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OBJECTIVE--The purpose of this study was to determine whether custom insoles tailored to contours of the barefoot pressure distribution and shape of a patient's foot can reduce plantar pressures in [...]

OBJECTIVE--Using the common-sense model of illness behavior, we developed and validated a self-report instrument for assessment of patients' cognitive and emotional representations of diabetic peripheral neuropathy (DPN) influencing foot self-care. [...]

OBJECTIVE--We examined the association between severity of diabetic peripheral neuropathy and depressive symptoms and investigated the potential mediators of this association. RESEARCH DESIGN AND METHODS--The Hospital Anxiety and Depression Scale [...]

OBJECTIVE--The aim of this study was to quantify the association between claw/hammer toe deformity and changes in submetatarsal head (sub-MTH) fat-pad geometry in diabetic neuropathic feet. RESEARCH DESIGN AND METHODS--Thirteen [...]

OBJECTIVE -- The objectives of this study were to compare intrinsic foot muscle cross-sectional area (CSA) in patients with diabetic polyneuropathy and nondiabetic control subjects and to examine the association [...]

This article analyzes the differences in men and women's foot shapes, finding that men have broader and longer feet than women for their stature. Results show that women's feet and legs have different shape characteristics than men's, especially in the arch, the first toe, the lateral side, and the ball of the foot, which should be considered when designing sports shoes for women.

Key factors associated with difficulty and safety on stairs are defined in this review article. Study findings reported in the literature are interpreted in the light of possible interventions that could increase stair safety. Locomotion on stairs is one of the most hazardous and challenging things that older people do on a daily basis with falls on stairs accounting for 10%+ of fatal fall accidents. The cardiovascular and muskuloskeletal systems are called upon by need for input from the visual, somatosensory, and vestibular systems at various task stages.

People with injuries often experience lower-extremity pain and weakness during weight-bearing activities, which often leads rehabilition specialists to avoid weight-bearing activities when designing therapeutic exercise programs for their patients. Instead, [...], Background and Purpose. Harness-supported treadmill ambulation has been advocated for patients to provide reduction in weight bearing to healing tissues and to reduce the energy cost of treadmill ambulation. The purposes of this technical report are to analyze the ability of one of these devices (Zuni Exercise System) to support a specific percentage of a subject's body weight during walking and running and to explore the relationship of unloading to pressure reduction in selected plantar surface regions of the foot. Subjects. Ten male volunteers with no known foot pathology participated. Methods. In-shoe plantar pressure and vertical ground reaction forces (GRFs) were measured during walking and running at full body weight and at 20% of body weight supported. Results. Walking at a setting of 20% of body weight supported resulted in a reduction of the first and second vertical force peaks of 23.8% (SD=7.3%) and 27.2% (SD=4.1%), respectively. The total force-time integral during walking unloaded was (SD=3.3%). During running, the active vertical force peak and total force-time integral were reduced by 19.9% (SD-4.1%) and 20.0% (SD=3.3%), respectively, in the unloaded condition. Plantar pressures were reduced from 6.8% to 27.8% in the body weight-supported conditions. The reduction was variable across different regions of the foot. Conclusion and Discussion. The Zuni Exercise System appears to reduce the vertical component of the GRF during walking and running with 20% of body weight supported. Plantar pressures were reduced during body weight-supported conditions, but the reduction varied at different regions of the foot. [Flynn TW, Canavan PK, Cavanagh PR, Chiang J-H. Plantar pressure reduction in an incremental weight-bearing system. Phys Ther. 1997:410-416.]

Some specific behaviors used by older adults while ascending and descending stairs and to assess the relationships between confidence and stair performance are examined. It was observed that confidence related to stair performance played an important role in determining risk-taking propensity during stair use in older adults.

The value of cultures in the management of mild diabetic foot cellulitis has not been clearly determined. Since the microbiologic etiology is reasonably predictable, a culture might not provide clinically [...]

Response to Tan et al. We read with some interest the commentary by Tan et al. (1) on the management of the Charcot foot in diabetes. While we agree entirely [...]

Although the benefits of total contact casting for healing plantar neuropathic ulcers are consistent throughout a large body of available literature, the method of cast application varies (1-17). Cast structure [...]

In a guest editorial for the Summer 2004 issue of The Diabetic Foot (Vol 7, No 2, pages 60-64) I identified a number of areas in the screening and prevention [...]

