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Biomedical subjects

P R Cavanagh

Publications and source records attributed to P R Cavanagh.

At least 73 records · Page 4Linked to original sources
PubMed1991

The free moment of ground reaction in distance running and its changes with pronation.

Many running injuries are successfully treated with footwear modifications designed to reduce pronation, but the underlying mechanism of treatment is not well understood. Previous attempts to correlate reduction in pronation with changes in ground reaction parameters have been unsuccessful. In this study, the free moment of ground reaction (Mz') was measured for 10 rearfoot strikers running at 4.5 m s-1 in each of three different pairs of running shoes designed to vary the extent of pronation during ground contact. Mz' patterns were highly variable between feet, but were repeatable within a given foot/footwear combination. Mz' was greatest in magnitude during the first half of support, when it acted in a direction resisting foot abduction, a component of pronation. It was opposite in sign and smaller in magnitude during the last 30% of support. The peak magnitude and the net angular impulse of Mz' were both increased significantly with increases in pronation. A net ground reaction moment was also calculated about a vertical axis fixed in the shoe, and was used in a first approximation model of the shoe/ground interface to predict when the foot is most likely to ab/adduct during running. In conclusion, this study characterized the Mz' pattern for a well-defined group of runners, and found that Mz' is sensitive to relatively large within-subject changes in pronation.

Adult↗
PubMed1991

The influence of visual factors on fall-related kinematic variables during stair descent by older women.

Despite the documented health hazards associated with stair descent, the mechanisms of falling on stairs remain relatively unexamined. The objectives of this study were to define kinematic variables that could be used to describe foot-stair spatial relationships during the mid-stair phase of stair descent, and to investigate the effects of various visual and environmental conditions on those variables in a group of 36 healthy women between the ages of 55 and 70. Foot clearance and foot placement were measured through high-speed film analysis. Clearance between the foot and the stair during swing phase was small under all visual conditions. Degraded visual acuity had a significant effect on cadence, foot placement, and foot clearance, but visual surround conditions did not. The kinematic variables used in this experiment may be helpful in future studies to assess the results of interventions aimed at reducing the frequency of falls on stairs.

Accidental Falls↗
PubMed1991

Body mass is a poor predictor of peak plantar pressure in diabetic men.

OBJECTIVE: To examine the relationship between peak plantar pressure during walking and body mass in diabetic patients and age-matched control subjects. RESEARCH DESIGN AND METHODS: A volunteer sample of 56 male diabetic veterans (12 insulin dependent, 44 non-insulin dependent) with a mean age of 58.9 yr, mean duration of diabetes of 16.9 yr, and mean vibration perception threshold of 30.8 and 27 age-matched nondiabetic control subjects comprised the study. RESULTS: Peak plantar pressure was measured with a 1000-element piezoelectric platform during the first step of gait. The correlation between body mass and peak pressure was found to be only 0.37 in the patients with diabetes and 0.36 in the control subjects, indicating that body mass accounts for less than 14% of the variance in peak plantar pressure. The body mass and peak plantar pressure of the 14 patients who experienced plantar ulcers was not significantly different from those who did not ulcerate, but vibration perception thresholds and monofilament perception thresholds of the ulcer patients were significantly higher. CONCLUSIONS: Although the correlation between body mass and peak plantar pressure is statistically significant, the functional relationship between the two variables is weak. Elevated plantar pressures are as likely to occur in small individuals as they are in those with large body mass. Foot deformity, in the presence of neuropathy and other permissive factors, is itself likely to be an important risk factor for plantar ulceration in diabetes, and this hypothesis deserves further exploration.

Body Mass Index↗
PubMed1990

Segment interactions within the swing leg during unloaded and loaded running.

In this study, designed to determine the effect of lower extremity inertia manipulation on joint kinetics and segment energetics during the swing phase, 15 male distance runners were filmed as they performed treadmill running (3.35 m s-1) under five load conditions: no added load and loads of 0.25 kg and 0.50 kg added to each thigh or each foot. Results of this study demonstrated that the energetics of the lower extremity movements during the swing phase of the running cycle were dominated by mechanical energy transfers between adjacent segments attributed to the joint reaction forces, which acted to redistribute mechanical energy within the system. These contributions were considerably greater than those of the net joint moments, which primarily reflected muscular generation and dissipation of mechanical energy. Lower extremity loading caused little change in the movement pattern of the swing leg. However, increases in the joint reaction forces and net moments and in the amount of work done and the energy transfer attributed to the reaction forces and moments were observed, but were limited to the joints proximal to the location of the added load. These results were consistent with the increased aerobic demand associated with increases in lower extremity inertia that have been reported elsewhere and also have implications for the manner in which the neuromuscular system controls the motion of the legs during running.

Adult↗
PubMed1990

Power equations in endurance sports.

