Influence of cold-water immersion on limb blood flow after resistance exercise*

This study determined the influence of cold (8°C) and cool (22°C) water immersion on lower limb and cutaneous blood flow following resistance exercise. Twelve males completed 4 sets of 10-repetition maximum squat exercise and were then immersed, semi-reclined, into 8°C or 22°C water for 10-min, or rested in a seated position (control) in a randomized order on different days. Rectal and thigh skin temperature, muscle temperature, thigh and calf skin blood flow and superficial femoral artery blood flow were measured before and after immersion. Indices of vascular conductance were calculated (flux and blood flow/mean arterial pressure). The colder water reduced thigh skin temperature and deep muscle temperature to the greatest extent (P?<?.001). Reductions in rectal temperature were similar (0.2–0.4°C) in all three trials (P?=?.69). Femoral artery conductance was similar after immersion in both cooling conditions, with both conditions significantly lower (55%) than the control post-immersion (P?<?.01). Similarly, there was greater thigh and calf cutaneous vasoconstriction (40–50%) after immersion in both cooling conditions, relative to the control (P?<?.01), with no difference between cooling conditions. These findings suggest that cold and cool water similarly reduce femoral artery and cutaneous blood flow responses but not muscle temperature following resistance exercise.     

The within-participant correlation between perception of effort and heart rate-based estimations of training load in elite soccer players

ABSTRACT

The measurement of relative physiological stress during training is important because this is the stimulus for the long-term adaptive response. Measurements of perceived exertion (RPE) have been reported to correlate with the heart rate during field-based training sessions. Nevertheless, there are few studies on how well RPE tracks with the heart rate over repeated training sessions in elite soccer players. Therefore, we aimed to quantify the within-participant correlations between variability in session-RPE (sRPE) and the heart rate in elite male soccer players, and to determine whether the playing position moderated these correlations. The field-based training of four central defenders, four wide defenders, six central midfielders, two wide midfielders and three attackers from an elite English Premier League squad were monitored over an entire in-season competitive period, giving a total of 1010 individual training sessions for study. Correlations between session-RPE and heart rates were quantified using a within-participant model. The correlation between changes in sRPE and heart rates was r = 0.75 (95% CI: 0.71–0.78). This correlation remained high across the various player positions (wide-defender, r = 0.81; central-defender, r = 0.74; wide midfielder, r = 0.70; central midfielder, r = 0.70; attacker, r = 0.84; P < 0.001). The correlation between changes in RPE and heart rates, measured during a season-long period of field-based training, is high in a sample of elite soccer players.     

Process gain and process loss: comparing interpersonal processes and performance of culturally diverse and non-diverse teams across time

Members of 82 student groups involved in a Team Learning instructional format were surveyed with the Group Style Instrument (GSI) to examine the possible dimensions of team oriented behaviors and individualistically oriented behaviors. Exploratory factor models and confirmatory factor models were compared to find the best factor structure fit. The GSI was found to have dimensions that were team and individualistically oriented. From a second sample data was collected across four months on the group process and group performance of culturally non-diverse and culturally diverse groups. Data were evaluated in two significant ways. First, the team orientation and individual orientation dimensions were used to define interpersonal processing. Second, the team process dimensions were used to define interpersonal processing. Second, the team process dimensions were examined further to evaluate their relation to group performance. Early on the diverse teams showed less team orientation and more individual orientation than non-diverse teams, but through frequent feedback on task and interpersonal processing, the diverse teams caught up by the third time period. By the end, diverse teams maintained high team orientation but also allowed a reasonable extent of individual orientation. The diverse teams were beginning to utilize diversity to their advantage. Team and Individualistic orientations showed significant relations to team performance across time. Suggestions are given for future research.     

The Value of Natural History Collections

The value of museum natural history collections is commonly poorly explained to, and therefore commonly misunderstood by, the general public. This is an increasingly dangerous situation at a time of tight fiscal constraints; if natural history collections are to survive, those charged with their care will have to do more to broadcast their value as both resources for research and public education. Research values include documenting biotas no longer available and present and past biogeographic distributions, housing type, voucher specimens, and (perhaps most importantly) serving as fertile places for scientific discovery and inspiration. Public values include serving as resources for identification of unknown specimens, hands-on education and the support of systematics, and (perhaps most importantly) as the depository for the final physical evidence for the history and diversity of life on Earth.     

Training load and schedule are important determinants of sleep behaviours in youth-soccer players

The current study examined how sleep may be influenced by the scheduling of training and match load within 10 youth-soccer players. Sleep was measured over a 14-day in-season period using a commercially available wireless sleep monitor. Each collected sleep variable; lights out, sleep latency, total sleep time wake after sleep onset and final awakening, was compared for the specific day within the training schedule (e.g. match day [MD], day after match [MD?+?1]) and to training/match load (high-speed distance (>5.5 m/s) [HSD] and rating of perceived exertion. The data were analysed using mixed models and effect sizes, to describe the magnitude of effects that training schedule and training load may have on sleep. A reduction of sleep duration was observed on the day after the match (MD?+?1) in relation to the training days preceding the match (MD-2: ?65 min, ES: 0.89?±?0.79; MD-1 ?61 min, ES: 0.82?±?0.64) and reduction on match day (+45 min; ES: 1.91?±?1.69). This may suggest youth-soccer players actively change their sleep scheduling behaviours in relation to the imposed soccer schedule. Increased high-speed running (for every 100 m) showed a small increase to total sleep time (+9 min; ES: 0.48?±?0.31). This may suggest that increases in training load may be associated with small increases in sleep quantity. Such observations may highlight that the type of day and the associated load within the training microcycle may have important consequences for sleep within youth-soccer players.     

Intensity and physiological strain of competitive ultra-endurance exercise in humans

The aim of this study was to determine the magnitude and pattern of intensity, and physiological strain, of competitive exercise performed across several days, as in adventure racing. Data were obtained from three teams of four athletes (7 males, 5 females; mean age 36 years, s = 11; cycling .VO(2 peak) 53.9 ml . kg(-1) . min(-1), s = 6.3) in an international race (2003 Southern Traverse; 96 - 116 h). Heart rates (HR) averaged 64% (95% confidence interval: +/- 4%) of heart rate range [%HRR = (HR - HR(min))/(HR(max) - HR(min)) x 100] during the first 12 h of racing, fell to 41% (+/-4%) by 24 h, and remained so thereafter. The level and pattern of heart rate were similar across teams, despite one leading and one trailing all other teams. Core temperature remained between 36.0 and 39.2 degrees C despite widely varying thermal stress. Venous samples, obtained before, during, and after the race, revealed increased neutrophil, monocyte and lymphocyte concentrations (P < 0.01), and increased plasma volume (25 +/- 10%; P < 0.01) with a stable sodium concentration. Standardized exercise tests, performed pre and post race, showed little change in the heart rate-work rate relationship (P = 0.53), but a higher perception of effort post race (P < 0.01). These results provide the first comprehensive report of physiological strain associated with adventure racing.     

Response deprivation and response satiation as determinants of instrumental performance: Some data and theory

Sixteen human subjects were presented with an instrumental task in which pressing a button to produce a visual stimulus was followed by an auditory stimulus. Half of the subjects were assigned to a condition under which pressing the button at the subject’s operant level produced less of the auditory stimulus than the subject would normally choose to receive. For the others, pressing the button at operant level produced more of the auditory stimulus than the subject would choose. Subjects in the former condition showed increases in instrumental performance; those in the latter showed decreases. The results indicated that the rewarding or punishing effects of an event depend upon the relation of the instrumental contingency to the subject’s unconstrained behavior.