The purpose of this investigation was to quantify the differences between one- and two-foot vertical jumping performances. Fourteen subjects performed both jump styles with a four-step, self-paced approach. While overall jump and reach heights were similar between one-foot and two-foot jumps, the strategies employed to achieve these results were notably different. One-foot jumps benefited from an increased takeoff height that was largely attributable to the elevation of the free swinging leg. Further, it was suggested that the actions of this limb may have helped slow the rate of extension of the support leg during the propulsion phase. Greater flight heights were achieved during two-foot jumps, as expected, but the magnitude of this difference was only about 9 cm. It was suggested that factors associated with the development of muscular tension, vertical velocity at touchdown, and horizontal approach speed may have all contributed to the unexpectedly small differences in flight height between one-foot and two-foot jumping performances.
Peter F. Vint and Richard N. Hinrichs
Peter F. Vint and Richard N. Hinrichs
Isometric knee extension force and average integrated EMG of the vastus lateralis muscle were obtained from 27 healthy subjects using a maximum effort, ramp and hold protocol. In each of the 125 total trials mat were included in the analysis, a 2-s plateau region was extracted and divided into two adjacent 1000-ms bins. Variability and reliability of bin-to-bin measurements of force and EMG were then evaluated across 14 different integration intervals ranging from 10 to 1000 ms. Statistical analyses of bin-to-bin variability measures demonstrated that integration intervals of 250 ms and longer significantly reduced variability and improved reliability of average integrated EMG values during maximum effort isometric exertions. Bin-to-bin EMG reliability increased from .728 at 10 ms to .991 at 1000 ms. Force parameters appeared less sensitive to changes in length of the integration interval. It was suggested that longer intervals might also improve the validity of the EMG-force relationship during maximum effort isometric exertions by reducing problems associated with electromechanical delay.
Patrick Kennedy, Peter Brown, Somadeepti N. Chengalur and Richard C. Nelson
The performance of male and female swimmers (N = 397) competing in the preliminary heats of the four 100-meter swimming events during the Seoul Olympic Games was videotaped and later analyzed to determine stroke rate (SR) and stroke length (SL). These data were combined with age, height, and final time (FT) values for statistical analyses which included the relationships among these variables, comparison of male and female performance, and assessment of differences in the four events. The results revealed the following ranges of correlations between SR and SL (rs from −0.65 to −0.90), SL and FT (rs from −0.32 to −0.80), height and SL (0.19 to 0.58), and age and FT (-0.16 to −.051). The factor of SL was identified as the dominant feature of successful swimming performance. The men were older and taller, had longer stroke lengths and higher stroke rates (two of four events), and swam faster than the women. The differences in final times across the four events (freestyle fastest, breaststroke slowest) were due to specific combinations of SR and SL, with neither parameter being consistently dominant.
Raul Arellano, Peter Brown, Jane Cappaert and Richard C. Nelson
The performances of 335 male and female swimmers competing in 50-, 100-, and 200-m freestyle events at the 1992 Barcelona Olympic Games were videotaped and analyzed to determine stroke length (SL), stroke rate (SR), starting time (ST), turning times (TI = turn in, TO = turn out), finishing (end) time (ET), and average velocity (AV); relationships were then determined among these variables in addition to height, weight, age, and final time (FT). Differences were subsequently assessed within and among the events, and comparisons were made between male and female performances. ST, TI, TO, ET, and SL were identified as principal components of successful swimming performance at each distance. Results revealed statistically significant correlations between factors for all events. The men were older and taller; possessed longer stroke lengths; and started, turned, and swam faster than the women. As the race distance increased from 50 to 200 m, ST, TI, TO, SL, and ET increased for both men and women, while age, SR, and AV decreased.
Richard N. Hinrichs, Peter R. Cavanagh and Keith R. Williams
Ten male recreational runners were filmed using three-dimensional cinematography while running on a treadmill at 3.8 m/s, 4.5 m/s, and 5.4 m/s. A 14-segment mathematical model was used to examine the influence of the arm swing on the three-dimensional motion of the body center of mass (CM), and on the vertical and horizontal propulsive impulses (“lift” and “drive”) on the body over the contact phase of the running cycle. The arms were found to reduce the horizontal excursions of the body CM both front to back and side to side, thus tending to make a runner's horizontal velocity more constant. The vertical range of motion of the body CM was increased by the action of the arms. The arms were found to make a small but important contribution to lift, roughly 5–10% of the total. This contribution increased with running speed. The arms were generally not found to contribute to drive, although considerable variation existed between subjects. Consistent with the CM results, the arms were found to reduce the changes in forward velocity of the runner rather than increasing them. It was concluded that there is no apparent advantage of the “classic” style of swinging the arms directly forward and backward over the style that most distance runners adopt of letting the arms cross over slightly in front. The crossover, in fact, helps reduce side-to-side excursions of the body CM mentioned above, hence promoting a more constant horizontal velocity.
