Some factors affecting eccentric contraction strength

Some factors affecting eccentric contraction strength


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Abstracts-International Societyof BiomechanicsXII Congress I?#)

SHORT TERM EFFECTS OF VOLUMINOUS HEAVY RESISTANCE TRAINING AND RECOVERY ON THE SNATCH TECHNIQUE IN‘WEIGHTLIFTING Heikki Kauhanen* and Keijo Hlkkinen** * Research Unit for Sport and Physical Fitness, Jyvaskyll, Finland ** Department of Biology of Physical Activity, University of Jyvaskyll, Finland Biomechanical structure of the Olympic snatch lift was investigated during a voluminous heavy resistance weight‘lifting training period of one week with two training sessions per day. after two voluminous training The measurements were performed at the start (Ml), days (MZ), after one "normal" training day (M3) and after one day of rest at the end of the experiment (M4). No significant changes occured in the maximal snatch performance during the one week experimental period. The maximal vertical ground reaction forces during the first and third pull of the snatch increased (p
CHANGES IN PEDALLING TECHNIQUE OF ELITE CYCLISTS WITH INCREASED WORKLOAD StevenA. Kautz, Michael E. Feltner*, Edward F. Coyle, and Ann M. Baylor. Department of Kinesiology and Health Education, University of Texas, Austin, TX, 78712, USA. *Now at Dep‘artmentof Sports Medicine and PhysicalEducation, PepperdineUniversity, Malibu, CA, 90265. A speciallyinstrumented pedal recordedthe applied forces. This pedal allowed the subjectto useregular racing cleats,and was mounted on the right side of an ergometer that was modified to simulate the subject’s bike. Force recordswere collected (at 90 rpms) for fourteen elite male cyclists(USCF category 1 and 2) at 46 workloads (single leg power outputs of 92-280 W). Oxygen consumption was measuredduring the testing, and workload was calculatedas a percent of V02 max. Mean force recordswere calculatedat the lowest (range=56-68%of V02 max) and the highest workload that was not above their V02 max (range=83-100%). Individual responsesto the increasedworkload were alsodetermined. The subjectsdid not significantly increaseapplied forces during the upstroke at the higher workload. Elite subjectsshowed two main strategies for adapting to increasedworkload. Some subjectsincreasedthe pedal angle during the downstroke to increasethe horizontal component of the force aswell asthe vertical, while the others tended to increaseonly the vertical component. To summarize,elite subjectsshowedno tendency to produce significant propulsive torque about the crank during the upstroke. Even at a workload of approximately 92% of VO2 max, they produced 96% of the propulsive torque during the downstroke.








and M.Miyashita*

*Laboratory for Exercise Physiology, Biomechanics and Sports Sciences, Faculty of Education, University of Tokyo, Tokyo, Japan **Department of Sports Sciences, College of Arts and Sciences, University of Tokyo ***International Budo University, Chiba Pref., Japan Properties of the force developed during eccentric contractions were investigated using a specially designed dynamometer. Elbow flexion was performed at the maximal voluntary contraction level. A force transducer was placed on the anterior surface of the wrist to measure elbow flexion force. Immediately after an isometric contraction of 2 seconds (STl), the elbow joint was eccentrically stretched about 15"(ECC), and again put in an isometric state (ST2). Starting elbow angles were randomly assigned every 15" from 70" to 130' (full extension 180") and stretch speeds ranged from 2.5 to 20 rpm. The muscle force during ECC was always greater than those during ST1 and ST2, and the difference between starting isometric force and eccentric peak force was greater at a higher speed. Maximum eccentric force was observed at the elbow angle of 92" f 13" (mean+S.D.; PA). In trials where final elbow angles were lower than PA, peak-force elbow angles during ECC were closer to the final elbow angles, whereas in other trials where starting elbow angles were larger than PA, peak-force angles during ECC were closer to contraction force depended on the starting elbow angles. It was suggested that eccentric starting and increase of stretch speed enlarged augmentation of force above angles isometric value, as have been found in isolated muscles.