To determine the contributions of the motions of the body segments to the vertical ground reaction force (F-Z), the joint torques produced by the leg muscles, and the time course of vertical velocity generation during a vertical jump, 15 men were videotaped performing countermovement vertical jumps from a force plate with and without an arm swing. Linear kinematic, F-Z, and joint torque data were computed and compared using repeated measures analysis of variance. Maximum jump height was significantly larger in the arm swing jumps compared to the no arm swing jumps and was due to both a higher height of the center of mass (CM) at takeoff (54%) and a larger vertical velocity of the CM at takeoff (46%). The net vertical impulse created during the propulsive phase of the arm swing jumps was greater due to a trend of an increased duration (0.021 s) of the propulsive phase and not to larger average values of F-Z. In the arm swing jumps, the arm motion resulted in the arms making a larger maximal contribution to F-Z during the middle of the propulsive phase and decreased the negative contribution of the trunk-head and thigh to F-Z late in the propulsive phase. Last, the arm swing decreased the extensor torques at the hip (13%), knee (10%), and ankle (10%) early in the propulsive phase but augmented these same extensor torques later in the propulsive phase.

Feltner et al. (J. Sports Sci., 1999) showed that a rapid arm swing altered the resultant joint torque (RJT) at the hip and knee during CMJs. PURPOSE To determine the EMG, length, and contraction velocity of leg muscles to identify the muscular factors responsible for changes in hip and knee RJTs associated with arm action during CMJs. METHODS Coordinate data (120 Hz) were obtained from 15 males performing CMJs from a force plate (1kHz) with (ARM) and without (NA) an arm swing, and squat jumps without an arm swing. Three trials per jump were analyzed. Inverse dynamics computed the RJT at the hip and knee. Surface EMG (2 kHz) recorded muscle activity from the leg muscles. Root mean square (RMS) EMG data (25 ms window) for each muscle were computed and normalized using the mean RMS-EMG data from the propulsive phase (PP) of the squat jumps. Muscle length was estimated using the method of Hawkins et al. (J. Biomechanics, 1990) and the segment lengths. Contraction velocity was computed as the first derivative of muscle length with respect to time. Repeated measures ANOVA compared the data from the ARM and NA jumps. RESULTS The NA jumps produced larger RJTs at the hip and knee during the first third of the PP, but the ARM jumps produced larger RJTs at these joints during the rest of the PP. The gluteus maximus, vastus lateralis and gastrocnemius exhibited no differences in EMG activity, muscle length, or contraction velocity during the PP. The bicep femoris (BF) had greater EMG activity (ARM: 138±80%; NA: 90±42%) and experienced faster concentric conditions (ARM: 0.16±0.08; NA: 0.06±0.06 m/s) during the initial portion of the PP of ARM jumps. Near the end of the PP in ARM jumps, the BF had less EMG activity (ARM: 87±36.; NA: 121±54%) and was in eccentric conditions. The rectus femoris (RF) had less EMG activity during most of the PP in the ARM jumps. In the ARM jumps, the RF was in faster eccentric conditions (ARM: −0.10±0.07; NA: −0.03±0.06 m/s) during the initial portion of the PP, but in faster concentric conditions (ARM: 0.31±0.07; NA: 0.22±0.05 m/s) near the end of the PP. CONCLUSION Arm action alters BF and RF muscle activity partially explaining differences in hip and knee RJTs during CMJs.

In prior work, (Feltner et al., J Sports Sci, 17(6), 1999) the hip and knee extensor torques (Ts) produced in the first third of the propulsive phase (PP) of CM jumps using an arm swing (ASJ) were smaller relative to CM jumps using no arm swing (NAJ). However, the ASJs produced larger hip and knee extensor Ts during the rest of the PP. The vertical velocity of the center of mass (VG) in the ASJs always equaled or exceed its corresponding values during the NAJs suggesting that the smaller extensor Ts during the first third of the PP did not alter vertical ground reaction force (VGRF) generation. PURPOSE: To examine the effects of an arm swing on VGRF production and vG generation in CM jumps. METHODS: 15 male subjects with prior experience in jumping-related sports were videotaped (120 Hz) performing ASJs and NAJs from a force plate (1 kHz). Repeated measures ANOVA compared the VGRF and vG data at four instants defining the PP: t(LP), vG = 0; t(PV), maximum vG; t(1)=t(LP)+1/3[t(PV)-t(LP)]; and, t(2)=t(LP)+2/3[(t(PV)-t(LP)]. RESULTS: During the PP, the net vertical impulse and the average value of the VGRF did not differ between the ASJs and the NAJs, but the impulses due to body weight and VGRF were greater for the ASJs. The duration of the PP was longer in the ASJs (mean ± SD, ASJ: 0.30 ± 0.05 s, NAJ: 0.28 ± 0.05 s). Instantaneous values of VGRF and vG are shown in the table (*p < 0.05). The NAJs created larger VGRFs and had larger values for vG during the first third of the PP. The ASJs had a larger values for vG and produced larger VGRFs during the latter two-thirds of the PP.Table: No Caption AvailableCONCLUSION: The larger vG values at t(PV) in the ASJs resulted from the longer duration of the PP, not to the application of larger average VGRFs. The current findings, and the similar findings in a study by Harman et al. (Med Sci Sports Exerc, 22(6), 1990) for a group of physically active males, are in contrast to our study of collegiate volleyball players (Feltner et al., 1999). The volleyball players decreased the length of the PP in the ASJs relative to the NAJs and increased the average value of the VGRF. The collective findings suggest that training induces a performance enhancing, skill-specific adaptation in VGRF creation and vG generation during ASJs.

