstrated that 02SC is observed also in swimming-pool conditions and that TLim-vV02max values are in accordance with typical formulations of aerobic power training sets for swimmers.We wish to thank Prof Dr. José Soares, from the Laboratory of Exercise Physiology of our faculty, for his significant contribution.info:eu-repo/semantics/publishedVersio

Improvement of adiponectin in relation to physical performance and body composition in young obese males subjected to twenty-four weeks of training programs

Obesity and related metabolic diseases represent a worldwide health problem. The main factor predisposing to obesity is an unhealthy lifestyle including the lack of physical activity. A pivotal role in the etio-pathogenesis of obesity is carried out by adipose tissue, an endocrine organ secreting several adipokines involved in numerous metabolic and inflammatory processes. Among these, of particular importance is adiponectin, an adipokine involved in the regulation of insulin sensibility and in anti-inflammatory processes. The aim of the study was to determine the effects of 24 weeks of two different training programs polarized (POL) and threshold training (THR) on body composition, physical capacities and adiponectin expression. Thirteen male obese subjects (BMI: 32.0 ± 3.0 kg m-2) followed 24 weeks of two different training programs, POL and THR, consisting of walking or running (or a combination of the two methods) in their normal living conditions. Before (T0) and after the end of the program (T1), the assessment of body composition was assessed by bioelectrical impedance and the concentration of salivary and serum adiponectin was analyzed by enzyme-linked immunosorbent assay and western blotting. Although the results obtained did not show significant differences between the two training programs, body mass and body mass index decreased by a mean of −4.46 ± 2.90 kg and 1.43 ± 0.92 kg m−2 (P < 0.05). Fat mass decreased by −4.47 ± 2.78 kg (P < 0.05). V′O2max increased by a mean of 0.20 ± 0.26 L min−1 (P < 0.05) Also, we observed an increase in saliva and in serum of adiponectin concentrations at T1 compared to T0 by 4.72 ± 3.52 μg mL−1 and 5.22 ± 4.74 ng mL−1 (P < 0.05) respectively. Finally, we found significant correlations between Δ serum adiponectin and Δ Hip (R = −0.686, P = 0.001) and between Δ salivary adiponectin and ΔWaist (R = −0.678, P = 0.011). Our results suggest that a 24 weeks training program, independently from intensity and volume, induces an amelioration of body composition and fitness performance. These improvements are associated with an increase in total and HMW adiponectin expression in both saliva and in serum

Coordination in climbing: effect of skill, practice and constraints manipulation

BACKGROUND: Climbing is a physical activity and sport involving many subdisciplines. Minimization of prolonged pauses, use of a relatively simple path through a route and smooth transitions between movements broadly define skilled coordination in climbing. OBJECTIVES: To provide an overview of the constraints on skilled coordination in climbing and to explore future directions in this emerging field. METHODS: A systematic literature review was conducted in 2014 and retrieved studies reporting perceptual and movement data during climbing tasks. To be eligible for the qualitative synthesis, studies were required to report perceptual or movement data during climbing tasks graded for difficulty. RESULTS: Qualitative synthesis of 42 studies was carried out, showing that skilled coordination in climbing is underpinned by superior perception of climbing opportunities; optimization of spatial-temporal features pertaining to body-to-wall coordination, the climb trajectory and hand-to-hold surface contact; and minimization of exploratory behaviour. Improvements in skilled coordination due to practice are related to task novelty and the difficulty of the climbing route relative to the individual's ability level. CONCLUSION: Perceptual and motor adaptations that improve skilled coordination are highly significant for improving the climbing ability level. Elite climbers exhibit advantages in detection and use of climbing opportunities when visually inspecting a route from the ground and when physically moving though a route. However, the need to provide clear guidelines on how to improve climbing skill arises from uncertainties regarding the impacts of different practice interventions on learning and transfer

How Do Humans Control Physiological Strain during Strenuous Endurance Exercise?

Background: Methodology/principal Findings: Conclusions/significance: Distance running performance is a viable model of human locomotion.To evaluate the physiologic strain during competitions ranging from 5-100 km, we evaluated heart rate (HR) records of competitive runners (n = 211). We found evidence that: 1) physiologic strain (% of maximum HR (%HRmax)) increased in proportional manner relative to distance completed, and was regulated by variations in running pace; 2) the %HRmax achieved decreased with relative distance; 3) slower runners had similar %HRmax response within a racing distance compared to faster runners, and despite differences in pace, the profile of %HRmax during a race was very similar in runners of differing ability; and 4) in cases where there was a discontinuity in the running performance, there was evidence that physiologic effort was maintained for some time even after the pace had decreased.The overall results suggest that athletes are actively regulating their relative physiologic strain during competition, although there is evidence of poor regulation in the case of competitive failures.2.308 SJR (2008) Q1, 60/1774 Medicine (miscellaneous), 19/144 Biochemistry, genetics and molecular biology (miscellaneous), 15/175 Agricultural and biological sciences (miscellaneous)UE