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Ernst A. Hansen and Gerald Smith

Cadence choice during cycling has been of considerable interest among cyclists, coaches, and researchers for nearly 100 years. The present review examines and summarizes the current knowledge of factors affecting the freely chosen cadence during submaximal cycling and of the influence of cadence choice on performance. In addition, suggestions for future research are given along with scientifically based, practical recommendations for those involved in cycling. Within the past 10 years, a number of papers have been published that have brought novel insight into the subject. For example, under the influence of spinal central pattern generators, a robust innate voluntary motor rhythm has been suggested as the primary basis for freely chosen cadence in cycling. This might clarify the cadence paradox in which the freely chosen cadence during low-to-moderate submaximal cycling is considerably higher and thereby less economical than the energetically optimal cadence. A number of factors, including age, power output, and road gradient, have been shown to affect the choice of cadence to some extent. During high-intensity cycling, close to the maximal aerobic power output, cyclists choose an energetically economical cadence that is also favorable for performance. In contrast, the choice of a relatively high cadence during cycling at low-to-moderate intensity is uneconomical and could compromise performance during prolonged cycling.

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Gerald A. Smith and Brian S. Heagy

A project involving 3-D analysis of skiing technique during the 1992 Olympic Winter Games (Albertville, France) was carried out. This part of the project focused on the open field skating technique of the male skiers of the 50-km race. Three synchronized, high-speed video cameras were used to record the motion of all racers as they passed a site on flat terrain. Analysis was limited to those using the open field technique and whose skating cycle fit within the boundaries of the field being analyzed (n = 17). Several kinematic variables were determined: cycle velocity, cycle length, and cycle rate. Several significant correlations (p < .05) were observed related to performance: cycle velocity was positively related to cycle length (r = .76) but not cycle rate; cycle velocity and cycle length were positively related to strong side knee extension (r = .48 and r = .51, respectively). Thus, faster skiers on flat terrain tended to ski with longer cycle lengths, which perhaps derived from more vigorous knee extension.

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Gerald A. Smith, Jon B. Fewster and Steven M. Braudt

Olympic skiers in the women's 30-km race were analyzed as they double poled on a moderate downhill slope. Movement patterns of 20 skiers were analyzed 10 from a top finishing group and 10 from slower finishers in the bottom third of the field. Skiers in the faster group not only were faster overall in the race but were faster as they double poled through the site (6.75 vs. 6.43 m/s). Cycle length was significantly correlated with cycle velocity (r = .81). Trunk flexion and shoulder extension during poling were similar between groups; however, considerable variability of shoulder positioning was noted for both groups of skiers. Distinct shoulder-elbow-pole positioning differences were noted among skiers. Disadvantageous positionin» of the shoulder at the beginning of poling was related to poorer pole inclination during elbow extension. While many skiers in both fast and slow groups double poled with good positioning, others would benefit from greater shoulder flexion to maximize double poling performance.

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Gerald A. Smith, Jill McNitt-Gray and Richard C. Nelson

Cross-country ski technique is undergoing rapid evolution. Alternate stride skating was the dominant technique during the 1985–86 racing season (double poling is synchronized with the “strong” side skate; no poling occurs with the “weak” side skate). High-speed films were made of elite male racers at the Holmenkollen World Cup races, Oslo, Norway (March 1986), skating up a 7° hill. Digitized data were filtered and processed to determine three-dimensional coordinates throughout a complete skating cycle. Ten skiers were analyzed, representing a range of performances. Over the 10-km race length, cycle rates for all skiers were similar; however, cycle lengths were significantly related to cycle velocity. The correlation between cycle velocity and length was r = 0.85. Ski angles were found to be asymmetrical. Weak-side ski angles were negatively related to cycle velocity; strong-side ski angles were similar for all skiers. Center of mass (CM) position throughout the cycle exhibited characteristic differences between faster and slower skiers. CM velocity vector direction was related to cycle velocity. Thus, faster skiers tended to maintain CM motion more nearly aligned with the forward direction.

