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Effects of seat height changes on joint force and moment patterns in experienced cyclists
Abstracts
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A PERTURBATION METHOD FOR THE STUDY OF RUNNING ECONOMY T. A. Miller* & M. Carlssont M. J. Milliron’, P. R. Cavanagh*, *‘The Ccntcr for Locomotion Studies, Penn State University, University Park, PA 16802 tSELSPOT AB, Molndal, Swcdcn Since success in distance running has been correlated with economical running, it is believed that small decreases in Because running style is believed to be a factor which oxygen consumption should lead to improved performance. intluences running economy, modification of mechanics may lead to improved economy. Two important questions must be addressed in the design of a method to achieve this goal. First, can running mechanics be altered such that new patterns of movements are learned? Second, can changes in running mechanics be made such that running economy is improved? The purpose of our research is to develop a method for identifying desirable changes in running mechanics on an individual basis and for providing feedback during training. An initial screening of 73 trained male distance runners was completed to obtain a group of 20 uneconomical runners. The next phase was to determine the style parameter thought to contribute to the uneconomical state of each runner. This involved running each individual overground across a force platform and on the treadmill for a kinematic analysis using SELSPOT, an optoelectronic device. In order to provide meaningful instruction on running style a system capable of real time collection, processing and feedback of mechanical variables was developed. Our system involved a modification of the typical use of SELSPOT so as to provide quasi “real time” feedback of mechanical variables in two dimensions. During a training period, LEDs attached to anatomical landmarks defining the key style parameter of each individual were monitored, processed and used in feedback. A monitor placed in view of the subject provided a graphic display of a target score and the sbbject’s most rcccnt value. Initial results have shown that this type of modification is possible. This use of visual feedback to modify kinematic patterns in a complex skill such as running requires quasi “real time” knowledge of performance. If the mechanical variable most influential in a runner’s uneconomical style can be identified and subsequently used as the paramctcr in our continuous feedback system, successful alterations in running economy should be seen.
SESSION 14. SPORTS MECHANICS: CYCLING AND GYMNASTICS THE EFFECT OF POSITION AND CADENCE ON THE BIOMECHANKAL CHARACTERISTICS OF HILL CLIMBING CYCLISTS. T. A. Miller*, P. E. Martint, and C. L. Wellst. *The Center for Locomotion Studies, The Pennsylvania State University, University Park, PA. 16802. iExercise and Sport Research Institute, Arizona State University, Tempe, AZ. 85287. Research investigating biomechanical factors in the sport of cycling is abundant. However, studies isolating on the hill climbing aspect of cycling are less numerous. The purpose of this study was to determine the effects of four position/cadence combinations (sit/60 rev.min-1, stand/60 rev.min-1, sit/75 rev.min-1 and stand/75 rcv.min-1) on center of mass displacement, rear hub acceleration and the kinematic characteristics of hill climbing cyclists. The kinematic variables measured included trunk segment angle range and mean, hip joint angle range and mean, knee joint angle range and mean, and ankle joint angle range and mean Fourteen highly trained United States Cycling Federation (USCF) licensed cyclists served as subjects. They were filmed at 60 fps while they rode their own racing bicycles on a motorizcd treadmill at 19 kmhr-1 and 5 46 grade. Each subject rode for 8 minutes in each of the four position/cadence combinations The standing position resulted in a significantly larger rear hub acceleration, center of mass displacement, mean trunk segment angle, and trunk, hip and knee angle range of motion than the sitting position. However, mean trunk, hip, knee, and ankle angles were all significantly greater in the sitting position as eomparcd to the standing position. The ankle angle range of motion was not different between positions. Only center of mass displacement, knee angle range of motion, and mean ankle angle were significantly efl’cctcd by a change in CddenCe. All three variables were significantly larger at the 60 revmin-1 cadence. However, because power outputs were held constant between all treatments and all data was normalized to one pedal revolution the differences between cadences may have resulted from the greater forces applied per cycle at the slower cadence rather than from the difference in angular velocity. It is evident that uphill cycling mechanics am effected more by a change in the riding position than by gear selection. The kinematic analysis implies that the two positions place the lower extremity musculature at different places on their length-tension curves. Assuming that the force required per pedal revolution is equivalent, it appears that the energy expenditure as a result of leg muscle action will differ between the two positions.
