Barry T. Bates

Injuries to runners

overuse syndromes. While there is abundant literature which describes the etiology, symptoms and management of various injuries sustained by runners, there is limited information regarding the incidence and distribution of these injuries with respect to such variables as classification, site (anatomic) and competitive event (running). A knowledge of the relative incidence, treatment and results of treatment of injuries to runners should provide not only a basis for better management but also a probable basis for increased utilization of preventive measures and earlier recognition and treatment of these injuries.

Contributions of lower extremity joints to energy dissipation during landings.

PURPOSE The purpose of the study was to investigate changes in lower extremity joint energy absorption for different landing heights and landing techniques. METHODS Nine healthy, active male subjects volunteered to perform step-off landings from three different heights (0.32 m, 2.5 m(-s); 0.62 m, 3.5 m(-s); and 1.03 m, 4.5 m(-s)) using three different landing techniques (soft, SFL; normal, NML; and stiff landing, STL). Each subject initially performed five NML trials at 0.62 m to serve as a baseline condition and subsequently executed five trials in each of the nine test conditions (3 heights x 3 techniques). RESULTS The results demonstrated general increases in peak ground reaction forces, peak joint moments, and powers with increases in landing height and stiffness. The mean eccentric work was 0.52, 0.74, and 0.87 J x kg(-1) by the ankle muscles, and 0.94, 1.31, and 2.15 J x kg(-1) by the hip extensors, at 0.32, 0.62, and 1.03 m, respectively. The average eccentric work performed by the knee extensors was 1.21, 1.63, and 2.26 J x kg(-1) for the same three heights. CONCLUSIONS The knee joint extensors were consistent contributors to energy dissipation. The ankle plantarflexors contributed more in the STL landings, whereas the hip extensors were greater contributors during the SFL landings. Also a shift from ankle to hip strategy was observed as landing height increased.

The evaluation and prediction of impact forces during landings

The investigation of impact force attenuation during landings may help identify performance strategies. The purpose of the study was to evaluate the effects of height (three), distance (three), and technique (three) on impact forces during landings. Three male volunteer subjects were filmed while performing three right foot landings onto a force platform for each combination of height, distance, and technique for a total of 81 trials per subject. Between- and within-subject three-way ANOVAs and three regression models (mechanical, biomechanical, refined biomechanical) were computed on the dependent variables of first (F1) and second (F2) maximum vertical force. Results of the between-subject ANOVAs indicated significant (P less than 0.05) height, distance, and technique main effects for F1 and a height x technique interaction for F2. The within-subject ANOVA results identified unique models for each of the three subjects. The biomechanical regression model exhibited the best predictions of F1 and F2 for S1 (81.0 and 72.0% explained variance, respectively), while the refined biomechanical model accounted for 83.4, 81.3, 80.9, and 88.0% of the F1 and F2 variances for S2 and S3, respectively. In conclusion, the within-subject results identified unique individual landing strategies that were masked by the group analyses suggesting that caution be exercised in using between-subject analysis techniques.

Biomechanical factors associated with injury during landing in jump sports

SummaryMany sport and movement activities contain a jumping component which necessitates landing. Several injury surveys across a variety of jump sports have identified the lower extremities and specifically the knee joint as being a primary injury site. Factors which might contribute to the frequency and severity of such injuries include stresses to which the body is subjected during performance (forces and torques), body position at landing, performance execution and landing surface. Most of the initial landing studies were primarily descriptive in nature with many of the more recent efforts being directed toward identifying the specific performance factors that could account for the observed system stresses. Continued investigations into landing are necessary to more thoroughly understand the force attenuation mechanisms and critical performance variables associated with lower extremity injuries.

Relationship between selected static an dynamic lower extremity measures

Abstract Twenty-four non-symptomatic subjects were recruited for this study. They were evaluated for foot-type and selected static parameters to determine their influence on kinematic and kinetic variables measured during barefoot overground walking. Foot-type and lower extremity characteristics were examined through the measurement of arch index, range of motion measurements of the ankle, subtalar, first metatarsal and hip joints, and the measurement of the orientation of the calcaneus and tibia. Measurements collected during the support phase of the gait cycle included kinetic measures via a force platform, kinematic measures of the knee joint using a three-dimensional electrogoniometer and kinematic measures of the rearfoot angle using a high speed motion camera. Angle of gait and step parameters were also measured utilizing an inked paper track system. Using the static evaluation measures to predict dynamic gait resulted in significant canonical correlations between first ray mobility and rotational values at the knee, first ray mobility and anteroposterior ground reaction force variables, and static hip internal-external rotation with varus-vaigus motion at the knee. The results suggest that static lower extremity measures have limited value in predicting dynamic lower extremity function to any great degree.

Timing of lower extremity joint actions during treadmill running.

