Extremity Overuse Research Articles

The Effect of Environmental Temperature on the Shock Absorption Capacity of Running Shoes

0092 Various shock absorption systems (SAS) are used in contemporary running shoes to decrease lower extremity overuse injuries in runners. SAS typically include different polymeric materials with temperature sensitive biomechanical properties that may ultimately affect performance. PURPOSE: To determine the effect of temperature changes on the shock absorption capacity of four running shoes constructed with four different SAS. METHODS: Four brands of running shoes representing the most common SAS were chosen: Nike Air Triax (air-fllled units), Asics Gel Cumulus IV (gel-fllled units), Adidas Supernova (ethylene vinyl acetate or EVA), and Adidas A3 (polyurethane foam). One pair of each brand was tested (total of 4 pairs or 8 shoes). The shoes were frozen to −20° C using dry ice and gradually heated to +50° C in a portable incubator. Shoes were tested by an impactor following ASTM Standard F1614-99 at the following temperatures: −20°, −10°, 0°, +10°, +20°, +30°, +40°, +50° Celsius. The impact tester is a free-fall type impactor with instrumented force and position transducers. Output signals from both the force and position transducers were low-pass filtered at 500 Hz and sampled at 1500 Hz. From each data trial, the peak deceleration (G) was determined as an estimate of the shock absorption capacity. To assess the differences between the shoes, a repeated measures analysis of variance was used, the independent variables being the SAS and the temperature. RESULTS: There was a quadratic trend in the curves that differed between the shoe types (p< .001), indicating that for each SAS, the drop of the peak deceleration (G) with the increase of temperature was significant. There was also a significant overall difference when comparing the four different SAS over the temperature range. The polyurethane foam had much higher peak deceleration at cold temperatures than any of the other shoes tested. CONCLUSION: As the ambient temperature gets colder, the shock absorption capacity of the running shoes in the current study decreased. Temperature induced changes were most marked for the polyurethane foam SAS. These findings may have important clinical implications for individuals training in cold environments.

The Effect of Environmental Temperature on the Shock Absorption Capacity of Running Shoes

0092 Various shock absorption systems (SAS) are used in contemporary running shoes to decrease lower extremity overuse injuries in runners. SAS typically include different polymeric materials with temperature sensitive biomechanical properties that may ultimately affect performance. PURPOSE: To determine the effect of temperature changes on the shock absorption capacity of four running shoes constructed with four different SAS. METHODS: Four brands of running shoes representing the most common SAS were chosen: Nike Air Triax (air-fllled units), Asics Gel Cumulus IV (gel-fllled units), Adidas Supernova (ethylene vinyl acetate or EVA), and Adidas A3 (polyurethane foam). One pair of each brand was tested (total of 4 pairs or 8 shoes). The shoes were frozen to −20° C using dry ice and gradually heated to +50° C in a portable incubator. Shoes were tested by an impactor following ASTM Standard F1614-99 at the following temperatures: −20°, −10°, 0°, +10°, +20°, +30°, +40°, +50° Celsius. The impact tester is a free-fall type impactor with instrumented force and position transducers. Output signals from both the force and position transducers were low-pass filtered at 500 Hz and sampled at 1500 Hz. From each data trial, the peak deceleration (G) was determined as an estimate of the shock absorption capacity. To assess the differences between the shoes, a repeated measures analysis of variance was used, the independent variables being the SAS and the temperature. RESULTS: There was a quadratic trend in the curves that differed between the shoe types (p< .001), indicating that for each SAS, the drop of the peak deceleration (G) with the increase of temperature was significant. There was also a significant overall difference when comparing the four different SAS over the temperature range. The polyurethane foam had much higher peak deceleration at cold temperatures than any of the other shoes tested. CONCLUSION: As the ambient temperature gets colder, the shock absorption capacity of the running shoes in the current study decreased. Temperature induced changes were most marked for the polyurethane foam SAS. These findings may have important clinical implications for individuals training in cold environments.

