A task failure has no effect on the electromechanical delay of the peroneus longus.

OBJECTIVE: Ankle inversion injuries represent the most common trauma sustained by athletes. Muscle fatigue from activity may contribute to a delay in the response of the ankle proprioceptors and dynamic restraints during unexpected inversion. The purpose of this investigation was to determine if the electromechanical delay (EMD) of the peroneus longus is influenced by a task failure exercise. SUBJECTS: Sixteen subjects (age 20 +/- 1.1 y; mass 71.6 +/- 12.5 kg; height 173.0 +/- 8.7 cm; 9 male, 1 female) with no lower extremity injuries reported for data collection. MEASUREMENTS: Data were collected from each subject's dominant leg using surface electromyography (EMG). Electrodes were applied over the peroneus longus (PL) using a standard protocol. A stimulating electrode was applied to the common peroneal nerve. Subjects were placed in a monopedal stance on a force platform. A low amplitude, short duration stimulus was applied to the common peroneal nerve. The EMG was used to determine timing of the M wave and the force platform was used to determine the onset of foot pronation. Once 6 trials were recorded, subjects completed 2 sets of an isotonic activity that isolated the peroneals. The task was completed to failure for each set. Immediately following the task failure exercise, subjects returned to the force platform for 6 additional trials recorded as before. Analysis of data was performed by determining the onset of the M wave as the beginning of positive EMG activity following the end of the imposed stimulus response. This point was superimposed on the force platform curve and the point at which a 10 N.m force change occurred was used to calculate the EMD (time difference between the force platform indicator and the M wave indicator). RESULTS: Average EMD prior to the task failure exercise was 13.35 +/- 3.47 ms. Following the task failure exercise, the average EMD was 12.67 +/- 3.86 ms. A paired samples t test revealed no significant differences with regard to EMD between pre- and post-task failure exercise for the PL (p = 0.448). CONCLUSION: We concluded that the task failure exercise did not affect the electromechanical delay of the PL.

Leg length inequality. Implications for running injury prevention.

Leg length inequality is a relatively common musculoskeletal malalignment related to structural, postural and environmental factors. The inequality is a plausible aetiological factor in the development of a variety of overuse injuries because it alters the magnitude and distribution of mechanical stress within the body. Leg length inequality has been linked with lower extremity stress fractures, low back pain, hip pain and vertebral disk problems of runners. The appropriateness of using inshoe lifts to reduce or eliminate the inequality has not been rigorously evaluated. Further research is needed to quantify the biomechanical effects of leg length inequality as it interacts with other factors related to running injury.

Prophylactic ankle stabilizers affect ankle joint kinematics during drop landings.

PURPOSE: Ankle joint dorsiflexion contributes to energy absorption during landing, but wearing ankle stabilizers is known to restrict passive measures of dorsiflexion. This study compared the effects of various ankle stabilizers on ankle joint kinematics during soft and stiff landings. METHODS: Subjects (N = 14) performed two-legged landings off a 0.59-m platform. Kinematics of the right ankle were calculated from a sagittal plane video recording (120 Hz). Five soft and five stiff landings were performed in five ankle stabilizer conditions (no stabilizer, taping, Swede-O, AirCast, and Active Ankle), a total of 50 trials per subject. Style and stabilizer conditions were randomized across subjects. Each subject's five-trial mean value of selected kinematic variables for each landing style/stabilizer condition was entered into a two-way repeated MANOVA (alpha = 0.05). RESULTS: Differences between soft and stiff landing conditions were similar to those reported in the literature. Compared with the No stabilizer condition, most stabilizer conditions significantly reduced ankle dorsiflexion ROM and angular velocity during landing. CONCLUSIONS: The results indicate that some ankle stabilizers adversely affect ankle joint kinematics during landing.

Stance width and bar load effects on leg muscle activity during the parallel squat.