It has been suggested that a disruption in timing between the subtalar and knee joints may be a possible mechanism for knee injury. It has also been documented that shoe construction can alter rearfoot motion. The purpose of the study was to describe the relationship between the subtalar and knee joint actions during the support phase of treadmill running while wearing different shoes. Twelve healthy subjects ran in each of three running shoes with unique midsole durometers (C1, 70; C2, 55; C3, 45). High-speed video (200 Hz) of the rear and sagittal views of each subject/condition were taken during the last minute of a 5-min run. Retro-reflective markers were processed to determine the rearfoot angle and the sagittal view knee angle. The shoes were also subjected to a midsole material impact test. The impact test results indicated a linear trend in peak g and time to peak g across midsoles with the firmer midsole having a greater peak g and a shorter time to peak g. The results of the kinematic analysis indicated that there were no significant differences among the shoe conditions for the knee flexion parameters. However, there were significant differences in both the magnitude and the time to maximum pronation between the two firmer midsole conditions (C1 and C2) and the softer midsole condition (C3), indicating a nonlinear trend for these parameters. The softer midsole exhibited greater pronation values and a shorter time to maximum pronation.(ABSTRACT TRUNCATED AT 250 WORDS)

Single-subject methodology: an alternative approach

The purpose of this paper is to identify and discuss an alternative experimental methodology, single-subject (SS) design. The primary premise for SS analyses forms the basis for many research questions in areas such as movement/motor control, individual performance patterns/strategies, and injury mechanisms. A brief historical perspective elucidating the evolution of modern-day group statistical techniques and the relationship to the individual is presented. Rationale for the SS design within this context is also discussed. Specific statistical applications include mean comparison tests (ANOVA, Model Statistics), correlation, and multiple regression. Validation of the underlying statistical assumptions of independence and normality relative to the applications are briefly discussed. Finally, several examples are included.

Variations in ground reaction force parameters at different running speeds

Abstract Ground reaction forces are often used as a primary descriptive component in the analysis of the support phase of running. The purpose of this study was to investigate the changes in ground reaction force parameters during the support phase of the running stride at different running speeds. Ten skilled distance runners, who ran with a heel-toe football pattern at all running speeds, served as subjects. The experimental set-up consisted of a Kistler force platform interfaced to a Tektronix 4051 Graphics Calculator. Each subject performed 10 successful trials at each of 4 running speeds ranging from a sprint pace (7m/s) to a jogging pace (4m/s). Running speed was monitored by a photoelectric timing system. Data processing consisted of the evaluation of 19 descriptive variables of the relative ground reaction force-time curves for each of the 4 10-trial conditions. Ten vertical, 5 antero-posterior and 4 medio-lateral variables were used in the analysis. The relative force-time curves were generated using a cubic spline technique which transformed the absolute time events into 200 equally spaced data points to assist in making between speed comparisons. Separate multivariate analyses of variance with planned comparisons were carried out on each of the 3 relative data sets. Statistically significant differences were found for the relative ground reaction force parameters at the different running speeds ( p

The effect of trial size on statistical power.

Many research studies produce results that falsely support a null hypothesis due to a lack of statistical power. The purpose of this research was to demonstrate selected relationships between single subject (SS) and group analyses and the importance of data reliability (trial size) on results. A computer model was developed and used in conjunction with Monte Carlo procedures to study the effects of sample size (subjects and trials), within- and between-subject variability, and subject performance strategies on selected statistical evaluation procedures. The inherent advantages of the approach are control and replication. Selected results are presented in this paper. Group analyses on subjects using similar performance strategies identified 10, 5, and 3 trials for sample sizes of 5, 10, and 20, respectively, as necessary to achieve statistical power values greater than 90% for effect sizes equal to one standard deviation of the condition distribution. SS analyses produced results exhibiting considerably less power than the group results for corresponding trial sizes, indicating how much more difficult it is to detect significant differences using a SS design. These results should be of concern to all investigators especially when interpreting nonsignificant findings.

Asynchrony between subtalar and knee joint function during running

PURPOSE It has been suggested that during running proper coordination between subtalar joint pronation/supination and knee joint flexion/extension via tibial rotation is important to attenuate ground reaction impact forces (GRIF). Lack of coordination may produce over time a wide range of injuries. The goal of this study was to investigate the relationship between subtalar pronation/supination and knee flexion/extension with GRIF increases during distance running. METHODS Eight subjects ran under different speeds (a self-selected pace, 10% faster, 10% slower, and 20% faster) and over different obstacle heights (5%, 10%, and 15% of their standing height) on their self-selected pace. Sagittal, rear-view kinematic, and GRIF data were collected. The biomechanical results were also compared with data from a clinical evaluation of the subjects. RESULTS Speed changes and obstacle heights produced increases in GRIF and differences between rearfoot and knee angular velocities. The higher the obstacle and the faster the speed, the greater the GRIF and the greater the velocity differences. A change of the rearfoot angle curve from a unimodal (one minimum) to a bimodal (two minimums) parabolic configuration was also observed. The appearance of the second minimum was attributed to a lateral deviation of the tibia as a rebound effect due to the increased impact with the ground. The velocity differences between the actions of the subtalar and the knee joint, which in essence capture the antagonistic nature of their relationship, produced the highest correlation with the clinical evaluation. CONCLUSIONS It was suggested that a possible mechanism responsible for various running injuries could be lack of coordination between subtalar and knee joint actions. This mechanism may have potential for predicting runners with susceptibility to injury.