Exercise-Derived Microvesicles: A Review of the Literature

Initially suggested as simple cell debris, cell-derived microvesicles (MVs) have now gained acceptance as recognized players in cellular communication and physiology. Shed by most, and perhaps all, human cells, these tiny lipid-membrane vesicles carry bioactive agents, such as proteins, lipids and microRNA from their cell source, and are produced under orchestrated events in response to a myriad of stimuli. Physical exercise introduces systemic physiological challenges capable of acutely disrupting cell homeostasis and stimulating the release of MVs into the circulation. The novel and promising field of exercise-derived MVs is expanding quickly, and the following work provides a review of the influence of exercise on circulating MVs, considering both acute and chronic aspects of exercise and training. Potential effects of the MV response to exercise are highlighted and future directions suggested as exercise and sports sciences extend the realm of extracellular vesicles

Predicting Temporal Gait Kinematics: Anthropometric Characteristics and Global Running Pattern Matter

Equations predicting stride frequency (SF) and duty factor (DF) solely based on running speed have been proposed. However, for a given speed, kinematics vary depending on the global running pattern (GRP), i.e., the overall individual movement while running, which depends on the vertical oscillation of the head, antero-posterior motion of the elbows, vertical pelvis position at ground contact, antero-posterior foot position at ground contact, and strike pattern. Hence, we first verified the validity of the aforementioned equations while accounting for GRP. Kinematics during three 50-m runs on a track (n = 20) were used with curve fitting and linear mixed effects models. The percentage of explained variance was increased by ≥133% for DF when taking into account GRP. GRP was negatively related to DF (p = 0.004) but not to SF (p = 0.08), invalidating DF equation. Second, we assessed which parameters among anthropometric characteristics, sex, training volume, and GRP could relate to SF and DF in addition to speed, using kinematic data during five 30-s runs on a treadmill (n = 54). SF and DF linearly increased and quadratically decreased with speed (p < 0.001), respectively. However, on an individual level, SF was best described using a second-order polynomial equation. SF and DF showed a non-negligible percentage of variance explained by random effects (≥28%). Age and height were positively and negatively related to SF (p ≤ 0.05), respectively, while GRP was negatively related to DF (p < 0.001), making them key parameters to estimate SF and DF, respectively, in addition to speed

The match-play activity cycles in elite U17, U21 and senior hurling competitive games

Purpose The current study aimed to investigate the ball-in-play (BIP) and ball-out-of-play (BOP) differences between U17, U21 and senior hurling matches. Methods Video recordings of matches (n = 36) were coded and analysed for BIP and BOP. Time when the ball was continuously in-play was considered BIP, whereas any stoppages were considered BOP. Results The total and mean BIP cycle duration showed no difference between levels. The number of BIP cycles were higher in senior matches compared to U17 (ES = 1.80: large) and U21 (ES = 1.27: large). U17 matches had a lower frequency of BIP cycles between 16 and 30 s (ES = − 1.75: large) compared to senior. Total BOP duration was longer in senior (45:30 ± 4:13 min) matches compared to U17 (36:31 ± 2:30 min, ES = 2.59: very large) and U21 (36:48 ± 2:53 min, ES = 2.40: very large). Senior matches had a longer BOP duration and greater number of BOP cycles than U17 (ES = 0.17: trivial, ES = 2.20: very large, respectively) and U21 (ES = 0.17: trivial, ES = 0.99: moderate, respectively). U17 matches had a lower frequency of BOP cycles \u3e 60 s (ES = − 1.33: large) compared to senior. Conclusion Although there was a difference in the total match duration, U17 and U21 matches have similar BIP time as seniors, suggesting that U17 and U21 players should be conditioned to withstand the elite senior BIP duration. In training practice, high-intensity short-duration games are suggested for repeating the duration demands of competition

Anisotropic self-affine properties of experimental fracture surfaces

The scaling properties of post-mortem fracture surfaces of brittle (silica glass), ductile (aluminum alloy) and quasi-brittle (mortar and wood) materials have been investigated. These surfaces, studied far from the initiation, were shown to be self-affine. However, the Hurst exponent measured along the crack direction is found to be different from the one measured along the propagation direction. More generally, a complete description of the scaling properties of these surfaces call for the use of the 2D height-height correlation function that involves three exponents zeta = 0.75, beta = 0.6 and z = 1.25 independent of the material considered as well as of the crack growth velocity. These exponents are shown to correspond to the roughness, growth and dynamic exponents respectively, as introduced in interface growth models. They are conjectured to be universal.Comment: 12 page