Some thought leaders believe that we are about to leave the era of evidence-based medicine and enter the uncharted waters of genome-based medicine (Guttmacher and Collins, 2003). Although the first [...]

Foot loading rate, load magnitude, and the presence of diseases such as diabetes can all affect the mechanical properties of the plantar soft tissues of the human foot. The hydraulic plantar soft tissue reducer instrument was designed to gain insight into which variables are the most significant in determining these properties. It was used with gated magnetic resonance imaging to capture three-dimensional images of feet under dynamic loading conditions. Custom electronics controlled by LabVIEW software simultaneously recorded system pressure, which was then translated to applied force values based on calibration curves. Data were collected for two subjects, one without diabetes (Subject A) and one with diabetes (Subject B). For a 0.2-Hz loading rate, and strains 0.16, 0.18, 0.20, and 0.22, Subject A’s average tangential heel pad stiffness was 10 N/mm and Subject B’s was 24 N/mm. Maximum test loads were approximately 200 N. Loading rate and load magnitude limitations (both were lower than physiologic values) will continue to be addressed in the next version of the instrument. However, the current hydraulic plantar soft tissue reducer did produce a data set for healthy versus diabetic tissue stiffness that agrees with previous trends. These data are also being used to improve finite element analysis models of the foot as part of a related project.

The dose-response effects of exercise in reduced gravity on musculoskeletal health have not been well documented. It is not known whether or not individualized exercise prescriptions can be effective in preventing the substantial loss in bone mineral density and muscle function that have been observed in space flight and in bed rest. In this study, typical daily loads to the lower extremities were quantified in free-living subjects who were then randomly assigned to control or exercise groups. Subjects were confined to 6-degree head-down bed rest for 84days. The exercise group performed individually prescribed 1g loaded locomotor exercise to replace their free-living daily load. Eleven subjects (5 exercise, 6 control) completed the protocol. Volumetric bone mineral density results from quantitative computed tomography demonstrated that control subjects lost significant amounts of bone in the intertrochanteric and total hip regions (p<0.0125), whereas the exercise group showed no significant change from baseline in any region (p>0.0125). Pre-and post-bed rest muscle volumes were calculated from analysis of magnetic resonance imaging data. The exercise group retained a larger percentage of their total quadriceps and gastrocnemius muscle volume (−7.2%±5.9, −13.8%±6.1, respectively) than their control counterparts (−23.3%±5.9, −33.0±8.2, respectively; p<0.01). Both groups significantly lost strength in several measured activities (p<0.05). The declines in peak torque during repeated exertions of knee flexion and knee extension were significantly less in the exercise group than in the control group (p<0.05) but work done was not significantly different between groups (p>0.05). The decline in VO2maxwas 17%±18 in exercising subjects (p<0.05) and 31%±13 in control subjects (p=0.003; difference between groups was not significant p=0.26). Changes in blood and urine measures showed trends but no significant differences between groups (p>0.05). In summary, the decline in a number of important measures of musculoskeletal and cardiovascular health was attenuated but not eliminated by a subject-specific program of locomotor exercise designed to replace daily load accumulated during free living. We conclude that single daily bouts of exposure to locomotor exercise can play a role in a countermeasures program during bed rest, and perhaps space flight, but are not sufficient in their own right to ensure musculoskeletal or cardiovascular health.

Changes in the mechanical properties of the plantar soft tissue in people with diabetes may contribute to the formation of plantar ulcers. Such ulcers have been shown to be in the causal pathway for lower extremity amputation. The hydraulic plantar soft tissue reducer (HyPSTER) was designed to measure in vivo, rate-dependent plantar soft tissue compressive force and three-dimensional deformations to help understand, predict, and prevent ulcer formation. These patient-specific values can then be used in an inverse finite element analysis to determine tissue moduli, and subsequently used in a foot model to show regions of high stress under a wide variety of loading conditions. The HyPSTER uses an actuator to drive a magnetic resonance imaging–compatible hydraulic loading platform. Pressure and actuator position were synchronized with gated magnetic resonance imaging acquisition. Achievable loading rates were slower than those found in normal walking because of a water-hammer effect (pressure wave ringing) in the hydraulic system when the actuator direction was changed rapidly. The subsequent verification tests were, therefore, performed at 0.2 Hz. The unloaded displacement accuracy of the system was within 0.31%. Compliance, presumably in the system’s plastic components, caused a displacement loss of 5.7 mm during a 20-mm actuator test at 1354 N. This was accounted for with a target to actual calibration curve. The positional accuracy of the HyPSTER during loaded displacement verification tests from 3 to 9 mm against a silicone backstop was 95.9% with a precision of 98.7%. The HyPSTER generated minimal artifact in the magnetic resonance imaging scanner. Careful analysis of the synchronization of the HyPSTER and the magnetic resonance imaging scanner was performed. With some limitations, the HyPSTER provided key functionality in measuring dynamic, patient-specific plantar soft tissue mechanical properties.