EFFECT OF CUSTOM FOOT ORTHOTIC INTERVENTION ON 3-DIMENSIONAL LOWER EXTREMITY KINEMATICS AND KINETICS DURING RUNNING

It is generally accepted that custom foot orthoses (CFOs) are an effective therapeutic modality in the management of lower extremity overuse running injuries. This being said, there is very little known about how this intervention mechanically produces positive clinical outcomes. Several previous studies have included subjects who exhibit within normal limits (WNL) maximum ankle eversion angle and have shown that CFO intervention has minimal effects on lower extremity kinematics. These studies employed a variety of inserts not necessarily manufactured by an accredited laboratory or designed by Rootian convention. PURPOSE To compare 3-dimensional (3-D) ankle and knee kinematics and kinetics with and without CFO intervention in a group of female runners who exhibit WNL maximum ankle eversion. METHODS This study included 10 recreational and competitive runners who exhibited a maximum ankle eversion angle <10 degrees eversion. Subjects performed 5 overground running trials with and without CFOs. During each running trial, 3-D kinematics and kinetics were collected from which ankle and knee, joint angles and moments were calculated. Ankle and knee kinematics and kinetics were compared for with and without CFO conditions using t-tests (p < 0.05). RESULTS The maximum ankle and knee 3-D joint angles did not significantly differ with and without CFOs. In addition, there were no significant differences in ankle and knee 3-D moments with and without the intervention. CONCLUSION CFO intervention did not elicit any significant changes in the 3-D kinematics or kinetics in the current sample of female runners. Intuitively, this is what would be expected given runners who exhibit WNL ankle eversion are not typically candidates for foot orthotic therapy. The findings of the current study suggest that further research should include subjects who exhibit excessive ankle eversion and the question is raised as to whether more stringent inclusion criteria need to be employed when studying the effect of CFO intervention.

Isokinetic profile of elbow flexion and extension strength in elite junior tennis players.

Descriptive study. To determine whether bilateral differences exist in concentric elbow flexion and extension strength in elite junior tennis players. The repetitive nature of tennis frequently produces upper extremity overuse injuries. Prior research has identified tennis-specific strength adaptation in the dominant shoulder and distal upper extremity musculature of elite players. No previous study has addressed elbow flexion and extension strength. Thirty-eight elite junior tennis players were bilaterally tested for concentric elbow flexion and extension muscle performance on a Cybex 6000 isokinetic dynamometer at 90 degrees/s, 210 degrees/s, and 300 degrees/s. Repeated-measures ANOVAs were used to test for differences between extremities, muscle groups, and speed. Significantly greater (P<0.002) dominant-arm elbow extension peak torque values were measured at 90 degrees/s, 210 degrees/s, and 300 degrees/s for males. Significantly greater (P<0.002) dominant-arm single-repetition work values were also measured at 90 degrees/s and 210 degrees/s for males. No significant difference was measured between extremities in elbow flexion muscular performance in males and for elbow flexion or extension peak torque and single-repetition work values in females. No significant difference between extremities was measured in elbow flexion/extension strength ratios in females and significant differences between extremities in this ratio were only present at 210 degrees/s in males (P<0.002). These data indicate muscular adaptations around the dominant elbow in male elite junior tennis players but not females. These data have ramifications for clinicians rehabilitating upper extremity injuries in patients from this population.

Effects of injury proneness and task difficulty on joint kinetic variability.

