Exercise does not necessarily influence the phase of the circadian rhythm in temperature in healthy humans

Seventeen healthy adults exercised for 30 min (70% V O 2max ), at different times of the day and night throughout a 24 h period. The effect on the phase of core temperature rhythm was assessed by comparing the rhythms on the day immediately before and immediately after the day of exercise with the participants living normally on these 2 days. Assessments were made upon data that had been corrected for the thermogenic effects of sleep and activity. When exercise was performed in the period between 4 h before and 1 h after the temperature minimum, there was a phase delay of 1.03 - 0.78 h (mean - s ; n = 6); when performed between 3 and 8 h after the temperature minimum, there was a phase advance of 1.07 - 1.23 h ( n = 9). Both means were significantly different from zero (Student's one-sample t -tests: P ? 0.05). Performed at other times, exercise had no significant effect on the phase of the temperature rhythm. The phase changes were not significantly different from those previously observed by us in sedentary individuals exposed to domestic lighting. We conclude that the amount of physical activity has very little effect on the body clock.     

The effect of biofeedback training on affective regulation and simulated car-racing performance: A multiple case study analysis

Abstract

In this study, we wished to investigate the factors that determine the direction of the spin axis of a pitched baseball. Nineteen male baseball pitchers were recruited to pitch fastballs. The pitching motion was recorded with a three-dimensional motion analysis system (1000 Hz), and the orientations of the hand segment in a global coordinate system were calculated using Euler rotation angles. Reflective markers were attached to the ball, and the direction of the spin axis was calculated on the basis of their positional changes. The spin axis directions were significantly correlated with the orientations of the hand just before ball release. The ball is released from the fingertip and rotates on a plane that is formed by the palm and fingers; the spin axis of the ball is parallel to this plane. The lift force of the pitched baseball is largest when the angular and translational velocity vectors are mutually perpendicular. Furthermore, to increase the lift forces for the fastballs, the palm must face home plate.     

The effects of eccentric phase duration on concentric outcomes in the back squat and bench press in well-trained males

ABSTRACT

The velocity and magnitude in which the eccentric phase of an exercise is completed directly affects performance during the concentric phase. Therefore, the purpose of this research was to investigate the effects of eccentric phase duration on concentric outcomes at 60% and 80% of one-repetition maximum (1RM) in the squat and bench press. Sixteen college-aged, resistance-trained males completed 1RM testing, established normative eccentric durations, and performed fast (0.75 times normative) and slow (2.0 times normative) metronome-controlled eccentric duration repetitions. Outcome measures assessed during the concentric phase were: average concentric velocity (ACV), peak concentric velocity (PCV), rating of perceived exertion (RPE), range of motion (ROM), and barbell path. Eccentric duration was significantly and inversely correlated with ACV at 60% (r = ?0.408, p = 0.004) and 80% (r = ?0.477, p = 0.001) of 1RM squat. At 60% of 1RM squat, both fast and slow eccentric conditions produced greater (p < 0.001) PCV than normative duration with fast also producing greater PCV than slow (p = 0.044). Eccentric duration had no impact on RPE, ROM, or barbell path. Our results report for the first time that resistance-trained males performing a deliberately faster eccentric phase may enhance their own squat and bench press performance.     

Do habitual foot-strike patterns in running influence functional Achilles tendon properties during gait?

ABSTRACT

The capacity of foot-strike running patterns to influence the functional properties of the Achilles tendon is controversial. This study used transmission-mode ultrasound to investigate the influence of habitual running foot-strike pattern on Achilles tendon properties during barefoot walking and running. Fifteen runners with rearfoot (RFS) and 10 with a forefoot (FFS) foot-strike running pattern had ultrasound transmission velocity measured in the right Achilles tendon during barefoot walking (≈1.1 ms^?1) and running (≈2.0 ms^?1). Temporospatial gait parameters, ankle kinematics and vertical ground reaction force were simultaneously recorded. Statistical comparisons between foot-strike patterns were made using repeated measure ANOVAs. FFS was characterised by a significantly shorter stance duration (?4%), greater ankle dorsiflexion (+2°), and higher peak vertical ground reaction force (+20% bodyweight) than RFS running (P < .05). Both groups adopted a RFS pattern during walking, with only the relative timing of peak dorsiflexion (3%), ground reaction force (1–2%) and peak vertical force loading rates (22–23%) differing between groups (P < .05). Peak ultrasound transmission velocity in the Achilles tendon was significantly higher in FFS during walking (≈100 ms^?1) and running (≈130 ms^?1) than RFS (P < .05). Functional Achilles tendon properties differ with habitual footfall patterns in recreational runners.     

