Gender differences among sagittal plane knee kinematic and ground reaction force characteristics during a rapid sprint and cut maneuver

Women are more prone to anterior cruciate ligament (ACL) injury during cutting sports than men. The purpose of this study was to examine knee kinematic and ground reaction forces (GRF) differences between genders during cutting. Male and female athletes performed cutting trials while force platform and video data were recorded (180 Hz). Differences (p < . 05) were observed between groups for knee flexion at contact and GRF at maximum knee flexion. Women averaged 5.8 degrees less flexion at contact and 1.0 N. (kg x m x s(-1))(-1) greater GRF at maximum flexion. Knee range of motion and peak GRF variables were not significantly different, but women had greater values. Women exhibited technique characteristics believed to increase ACL injury risk, but men exhibiting similar characteristics were also observed and could also be at risk.     

Temporal aspects of the VO2 response at the power output associated with VO2peak in well trained cyclists--implications for interval training prescription

The power output achieved at peak oxygen consumption (VO2peak) and the time this power can be maintained (i.e., Tmax) have been used in prescribing high-intensity interval training. In this context, the present study examined temporal aspects of the VO2 response to exercise at the cycling power that output well trained cyclists achieve their VO2peak (i.e., Pmax). Following a progressive exercise test to determine VO2peak, 43 well trained male cyclists (M age = 25 years, SD = 6; M mass = 75 kg, SD = 7; M VO2peak = 64.8 ml x kg(-1) x min(-1), SD = 5.2) performed two Tmax tests 1 week apart. Values expressed for each participant are means and standard deviations of these two tests. Participants achieved a mean VO2peak during the Tmax test after 176 s (SD = 40; M = 74% of Tmax, SD = 12) and maintained it for 66 s (SD = 39; M = 26% of Tmax, SD = 12). Additionally, they obtained mean 95% of VO2peak after 147 s (SD = 31; M = 62% of Tmax, SD = 8) and maintained it for 95 s (SD = 38; M = 38% of Tmax, SD = 8). These results suggest that 60-70% of Tmax is an appropriate exercise duration for a population of well trained cyclists to attain VO2peak during exercise at Pmax. However, due to intraparticipant variability in the temporal aspects of the VO2 response to exercise at Pmax, future research is needed to examine whether individual high-intensity interval training programs for well trained endurance athletes might best be prescribed according to an athlete's individual VO2 response to exercise at Pmax.     

Multitrait-multimethod investigation of a novel body image measurement technique

A multitrait-multimethod (MTMM) matrix was used to evaluate validity evidence for a digital image manipulation (DIM) body image measurement technique in young women. One hundred one young women completed the DIM procedure and the Thompson and Gray (1995) Contour Drawing Rating Scale to measure self-ideal discrepancy and size perception accuracy components of body image. Seven-day test-retest reliability was acceptable (R = .81-.95). Convergent validity for self-ideal discrepancy was higher (r = .74) than the corresponding heterotrait, monomethod coefficients (r = .46, r = .23) and heterotrait-heteromethod coefficients (r = .18, r = .12). However, the convergent validity coefficient for size perception accuracy was r = .12. The pattern of correlations in the MTMM matrix met the criteria of Campbell and Fiske (1959) for validity of these procedures to measure self-ideal discrepancy but not size perception accuracy. The DIM procedure addresses some of the criticisms associated with figure-rating scales, such as unrepresentativeness of the figures, scale coarseness, and restriction of range in responses. DIM, therefore, represents a realistic, valid alternative to figure-rating scales for measuring self-ideal discrepancy.     

