Neuromuscular and biomechanical characteristic changes in high school athletes: a plyometric versus basic resistance program.

BACKGROUND: In order to improve neuromuscular and biomechanical characteristic deficits in female athletes, numerous injury prevention programs have been developed and have successfully reduced the number of knee ligament injuries. However, few have investigated the neuromuscular and biomechanical changes following these training programs. It is also largely unknown what type of program is better for improving the landing mechanics of female athletes. OBJECTIVES: To investigate the effects of an 8 week plyometric and basic resistance training program on neuromuscular and biomechanical characteristics in female athletes. METHODS: Twenty seven high school female athletes participated either in a plyometric or a basic resistance training program. Knee and hip strength, landing mechanics, and muscle activity were recorded before and after the intervention programs. In the jump-landing task, subjects jumped as high as they could and landed on both feet. Electromyography (EMG) peak activation time and integrated EMG of thigh and hip muscles were recorded prior to (preactive) and subsequent to (reactive) foot contact. RESULTS: Both groups improved knee extensor isokinetic strength and increased initial and peak knee and hip flexion, and time to peak knee flexion during the task. The peak preactive EMG of the gluteus medius and integrated EMG for the gluteus medius during the preactive and reactive time periods were significantly greater for both groups. CONCLUSIONS: Basic training alone induced favourable neuromuscular and biomechanical changes in high school female athletes. The plyometric program may further be utilised to improve muscular activation patterns.

No acute changes in postural control after soccer heading.

BACKGROUND: Soccer heading has been proposed as a potential cause of cerebral dysfunction. OBJECTIVE: To examine the acute effects of two types of soccer heading on postural control. METHODS: Collegiate soccer players were randomly assigned to one of four groups: control, linear heading, simulated rotational heading, or rotational heading. Each subject completed a baseline postural stability assessment on day 1. On day 2 the same assessment was completed for the control subjects. The simulated rotational heading group completed a simulated heading drill before postural stability testing. The linear and rotational heading groups performed a heading drill with 20 balls at 88.71 km/h (55 mph), before postural stability testing. Separate one between (group), three within (surface, eyes, and day), mixed model, repeated measures analyses of variance were conducted on values for total sway and mean centre of pressure. RESULTS: The mixed model analysis of variance of results showed no significant differences (p>0.05) for the interactions of interest for either variable. Results suggest no acute changes in measures of postural control in soccer players completing either a linear or rotational soccer heading drill of 20 balls at a fixed speed. CONCLUSION: Non-significant interactions between surface, eyes, day, and group indicate that sensory interaction of the balance mechanism components are not be compromised by the heading drill. This research supports previous studies suggesting that there are no acute risks associated with routine soccer heading. A direct comparison between these findings and those suggesting long term chronic deficits, however, cannot be made. Other studies that report chronic cerebral deficits in soccer players may have resulted from factors other than soccer heading and warrant further examination.

Effect of sex on preactivation of the gastrocnemius and hamstring muscles.

BACKGROUND: The reason for the higher incidence of anterior cruciate ligament injury from non-contact mechanisms in female athletes is not known. Stability of the joint from dynamic restraints occurs through proprioceptive and kinaesthetic mechanisms providing a flexion moment. Reflexive muscle activation is different between the sexes, but it is unclear if sex differences exist in the ability to dynamically stabilise joints through a neuromuscular feed forward process as measured by preactivation of the muscles. OBJECTIVE: To determine if the level of preactivation of the gastrocnemius and hamstring muscles during dynamic activity is affected by sex. METHODS: Thirty four healthy active subjects, evenly grouped by sex, participated in the study. Maximum voluntary contraction normalised electromyographic (EMG) activity of the quadriceps, hamstrings, and gastrocnemius muscles was recorded during downhill walking (0.92 m/s) and running (2.08 m/s) on a 15 degrees declined treadmill. Preactivation of the EMG signal was calculated by setting a mark 150 milliseconds before foot strike, as indicated by a footswitch. Multiple t tests for sex differences of preactivity mean percentage (M-EMG%) during the downhill activities were performed. RESULTS: The female subjects had a higher M-EMG% for the medial hamstrings than the male subjects (31.73 (9.89) and 23.04 (8.59) respectively; t((2,32)) = 2.732, p = 0.01) during walking. No other muscles exhibited a sex difference in M-EMG% during either activity. CONCLUSION: The female subjects in this study showed higher medial hamstring preactivation. However, this may be because they were not injured, indicating their propensity for joint stabilisation. A long term prospective study is required to eliminate this potential explanation. No sex difference in gastrocnemius preactivation was seen, adding to the controversy about whether this muscle contributes to feed forward joint stability. Further research of preactivation of the musculature of the leg is required.