Precision of Knowledge of Results: Consideration of the Accuracy Requirements Imposed by the Task

Abstract

To investigate whether spatial assimilation effects are due to premovement control processes or postinitiation feedback processes, surface EMG recordings were made from two agonists and one antagonist during both single and dual movements involving the upper limb(s). In the single condition, subjects (N=7) made 25 Short (20°) and 25 Long (60°) reversal movements using levers in the sagittal plane, in 195 ms to reversal. In the dual condition, both Short and Long movements were performed simultaneously for 75 trials, the last 25 of which were without knowledge of results. Subjects overshot the Short target in the dual condition, showing spatial assimilation effects. Overshooting was associated with increased peak EMG in the initial (premovement) agonist burst, supporting the notion that spatial assimilation effects are modulated via premovement control processes.     

The Effects of Static Stretching and Warm-Up on Prevention of Delayed-Onset Muscle Soreness

Abstract

It has been suggested in the lay literature that static stretching and/or warm-up will prevent the occurrence of Delayed-Onset Muscle Soreness (DOMS). The primary purpose of this study was to determine the effects of static stretching and!or warm-up on the level of pain associated with DOMS. Sixty-two healthy male and female volunteers were randomly assigned to four groups: (a) subjects who statically stretched the quadriceps muscle group before a step, (b) subjects who only performed a stepping warm-up, (c) subjects who both stretched and performed a stepping warm-up prior to a step test, and (d) subjects who only performed a step test. The step test (Asmussen, 1956) required subjects to do concentric work with their right leg and eccentric work with their left leg to voluntary exhaustion. Subjects rated their muscle soreness on a ratio scale from zero to six at 24-hour intervals for 5 days following the step test. A 4×2×2 ANOVA with repeated measures on legs and Duncan's New Multiple Range post-hoc test found no difference in peak muscle soreness among the groups doing the step test or for gender (p > .05). There was the expected significant difference in peak muscle soreness between eccentrically and concentrically worked legs, with the eccentrically worked leg experiencing greater muscle soreness. We concluded that static stretching and!or warm-up does not prevent DOMS resulting from exhaustive exercise.     

Relationship of Reaction Time to the Speed of a Softball

Abstract

Reaction time of the batter in Softball is important because of short pitching distance and the speed of the pitcher. Nine pitchers were tested for speed and had an average velocity of 59.95 mph and a mean reaction time of .215 sec. was found for 258 students tested. With these averages, the ball would be 29.33 ft. from home plate before 116 of these students began their swing and in 41 cases the ball would be less than 20 ft from the plate. Pitchers with greater velocity would decrease the success of the batter if the reaction time remains the same.     

Development and validation of the Decision-Specific Reinvestment Scale

Abstract

Items from the Reinvestment Scale were modified to create a decision-specific version of the scale. Principal components analysis of responses from 165 participants revealed one-, two-, three-, and four-factor solutions for the Decision-Specific Reinvestment Scale. Confirmatory factor analysis of responses from a second sample of 111 participants revealed that a 13-item two-factor solution showed the best fit. The first factor comprised six items referring to conscious monitoring of the process involved in making a decision, and was termed decision reinvestment. The second factor, decision rumination, comprised seven items related to focus on negative evaluations of previous poor decisions. In an initial assessment of predictive validity, Decision-Specific Reinvestment Scale scores of 59 skilled team sport players were found to be highly correlated with coaches' ratings of players' tendency to choke under pressure (r = 0.74), with high Decision-Specific Reinvestment Scale scores indicating greater susceptibility to poor decision-making under pressure. It was concluded that the Decision-Specific Reinvestment Scale highlights a performer's predisposition to engage in behaviours detrimental to performance under pressure, namely decision reinvestment and decision rumination.