Urea production during prolonged swimming

Male interscholastic swimmers (n = 8) completed a 4572 m training swim in 62 ±1.1 min (x ± s.e.) with terminal heart rate and blood lactate of 152 ± 6 beats min^‐1 and 6.9±0.89 mM, respectively. Sweat rate (0.48±0.0951. h^‐1) was lower than similar intensity cycling (1.5±0.13 1. h^‐1) or running (1.1 ± 0.14 l.h^‐1). Post‐swim serum urea N (11.6±0.71 mM) was elevated (P<0.05) vs pre‐swim (4.6±0.39 mM). Post‐swim urine volume (860±75 ml 24 h^‐1) was reduced (P<0.07) and resulted in an elevated (P<0.05), but delayed (24–84 h), post‐exercise urea N excretion. Although the reduced urine and sweat production during the swim undoubtedly contributed to the elevated serum urea, there must be another explanation because together they could only account for 38% of the observed increase. On the basis of the magnitude of serum urea increase, it appears that the swim caused an increase in urea production (amino acid oxidation). The failure to observe larger increases in urinary urea during recovery indicates that either urea excretion following exercise continues for prolonged periods of time (>48 h) or another significant mode of nitrogen excretion exists.     

Optimized versus corrected peak power during friction-braked cycle ergometry in males and females

Abstract

The aim of this study was to compare optimization and correction procedures for the determination of peak power output during friction-loaded cycle ergometry. Ten male and 10 female sports students each performed five 10-s sprints from a stationary start on a Monark 864 basket-loaded ergometer. Resistive loads of 5.0, 6.5, 8.0, 9.5, and 11.0% body weight were administered in a counterbalanced order, with a recovery period of 10 min between sprints. Peak power was greater and occurred earlier, with less work having been done before the attainment of peak power, when the data were corrected to account for the inertial and frictional characteristics of the ergometer. Corrected peak power was independent of resistive load (P > 0.05), whereas uncorrected peak power varied as a quadratic function of load (P < 0.001). For males and females, optimized peak power (971 ± 122 and 668 ± 37 W) was lower (P < 0.01) than either the highest (1074 ± 111 and 754 ± 56 W respectively) or the mean (1007 ± 125 and 701 ± 45 W respectively) of the five values for corrected peak power. Optimized and mean corrected peak power were highly correlated both in males (r = 0.97, P < 0.001) and females (r = 0.96, P < 0.001). The difference between optimized and mean corrected peak power was 37 ± 30 W in males and 33 ± 14 W in females, of which approximately 15 W was due to the correction for frictional losses. We conclude that corrected peak power is independent of resistive load in males and females.     

Test–retest reliability of a battery of field-based health-related fitness measures for adolescents

Abstract

The main aim of this study was to determine the test–retest reliability of existing tests of health-related fitness. Participants (mean age 14.8 years, s = 0.4) were 42 boys and 26 girls who completed the study assessments on two occasions separated by one week. The following tests were conducted: bioelectrical impedance analysis (BIA) to calculate percent body fat, leg dynamometer, 90° push-up, 7-stage sit-up, and wall squat tests. Intra-class correlation (ICC), paired samples t-tests, and typical error expressed as a coefficient of variation were calculated. The mean percent body fat intra-class correlation coefficient was similar for boys (ICC = 0.95) and girls (ICC = 0.93), but the mean coefficient of variation was considerably higher for boys than girls (22.2% vs. 12.2%). The boys' coefficients of variation for the tests of muscular fitness ranged from 9.0% for the leg dynamometer test to 26.5% for the timed wall squat test. The girls' coefficients of variation ranged from 17.1% for the sit-up test to 21.4% for the push-up test. Although the BIA machine produced reliable estimates of percent body fat, the tests of muscular fitness resulted in high systematic error, suggesting that these measures may require an extensive familiarization phase before the results can be considered reliable.     

Velocity and acceleration before contact in the tackle during rugby union matches