Shoulder proprioception in baseball pitchers.

We examined proprioceptive differences between the dominant and nondominant shoulders of 21 collegiate baseball pitchers without a history of shoulder instability or surgery. A proprioceptive testing device was used to measure kinesthesia and joint position sense. Joint position sense was significantly (P =.05) more accurate in the nondominant shoulder than in the dominant shoulder when starting at 75% of maximal external rotation and moving into internal rotation. There were no significant differences for proprioception in the other measured positions or with kinesthesia testing. Six pitchers with recent shoulder pain had a significant (P =.04) kinesthetic deficit in the symptomatic dominant shoulder compared with the asymptomatic shoulder, as measured in neutral rotation moving into internal rotation. The net effect of training, exercise-induced laxity, and increased external rotation in baseball pitchers does not affect proprioception, although shoulder pain, possibly due to rotator cuff inflammation or tendinitis, is associated with reduced kinesthetic sensation.

Hop tests as predictors of dynamic knee stability.

Single leg hop tests are commonly used as physical performance measures of function and are also commonly used to evaluate progress in knee rehabilitation programs, particularly for individuals recovering from anterior cruciate ligament injury or reconstructive surgery. While there is some evidence that hop tests may show promise as a predictive measure for identifying individuals who are at risk for recurrent dynamic instability, further work is needed to clearly define the role of hop test measurements for this purpose. The purposes of this clinical commentary are to review the research that has been done to establish hop tests as a physical performance measure of function, to discuss neuromuscular and biomechanical considerations related to hop performance and dynamic knee stability, to discuss existing evidence that supports the potential for hop tests as a predictor of dynamic knee stability, and to discuss considerations for future studies that are designed to more clearly define the role of hop tests in predicting dynamic knee stability.

The role of the sensorimotor system in the athletic shoulder.

OBJECTIVE: To discuss the role of the sensorimotor system as it relates to functional stability, joint injury, and muscle fatigue of the athletic shoulder and to provide clinicians with the necessary tools for restoring functional stability to the athletic shoulder after injury. DATA SOURCES: We searched MEDLINE, SPORT Discus, and CINAHL from 1965 through 1999 using the key words "proprioception," "neuromuscular control," "shoulder rehabilitation," and "shoulder stability." DATA SYNTHESIS: Shoulder functional stability results from an interaction between static and dynamic stabilizers at the shoulder. This interaction is mediated by the sensorimotor system. After joint injury or fatigue, proprioceptive deficits have been demonstrated, and neuromuscular control has been altered. To restore stability after injury, deficits in both mechanical stability and proprioception and neuromuscular control must be addressed. A functional rehabilitation program addressing awareness of proprioception, restoration of dynamic stability, facilitation of preparatory and reactive muscle activation, and implementation of functional activities is vital for returning an athlete to competition. CONCLUSIONS/RECOMMENDATIONS: After capsuloligamentous injury to the shoulder joint, decreased proprioceptive input to the central nervous system results in decreased neuromuscular control. The compounding effects of mechanical instability and neuromuscular deficits create an unstable shoulder joint. Clinicians should not only address the mechanical instability that results from joint injury but also implement both traditional and functional rehabilitation to return an athlete to competition.

Comparison of two abdominal training devices with an abdominal crunch using strength and EMG measurements.