The purpose was to investigate the effects of lower extremity overuse injury proneness and landing height on the variability of selected joint moment characteristics. Ten subjects from each of two groups (healthy and injury prone) performed 10 landings from a platform (heights: 50, 100, and 200% of maximum vertical jump). Force platform (1000 Hz) and video (200 Hz) information were collected and used to compute ankle, knee, and hip joint moment values during impact (0-100 ms post contact). Moment peak, time to peak, and impulse values were used to determine variability across 10 trials for each subject and height. MANOVAs and univariate follow-up tests were used to assess variability differences between groups and among heights. Results revealed ankle moment variability differences (P < or = 0.05; Tukey) between groups for peak and time to peak variables at the 100% and 50% heights, respectively. The injury-prone group exhibited greater variability for the peak variable, whereas the healthy group showed greater variability for the temporal variable. Groups also differed on the impulse variables (P < or = 0.02; MANOVA), but follow-up tests failed to determine specific joints or directions of differences. Both groups exhibited tendencies for greater variability (P < or = 0.05; Tukey) with increases in height up to 100% MVJ and decreases in variability with further height increases. Results suggest that groups differed in joint moment variability, possibly indicating a relationship between variability and overuse injuries, although the variables and directions of differences were inconsistent. For some variables, variability increased and then decreased with height increases for both groups, suggesting a range of heights within which the neuromuscular system adapted.

Evaluation of lower extremity overuse injury potential in runners.

The purpose of this study was to identify biomechanical and anthropometric variables that contribute to overuse injuries in runners. Comparisons were made between a group of runners who had sustained at least one overuse running injury and a group of runners who had been injury free throughout their running careers. Groups were well matched in important training variables. Synchronized kinetic and rearfoot kinematic variables of both feet were collected by filming subjects running over a force platform at a speed of 4 m x s(-1). The injury-free group demonstrated significantly greater posterior thigh (hamstring) flexibility, as measured by a standard sit and reach test. This was the only anthropometric variable in which the groups differed. Within each group, there were no significant differences between left and right foot landing for any biomechanical variable. Biomechanical variables that demonstrated significantly lower values for the injury free group were the vertical force impact peak and the maximal vertical loading rate, with the maximal rate of rearfoot pronation and the touchdown supination angle showing a trend toward being greater in the injury free group. These results suggest that runners who have developed stride patterns that incorporate relatively low levels of impact forces, and a moderately rapid rate of pronation are at a reduced risk of incurring overuse running injuries.

Biomechanical analysis of the effect of orthotic shoe inserts: a review of the literature.

Physical activity is increasingly recognised as an important component of primary disease prevention. Overuse injuries are common sequelae of exercise and sporting activities in general, and of running in particular, frequently resulting in cessation of activity. It has been proposed that there is a link between foot shape, foot function and the occurrence of injury. As a means of treatment and prevention of further injury, orthoses and shoe inserts are widely prescribed in the belief that they can alter the pattern of lower extremity joints' alignment and movement. Although this is an assumption widely made in the treatment of many joint conditions, the manner through which this treatment could be effective is not clear. This article aims to examine the literature to gain an improved understanding of the present state of knowledge regarding the effect of foot shape and orthotic use on foot kinematic and plantar pressure characteristics. The effects of foot type on the occurrence of lower limb injury during sporting activities and different aspects of biomechanics are reviewed, and the effects of applying orthoses on injury treatment and prevention and on various aspects of biomechanics of the lower limb joints are discussed. Further research is required, firstly to establish the casual effect of foot type and function on the risk of lower extremity overuse injury, and secondly to document the specific effect of orthotic therapy on injury treatment and prevention. Specifically, more prospective studies are necessary to investigate the long term effect of orthotic intervention.

The effect of foot structure and range of motion on musculoskeletal overuse injuries.

The purpose of this prospective study was to determine whether an association exists between foot structure and the development of musculoskeletal overuse injuries. The study group was a well-defined cohort of 449 trainees at the Naval Special Warfare Training Center in Coronado, California. Before beginning training, measurements were made of ankle motion, subtalar motion, and the static (standing) and dynamic (walking) characteristics of the foot arch. The subjects were tracked prospectively for injuries throughout training. We identified risk factors that predispose people to lower extremity overuse injuries. These risk factors include dynamic pes planus, pes cavus, restricted ankle dorsiflexion, and increased hindfoot inversion, all of which are subject to intervention and possible correction.

