Wolfgang Kroll

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The effects of 50 depth-vertical jumps (DJ) on counter-movement vertical jump (CMJ), squat jump (SJ), and DJ, isometric knee extension force (MVC), and patellar tendon response were examined in 12 men. There was no reduction in the height of the 50 DJs, but the contact time lengthened by 16%. Height of CMJ and DJ did not change after the 50 DJs, but the(More)
Maximally fast, self-terminated elbow flexion movements were performed by 10 male and 10 female college-aged subjects to assess potential gender-related differences in kinematics and the triphasic electromyographic (EMG) pattern. The subjects were instructed to move their forearms as fast as possible through 90 degrees of elbow flexion range of motion and(More)
In an effort to identify neuromuscular parameters which differentiate between power-type and endurance-type athletes, an investigation was conducted to determine the effects of an isometric exercise task upon patellar and Achilles fractionated reflex time components in a group of weight lifters and long-distance runners. A reflex hammer was used to deliver(More)
Two days of practice on simple and choice reaction (RT) and movement time (MT) were studied using 60 males placed into four groups based upon age and physical activity level. Practice effects upon simple and choice RTs were different for young and old groups. Only the two inactive groups improved on simple and choice MT, with greatest improvement occurring(More)
The relationship of age and a life style of physical activity with isometric knee extension strength and a simple and choice resisted response time was examined in 60 male subjects divided into four equal groups: Old Active, Old Inactive, Young Active, Young Inactive. Each response measure consisted of a visual reaction time followed by a movement to a(More)
A model of human muscle action is presented for a maximally fast, large-amplitude forearm movement to target. The inputs to the model are approximately the biceps and triceps EMG envelopes over a single movement. The model's output gives the corresponding displacement angle of the forearm about a fixed elbow position as a function of time. The idea of the(More)
Plantar flexion fatigue and muscle fiber type in power and endurance athletes. Med. Sci. Sports Exercise, Vol. 12, No. 4, pp. 262-267, 1980. The relationship between isometric plantar flexion strength fatigue patterns and muscle fiber type composition of the gastrocnemius was assessed in endurance (N = 8) and power (N = 8) trained males. Following baseline(More)
Fractionated knee extensor and plantar flexor reaction time (RT) components were assessed in a group of eight weightlifters and eight long distance runners. Following a 4-day period of baseline stabilization for each muscle group, a 50% maximal voluntary contraction (MVC) holding-time exercise was administered. Results showed that the runners had longer(More)
Rapid, goal-directed elbow flexion movements were examined under interacting conditions of inertial loading and resistance to movement initiation. The resistance ceased when movement began, resulting in quick release movements. Inertial load slowed the movement and lengthened the agonist and antagonist electromyographic (EMG) burst durations. The quick(More)
Human stretch reflexes (SRs) are often too weak and ineffectual to provide adequate postural regulation or rhythmic movement boosting (e.g. in ankle pushoff at the end of stance phase in fast running). Recent improvements in methods of artificially enhancing skeletomotor responses, especially in therapeutic regimens, should not be widely employed until the(More)