BACKGROUND: The purpose of this study was to compare the training effects of the Ab-Flex (F), Ab-Roller (R) and standard crunch (C) on EMG production, isometric maximum voluntary contraction (MVC), and isokinetic average peak torque at 30 degrees/sec (ISO) of the abdominal muscles. It was hypothesized that the training devices would have similar value in a strength training program. EXPERIMENTAL DESIGN: this was a prospective study involving 18 training sessions of progressively increasing repetitions. SETTING: Neuromuscular Research Laboratory, University of Pittsburgh. SUBJECTS: thirty-two subjects volunteered for this study, but only 26 completed the training. Each subject participated in recreational activity, but had not performed any abdominal training prior to starting this study. Each subject was randomly assigned to either the control group or one of the treatment groups. INTERVENTIONS: there were three interventions: two training devices (Ab-Flex and Ab-Roller) and the standard crunch, considered a control group. MEASURES: the pretest consisted of skin fold measurements (%), EMG activity (V) during the three interventions, and peak torque (Nm) plus EMG during the MVC and ISO tasks. The 18 training sessions over three weeks consisted of three sets of exercise with increasing repetitions from 10 to 20, by 2, every three sessions. The difference in pretest/posttest scores were compared using a One-way ANOVA on the mean differences (Mdiff) for each of: MVC, ISO (peak torque), and EMG for upper rectus (UR), lower rectus (LR), internal oblique (IO), and external oblique (EO). A T-Test was used to detect significance for the body fat measures. RESULTS: Mean differences (Mdiff) were normally distributed about zero for both MVC and ISO (MVC = -0.55, ISO = 4.57). The analysis by group showed no difference (p = 0.596) on the reported means (Nm) -3.16 (C), 5.84 (F) and -4.83 (R). The change associated to the treatment during MVC was only 4% (eta = 0.04). For the ISO the Mdiff (Nm) were 1.39 (C), 13.66 (F) and -2.06 (R) which were not significant (p = 0.127). The Ab-Flex was the only group to have a 95% confidence interval above zero, increasing by an average of 16.5%. There were no significant differences for the EMG activity for Mdiff or between group scores. CONCLUSIONS: No significant differences were found with this study. These results would suggest that using these devices does not add significantly to overall abdominal strength development, or reduction of body fat. A suggestion could be made that certain devices influence muscles differently.

Proprioception in the posterior cruciate ligament deficient knee.

This study was undertaken to evaluate knee proprioception in patients with isolated unilateral posterior cruciate ligament (PCL) injuries. Eighteen subjects with isolated PCL tears were studied 1-234 months after injury. The threshold to detect passive motion (TTDPM) was used to evaluate kinesthesia and the ability to passively reproduce passive positioning (RPP) to test joint position sense. Two starting positions were tested in all knees: 45 degrees (middle range) and 110 degrees (end range) to evaluate knee proprioception when the PCL is under different amounts of tension. TTDPM and RPP were tested as the knee moved into flexion and extension from both starting positions. A statistically significant reduction in TTDPM was identified in PCL-injured knees tested from the 45 degrees starting position, moving into flexion and extension. RPP was statistically better in the PCL-deficient knee as tested from 110 degrees moving into flexion and extension. No difference was identified in the TTDPM starting at 110 degrees or in RPP with the presented angle at 45 degrees moving into flexion or extension. These subtle but statistically significant findings suggest that proprioceptive mechanoreceptors may play a clinical role in PCL-intact and PCL-deficient patients. Further, it appears that kinesthesia and joint position sense may function through different mechanisms.

Balance training for persons with functionally unstable ankles.

STUDY DESIGN: A nonrandomized 2-group pretest-posttest design. OBJECTIVES: To determine the effects of a 4-week balance training program during stance on a single leg. BACKGROUND: Individuals who have experienced multiple episodes of inversion ankle sprains often participate in balance training programs. Balance training is performed to treat existing proprioceptive deficits and to restore ankle joint stability, presumably by retraining altered afferent neuromuscular pathways. The effectiveness of such programs on individuals with functionally unstable ankles has yet to be established. METHODS AND MEASURES: Prior to and following training, subjects with self-reported functionally unstable ankles (5 women and 8 men, mean age = 21.9 +/- 3.1 years) and nonimpaired subjects (6 women and 7 men, mean age = 21.2 +/- 2.5 years) completed a static balance assessment for both limbs as well as the ankle joint functional assessment tool questionnaire (AJFAT). The subjects from both groups participated in a unilateral, multilevel, static and dynamic balance training program 3 times a week for 4 weeks. Subjects from the experimental group trained only the involved limb, and the nonimpaired group trained a randomly selected limb. A stability index (SI) was calculated during the balance assessment to indicate the amount of platform motion. Compared to low stability indices, high stability indices indicate greater platform motion during stance and therefore less stability. RESULTS: Following training, subjects from both groups demonstrated significant improvements in balance ability. When balance was assessed at a low resistance to platform tilt (stability level 2), the posttraining scores of both the subjects with unstable ankles (mean SI = 2.63 +/- 1.92) and the nonimpaired subjects (mean SI = 2.69 +/- 2.32) were significantly better than their pretraining scores (mean SIs = 5.93 +/- 3.65 and 4.67 +/- 3.43, respectively). Assessed at a high resistance to platform tilt (stability level 6), the posttraining scores of both subjects with unstable ankles (mean SI = 1.27 +/- 0.66) and the nonimpaired subjects (mean SI = 1.37 +/- 0.66) were significantly better than their pretraining scores (mean SIs = 2.30 +/- 1.88 and 2.04 +/- 1.43, respectively). Additionally, the posttraining AJFAT scores of subjects with unstable ankles (25.78 +/- 3.80) and the nonimpaired subjects (29.15 +/- 5.27) were significantly greater than their pretraining scores (17.11 +/- 3.44 and 22.92 +/- 5.22, respectively), indicating an overall improvement in perceived ankle joint functional stability. CONCLUSIONS: This study suggests that balance training is an effective means of improving joint proprioception and single-leg standing ability in subjects with unstable and nonimpaired ankles.

