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The sprint starts of 12 skilled collegiate sprinter/hurdlers were filmed for four different sprint start conditions. Ground reaction forces were collected for the first step out of the blocks and velocities through a 2-m speed trap immediately following the first support phase were recorded. The subjects employed their preferred right-left leg placement in the blocks, while the anterior-posterior spacing of the front block with respect to the starting line and the amount of forward lean in the set position were varied. Four positions were constructed that accounted for anthropometric differences. The four positions consisted of combinations of two arm orientations (forward lean and perpendicular to ground) and two front block to starting line distances (bunched and elongated). Kinematic data were reduced to provide center of mass position and velocity measures and analyzed for critical periods throughout the starting action. Selected critical events from the first step kinetic records were also analyzed. The results indicated that the elongated starting positions resulted in greater horizontal displacement, greater propelling impulse, increased first step toe-off velocity, and greater average velocity through a 2-m speed trap. Arm orientation effects were less well defined. Forward lean tended to result in greater vertical velocity at block clearance and horizontal velocity at first step toe-off, whereas perpendicular arm positioning resulted in greater 2-m speed trap velocity.

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Explosive resistance training (ERT) improves older adults' strength and power, and methods to make this form of training more accessible and useful to older adults are needed. The purpose of this study was to evaluate whether the rating of perceived exertion (RPE) scale would predict a broad range of ERT intensities on the leg press with older adults. If successful, then a load-RPE relationship could be used to regulate the intensity of training loads for ERT with older adults, allowing the elimination of maximal strength testing. Twenty-one older adults (≥65 years) with resistance training experience took part in 2 testing sessions. Session 1: Subjects performed high-velocity repetitions on the leg press for up to 9 loads (from 60 to 140% body weight) presented in quasi-randomized order, and then reported their RPE for each load. Session 2: A 1 repetition maximum (1RM) strength test was conducted. Regression analysis revealed that the average RPE across subjects for each load strongly predicted the average %1RM across subjects (R2 = 99.5%; p < 0.001). This allows the establishment of a load-RPE relationship for use in selecting ERT loads for older adults on the leg press. For example, high-intensity loads (70-90% 1RM) that would elicit both strength and power gains when used with ERT aligned with an RPE of 14-16. Lighter loads that may be useful for training for power, but not strength (<70% 1RM), were identified with RPE scores of 13 and lower. The load-RPE relationship may simplify the regulation of intensity of ERT with older adults on the leg press, where the exercising older adult could be guided to select loads according to their RPE.

Soleus Hoffman-reflex (H-reflex) gain was compared at the same background level of electromyographic activity across lying, natural standing, and tandem stance postures, in 12 young and 16 elderly adults. When compared to a lying posture, young adults significantly depressed soleus H-reflex gain when in a natural standing (19% decrease) and a tandem stance position (30% decrease; p <.0125 for both positions). For elderly adults, there was no significant decrease in H-reflex gain while standing naturally, but there was a significant 28% decrease when performing tandem stance (p <.0125). The data indicate that, although the mild motor control challenge of natural standing does not induce a decrease in soleus H-reflex gain in the elderly adults, as it does in young adults, in the more difficult task of tandem stance, soleus H-reflex gain is significantly decreased in both young and elderly adults.