Introduction: Humans will eventually return to the Moon and thus there is a need for a ground-based analogue to enable the study of physiological adaptations to lunar gravity. An important unanswered question is whether or not living on the lunar surface will provide adequate loading of the musculoskeletal system to prevent or attenuate the bone loss that is seen in microgravity. Previous simulations have involved tilting subjects to an approximately 9.5° angle to achieve a lunar gravity com-ponent parallel to the long-axis of the body. However, subjects in these earlier simulations were not weight-bearing, and thus these protocols did not provide an analogue for load on the musculoskeletal system. Methods: We present a novel analogue which includes the capability to simulate standing and sitting in a lunar loading environment. A bed ori-ented at a 9.5° angle was mounted on six linear bearings and was free to travel with one degree of freedom along rails. This allowed approximately 1/6 body weight loading of the feet during standing. "Lunar" sitting was also successfully simulated. Results: A feasibility study dem-onstrated that the analogue was tolerated by subjects for 6 d of continu-ous bed rest and that the reaction forces at the feet during periods of standing were a reasonable simulation of lunar standing. During the 6 d, mean change in the volume of the quadriceps muscles was -1.6% ± 1.7%. Discussion: The proposed analogue would appear to be an acceptable simulation of lunar gravity and deserves further exploration in studies of longer duration. [ABSTRACT FROM AUTHOR]

Introduction: Human activity monitoring is a useful too! in medical monitoring, military applications, athletic coaching, and home healthcare. We propose the use of an accelerometer-based system to track crewmember activity during space missions in reduced gravity environments. It is unclear how the partial gravity environment of the Moon or Mars will affect human locomotion. Here we test a novel analogue of lunar gravity in combination with a custom wireless activity tracking system. Methods: A noninvasive wireless accelerometer-based sensor system, the activity tracking device (ATD), was developed. The system has two sensor units; one footwear-mounted and the other waistmounted near the midlower back. Subjects (N = 16) were recruited to test the system in the enhanced Zero Gravity Locomotion Simulator (eZLS) at NASA Glenn Research Center. Data were used to develop an artificial neural network for activity recognition. Results: The eZLS demonstrated the ability to replicate reduced gravity environments. There was a 98°! agreement between the ATD and force plate-derived stride times during running (9.7 km h-1) at both 1 g and 1/6 g. A neural network was designed and successfully trained to identify lunar walking, running, hopping, and loping from ATD measurements with 100% accuracy. Discussion: The eZLS is a suitable tool for examining locomotor activity at simulated lunar gravity. The accelerometer-based ATD system is capable of monitoring human activity and may be suitable for use during remote, long-duration space missions. A neural network has been developed to use data from the ATD to aid in remote activity monitoring. [ABSTRACT FROM AUTHOR]

Retrospective and prospective studies have shown that elevated plantar pressure is a causative factor in the development of many plantar ulcers in diabetic patients and that ulceration is often a precursor of lower-extremity amputation. Herein, we review the evidence that relieving areas of elevated plantar pressure (off-loading) can prevent and heal plantar ulceration.