Knee joint laxity and neuromuscular characteristics of male and female soccer and basketball players.

Anterior cruciate ligament injuries are occurring at a higher rate in female athletes compared with their male counterparts. Research in the area of anterior cruciate ligament injury has increasingly focused on the role of joint proprioception and muscle activity in promoting knee joint stability. We measured knee joint laxity, joint kinesthesia, lower extremity balance, the amount of time required to generate peak torque of the knee flexor and extensor musculature, and electromyographically assessed muscle activity in 34 healthy, collegiate-level athletes (average age, 19.6 +/- 1.5 years) who played soccer or basketball or both. Independent t-tests were used to determine significant sex differences. Results revealed that women inherently possess significantly greater knee joint laxity values, demonstrate a significantly longer time to detect the knee joint motion moving into extension, possess significantly superior single-legged balance ability, and produce significantly greater electromyographic peak amplitude and area of the lateral hamstring muscle subsequent to landing a jump. The excessive joint laxity of women appears to contribute to diminished joint proprioception, rendering the knee less sensitive to potentially damaging forces and possibly at risk for injury. Unable to rely on ligamentous structures, healthy female athletes appear to have adopted compensatory mechanisms of increased hamstring activity to achieve functional joint stabilization.

Changes in forearm blood flow during single and intermittent cold application.

STUDY DESIGN: Two-factor repeated measures design. OBJECTIVES: To compare the effects of a 20-minute cold application to the effects of a 20-minute cold application followed by 20 additional minutes of intermittent cold on forearm blood flow over a 60-minute period. BACKGROUND: The appropriate duration of cold application as a therapeutic modality following soft tissue trauma is an important clinical question because the goal of using this modality is to limit edema, decrease pain, and produce effective muscle relaxation without causing cold-induced reactive vasodilatation or nerve damage. METHODS AND MEASURES: Thirteen subjects (mean age, 21.46 +/- 4.01 years) volunteered to participate in this study. A bilateral tetrapolar impedance plethysmograph was used with venous occlusion to measure changes in local limb blood volume at the forearm for a period of 60 minutes under 2 conditions: Condition 1: Prolonged intermittent cold application (20 minutes ice application; 10 minutes off; 10 minutes ice on; 10 minutes off; 10 minutes ice on); Condition 2: Cold followed by application of a room-temperature pack of equal weight to the ice bag (20-minute ice application; 10 minutes off; 10 minute room-temperature pack on; 10 minutes off; 10-minute room-temperature pack on). RESULTS: A significantly lower blood flow was noted during the last 10 minutes of Condition 1 compared with Condition 2. CONCLUSIONS: The findings of this study indicate that blood flow is reduced when a prolonged intermittent cold application (Condition 1) is used compared to a single cold application (Condition 2).

Neuromuscular activation and RPE in the quadriceps at low and high isometric intensities.

INTRODUCTION: The purpose of this study was to examine neuromuscular activation and ratings of perceived exertion (RPE) at 10% and 80% quadriceps MVC in healthy males. METHODS: Seventeen college-aged volunteers (mean age = 22.6 years, mean height = 178.9 cm, mean weight = 78.8 kg) were assessed for isometric EMG activity of the vastus medialis (VM) and vastus lateralis (VL) at 10% and 80% MVC, and RPE at 80% MVC. Perceived exertion was measured with a modified category ratio scale (CR-10) and was anchored with 1 high and 1 low anchor. Raw EMG signals were sampled via telemetry (rate = 1,000 Hz) and integrated (3 sec) for each contraction for each muscle (bandpass = 16-500 Hz, CMRR = 130 dB). A one-sample t-test was performed for each variable and 95% confidence intervals were calculated. RESULTS: Means and CI for each variable are as follows: 10% MVC VM IEMG (t16 = 5.05, p < 0.001, .95 CI = 3.11 +/- 1.3), 80% MVC VM IEMG (t16 = 22.51, p < 0.001, .95 CI = 73.2 +/- 6.89), 10% MVC VL IEMG (t16 = 8.10, p < 0.001, .95 CI = 9.41 +/- 2.47), 80% MVC VL IEMG (t16 = 39.56, p < 0.001, .95 CI = 87.32 +/- 4.68), and 80% MVC RPE (t16 = 11.85, p < 0.001, .95 CI = 5.24 +/- 0.93). DISCUSSION: The major findings illustrate an apparent underestimation of RPE at 80% MVC for the quadriceps. Neuromuscular activation appears to be lower than the expected force output at both intensities for the VM while VL activation corresponded closely at 10% MVC and was higher at 80% MVC.