The Effect of Leg Strength on the Incidence of Lower Extremity Overuse Injuries during Military Training

This study examined the effects of strength, aerobic fitness, and activity profile on the incidence of overuse injuries, particularly stress fractures, during military training. A total of 136 military recruits were followed during 9 weeks of basic training. Maximal strength and aerobic fitness were determined by a one-repetition maximum leg press and a 2,000-m run, respectively. An activity profile was determined by the recruit's activity history. Twelve recruits (8.8%) were diagnosed with stress fractures. Recruits who were 1 SD below the population mean in both absolute (98.4 +/- 36.6 kg) and relative strength (1.72 +/- 0.61 kg/kg of body weight) had a five times greater risk for stress fracture (p < 0.05) than stronger recruits. Poor aerobic fitness did not appear to be related to any increased incidence of stress fracture. It appears that recruits with lower body strength levels, within 1 SD of the population mean, have a reduced incidence of stress fractures during military training.

The Role of Active Release Manual Therapy for Upper Extremity Overuse Syndromes—A Preliminary Report

The study was carried out to evaluate the efficacy of a specific protocol for treatment of overuse syndromes known as Active Release. This treatment protocol was taught to an athletic trainer who had six months experience before initiating a prospective study. Most of the 28 patients who were in the study had failed previous medical treatment for epicondylitis, tendonitis, and carpal tunnel. These patients refused to be randomized as to routine medical care. Results at one month and three months demonstrated a 71% efficacy rate, which when compared to similar studies in literature was superior. As a result of this study, recommendation of further use of this innovative technique is justified.

Lower extremity morphology and alignment and risk of overuse injury.

Lower extremity alignment factors, including tibiofemoral angle, quadriceps angle (Q-angle), and limb length discrepancies, are commonly thought to be clinically relevant as contributing factors to overuse injuries of the lower extremities. To explore the scientific rationale for these clinical beliefs, we conducted a review of the available English language literature from 1966 to July 1997 relating overuse injury to lower extremity alignment. MEDLINE was searched for medical subject headings and title key words to locate published works relating lower extremity morphologic characteristics to risk of overuse injury. Additional references were reviewed from reprint collections and reference lists of published work. Relevant studies were reviewed for strengths and weaknesses in design, analysis, and conclusions. Synthesis across studies concentrated on commonalities and differences of methods in definition of exposure and outcome variables. Six population-based studies have been conducted evaluating some aspect of lower extremity alignment as a risk factor for overuse injury. Three of these studies evaluated military recruits in basic training, two studied mixed groups of athletes and one studied folk dancers. The time frame across studies ranged from 12 weeks to 52 weeks. A key finding was the considerable variation in the measure of lower limb alignment used as the exposure variable, as well as the method of measurement used to quantify the exposure. Some studies relied on visual examination, whereas others used digitized photographic techniques. Moreover, each study varied in the definition used for overuse injury; outcomes ranged from self-reported cases of shin splints to radiographic confirmation of stress fracture. Five of the six studies evaluated some aspect of foot morphology, whereas only one evaluated full leg alignment parameters. Results were conflicting but, in general, did not support clinical beliefs of the detrimental effects of decreased longitudinal foot arch and varus tibiofemoral alignment as risk factors for lower extremity overuse injury. Differences in methodologic rigor and outcome definition prevent a meaningful synthesis of existing work. Directions for future research are suggested.

A familial predisposition toward lumbar disc injury.

A retrospective case-control study was performed. To test the hypothesis that there is a familial predisposition to lumbar disc pain and injury. The few studies that have addressed this question have suggested that a familial predisposition is present, but the techniques used for identifying discogenic pain and accounting for potentially confounding extrinsic factors make it difficult to formulate a clear conclusion. Immediate relatives of index patients who had surgically proven lumbar disc herniations (disc/case subjects) or repetitive upper extremity overuse syndromes (upper extremity/control subjects) were given a questionnaire that had been tested previously and found to reliably identify discogenic lower back pain. The prevalence of lumbar disc pain and injury was determined in the two groups of patients; logistic regression was used to control for demographic factors and activities known to increase risk for lumbar disc injury. The questionnaire was returned by 60 (59%) of 102 disc subjects and 41 (50%) of 81 upper extremity subjects. Sixteen (28%) disc subjects and one (2%) of the upper extremity subjects met questionnaire criteria for discogenic lumbar pain; seven (12%) disc subjects and no upper extremity subjects had received surgical therapy for lumbar disc pain. Logistic regression analysis identified familial grouping and a history of lifting as the only variables associated with a positive response on the questionnaire. Information obtained from index patients about their nonresponding relatives' history of significant back pain suggested similar findings. There is a familial predisposition toward lumbar disc pain and injury. This information may be helpful in occupational counseling or for targeting specific populations with preventative, interventional strategies.