EFFECTS OF SEAT HEIGHT CHANGES ON JOINT FORCE AND MOMENT PA-ITERNS IN EXPERIENCED CYCLISTS. R.C. BROWNING, R.J. GREGOR, J.P. BROKER, W.C. WHITING DEPARTMENT OF KINESIOLOGY, UCLA, LOS ANGELES, CA 90024-1568 Establishing the correct seat height has traditionally been based on either minimum oxygen requirements (106% crotch height, CH), or maximum power output (109% CH). The purpose of this study was to determine the effect of seat height changes on joint force and moment patterns at the hip, knee, and ankle. Six experienced male cyclists rode a racing bicycle at 250W (90 rpm) for 5 minutes at their preferred seat height (X = 108% CH), and at 100% CH and 115% CH. The bicycle was mounted on a Velondyne Trainer which simulated inertial and non-inertial loading. Normal and tangential components of the pedal reaction force were monitored by dual piezoelectric force transducers mounted within each pedal. Kinematic data were collected for the right lower extremity using a Watsmart motion analysis system. Joint forces in the anterior-posterior (AP) direction at 115% CH were significantly lower (30 to 50%) when compared to the 100% CH and preferred seat height conditions at all joints between 90 and 180 degrees of the pedalling cycle. Vertical forces were similarly reduced at the ankle and knee joints. These data suggest that a high seat height may be appropriate for reducing lower extremity loads in a rehabilitative environment. Moment patterns were similar at the hip, knee, and ankle for the preferred seat height and 100% CH conditions. At 115%CH greater extensor moments at the hip, lower extensor moments at the ankle, lower peak extensor and higher peak flexor moments at the knee were observed during the power phase.
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A PERTURBATION METHOD FOR THE STUDY OF RUNNING ECONOMY T. A. Miller* & M. Carlssont M. J. Milliron’, P. R. Cavanagh*, *‘The Ccntcr for Locomotion Studies, Penn State University, University Park, PA 16802 tSELSPOT AB, Molndal, Swcdcn Since success in distance running has been correlated with economical running, it is believed that small decreases in Because running style is believed to be a factor which oxygen consumption should lead to improved performance. intluences running economy, modification of mechanics may lead to improved economy. Two important questions must be addressed in the design of a method to achieve this goal. First, can running mechanics be altered such that new patterns of movements are learned? Second, can changes in running mechanics be made such that running economy is improved? The purpose of our research is to develop a method for identifying desirable changes in running mechanics on an individual basis and for providing feedback during training. An initial screening of 73 trained male distance runners was completed to obtain a group of 20 uneconomical runners. The next phase was to determine the style parameter thought to contribute to the uneconomical state of each runner. This involved running each individual overground across a force platform and on the treadmill for a kinematic analysis using SELSPOT, an optoelectronic device. In order to provide meaningful instruction on running style a system capable of real time collection, processing and feedback of mechanical variables was developed. Our system involved a modification of the typical use of SELSPOT so as to provide quasi “real time” feedback of mechanical variables in two dimensions. During a training period, LEDs attached to anatomical landmarks defining the key style parameter of each individual were monitored, processed and used in feedback. A monitor placed in view of the subject provided a graphic display of a target score and the sbbject’s most rcccnt value. Initial results have shown that this type of modification is possible. This use of visual feedback to modify kinematic patterns in a complex skill such as running requires quasi “real time” knowledge of performance. If the mechanical variable most influential in a runner’s uneconomical style can be identified and subsequently used as the paramctcr in our continuous feedback system, successful alterations in running economy should be seen.