Richard Cooke, Helena Trebaczyk, Peter Harris and Alison J. Wright
The present study tests whether a self-affirmation intervention (i.e., requiring an individual to focus on a valued aspect of their self-concept, such as honesty) can increase physical activity and change theory of planned behavior (TPB) variables linked to physical activity. Eighty young people completed a longitudinal intervention study. Baseline physical activity was assessed using the Godin Leisure-Time Physical Activity Questionnaire (LTPAQ). Next, participants were randomly allocated to either a self-affirmation or a nonaffirmation condition. Participants then read information about physical activity and health, and completed measures of TPB variables. One week later, participants again completed LTPAQ and TPB items. At follow up, self-affirmed participants reported significantly more physical activity, more positive attitudes toward physical activity, and higher intentions to be physically active compared with nonaffirmed participants. Neither attitudes nor intentions mediated the effects of self-affirmation on physical activity. Self-affirmation can increase levels of physical activity and TPB variables. Self-affirmation interventions have the potential to become relatively simple methods for increasing physical activity levels.
Wayne W. Campbell, Lyndon J.O. Joseph, Richard E. Ostlund Jr., Richard A. Anderson, Peter A. Farrell and William J. Evans
This study assessed the effects of resistive training (RT) with or without chromium picolinate (Cr-pic) supplementation on the 24-h urinary excretions of myo-inositol, D-chiro-inositol, and pinitol, as well as clinical indices of kidney and liver functions. Thirty-two nondiabetic subjects, age 62 ± 4 y, performed RT twice weekly for 12 wk and consumed either 924 μg Cr/d as Cr-pic (n = 17) or a placebo (n = 15). Whole-body strength increased in all subjects by 20% and urinary chromium excretion increased 47-fold in the Cr-pic group. Urinary myo-inositol, D-chiro-inositol, and pinitol were not changed with RT or influenced by Cr-pic. Serum indices of kidney and liver functions were within clinically normal ranges at baseline and the end of the study. These results suggest that RT did not influence the urinary excretions of inositols. High dose Cr-pic did not influence the urinary excretion of inositols and the selected indices of kidney and liver functions in conjunction with RT
Kevin J. Cole, Peter W. Grandjean, Richard J. Sobszak and Joel B. Mitchell
This study examined the effects of serial feedings of different carbohydrate (CHO) solutions on plasma volume, gastric emptying (GE), and performance during prolonged cycling exercise. Solutions containing 6 g% glucose-sucrose (CHO-6GS), 83 g% high fructose com syrup (CHO-8HF), 6.3 g% high fructose corn syrup + 2 g% glucose polymer (CHO-8HP), and a water placebo (WP) were compared. Ten trained male cyclists performed four cycling trials consisting of 105 min at 70% VQ2max followed by a 15-min all-out, self-paced performance ride. Every 15 min the men consumed one of the four test solutions. Blood samples were taken before, during, and after exercise to determine blood glucose and plasma volume changes. There were no significant differences in performance, GE, or plasma volume changes between trials. Blood glucose was significantly elevated at the 105-min timepoint in all CHO trials when compared to WP. The CHO-8HF and CHO-8HP drinks resulted in a significantly higher delivery of CHO to the intestine. Higher rates of CHO oxidation during the steady-state ride were observed only with the CHO-6GS drink.
Florian Herbolsheimer, Stephanie Mosler, Richard Peter and the ActiFE Ulm Study Group
Social relationships have a powerful effect on physical activity. However, it is unclear how physical activity patterns are associated with perceived social isolation. A cohort study was performed on 1,162 community-dwelling older adults. In cross-sectional analyses, social isolation was screened using the Lubben Social Network Scale (LSNS-6). Physical activity was measured by an accelerometer (activPAL). Participants kept a contemporary physical activity diary to report outdoor physical activity timeframes. Low levels of physical activity were associated with perceived social isolation. Low indoor physical activity was associated with being socially isolated from family and low outdoor physical activity was associated with being socially isolated from friends and neighbors (−4.5 minutes; p = .012). These findings suggest the need for a more nuanced assessment of nonkin networks and a differentiated analysis of the locations in which physical activity is done in order to understand how social isolation affects everyday physical activity.
Scott P. McLean, Michael J. Holthe, Peter F. Vint, Keith D. Beckett and Richard N. Hinrichs
Ten male collegiate swimmers (age = 20.2 ± 1.4 years, height = 184.6 ± 5.8 cm, mass = 82.9 ± 9.3 kg) performed 3 swimming relay step starts, which incorporated a one or two-step approach, and a no-step relay start. Time to 10 m was not significantly shorter between step and no-step starts. A double-step start increased horizontal takeoff velocity by 0.2 m/s. A single-step together start decreased vertical takeoff velocity by 0.2 m/s but increased takeoff height by 0.16 m. Subjects were more upright at takeoff by 4°, 2°, and 5° in the double-step, single-step apart, and single-step together starts, respectively, than in the no-step start. Entry angle was steeper by 2°, entry orientation was steeper by 3°, and entry vertical velocity was faster by 0.3 m/s in the single-step together start. Restricting step length by 50% had little effect on step starts with the exceptions that horizontal velocity was significantly reduced by 0.1 m/s in the double-step start and vertical takeoff velocity was increased by 0.2 m/s in the single-step together start. These data suggested that step starts offered some performance improvements over the no-step start, but these improvements were not widespread and, in the case of the double-step start, were dependent on the ability to take longer steps.