ETIOLOGY AND PREVENTION OF LOWER EXTREMITY RUNNING INJURIES: A MULTI-DISCIPLINARY PERSPECTIVE 5

Many people run for a variety of reasons, e.g. pleasure, health, relaxation, as part of training for other sports, etc. However many runners sustain injuries of the lower extremity, the vast majority being of an overuse type. Reported incidences of overuse lower extremity running injuries vary from 24% to 77%. When exposure time is taken into account the incidences vary from 2.5 to 12.1 injuries per 1000 hours of running. In order to prevent such running injuries it is necessary to have knowledge of the etiological factors and the mechanisms that predispose and lead to injury. This knowledge can be gained from epidemiological studies. Also the outcome of biomechanical and clinical studies will add to our knowledge base. Finally when, based on this knowledge, attempts are made to prevent lower extremity overuse running injuries it is necessary to take health educational principles into account. When looking at the literature it appears that in order to prevent running injuries there is little exchange between the above mentioned fields of expertise; i.e. epidemiology, biomechanics, clinical medicine and health education. Purpose of this symposium is to bring together experts from these 4 different scientific domains in order to provide a multi disciplinary rationale for the prevention of lower extremity overuse running injuries.

Subtalar joint motion and the relationship to lower extremity overuse injuries.

The purpose of this study was to determine if there was a difference between the subtalar joint ratio (transverse plane component to frontal plane component) in subjects with overuse symptoms in the foot compared with subjects with overuse symptoms in the leg and knee. Superior and posterior photographs were taken with the subtalar joint in pronation and supination while the subjects were in a seated position. The ratio of the transverse plane to frontal plane components of subtalar joint motion was calculated. A significant (p < 0.05) difference in the subtalar joint ratio existed between subjects with foot overuse symptoms and subjects with leg and knee overuse symptoms.

LOW BACK PAIN IN COLLEGE ATHLETES: A PROSPECTIVE ANALYSIS 620

A prospective evaluation of the incidence of low back pain in college athletes was undertaken. Two hundred and fifty seven (257) college athletes representing 9 varsity sports were screened during the pre-season sports physical. Athletes were evaluated in 4 stations concentrating on a detailed evaluation of the lower extremities and back. Measures of flexibility, ligamentous stability. leg length discrepancy and overuse syndromes were recorded. Athletes were followed throughout the ensuing year for low back pain requiring treatment by the athletic trainer. Those athletes with low back pain as the result of direct trauma to the region were excluded from the data. Twenty-four athletes representing 9.3% of all athletes received treatment for low back pain. Thirteen out of 74 females representing 15% of female athletes compared with 11/170 males or 6% of male athletes required treatment for low back pain (p=.048). Of these athletes with lower extremity instability or overuse, 9/57 developed low back pain (p=0.58). Those athletes with lower extremity inflexibility or leg length discrepancies had no significant increase in low back pain. In conclusion, both female athletes and those athletes with lower extremity instability or overuse, may be at risk for the development of low back pain during athletic competition.

Measurement of tibiofibular varum in subjects with unilateral overuse symptoms.