Retrospective and prospective studies have shown that elevated plantar pressure is a causative factor in the development of many plantar ulcers in diabetic patients and that ulceration is often a precursor of lower-extremity amputation. Herein, we review the evidence that relieving areas of elevated plantar pressure (off-loading) can prevent and heal plantar ulceration.There is no consensus in the literature concerning the role of off-loading through footwear in the primary or secondary prevention of ulcers. This is likely due to the diversity of intervention and control conditions tested, the lack of information about off-loading efficacy of the footwear used, and the absence of a target pressure threshold for off-loading. Uncomplicated plantar ulcers should heal in 6 to 8 weeks with adequate off-loading. Total-contact casts and other nonremovable devices are most effective because they eliminate the problem of nonadherence to recommendations for using a removable device. Conventional or standard therapeutic footwear is not effective in ulcer healing. Recent US and European surveys show that there is a large discrepancy between guidelines and clinical practice in off-loading diabetic foot ulcers. Many clinics continue to use methods that are known to be ineffective or that have not been proved to be effective while ignoring methods that have demonstrated efficacy.A variety of strategies are proposed to address this situation, notably the adoption and implementation of recently established international guidelines, which are evidence based and specific, by professional societies in the United States and Europe. Such an approach would improve the often poor current expectations for healing diabetic plantar ulcers. (J Am Podiatr Med Assoc 100(5): 360–368, 2010)

Introduction: Decrements in muscular strength during long-duration missions in space could be mission-critical during construction and exploration activities. The purpose of this study was to quantify changes in muscle volume, strength, and endurance of crewmembers on the International Space Station (ISS) in the context of new measurements of loading during exercise countermeasures. Methods: Strength and muscle volumes were measured from four male ISS crewmembers (49.5 ± 4.7 yr. 179.3 ± 7.1 cm, 85.2 ± 10.4 kg) before and after long-duration spaceflight (181 ± 15 d). Preflight and in-flight measurements of forces between foot and shoe allowed comparisons of loading from 1-g exercise and exercise countermeasures on SS. Results: Muscle volume change was greater in the calf (-10 to 16%) than the thigh (-4% to -7%), but there was no change in the upper arm (+0.4 to -0.8%). Isometric and isokinetic strength changes at the knee (range -10.4 to -24.1%,), ankle (range -4 to -22.3%), and elbow (range -7.5 to -16.7%) were observed. Although there was an overall postflight decline in total work (-14%) during the endurance test, an increase in postflight resistance to fatigue was observed. The peak in-shoe forces during running and cycling on ISS were approximately 46% and 50% lower compared to 1 -g values. Discussion: Muscle volume and strength were decreased in the lower extremities of crewmembers during longduration spaceflight on ISS despite the use of exercise countermeasures. In-flight countermeasures were insufficient to replicate the daily mechanical loading experienced by the crewmembers before flight. Future exercise protocols need careful assessment both in terms of intensity and duration to maximize the "dose" of exercise and to increase loads compared to the measured levels. [ABSTRACT FROM AUTHOR]

Introduction: It has been hypothesized that bone loss arising from long-duration space travel is caused by a reduction in mechanical stimuli to the skeleton. The daily load stimulus (DLS) theory was first proposed to relate daily time histories of mechanical loading from ground reaction forces to bone homeostasis. In this methods paper, an enhanced daily load stimulus (EDLS) is proposed to account for recently developed theories on saturation and recovery of the osteogenic potential of bone with repeated cyclic loading and the potential benefits of standing. Model Development: To determine periods of continuous activity (sitting, standing, walking, running, and other activity), an activity determination algorithm based on entire days of in-shoe forces was developed. The rainflow peak counting method was used to analyze the in-shoe force data from entire working days in preparation for the calculation of the EDLS. Parameters characterizing saturation and recovery with cyclical loading from running and walking as well as the effects of standing were estimated based on data in the literature. Discussion: The activity algorithm proved to he accurate and robust when applied to in-shoe force data from entire waking days. The EDLS may be useful in prescribing "dose-based" exercise prescriptions to crewmembers during longduration spaceflights and missions to the Moon and Mars. Validation of the proposed EDLS model will be possible with data from an ongoing human bed rest study examining changes in bone mineral density with controlled skeletal loading. [ABSTRACT FROM AUTHOR]