SESSION 14. SPORTS MECHANICS: CYCLING AND GYMNASTICS THE EFFECT OF POSITION AND CADENCE ON THE BIOMECHANKAL CHARACTERISTICS OF HILL CLIMBING CYCLISTS. T. A. Miller*, P. E. Martint, and C. L. Wellst. *The Center for Locomotion Studies, The Pennsylvania State University, University Park, PA. 16802. iExercise and Sport Research Institute, Arizona State University, Tempe, AZ. 85287. Research investigating biomechanical factors in the sport of cycling is abundant. However, studies isolating on the hill climbing aspect of cycling are less numerous. The purpose of this study was to determine the effects of four position/cadence combinations (sit/60 rev.min-1, stand/60 rev.min-1, sit/75 rev.min-1 and stand/75 rcv.min-1) on center of mass displacement, rear hub acceleration and the kinematic characteristics of hill climbing cyclists. The kinematic variables measured included trunk segment angle range and mean, hip joint angle range and mean, knee joint angle range and mean, and ankle joint angle range and mean Fourteen highly trained United States Cycling Federation (USCF) licensed cyclists served as subjects. They were filmed at 60 fps while they rode their own racing bicycles on a motorizcd treadmill at 19 kmhr-1 and 5 46 grade. Each subject rode for 8 minutes in each of the four position/cadence combinations The standing position resulted in a significantly larger rear hub acceleration, center of mass displacement, mean trunk segment angle, and trunk, hip and knee angle range of motion than the sitting position. However, mean trunk, hip, knee, and ankle angles were all significantly greater in the sitting position as eomparcd to the standing position. The ankle angle range of motion was not different between positions. Only center of mass displacement, knee angle range of motion, and mean ankle angle were significantly efl’cctcd by a change in CddenCe. All three variables were significantly larger at the 60 revmin-1 cadence. However, because power outputs were held constant between all treatments and all data was normalized to one pedal revolution the differences between cadences may have resulted from the greater forces applied per cycle at the slower cadence rather than from the difference in angular velocity. It is evident that uphill cycling mechanics am effected more by a change in the riding position than by gear selection. The kinematic analysis implies that the two positions place the lower extremity musculature at different places on their length-tension curves. Assuming that the force required per pedal revolution is equivalent, it appears that the energy expenditure as a result of leg muscle action will differ between the two positions.
EFFECTS OF SEAT HEIGHT CHANGES ON JOINT FORCE AND MOMENT PA-ITERNS IN EXPERIENCED CYCLISTS. R.C. BROWNING, R.J. GREGOR, J.P. BROKER, W.C. WHITING DEPARTMENT OF KINESIOLOGY, UCLA, LOS ANGELES, CA 90024-1568 Establishing the correct seat height has traditionally been based on either minimum oxygen requirements (106% crotch height, CH), or maximum power output (109% CH). The purpose of this study was to determine the effect of seat height changes on joint force and moment patterns at the hip, knee, and ankle. Six experienced male cyclists rode a racing bicycle at 250W (90 rpm) for 5 minutes at their preferred seat height (X = 108% CH), and at 100% CH and 115% CH. The bicycle was mounted on a Velondyne Trainer which simulated inertial and non-inertial loading. Normal and tangential components of the pedal reaction force were monitored by dual piezoelectric force transducers mounted within each pedal. Kinematic data were collected for the right lower extremity using a Watsmart motion analysis system. Joint forces in the anterior-posterior (AP) direction at 115% CH were significantly lower (30 to 50%) when compared to the 100% CH and preferred seat height conditions at all joints between 90 and 180 degrees of the pedalling cycle. Vertical forces were similarly reduced at the ankle and knee joints. These data suggest that a high seat height may be appropriate for reducing lower extremity loads in a rehabilitative environment. Moment patterns were similar at the hip, knee, and ankle for the preferred seat height and 100% CH conditions. At 115%CH greater extensor moments at the hip, lower extensor moments at the ankle, lower peak extensor and higher peak flexor moments at the knee were observed during the power phase.