This paper attempts to clarify the formulation of power equations applicable to a variety of endurance activities. An accurate accounting of the relationship between the metabolic power input and the mechanical power output is still elusive, due to such issues as storage and recovery of strain energy and the differing energy costs of concentric and eccentric muscle actions. Nevertheless, an instantaneous approach is presented which is based upon the application of conventional Newtonian mechanics to a rigid segment model of the body, and does not contain assumptions regarding the exact nature of segmental interactions--such as energy transfer, etc. The application of the equation to running, cycling, speed skating, swimming and rowing is discussed and definitions of power, efficiency, and economy are presented.

Bicycling↗
PubMed1990

Shoes for the insensitive foot: the effect of a "rocker bottom" shoe modification on plantar pressure distribution.

The purpose of this study was to examine the effects on plantar pressure of the rocker bottom shoe, which is a frequently used intervention for the ulcerated diabetic foot. In-shoe pressure distribution was recorded during walking in a conventional extra-depth shoe which was then modified into a rocker bottom configuration with a 24 degrees rocker, and the experiment was repeated. Peak pressures in the rocker shoe were reduce by approximately 30% compared to the conventional shoe in the medial and central forefoot and in the toe regions, but pressures were elevated in the heel, the midfoot, and in the lateral forefoot regions. These experiments suggest that a correctly designed rocker bottom show may reduce the risk of ulceration in certain areas of the foot. However, since pressures in some regions can also be elevated by this type of footwear, attention to individual design is critical.

Adult↗
PubMed1990

Stance phase knee and ankle kinematics and kinetics during level and downhill running.

To study possible mechanisms for muscle soreness in downhill running, ground reaction force and kinematic data were collected on seven male runners during 4.5 m.s-1 level running (LR) and 8.3% downhill grade running (DR). For DR, a force platform was mounted on a sloped concrete block flush with the surface of a ramp. A two-dimensional link segment model was used to calculate net stance phase moments for the knee and ankle. Data were averaged over all subjects for each condition. There was no significant difference (P less than 0.05) between DR and LR for peak flexion velocity, peak extensor moment, or peak power absorption at the knee. Negative work done on the extensor muscles of the knee during stance was significantly greater for DR (58.0 +/- 13 J) than for LR (30.0 +/- 9.0 J). Peak ankle power absorption was significantly greater for DR (619 +/- 85 W) than for LR (396 +/- 180 W). The negative work done on the extensor muscles of the ankle during stance was significantly greater for DR (26.1 +/- 3.2 J) than for LR (12.6 +/- 6.6 J). The results suggest that muscle soreness during DR may be related to high peak power absorption values since the peak joint extensor moments are similar between conditions.

Adult↗
PubMed1990

Use of augmented feedback for the modification of the pedaling mechanics of cyclists.

On-line computer representation of forces applied to the pedals during a 90-degree sector of the pedaling cycle were used to train a group of cyclists to alter their pattern of force application while they cycled on a stationary cycle. The subjects rode for 32 min each day for ten days. During these training rides, three cyclists were given augmented feedback on only their pedaling rate, while three other cyclists were presented with augmented, visual feedback on the magnitude of force application in the sector of interest as well as cadence. At the end of the training period it was noted that the experimental group showed significantly reduced pedal forces in the sector of interest while the control group did not. It was concluded that this technique of modifying a well-practised task was an effective one and that it could be used to explore various training modalities and other pedaling styles.

Adult↗
PubMed1989

Pressure distribution in Morton's foot structure.

The Morton foot structure (MFS) is a foot having, as its most prominent distinguishing feature, a second metatarsal head which is more distally placed than the head of the first. This structure has been associated with a variety of foot problems in athletes. The origin of these foot problems has been hypothesized to be an abnormal metatarsal head loading pattern found in the MFS. This study was conducted to determine whether the MFS produced a metatarsal head pressure profile which was different from the non-Morton foot. Plantar pressure distributions during walking were collected using a 1000 element piezoceramic pressure platform from the feet of 45 subjects (30 classified as having the MFS and 15 non-Morton or control subjects). The protrusion of the head of the second metatarsal beyond the first metatarsal head was determined by palpation and varied between 0.8 and 2.8 cm for the experimental group. Pressure distributions were collected from a mid-gait step onto the platform at a speed of 1.6 to 2 m.s-1 using a 15 m runway. Peak pressures and impulse values were determined for three forefoot regions. Results show that peak loading in both groups occurred under the second metatarsal but that the magnitudes of second metatarsal peak pressures were significantly higher in the MFS group (P less than 0.005). The results suggest that, although the loading pattern between MFS and normal feet is similar, the significantly higher second metatarsal head peak pressure in the MFS may predispose this foot type to problems associated with excessive localized pressure.

Adult↗
PubMed1989

Stride length in distance running: velocity, body dimensions, and added mass effects.