Identification of maximal running intensities during elite hurling match-play

The current study aimed to describe the duration-specific running intensities of elite hurling players during competition with respect to position using a rolling average method. Global positioning systems (10-Hz Viper; STATSport, Viper, Newry, Northern Ireland) were used to collect data from 36 elite hurling players across 2 seasons. Players were categorized according to playing positions (full-backs, half-backs, midfielders, half-forwards, and full-forwards). A total of 230 full match samples were obtained from 22 competitive games for analysis. The velocity-time curve was analyzed using a rolling average method, in which the maximum relative total distance (TD; m·min), high-speed running distance (HSR; m·min), and sprint distance (SD; m·min) intensities were calculated across 10 different rolling time durations (1-10 minutes) within each game. There were large to very large (effect sizes [ES] = 0.66-4.33) differences between 1 minute rolling averages and all other durations for TD, HSR, and SD. However, pairwise comparisons between 6 and 10 minutes for TD, HSR, and SD were smaller and more variable (ES = 0.07, trivial to ES = 0.85, moderate). Half-backs, midfielders, and half-forwards achieved a higher maximal relative TD and HSR in all duration-specific fields when compared with full-backs and full-forwards. No positional difference was observed in 1- and 2-minute durations for SD. Because the rolling average duration increased the maximum TD, HSR and SD running intensities decreased across all positions. These data provide knowledge of the peak running intensities of elite hurling competition and can be used to design training activities to sufficiently prepare players for these worst-case scenarios

Associations between heart rate variability–derived indexes and training load: Repeated measures correlation approach contribution

Associations between heart rate variability–derived indexes and training load: repeated measures correlation approach contribution. J Strength Cond Res XX(X): 000–000, 2020—This study aimed to evaluate whether similar associations between indexes derived from heart rate variability (HRV) analyses and training load (TL) could be obtained by using the commonly used Pearson correlation technique and the repeated measures correlation (rmcorr). Fourteen well-trained swimmers (18.5 6 1.6 years) participated. The training period lasted 4 weeks with a gradual increase in TL. Daily external TL (exTL) and internal TL (inTL) were summed to obtain a weekly TL, and HRV analyses were performed every Saturday morning. During the 4-week period, exTL and inTL increased (p , 0.05) together with a decrease (p , 0.05) in heart rateand an increase (p , 0.05) of cardiac parasympathetic indexes. No significant correlation was found using Pearson correlation while significant associations were found using rmcorr; considering exTL, positive (mean R-R interval [MeanRR], root mean square of differences between successive RR interval [RMSSD], low frequency [LF], high frequency [HF], instantaneous beat-to-beat variability [SD1], continuous beat-to-beat variability [SD2], SD1/SD2; r from 0.59 to 0.46, p value from ,0.001 to 0.002) and negative (mean heart rate [meanHR]; r 5 20.55, p , 0.001) associations were found. Considering inTL, positive (MeanRR, RMSSD, LF, HF, HFnu, SD1, SD2, SD1/SD2; r from 0.56 to 0.34, p-value from ,0.001 to 0.025) and negative (meanHR, LFnu, LF/HF; r from 20.49 to 20.34, p value from 0.001 to 0.025) associations were found. The rmcorr statistical method was able to show associations between parasympathetic indexes and TL contrary to Pearson correlation analysis. Because rmcorr is specifically designed to investigate within-individual association for paired measures assessed on 2 or more occasions for multiple individuals, it should constitute a tool for future training monitoring researches based on a repeated-measures protocol

The Match-Play Sprint Performance of Elite Senior Hurlers during Competitive Games