PURPOSE: Altering foot stance is often prescribed as a method of isolating muscles during the parallel squat. The purpose of this study was to compare activity in six muscles crossing the hip and/or knee joints when the parallel squat is performed with different stances and bar loads. METHODS: Nine male lifters served as subjects. Within 7 d of determining IRM on the squat with shoulder width stance, surface EMG data were collected (800 Hz) from the rectus femoris, vastus medialis, vastus lateralis, adductor longus, gluteus maximus, and biceps femoris while subjects completed five nonconsecutive reps of the squat using shoulder width, narrow (75% shoulder width), and wide (140% shoulder width) stances with low and high loads (60% and 75% 1RM, respectively). Rep time was controlled. A goniometer on the right knee was used to identify descent and ascent phases. Integrated EMG values were calculated for each muscle during phases of each rep, and the 5-rep means for each subject were used in a repeated measures ANOVA (phase x load x stance, alpha = 0.05). RESULTS: For rectus femoris, vastus medialis, and vastus lateralis, only the load effect was significant. Adductor longus exhibited a stance by phase interaction and a load effect. Gluteus maximus exhibited a load by stance interaction and a phase effect. Biceps femoris activity was highest during the ascent phase. CONCLUSION: The results suggest that stance width does not cause isolation within the quadriceps but does influence muscle activity on the medial thigh and buttocks.

The effect of comments about shoe construction on impact forces during walking.

UNLABELLED: Comparisons of ground reaction forces (GRF) during gait are not typically conducted with blinding of the varied shoe characteristic, raising concerns related to the existence of a placebo effect, or a subject response based on a perceived expectation of change. PURPOSE: To determine whether investigator comments on shoe construction influenced GRF measures and ratings of shoe cushioning during walking. METHODS: 19 female college students volunteered for a study presented as a test of a new shoe material. The study involved walking (2.5 m x s(-1)) under three shoe conditions (SC). Shoes in SC2 and SC3 were harder than those in SC1, but shoes in SC1 and SC3 looked similar. Subjects in a mislead group (N = 9) were told SC1 and SC3 were baseline measures in a standard shoe, with SC2 misleadingly described as a shoe constructed of unique new material. A control group performed the same three conditions without investigator description. GRF data were collected for 10 trials for each subject in each condition, and subjects rated the perceived cushioning of each shoe. GRF data and perceived cushioning scores were analyzed using mixed-factor (group by shoe) ANOVA. RESULTS: A significant shoe main effect was found for loading rate. Post hoc tests identified the difference between SC1 and both SC2 and SC3. The group main effect was not significant for any dependent variable. CONCLUSIONS: Results suggest that, as a group, GRF data and cushioning scores are not affected by investigator comments that do not match shoe construction characteristics. However, ratings of perceived shoe cushioning by some individual subjects reflected investigator comments and not the vertical GRF variables.

Errors in alignment of center of pressure and foot coordinates affect predicted lower extremity torques.

The purpose of the study was to quantify the effect of errors in spatial alignment between the center of pressure recorded from a force platform and the coordinates of the foot recorded from film on resultant joint torques in the lower extremity during the stance phase of gait. Two-dimensional kinematic and kinetic data from eight subjects performing walking and running were analyzed using inverse dynamics with the obtained center of pressure values and with +/- 0.5 and +/- 1.0 cm shifts in the anteroposterior location of the center of pressure under the support foot. Shifting the center of pressure posteriorly increased the flexor (dorsiflexor) torques at the hip and ankle and decreased the extensor (plantarflexor) torques at these joints. This shift also caused an increase in the extensor and a decrease in the flexor torques at the knee. Shifting the center of pressure anteriorly caused the opposite effects at each joint. The +/- 0.5 and +/- 1.0 cm shifts in the location of the center of pressure caused, on average, 7 and 14% changes, respectively, in maximum joint torque and angular impulse values. Relative transition times between flexor and extensor torques were either increased or decreased, on average, by 7 and 13%, respectively for the two conditions over all trials. Based on these results, it is concluded that due to potential errors in the spatial alignment of kinetic and kinematic data, joint torques in the literature on gait should be considered as approximations of the true values.

Winning the Stanley Cup Final Series is related to incurring fewer penalties for violent behavior.