Feltner et al. (J. Sports Sci., 17(6), 1999) showed that in the propulsive phase [from the low point [vertical velocity (Vv) = 0; t(LP)] through maximum Vv of center of mass; t(PV)] of CMJs, a rapid arm swing altered the joint torques (Ts) at the hip and knee joints in 25 collegiate volleyball players. To further investigate the casual mechanisms at the hip, 15 male subjects who played volleyball on a regular basis were videotaped (120 Hz) performing CMJs from a force plate (1kHz) both with (ARM) and without (NA) an arm swing and squat jumps without an arm swing. Surface EMG (2 kHz) recorded muscle activity from select lower extremity muscles. Root mean square (RMS) EMG data (25 ms window) were computed for each muscle. RMS-EMG data for ARM and NA jumps were normalized using the mean value of the RMS-EMG data during the propulsive phase of the squat jumps for each subject. Inverse dynamics were used to compute the Ts at the hip for three trials per subject per condition and were normalized using the product of the subject's weight and height squared. Repeated measures ANOVA compared the data at the four instants defining the propulsive phase - t(LP), t(1), t(2) and t(PV); where t(1) = t(LP) + 1/3* [(t(PV) - t(LP)] and t(2) = t(LP) + 2/3* [(t(PV) - t(PV) - t(LP)]. Angular velocity [(ω) see Table] and normalized T at the hip [(nT) see Table and Figure] exhibited the same relationship as in the previous study. TheTableFigure: No caption Available.NA jumps produced larger nTs as the hip muscles were in slower concentric actions near t(LP). From t(1) until t(2), the arm swing allowed the nT at the hip to stay relatively constant in ARM jumps, but it declined in the NA jumps due to faster rates of hip ω. RMS-EMG data indicated that the rectus femoris was active at a lower level in the ARM jumps between t(LP) and t(PV). In the ARM jumps, the bicep femoris was active at a higher level between t(LP) and t(1), but at a lower level between t(2) and t(PV). The findings indicate the arm motion altered the underlying muscle activity and resulted in changes in the nTs at the hip.

Twenty-five volleyball players (14 males, 11 females) were videotaped (60 Hz) performing countermovement vertical jumps with and without an arm swing. Ground reaction force and video-based coordinate data were collected simultaneously. The resultant joint force and torque at the hip, knee, ankle and shoulder for two trials per subject per condition were computed and normalized. Average kinematic, resultant joint force and torque data were compared using repeated-measures analysis of variance. Larger values were recorded for the vertical velocity of the centre of mass at take-off in the jumps with (mean 2.75, s = 0.3 m.s-1) versus without (mean 2.44, s = 0.23 m.s-1) an arm swing. The jumps with no arm swing produced larger torques at the hip during the first third of the propulsive phase (from zero to maximum vertical velocity of the centre of mass). During the final two-thirds of the propulsive phase, the arm swing augmented hip extensor torques by slowing the rate of trunk extension and placing the hip extensor muscles in slower concentric conditions that favoured the generation of larger forces and resultant joint torques. During the first two-thirds of the propulsive phase, knee extensor torque increased by 28% in the jumps with an arm swing, but maintained a relatively constant magnitude in the jumps with no arm swing.

1997 The symposium will examine how motions of the free (non-support) limbs alter lower extremity muscular mechanics during vertical jumps. It is well known that a vigorous swing of the arms and non-support leg increases the height of vertical jumps. A portion of the increase in jump height is due to a higher position of the body's center of mass at takeoff (Feltner et al, in press; Vint et al, 1996). Free limb motions also result in a larger vertical velocity of the center of mass at takeoff and ultimately higher jump heights. It has been speculated that free limb motions increase takeoff velocity because they exert downward forces on the trunk that slow the rate of extension of the hip and knee resulting in larger muscular forces (Harman, 1990). Current research by the authors participating in the session identifies how free limb motion affects the underlying mechanics of the lower extremity muscles and enhances the ability of the muscles to generate force.