The typical sprint profile in elite hurling has yet to be established. The purpose of this study was to investigate the sprinting demands of elite hurling competition and characterize the sprinting patterns of different playing positions. GPS (10-Hz, STATSports Viper) were used to collect data from 51 hurlers during 18 games. The total sprint (≥22 km·h-1) distance (TSD), the number of sprints (NOS) classified as length (\u3c20 m, ≥20 m) and relative speed thresholds (\u3c80%, 80–90%, \u3e90%), the between-sprint duration and the number of repeated-sprint bouts (≥2 sprints in ≤60 s) were analyzed. The NOS was 22.2 ± 6.8 accumulating 415 ± 140 m TSD. The NOS \u3c20 m, ≥20 m was 14.0 ± 4.7 and 8.1 ± 3.6 respectively. The NOS \u3c80%, 80–90% and \u3e90% was 10.6 ± 4.3, 8.2 ± 3.6, 3.4 ± 2.4 respectively. The between-sprint duration and the repeated-sprint bouts were 208 ± 86 s and 4.5 ± 2.6 respectively. TSD (ES = -0.20), NOS (ES = -0.34), NOS \u3c20 m (ES = -0.33), ≥20 m (ES = -0.24), 80–90% (ES = -0.35) \u3e90% (ES = -0.13) and repeated-sprint bouts (ES = -0.28) decreased between-halves. Full-backs performed a lower NOS \u3c80% than half-backs (ES = -0.66) and a shorter mean duration of sprints than half-backs (ES = -0.75), midfielders (ES = -1.00) and full-forwards (ES = -0.59). These findings provide a sprint profile of elite hurling match-play that coaches should consider to replicate the sprint demands of competition in training

Metabolic Power in Hurling with Respect to Position and Halves of Match-play

The current investigation compared the metabolic power and energetic characteristics in team sports with respect to positional lines and halves of match-play. Global positioning system (GPS) technology data were collected from 22 elite competitive hurling matches over a 3-season period. A total of 250 complete match-files were recorded with players split into positional groups of full-back; half-back; midfield; half-forward; full-forward. Raw GPS data were exported into a customized spreadsheet that provided estimations of metabolic power and speed variables across match-play events (average metabolic power [Pmet], high metabolic load distance [HMLD], total distance, relative distance, high-speed distance, maximal speed, accelerations, and deceleration). Pmet, HMLD, total, relative and high-speed distance were 8.9±1.6 W�kg-1, 1457±349 m, 7506±1364 m, 107±20 m�min-1 and 1169± 260 m respectively. Half-backs, midfielders and half-forwards outperformed full-backs (Effect Size [ES] = 1.03, 1.22 and 2.07 respectively), and full-forwards in Pmet (Effect Size [ES] = 1.70, 2.07 and 1.28 respectively), and HMLD (full-backs: ES = -1.23, -1.37 and -0.84 respectively, and full-forwards: ES = -1.77, -2.00 and -1.38 respectively). Half-backs (ES = -0.60), midfielders (ES = -0.81), and half-forwards (ES = -0.74) experienced a second-half temporal decrement in HMLD. The current investigation demonstrates that metabolic power may increase our understanding of the match-play demands placed on elite hurling players. Coaches may utilize these findings to construct training drills that replicate match-play demands

Stand up to excite the spine : neuromuscular, autonomic, and cardiometabolic responses during motor imagery in standing vs. sitting posture

Motor imagery (MI) for health and performance strategies has gained interest in recent decades. Nevertheless, there are still no studies that have comprehensively investigated the physiological responses during MI, and no one questions the influence of low-level contraction on these responses. Thus, the aim of the present study was to investigate the neuromuscular, autonomic nervous system (ANS), and cardiometabolic changes associated with an acute bout of MI practice in sitting and standing condition. Twelve young healthy males (26.3 % 4.4 years) participated in two experimental sessions (control vs. MI) consisting of two postural conditions (sitting vs. standing). ANS, hemodynamic and respiratory parameters, body sway parameters, and electromyography activity were continuously recorded, while neuromuscular parameters were recorded on the right triceps surae muscles before and after performing the postural conditions. While MI showed no effect on ANS, the standing posture increased the indices of sympathetic system activity and decreased those of the parasympathetic system (p < 0.05). Moreover, MI during standing induced greater spinal excitability compared to sitting posture (p < 0.05), which was accompanied with greater oxygen consumption, energy expenditure, ventilation, and lower cardiac output (p < 0.05). Asking individuals to perform MI of an isometric contraction while standing allows them to mentally focus on the motor command, not challenge balance, and produce specific cardiometabolic responses. Therefore, these results provide further evidence of posture and MI-related modulation of spinal excitability with additional autonomic and cardiometabolic responses in healthy young men