The preferred stride frequency (SF) and stride length (SL) of male recreational distance runners were measured on a level treadmill under a variety of conditions over the typical distance running speed range of 3.15-4.12 m.s-1. At a given speed, the correlation coefficients between the subjects' anthropometric variables (APV) (such as stature, leg length, and limb segment mass) and their preferred stride variables were consistently low (less than or equal to 0.36) and not significantly different from zero. As speed increased through the experimental range, SF remained nearly constant (only a 4% increase) while SL increased by 28%. The use of dimensionless velocity was shown to be no more effective than conventional methods in the prediction of a SL vs velocity relationship, but the dimensionless form of the relationship was remarkably similar to those observed for other animal species and other forms of gait. The addition of masses up to 1.1 kg at each ankle produced no significant change in SF or SL. The results indicate that factors other than APV are the primary determinants of preferred SF and SL. Since it has been shown previously that the preferred SL is usually the most economical, APV cannot be used to accurately predict or prescribe SF or SL on an individual basis.

Adolescent↗
PubMed1988

Risk factors in the diabetic foot. Recognition and management.

The most frequently reported diabetic foot complication is plantar ulceration. Neuropathic fractures occur less often than plantar ulcers but usually result in major structural deformities of the feet. The primary risk factors for plantar ulceration are believed to be loss of protective sensation and the presence of high plantar pressures. Principal etiologic factors in the development of neuropathic fractures are hypothesized to be loss of protective sensation and bone demineralization. Major diabetic foot injuries are preventable by the use of comprehensive screening examinations and patient education. Patients at highest risk of injury should be seen more frequently and receive more extensive therapy. Successful management of plantar ulcerations is dependent on reduction of pressures under the foot and control of infection. Neuropathic fractures require long-term immobilization to promote healing followed by careful monitoring after removal of casts to prevent reinjury. Future research needs include prospective studies on risk factors and validation of treatment techniques.

Autonomic Nervous System Diseases↗
PubMed1987

The arch index: a useful measure from footprints.

Previous methods of measuring footprints for the purpose of classifying foot type are reviewed. A planimetric method is presented for characterizing footprints using the ratio of the area of the middle third of the footprint to the entire footprint area (excluding the toes). This 'arch index' during 50% body weight standing provides an objective measure for comparative purposes with a measured reliability, within day and between day, of 0.96 and 0.94 respectively. Values measured from footprints taken during other activities show variable responses in different subjects. Examples of the arch index taken from static footprints of various feet are presented and data are reported from 107 randomly selected subjects during half body weight stance. Criteria are suggested for the classification of footprints as high, normal, and flat arch.

Anthropometry↗
PubMed1987

Biomechanical studies of elite female distance runners.

The experiments showed the elite women runners to be predominantly midfoot strikers. Their ground reaction forces showed peaks of 3.3 times body weight in the vertical component, 0.8 times body weight in the braking phase, and 0.3 times body weight in the mediolateral direction. The asymmetry in their ground reaction forces was expressed mainly in the mediolateral component. Only minor differences were found between ground reaction forces in racing and training shoes. More abduction during foot placement was associated with greater rearfoot motion and with greater change in mediolateral component of velocity. Among the numerous moderate to high correlations of interest were those between vertical oscillation and peak vertical force, crossover and change in mediolateral velocity, and between movements of the swing leg and mediolateral force values. There were very few correlations between running economy and biomechanical variables, and stride length correlated poorly with stature. The elite runners were shorter in stature, lighter, had shorter legs and considerably less iliac crest fat than a typical non-athletic female population. The runners also had narrower pelves than a student population of similar age. They were reasonably homogeneous and symmetrical in anthropometric dimensions. Compared with a group of elite male runners at the same running velocity, the elite women exhibited more hip flexion, greater angular velocities in hip flexion and extension, and longer stride lengths relative to leg length during running. Their vertical oscillation (expressed relative to leg length) was less than that shown by their male counterparts. On the issue of relative pelvic width, the women had greater relative bitrochanteric and bi-iliac crest widths but similar bispinous widths compared to the elite male runners (all values expressed relative to leg length). Clearly the issue of male-female pelvic width differences at the elite level is not as simple as had previously been suggested.

Adult↗
PubMed1987

Relationship between distance running mechanics, running economy, and performance.

The relationships between biocmechanical aspects of distance running, running economy (VO2 submax), and performance were investigated. A variety of biomechanical measures for 31 subjects running at 3.6 m/s was obtained, including three-dimensional angular and translational kinematics, ground reaction forces and center of pressure patterns, mechanical power, and anthropometric measures. Physiological measures obtained included maximal and submaximal O2 consumption, muscle fiber composition, and measures of the ability to store and return elastic energy during knee bends. A subset of 16 runners was also evaluated in relation to performance in a 10-km run. Biomechanical variables were identified which showed significant differences or consistent trends between groups separated on the basis of VO2 submax, establishing the importance of biomechanical influences on running economy. It appears that no single variable or small subset of variables can explain differences in economy between individuals but rather that economy is related to a weighted sum of the influences of many variables.

Aerobiosis↗