Catastrophic and disabling injuries are being reported more frequently in ice hockey. Within the science of injury prevention, all possible avenues are being explored to address this devastating problem, especially in the areas of protective equipment playing rules, teaching techniques, and awareness programs. Ice hockey injuries are in many cases caused by violent player behavior, which may be supported by coaches who believe that such behavior contributes to winning. To determine whether a relationship existed between violent player behavior and game outcome, 1462 recorded penalties from all 18 Stanley Cup Final Series from 1980 through 1997 were analyzed with a 2 x 2 chi-square analysis. A statistically significant association (chi-square = 7.111, P = .008) was found between violent player behavior and series outcome, with the team drawing fewer violent penalty minutes being the winner of 13 of the 18 series. A period-by-period analysis of violent penalties incurred by the losing teams revealed a statistically significant difference between the first and third periods, with losing teams demonstrating more violent player behavior in the first period than in the third period. The results suggest that violent player behavior may be counterproductive to a favorable game outcome. Coaches at the highest level of competition may wish to adjust their team policies and recruiting practices to benefit from the plausible strategic advantage of reducing violent player behavior. This research was presented at the 1998 Ice Hockey World Championship International Symposium on Medicine and Science in Ice Hockey in Zurich, Switzerland, on Saturday, May 9, 1998, and published in the symposium's supplement, "Safety in Ice Hockey IIHF 1998."

Biomechanical implications of mild leg length inequality.

The effect of mild leg length inequality (lower extremity length difference less than 3 cm) on posture and gait has been the source of much controversy. Many opinions have been expressed both for and against the need for intervention to reduce the magnitude of the discrepancy. This paper emphasizes the need for accurate and reliable assessment of leg length differences using a clinically functional radiographic technique, and reviews the biomechanical implications of leg length inequality as related to the development of stress fractures, low back pain and osteoarthritis.

Nasal strips do not affect cardiorespiratory measures during recovery from anaerobic exercise.

Nasal dilators supposedly aid recovery from exercise by reducing nasal airway resistance. Research has focused on the effectiveness of nasal dilators during exercise. The purpose of this study was to examine the effects of nasal dilators on heart rate (HR), minute ventilation (VE), and oxygen consumption (Vo2) during recovery from anaerobic exercise. Fourteen subjects (19-32 years) performed a modified Cunningham-Faulkner anaerobic treadmill test (1-minute walk at 2.0 miles per hour [mph], 0% grade; 1-minute jog at 5 mph, 0% grade; and sprint at 8 mph, 20% grade) under 3 randomly assigned conditions: (a) control, (b) nasal strip, and (c) placebo nasal strip. A 10-minute recovery period consisting of 5 minutes of walking (2 mph, 0% grade) and 5 minutes of passive recovery (seated) was completed. During the test and recovery periods, the participant wore a fireman's face mask to allow for simultaneous sampling of nose and mouth breathing. Vo2 and VE were monitored by a TEEM 100 metabolic analyzer. Each subject wore a Polar Heart Watch to monitor HR every minute during recovery. Mean time to exhaustion was 48.4 seconds (+/-14.9). One-way repeated-measures analyses of variance (ANOVAs) indicated no significant nasal dilator effect on 5-minute recovery HR or 10-minute recovery HR, 5-minute recovery Vo2 or 10-minute recovery Vo2, and 5-minute recovery VE or 10-minute recovery VE. Nasal strips appear to have no significant impact during recovery from anaerobic exercise.

The effects of continuous and discontinuous walking on physiologic response in college-age subjects.

The Surgeon General's Report on Physical Activity recommends an accumulation of 30 minutes of moderate physical activity on most, if not all, days of the week. The purpose of this study was to determine if 3 10-minute bouts of walking had the same effect on physiologic response as 1 30-minute bout of continuous walking when both were performed 3 d x wk(-1) for 12 weeks. Thirty (18 completed the study) college-aged subjects (VO2max: 44 ml x kg(-1) x min(-1) +/- 8.37) were randomly assigned to either a nonexercising group (N = 7), a group (N = 5) that performed 3 10-minute bouts, or a group (N = 6) that performed 1 30-minute bout of exercise. Intensity was set at 50-60% of estimated maximum heart rate. A mixed factor 2 x 3 analysis of variance (time by group) was used to analyze the data (alpha = 0.10). Controls demonstrated a significant decrease in VO2max, while the exercise groups demonstrated no significant change. There was no significant difference demonstrated for pre- and postmaximal heart rates or for pre- and postmaximal respiratory exchange ratio. Continuous and discontinuous walking were equally effective in maintaining, but not improving, VO2max.