Lower extremity overuse injuries due to repeated microtrauma are often asymmetrical in nature. The purpose of this study was to determine if the amount of tibiofibular varum was asymmetrical in individuals with unilateral overuse injuries. The subjects were 20 patients who developed unilateral overuse symptoms of the leg and foot due to compensatory subtalar joint pronation. The distal one-third of the leg was bisected with the subjects standing in their normal base of support. The angle of this bisection to vertical was measured with a fluid inclinometer to determine the amount of tibiofibular varum. This measurement was performed in relaxed calcaneal stance and subtalar joint neutral stance. A single examiner performed all of the measurements and was blinded to the side of the subject's symptoms. A two-way analysis of variance for repeated measures was performed. There was a significant difference in the amount of tibiofibular varum between the injured and the uninjured extremities. There was also a significant difference between the measurements of tibiofibular varum when comparing the resting calcaneal stance and the subtalar joint neutral stance positions. This difference in tibiofibular varum between the injured and uninjured extremities may be one example of an asymmetry that can cause unilateral overuse symptoms.

Rehabilitation of Shoulder and Elbow Injuries in Tennis Players

Optimization of treatment of the tennis player with an upper extremity overuse injury requires a thorough understanding and analysis of the biomechanical and physiologic stresses inherent in the game of tennis. Anatomic adaptations found in the upper extremity of elite tennis players provide the framework for evaluation and treatment of overuse injury through both an anatomically based total-arm strength program and efforts to normalize joint arthrokinematics. Integration of these key factors allows the clinician to rehabilitate the patient and design preventive conditioning programs in a scientifically based, sport-specific manner.

Cigarette Smoking, Physical Fitness, and Injuries in Infantry Soldiers

Reliable data on the impact of physical training on light infantry units in terms of injuries and time loss are sparse. This study evaluated a light infantry unit (n = 181) prospectively and followed it throughout one year of infantry training and operations. Fifty-five percent of the soldiers (n = 101) experienced one or more injuries. Eighty-eight percent of the injuries were training-related conditions, which resulted in 1,103 days of limited duty. Lower extremity overuse injuries were the most common type of injury documented. Fractures accounted for the greatest number of days of limited duty. Risk factors for training-related injuries identified by this study were cigarette smoking, high percentage of body fat, extremely high or low body mass index, low endurance levels, and low muscular endurance levels (sit-ups). Logistic regression showed that cigarette smoking and low endurance levels were independent risk factors for training injuries. These data indicate that the incidence of training-related injuries in infantry units is high. A number of modifiable injury risk factors were identified, suggesting that many of these injuries may be preventable.

Overuse Injuries of the Leg, Ankle, and Foot

A fundamental understanding of normal anatomy and biomechanics is necessary for the successful treatment of lower extremity overuse injuries. This article summarizes the mechanism of injury, pathophysiology, diagnosis, and rehabilitation of select overuse injuries of the leg, ankle, and foot.

Biomechanical factors associated with shoe/pedal interfaces. Implications for injury.

The principal demand on the body during cycling is on the lower extremities as they are responsible for producing a majority of the energy imparted to the bike. As a result the legs, due to high reactive forces between the foot and pedal, experience high loads on the joints. These loads may adversely affect joint tissues and contribute to overuse injuries, e.g. knee pain. The mechanical link between the leg and the bike is the shoe/pedal interface. This transmission site, by design, can either create smooth transfer of energy or abnormally high repetitive loads which are potentially injurious to the body. Incidence of lower extremity injury in cycling is high, and historically biomechanical analyses of this activity have focused their attention on either the rider or the bike, but not the link between the two. Recently, pedal designs have changed in response to complaints of sore knees with the development of pedals allowing varying degrees of float. This form of transmission is intended to enhance power transfer from rider to bike as well as minimise trauma to the legs by permitting the foot to rotate during the pedalling cycle in a toe-in/heel-out or heel-in/toe-out movement pattern. Recent evidence suggests this type of pedal design does reduce trauma and maintains power output. This article reviews common lower extremity overuse injuries and biomechanical factors during the pedalling cycle with the primary focus on the shoe/pedal interface. We will summarise information available on lower extremity kinematics and kinetics as well as recent data specifically related to shoe/pedal interface kinetics, evaluation of different pedal types-specifically comparison between clipless 'fixed' and clipless 'float' systems-and discuss their resultant effect on lower extremity dynamics and their implications for injury.