The purpose was to quantify the contributions of the thrower's linear translation and segmental rotations to the speed of the javelin. Eight male finalists at the 1995 USA Track and Field Championships were filmed at 100Hz. The two longest throws for each athlete were analyzed and the DLT method was used to obtain three-dimensional coordinates of thrower and javelin landmarks. Data were smoothed using quintic spline functions and the first derivatives of these functions provided instantaneous linear velocity values. Segment angular velocities and instantaneous contributions to javelin speed were computed using methods similar to those reported by Feltner et al. (J. Applied Biomech, 1996, 359-382). The general patterns of component contributions to javelin speed were similar for all analyzed throws. At left foot plant and the start of the double support period prior to release, over 75% of the speed of the javelin (X=7.4 m/s) was due to the linear velocity of the thrower's center of mass (c.m.). During the double support phase, the speed of the javelin rapidly increased and reached its release speed (X=28.1 m/s). During double support and until approximately 0.035 s before release, the horizontal adduction angular velocity of the upper arm was a major contributor to the speed of the javelin. However, the horizontal adduction angular velocity rapidly decreased immediately prior to release. At release, the largest contributors to the speed of the javelin were elbow extension angular velocity(X=34.7±8.1%), upper arm internal rotation angular velocity (X=13.3±9.8%), trunk twist (X=11.9±6.3%), translation of the thrower's c.m. (X=11.8±2.4%) and javelin distortion and recoil(X=9.0±6.7%). All remaining terms independently contributed less than 4% to javelin speed. For each throw, the aforementioned five terms accounted for over 80% of the javelin's release speed. However, the relative magnitudes of each term's percent contribution to javelin speed at release differed for the throws indicating possible technique variations among the athletes.

The purpose was to determine the effects of arm motion on lower extremity joint torques in countermovement vertical jumps (CMJs). 25 volleyball players(14 M, 11 W) were videotaped (60 Hz) performing CMJs with an arm swing (ARM) and hands on hips (NA). Ground reaction force and center of pressure data were collected simultaneously at 1000 Hz and synchronized with the video data. Inverse dynamics were used to compute joint torques (T) at the hip, knee and ankle for two trials per subject per condition. Ts were normalized by dividing by the product of the subject's mass and height squared. The propulsive phase of the jump, from the low point [vertical velocity (Vv)=0] through maximum Vv of center of mass (G), was divided into 3 equal periods. Average angular velocity (ω) and T data during each period were compared using repeated measures ANOVA. The T and ω data at the ankle were similar for both groups, but differed at the hip and knee (see Table). The NA condition produced larger Ts at the hip as the muscles performed slower concentric actions in period 1. The ARM condition generated larger Ts at the hip and knee in period 2 because the arm motion allowed the muscles to remain in slower concentric conditions. During period 3, the ARM condition generated larger torques at the knee despite being in faster concentric actions. Results indicate the arm motion augmented muscular forces in the legs and resulted in a larger Vv of the G at takeoff in the ARM (2.8±0.3 m/s) versus NA (2.4±0.2 m/s) jumps.

The purpose was to compute the instantaneous contributions of anatomical rotations of the trunk, upper arm, forearm, and hand to ball speed and to quantify the three-dimensional angular kinematics of the trunk and throwing arm during water polo penalty throws. The largest contributors to predicted ball speed |(vB)'| at release were forearm extension and a counterclockwise twisting rotation of the trunk. Upper arm internal rotation contribution to |(vB)'| at release was highly variable and exhibited a significant inverse relationship with the upper arm horizontal adduction contribution to |(vB)'| at release (r = −.70). Subjects with large internal rotation contributions to |(vB)'| tended to have the upper arm in positions of less external rotation, but internally rotating at a faster rate, at release. Subjects with large upper arm horizontal adduction contributions to |(vB)'| exhibited a trend for faster rates of upper arm horizontal adduction and positions of increased forearm pronation at release. Findings suggest that a continuum of technique styles are used by water polo players to produce ball speed at release.

The investigation examined isokinetic (IK) and nonisokinetic (NIK) strength training programs for the inversion (INV) and eversion (EV) muscles on pronation during running. Seventy-seven volunteers were videotaped running on a treadmill at 3.8 m.s-1 and total pronation (delta beta PRO) was computed. Eighteen heel-strike runners with the largest values of delta beta PRO (X = 16.7 degrees) were selected as subjects. During the pre- and posttests, isokinetic muscle strength at 20 and 180 degrees.s-1 was determined for the concentric (CON) and eccentric (ECC) actions of the INV and EV muscle groups. The subjects also were videotaped running on a treadmill (3.8 m.s-1). The IK training group performed three sets of eight CON and ECC repetitions at 20, 90, and 180 degrees.s-1 for both muscle groups; and the NIK subjects did exercises commonly used in ankle rehabilitation. Each group trained three times weekly for 8 wk. The IK group showed significantly (P < or = 0.05) CON and ECC strength increases for all INV test conditions and three of the four EV conditions (20 degrees.s-1 CON and ECC, and 180 degrees.s-1 CON). They also demonstrated significant decreases in the rearfoot (2.2 degrees) and pronation/supination (2.9 degrees) angles at heel strike and in delta beta PRO (-2.2 degrees).l The NIK group exhibited no change in rearfoot motion and only increased INV strength at the 180 degrees.s-1 ECC test condition. The findings suggest that pronation can be decreased by an isokinetic strength training program for the INV and EV muscles.