Muscle preactivity of anterior cruciate ligament-deficient and -reconstructed females during functional activities.

OBJECTIVE: Underlying the ability of the hamstrings to decrease tibial anterior shear is the time of firing in comparison with the quadriceps. This timing may be aided by neural programming during a planned or expected activity. It is theorized that individuals who have better programming ability will suffer fewer anterior cruciate ligament (ACL) injuries due to joint protection through muscular stabilization. A component of this dynamic restraint is the development of muscular tension before the knee is loaded. The objective of our study was to compare the muscular activity before footstrike in ACL-deficient (ACL-D), ACL-reconstructed (ACL-R), and control (C) females during functional activities. DESIGN AND SETTING: Active females were divided into groups based on their ACL status. The study was conducted in a neuromuscular research laboratory. SUBJECTS: Twenty-four female subjects (ACL-D = 6, ACL-R = 12, C = 6). MEASUREMENTS: Integrated electromyographic (IEMG) activity from the thigh (vastus medialis obliquus [VMO], vastus lateralis [VL], medial hamstring, and lateral hamstring) and leg (medial gastrocnemius and lateral gastrocnemius [LG]) and footswitch signals were recorded during downhill walking (15 degrees at 0.92 m/s), running (2.08 m/s), hopping, and landing from a step (20.3 cm). IEMG activity was normalized to the mean amplitude of the sample and analyzed for area and mean amplitude for 150 milliseconds before heelstrike. Side-to-side differences were determined by t tests, and separate one-way analyses of variance (ANOVA) were used to detect differences among the 3 groups for each muscle of each activity. RESULTS: IEMG area side-to-side differences for the ACL-D group appeared in the LG (involved [I] = 36.4 +/- 19.7, uninvolved [U] = 60.1 +/- 23.6) during landing, in the VMO (I = 11.4 +/- 3.8, U = 7.2 +/- 3.1) and VL (I = 13.3 +/- 2.7, U = 8.9 +/- 1.9) during running, and in the VMO (I = 9.2 +/- 4.2, U = 19.5 +/- 7.3) during downhill walking. IEMG mean amplitude side-to-side differences for the ACL-D group appeared in the LG (I = 79.7 +/- 30.3, U = 122.3 +/- 34.9) during downhill walking and in the VMO (I = 78.6 +/- 23.2, U = 45.8 +/- 18.9) during the run; IEMG mean amplitude side-to-side differences for the ACL-R group appeared in the LG (I = 74.7 +/- 40.0, U = 52.8 +/- 14.3) during the hop. The ACL-D group had higher IEMG means than control in the VL (ACL-D = 12.9 +/- 5.8, C = 7.1 +/- 3.9), but lower in the VMO (ACL-D = 9.2 +/- 4.2, C = 15.7 +/- 3.6). CONCLUSIONS: The side-to-side differences of the ACL-D and ACL-R groups, as well as the group differences between ACL-D and control, suggest that different muscle activation strategies are used by females when performing different dynamic activities. Therefore, muscle unit differentiation may be the cause of our results. These changes appear to be reversed through surgery or the associated postoperative rehabilitation.

Effects of muscular fatigue on knee joint laxity and neuromuscular characteristics of male and female athletes.