Introduction: Loss in bone mineral density and muscle strength in astronauts following long-duration spaceflight have been well documented, but the altered force and movement environments in microgravity which may contribute to these changes have not been well characterized. This paper describes the instrumentation, software, and data collection procedures developed for the "Foot" experiment that was conducted on the International Space Station (ISS) to provide insight into the biomechanics of daily activity in a microgravity environment. Methods: The instrumentation used for data collection included the Ambulatory Data Acquisition System (ADAS), ADAS electromyography (EMG) modules, the Joint Excursion System, and the Total Force-Foot Ground Interface system, which were all integrated into a specially designed Lower Extremity Monitoring Suit. There were 14 total channels of data that were collected at sampling rates between 8 Hz and 1024 Hz, including 7 channels of EMG, 4 channels of joint angle data, 2 channels of in-shoe ground reaction force, and a marker channel for event recording. Data were typically collected for between 6.5 and 11.8 h of activity during 4 d on Earth and 4-7 d in flight. Results: Exemplar data sets collected preflight on astronauts in 1 g to validate the instrumentation are presented. Discussion: We conclude that the system provides valid and useful biomechanical information on long-term activity. The analysis of data collected on-orbit using the system described here will be presented in a series of future papers characterizing the biomechanics of astronaut activity during complete working days on the Earth and on the ISS. [ABSTRACT FROM AUTHOR]

Biomechanical issues are now widely recognized as being important in the treatment of diabetic foot disease. The purpose of the present review is to identify advances that have occurred since the previous International Conference on the Diabetic Foot in 1995 in the understanding of foot biomechanics in relation to diabetes. Attention continues to be focused on the identification of a threshold plantar pressure that leads to tissue damage. Recent studies have suggested that peak barefoot pressure may be only 65% specific for the development of ulceration. The association between foot deformity and plantar pressure has been the subject of several quantitative studies, but new questions have been raised about the etiology of claw toes. The measurement of shear stress continues to be an elusive goal although several small studies have presented possibly feasible technical approaches. The importance of callus as a precursor to ulceration has been confirmed experimentally and quantitative measures of motor neuropathy have been presented. Although a number of new devices have been introduced as alternatives to the Total Contact Cast, few clinical studies of their efficacy are available yet. New information on the properties of insole materials has been published including data on changes with repeated cycling. Complications of prophylactic surgery have been shown to include a high rate of Charcot fractures. Two new series describing the fixation of such fractures have also been reported. Biomechanical issues have also been addressed in two sets of guidelines for treatment that have recently been published. These many studies confirm the central role of mechanical stress and its relief in the treatment of neuropathic foot problems in diabetes. Copyright © 2000 John Wiley & Sons, Ltd.

The elderly are at particular risk for stair related accidents due to the prevalence of age related functional declines in the visual, somatosensory and vestibular systems. Certain architectural features of some staircases may further magnify these age-dependent intrinsic risk factors. Altered visual conditions such as the use of bifocals or inadequate lighting may result in altered strategies used during stair descent. The purpose of this study was to examine strategies used to safely negotiate stairs in altered visual conditions (bifocals and low ambient lighting). The dependent variables examined were the ground reaction force profiles and the required coefficient of friction during stair descent.

Panmetatarsal head resection (variously called forefoot arthroplasty, forefoot resection arthroplasty, the Hoffman procedure, and the Fowler procedure) was developed for the relief of pain and deformity in rheumatoid arthritis. Although there are successful retrospective series reported in the literature, such an approach is not supported by carefully designed controlled trials. This procedure has also been advocated by some for the relief of plantar pressure in diabetic patients who are at risk for plantar ulceration. The efficacy of the procedure in this context is not supported by existing pressure measurements on rheumatoid arthritis patients in the literature, which has tended to show that although pain relief is obtained, the procedure results in elevation of forefoot pressure. Case reports are described of two patients (three feet) with sensory neuropathy who presented to our clinic 1 to 2 years after panmetatarsal head resections had been performed. Peak plantar pressures in these feet during first step gait were above the 99th percentile and outside the measuring range of the device used (EMED SF platform; NOVEL Electronics Inc., St. Paul, MN). Both patients had also experienced plantar ulcers subsequent to the surgery. Combining the information on patients with rheumatoid arthritis (RA) with that from our two case studies, we conclude that panmetatarsal head resection does not necessarily eliminate focal regions of elevated plantar pressure.

Pressures on the plantar surface of the foot during activities of daily living were measured in 12 young, healthy subjects using an in-shoe pressure-measuring device. The tasks chosen were standing, slow and fast walking, slow running, walking up and down stairs, rising from and sitting in a chair, and walking in a circle. All except the sitting tasks showed significantly higher pressures in all regions of the foot compared with standing, with the exception of walking up stairs and walking down stairs in the heel region. Both running and walking in a circle led to higher pressures (up to 1.42 times greater) in the total foot compared with “normal” walking. Furthermore, pressures during other activities were not always well predicted by walking pressures (r2= 0.10–0.77). Therefore, measurement during level walking alone cannot be considered to fully define the plantar pressure affecting a foot in a particular shoe during activities of daily life.