Abstract

The velocity and acceleration at which the ball-carrier or tackler enters the tackle may contribute to winning the contest and prevailing injury free. Velocity and acceleration have been quantified in controlled settings, whereas in match-play it has been subjectively described. The purpose of this study was to determine the velocity and acceleration of the ball-carrier and tackler before contact during match-play in three competitions (Super 14, Varsity Cup, and Under-19 Currie Cup). Using a two-dimensional scaled version of the field, the velocity and acceleration of the ball-carrier and tackler were measured at every 0.1 s to contact for 0.5 s. For front-on tackles, a significant difference (P < 0.05) between the ball-carrier (4.6 ± 1 m · s^–1) and tackler (7.1 ± 3.5 m · s^–1) was found at the 0.5 s time to contact interval in the Varsity Cup. For side-on tackles, differences between the two opposing players were found at 0.5 s (ball-carrier: 4.6 ± 1.7 m · s^–1; tackler: 3.1 ± 1.2 m · s^–1) and 0.4 s (ball-carrier: 6.3 ± 2.3 m · s^–1; tackler: 3.7 ± 1.6 m · s^–1) at Under-19 level. After 0.4 s, no significant differences (P > 0.05) were evident. Also, the ball-carrier's velocity over the 0.5 s was relatively stable compared with that of the tackler. Results suggest that tacklers adjust their velocity to reach a suitable relative velocity before making contact with the ball-carrier.     

The 1936 Olympic Games in Berlin: The Response of America's Black Press

Abstract

Eighty-seven female masters swimmers ranging in age from 20 to 69 were selected for a detailed study of their body composition and physiological responses at rest and during exercise. These women were then placed into two subsets, a highly trained group and a not highly trained group, on the basis of the frequency, duration, and intensity of swimming workouts. Significant differences were detected when comparing the highly trained and not highly trained subjects on measures of weight, body density, percent fat and lean body weight (p<.05). Significant differences which favored the highly trained group were also seen when comparing these same two groups for [Vdot]_E max, [Vdot]O₂ max (1/min), [Vdot]O₂ max (ml·kg^–1·min^–1), [Vdot]O₂ max (ml·kg·LBW^–1·min^–1), O₂ pulse (ml·kg^–1·beat^–1), and O₂ pulse (ml·kg·LBW^–1). Both the highly trained and not highly trained swimmers were considerably lower in percent fat than previously reported data for normal untrained women of similar ages. In both groups, however, percent fat across age levels within each training group showed significant increases at approximately 40 years of age (p<.05). In the highly trained swimmers, [Vdot]O₂ max (ml·kg^–1·min^–1) decreased at a mean rate of about 7% per decade, while in the not highly trained swimmers the decline was approximately 8% per decade. It appears that the rate of decline in [Vdot]O₂ max in women with aging may be independent of training status.     

Prolonged static stretching does not influence running economy despite changes in neuromuscular function

The aim of this study was to examine the acute effects of prolonged static stretching (SS) on running economy. Ten male runners (VO2(peak) 60.1 +/- 7.3 ml x kg(-1) x min(-1)) performed 10 min of treadmill running at 70% VO2(peak) before and after SS and no stretching interventions. For the stretching intervention, each leg was stretched unilaterally for 40 s with each of eight different exercises and this was repeated three times. Respiratory gas exchange was measured throughout the running exercise with an automated gas analysis system. On a separate day, participants were tested for sit and reach range of motion, isometric strength and countermovement jump height before and after SS. The oxygen uptake, minute ventilation, energy expenditure, respiratory exchange ratio and heart rate responses to running were unaffected by the stretching intervention. This was despite a significant effect of SS on neuromuscular function (sit and reach range of motion, +2.7 +/- 0.6 cm; isometric strength, -5.6% +/- 3.4%; countermovement jump height -5.5% +/- 3.4%; all P < 0.05). The results suggest that prolonged SS does not influence running economy despite changes in neuromuscular function.     

Extraordinary Animals and Expository Writing: Zoo in the Classroom

A zoo outreach program led to placing animals in classrooms where those animals became foci for numerous learning activities such as writing, observing, and care. Systematic debriefings suggested uniqueness to learning outcomes connected to zoo animals. Subsequent analysis of student writing indicated that students responded to situational interest by recording more observations, made use of more science facts, and used more science vocabulary when writing about unique animals (albino hedgehog, legless lizard) than ‘ordinary’ animals (rabbit, dove). The results are interpreted in terms of motivation, creating situational interest, and the familiarity of the schema available to the students. Policy implications are discussed.