A pedal dynamometer recorded changes in pedaling technique (normal and tangential components of the applied force, crank orientation, and pedal orientation) of 14 elite male 40-km time trialists who rode at constant cadence as the workload increased from similar to an easy training ride to similar to a 40-km competition. There were two techniques for adapting to increased workload. Seven subjects showed no changes in pedal orientation, and predominantly increased the vertical component of the applied force during the downstroke as the workload increased. In addition to increasing the vertical component during the downstroke, the other subjects also increased the toe up rotation of the pedal throughout the downstroke and increased the horizontal component between 0° and 90°. A second finding was that negative torque about the bottom bracket during the upstroke usually became positive (propulsive) torque at the high workload. However, while torque during the upstroke did reduce the total positive work required during the downstroke, it did not contribute significantly to the external work done because 98.6% and 96.3 % of the total work done at the low and high workloads, respectively, was done during the downstroke.

In this study we evaluated the physiological and biomechanical responses of "elite-national class" (i.e., group 1; N = 9) and "good-state class" (i.e., group 2; N = 6) cyclists while they simulated a 40 km time-trial in the laboratory by cycling on an ergometer for 1 h at their highest power output. Actual road racing 40 km time-trial performance was highly correlated with average absolute power during the 1 h laboratory performance test (r = -0.88; P less than 0.001). In turn, 1 h power output was related to each cyclists' VO2 at the blood lactate threshold (r = 0.93; P less than 0.001). Group 1 was not different from group 2 regarding VO2max (approximately 70 ml.kg-1.min-1 and 5.01 l.min-1) or lean body weight. However, group 1 bicycled 40 km on the road 10% faster than group 2 (P less than 0.05; 54 vs 60 min). Additionally, group 1 was able to generate 11% more power during the 1 h performance test than group 2 (P less than 0.05), and they averaged 90 +/- 1% VO2max compared with 86 +/- 2% VO2max in group 2 (P = 0.06). The higher performance power output of group 1 was produced primarily by generating higher peak torques about the center of the crank by applying larger vertical forces to the crank arm during the cycling downstroke. Compared with group 2, group 1 also produced higher peak torques and vertical forces during the downstroke even when cycling at the same absolute work rate as group 2. Factors possibly contributing to the ability of group 1 to produce higher "downstroke power" are a greater percentage of Type I muscle fibers (P less than 0.05) and a 23% greater (P less than 0.05) muscle capillary density compared with group 2. We have also observed a strong relationship between years of endurance training and percent Type I muscle fibers (r = 0.75; P less than 0.001). It appears that "elite-national class" cyclists have the ability to generate higher "downstroke power", possibly as a result of muscular adaptations stimulated by more years of endurance training.

Hammer speed increases gradually during a throw, but this general increasing trend has one fluctuation superimposed in each turn. In some throwers, gravity and the forward translation of the system produce most of the fluctuation; in others, a marked fluctuation remains after the effects of gravity and of the forward translation of the system have been subtracted out. The remaining fluctuation could be produced through two mechanisms: (a) pulling on the hammer cable in a direction alternately ahead and behind the position of the centroid of the hammer path and (b) alternately shortening and lengthening the distance between the hammer head and the centroid of its path. Three-dimensional film analysis of eight highly-skilled throwers showed that the portion of the hammer speed fluctuation not due to gravity nor to the forward motion is produced mainly by pulling alternately ahead and behind the position of the centroid of the hammer path.

A method for adjusting the effects of wind and altitude on the times of 100-meter sprint races was developed in three stages: (a) generation of an initial model, (b) evaluation of the initial model using a test based on statistical information from world-class sprinting races, and (c) modification of the model to make its predictions fit with the statistical data. The test used to check the accuracy of the model's predictions involved a compilation of the 100 best races ever run (after adjustment of the times for wind and altitude effects), and a comparison of the average wind reading of these races with the average wind reading of all races. The modified form of the model predicted a 0.07-second advantage for a 2-m/s tail wind, a 0.085-s disadvantage for a 2-m/s head wind, and a 0.05-s advantage for the altitude of Mexico City (2,250 m). These values were clearly smaller than those predicted by previous models. If the modified model is correct, this implies that times made with aiding wind and/or at high altitude have greater merit than was previously thought.