Although the total contact cast (TCC) has been shown to be an extremely effective treatment for the healing of plantar ulcers in diabetic patients, little is known about the biomechanics of its action. In this study, plantar pressure and ground reaction force measurements were obtained from over 750 foot contacts as five subjects with known elevated plantar forefoot pressures walked barefoot, in a padded cast shoe, and a TCC. Peak plantar pressures in the forefoot were markedly reduced in the cast compared with both barefoot and shoe walking (reductions of 75% and 86% respectively, P< 0.05). Peak plantar pressures in the heel were not, however, significantly different between the shoe and the TCC, and the longer duration of heel loading resulted in an impulse that was more than twice as great in the cast compared with the shoe (P< 0.05). An analysis of load distribution indicated that the mechanisms by which the TCC achieves forefoot unloading are (1) transfer of approximately 30% of the load from the leg directly to the cast wall, (2) greater proportionate load sharing by the heel, and (3) removal of a load-bearing surface from the metatarsal heads because of the “cavity” created by the soft foam covering the forefoot. These results point out some of the “essential design features” of the TCC (which are different from what had been previously supposed), support the use of the TCC for healing plantar ulcers in the forefoot, but raise questions about its utility in the healing of plantar ulcers on the heel.

The effects of changes in speed and resistance setting on the bilateral symmetry of work output on the bicycle ergometer were studied. The cranks of a Monarch bicycle ergometer were instrumented with foil strain gauges and the bridge outputs were integrated on-line and analyzed by a program running in a Hewlett Packard 2115A computer. Twenty male subjects performed three thirty-second trials at each of nine speed and resistance combinations. Indices of asymmetry from 66-178 were found using kicking dominance (n20) and 56-135 using a strength dominance classification (n13). Day to day reliability of the index of asymmetry was found to be only 0.47; within day reliability was 0.87 for day one and 0.79 for day two. No significant effects for speed or resistance changes were shown on either day for the strength dominant subjects. When kicking dominance was considered, main effects were encountered on both days for speed although there was no clear directional trend. The findings of these experiments have important implications for studies where measurements are made on the lower extremity during cycle ergometer exercise, and for competitive cyclists engaged in endurance competition.

This paper reviews specific examples of how energy expenditure during submaximal exercise is affected by mechanical and muscular factors. Structural biomechanical variables are discussed as a possible reason for economy differences between individuals. The practical question, “Can economy of performing a certain task be modified?” is posed. Examples of how the manipulation of a particular movement pattern results in an energetic minimum (optimal phenomena) are presented. The physiological mechanisms for these phenomena are summarized. The influence of positive vs negative work and storage of elastic energy in relation to the topic of economy and muscular efficiency is considered. The effects of athletic equipment such as footwear, track surfaces, and bicycle components on economy and muscular efficiency are presented. The prospects for improving athletic performance by improving economy are evaluated, and recommendations for future directions are made.

This paper is an introduction to a multidisciplinary series of papers on the efficiency of human movement. The problem is posed by citing the example of the large variation in oxygen uptake (per kg body weight) within a typical group of subjects running at the same submaximal speed. An analog of the possible causes of this variation is presented where “set points” for biomechanical, physiological, psychological, biochemical, and other factors combine in series to influence the overall energy cost. The various definitions of “efficiency” and “economy” are considered at the whole body and the isolated muscle level, and a discussion of baseline subtraction is presented. The concept of “effectiveness” is reviewed to illustrate the interaction of skilled performance and energy cost. It is recommended that the terms “muscular efficiency,” “muscle efficiency,” “economy,” and “effectiveness” be used in their respective contexts to replace the current diversity of overlapping and, at times, confusing terminology.