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Eadric Bressel, Gerald Smith, Andrew Miller and Dennis Dolny

Context: Quantification of the magnitudes of fluid resistance provided by water jets (currents) and their effect on energy expenditure during aquatic-treadmill walking is lacking in the scientific literature. Objective: To quantify the effect of water-jet intensity on jet velocity, drag force, and oxygen uptake (VO2) during aquatic-treadmill walking. Design: Descriptive and repeated measures. Setting: Athletic training facility. Participants, Interventions, and Measures: Water-jet velocities were measured using an electromagnetic flow meter at 9 different jet intensities (0-80% maximum). Drag forces on 3 healthy subjects with a range of frontal areas (600, 880, and 1250 cm2) were measured at each jet intensity with a force transducer and line attached to the subject, who was suspended in water. Five healthy participants (age 37.2 ± 11.3 y, weight 611 ± 96 N) subsequently walked (~1.03 m/s or 2.3 miles/h) on an aquatic treadmill at the 9 different jet intensities while expired gases were collected to estimate VO2. Results: For the range of jet intensities, water-jet velocities and drag forces were 0-1.2 m/s and 0-47 N, respectively. VO2 increased nonlinearly, with values ranging from 11.4 ± 1.0 to 22.2 ± 3.8 mL × kg-1 × min-1 for 0-80% of jet maximum, respectively. Conclusions: This study presented methodology for quantifying water-jet flow velocities and drag forces in an aquatic-treadmill environment and examined how different jet intensities influenced VO2 during walking. Quantification of these variables provides a fundamental understanding of aquatic-jet use and its effect on VO2. In practice, these results indicate that VO2 may be substantially increased on an aquatic treadmill while maintaining a relatively slow walking speed.

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Patrick W. Kennedy Jr., David L. Wright and Gerald A. Smith

The precision of the kinematic values depends upon the methods of recording a subject’s motion. With the introduction of video recording techniques, questions have arisen concerning the accuracy of video compared with that of 16-mm film. Accordingly, the purpose of this study was to compare the accuracy of the two techniques for point reprediction using the Direct Linear Transformation method. Range poles, serving as boundaries of a cube with 20 known spatial coordinates, were filmed and videotaped. The 20 control points on the film and video recordings were digitized by three individuals. Nine sets of digitized points (three digitizers × three trials) for both film and video were compared with the actual three-dimensional coordinate values. Resultant mean errors were statistically significantly different (p<.05), 4.8 mm and 5.8 mm for film and video, respectively. However, from a practical standpoint the video error was only .29% of the calibrated field compared to .24% for film. Thus it is concluded that video techniques are comparable in accuracy to 16-mm filming methods.

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Gerald A. Smith, Richard C. Nelson, Adam Feldman and Jeffrey L. Rankinen

The alternate stride or V1 skate technique was the predominant skiing method used in the free technique races of the 1988 Calgary Games. High-speed films were recorded of two free technique races: the Men’s 50 K and the Ladies' 20 K. A moderate and a steep uphill were sites of the filming, and both temporal and kinematic analyses were made. Times for a complete skating cycle tended to decrease on the steep hill (cycle rate increased). Cycle temporal proportions shifted to longer poling and recovery phases while the skating phases shortened on the steeper terrain. Mean cycle velocities (CV), cycle lengths (CL), and cycle rates (CR) were determined. Differences in kinematic relationships were noted: Male skiers included both those who emphasized CL to maximize CV and those who emphasized CR; females were relatively more consistent in emphasis on CR. In either case, center of mass (CM) motions were related to CR and CL. Increased lateral motion of CM tended to increase CL while decreasing CR. Ski edging angles were negatively correlated; a sharply edged ski on one side was usually associated with the other ski being relatively flat. The relationship of glide to ski flatness suggests that many skiers might benefit from skating with both skis relatively flat.

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Jeremy J. Bauer, Robyn K. Fuchs, Gerald A. Smith and Christine M. Snow

Drop landings increase hip bone mass in children. However, force characteristics from these landings have not been studied. We evaluated ground and hip joint reaction forces, average loading rates, and changes across multiple trials from drop landings associated with osteogenesis in children. Thirteen prepubescent children who had previously participated in a bone loading program volunteered for testing. They performed 100 drop landings onto a force plate. Ground reaction forces (GRF) and two-dimensional kinematic data were recorded. Hip joint reaction forces were calculated using inverse dynamics. Maximum GRF were 8.5 ± 2.2 body weight (BW). At initial contact, GRF were 5.6 ± 1.4 BW while hip joint reactions were 4.7 ± 1.4 BW. Average loading rates for GRF were 472 ± 168 BW/s. Ground reaction forces did not change significantly across trials for the group. However, 5 individuals showed changes in max GRF across trials. Our data indicate that GRF are attenuated 19% to the hip at the first impact peak and 49% at the second impact peak. Given the skeletal response from the drop landing protocol and our analysis of the associated force magnitudes and average loading rates, we now have a data point on the response surface for future study of various combinations of force, rate, and number of load repetitions for increasing bone in children.