The upward drift in oxygen uptake (UDO) that occurs during some prolonged sub-maximal exercises involving eccentric muscle action has received only scant attention in the literature. Those papers reporting UDO have generally used bicycling on an ergometer modified for eccentric exercise as the experimental activity. The purpose of this study was to quantify and propose an explanation for UDO during a different activity involving eccentric muscle action—downhill running. Oxygen consumption, quadriceps muscle electromyography, and stride length were collected from 10 experienced male runners (mean maximal oxygen consumption = 65.0 ± 5.2 ml·kg·min−1) during two 40-min sub-maximal runs at 3.83 m·s−1. The first run was on a level grade and required 66 of the subjects' mean maximal oxygen consumption. The second run, completed 2 d later, was performed on a 10 downhill grade and elicited 44 of the mean maximal oxygen consumption. Results of the level run showed non-significant changes in oxygen consumption, rectified integrated electromyography, and stride length between minutes 10 and 40. Significant (P< 0.05) increases in oxygen consumption (10) and integrated electromyography (23) were found across the same time period of the downhill run. No significant changes in downhill stride length were observed. Delayed-onset muscle soreness, a presumed indication of muscle damage, occurred only following the downhill run. It is hypothesized that UDO and increasing integrated electromyography during downhill running reflected increased motor unit recruitment within the eccentrically acting muscles caused by an ongoing combination of muscle damage, connective tissue damage, and local muscle fatigue.

ABSTRACT

CAVANAGH, PETER R. and KEITH R. WILLIAMS. The effect of stride length variation on oxygen uptake during distance running. Med. Sci. Sports Exercise,Vol. 14, No. 1, pp. 30–35, 1982. Ten recreational runners (mean VO2max) 64.7 ml.kg-1.min-1) underwent a 5-d acclimation period to treadmill running at a 7 min.mile-1pace (3.83 m.s-1) for 30 min each day. During these runs their freely chosen stride lengths were determined and expressed as a percentage of leg length (LL). On two subsequent testing days stride length was systematically varied over a range of ± 20 LL about the freely chosen value. O2uptake was determined by the Douglas Bag method. All subjects exhibited a stride length at which O2uptake was minimized, although the individual profiles varied considerably. The mean increases in VO2were 2.6 and 3.4 ml.kg-1.min-1at the short-and long-stride length extremes, respectively. During unrestricted running deviations from optimal stride length caused a mean increase in VO2of 0.2 ml.kg-1.min-1. The relatively efficient running patterns used by the subjects during unrestricted running indicate either an adaption to the chosen stride length through training or a successful process of energy optimization.

Running technique and economy (VO2submax) were examined before and after a 6-wk period of running training. Fifteen males were filmed and performed 10-min economy runs at 3.36 m·s-1on a treadmill. An incremental treadmill test was used to record running performance and maximal oxygen consumption (VO2max). Subjects were randomly assigned to a training group and a control group that did not participate in any running program. There were no significant changes in kinematic variables between pre- and post-training tests for either group. Neither were there any significant physiological changes over the 6 wk in the control group. However, the training group demonstrated a significantly (P< 0.01) increasedVO2max(57.7 ± 6.2 vs 61.3 ± 6.3 ml·kg-1·min-1) and running performance.VO2submaxin the training group was significantly (P< 0.05) worse (41.0 ± 4.5 vs 42.4 ± 4.3 ml·kg-1·min-1) post-training, although the percent utilization of VO2max(71.6 ± 7.9 vs 69.3 ± 6.9%) and submaximal heart rate (169 ± 15 vs 161 ± 15 beats·min-1) were significantly lower (P< 0.05). The training-induced improvements in running performance could be attributed to physiological rather than biomechanical modifications. There were no changes in biomechanical descriptors of running style that signaled changes in running economy.

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 (·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.

BUCZEK, F. L. and P. R. CAVANAGH. Stance phase knee and ankle kinematics and kinetics during level and downhill running. Med. Sci. Sports Exerc., Vol. 22, No. 5, pp. 669–677, 1990. 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−1level 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< 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.

Experiments to determine the effects of therapeutic shoe outsole modifications frequently require the examination of many different configurations and typically use in-shoe pressure measurement to determine the optimal design. A method is presented here to allow the foot-shoe interface to remain undisturbed as different outsole designs are used in the same patient. A standard extra-depth (or super extra-depth) shoe is modified to house three receptacles for quarter-turn fasteners in a carbon fiber plate. The fasteners pass through the outsole unit and secure it firmly to the plate. Results from a typical experiment are presented to illustrate the effectiveness of the approach. It is possible that a large clinic could use this approach in complex cases to assist with optimal footwear prescription.