OBJECTIVE: To elucidate the effects of muscular fatigue on knee joint laxity and the neuromuscular characteristics of male and female athletes. We were particularly interested in determining whether such effects would be more pronounced in female athletes than in males participating in the same sport. DESIGN AND SETTING: Subjects were assessed on 4 dependent variables during a rested and an isokinetically induced muscular fatigue state. We ensured that posttesting measurements were obtained in the fatigued state by testing only 2 dependent variables after each exercise bout. SUBJECTS: We recruited male (n = 17) and female (n = 17) subjects from a population of healthy collegiate basketball and soccer players. MEASUREMENTS: MEASURED DEPENDENT VARIABLES WERE AS FOLLOWS: anterior tibial translation, kinesthesia determined by assessing the threshold to detection of passive motion moving into knee flexion and extension; lower extremity balance ability quantified through a stability index value; and the electromyography-measured muscle activity of 6 knee-stabilizing muscles. RESULTS: In response to muscular fatigue, subjects demonstrated an overall decrease in the ability to detect joint motion moving into the direction of extension, an increase in the onset of contraction time for the medial hamstring and lateral gastrocnemius muscles, and an increase in the first contraction area of the vastus medialis and vastus lateralis muscles. Additionally, the increase in area of the vastus lateralis was greater for the males compared with the females. CONCLUSIONS: Our results suggest that both male and female athletes exhibit decrements in proprioceptive ability and alterations in muscular activity subsequent to muscular fatigue.

Reactive muscle firing of anterior cruciate ligament-injured females during functional activities.

OBJECTIVE: The high incidence of noncontact anterior cruciate ligament (ACL) injuries in females has attracted research to investigate the capacity of muscles to reflexively protect the knee joint from capsuloligamentous injury. Numerous reflex pathways link mechanoreceptors in the ACL with contractile fibers in the quadriceps and hamstring muscles. Loads placed on the ACL modify reactive muscle activity through the feed-back process of neuromuscular control and are critical for dynamic muscular stabilization. Noncontact ACL injuries may be the result of aberrations in reactive muscle firing patterns. Therefore, compensatory muscle activation strategies must be employed if functional stability is to be restored after injury or surgical reconstruction. The purpose of our study was to compare the amplitude of reactive muscle activity in females with ACL-deficient (ACLD), ACL-reconstructed (ACLR), and control knees during functional activities. DESIGN AND SETTING: Female volunteer subjects were stratified into groups based on the status of their ACLs. Each subject performed 4 functional activities, bilaterally, during a single test session. SUBJECTS: Twenty-four female subjects participated in this study (ACLD = 6, ACLR = 12, control = 6). MEASUREMENTS: Integrated electromyographic (IEMG) data were collected with surface electrodes from the vastus medialis, vastus lateralis, medial hamstring, and lateral hamstring during downhill walking (15 degrees , 0.92 m/s), level running (2.08 m/s), and hopping and landing from a jump (20.3 cm). IEMG was normalized to the mean amplitude of 3 to 6 consecutive test repetitions. The mean area and peak IEMG of a 250-millisecond period after ground contact was used to represent reactive muscle activity. Side-to-side differences were determined using dependent t tests, and group differences were determined using a one-way analysis of variance. RESULTS: During running, the ACLD group demonstrated significantly greater area and peak IEMG activity in the medial hamstring in comparison with the ACLR group and greater peak activity in the lateral hamstring when compared with the control group. The ACLD group also demonstrated greater peak activity in the vastus medialis and a smaller area of IEMG activity in the lateral hamstring than the control group during running. During landing, the ACLD group demonstrated significantly less area of IEMG activity in the vastus lateralis when compared with the control group. No significant differences were identified between the ACLR and control groups, nor were side-to side differences revealed. CONCLUSIONS: Our results suggest that adaptations occur in the reactive muscle activity of ACLD females during functional activities. Strategies to minimize the anterior tibial translation in response to joint loading included increased hamstring activity and quadriceps inhibition. The reactive muscle activity exhibited in ACLD subjects is presumably an attempt to regain functional stability through the dynamic restraint mechanism. The absence of side-to-side differences suggests that these adaptations occur bilaterally after ACL injury.

Comparison of performance-based and patient-reported measures of function in anterior-cruciate-ligament-deficient individuals.

There is a dearth of reliable and valid instrumentation that measures disability following injury and/or surgery of the knee joint that is responsive to clinically significant changes over time. The purpose of this investigation was to determine whether performance-based or patient-reported measures of function are more effective in estimating disability in individuals with an anterior-cruciate-ligament (ACL)-deficient knee. Subjective rating of knee function was used as the criterion measure for disability, and selected performance-based and patient-reported measures were used as estimation variables. Twenty-nine individuals with an ACL-deficient knee participated in this investigation. Step-wise regression analysis revealed that the Cincinnati Knee Scale, Lysholm Knee Scale, and hop index were the most effective estimates of disability. The results demonstrate that patient-reported measures are more related to the patient's level of disability in individuals with an ACL-deficient knee. More research is necessary to substantiate these findings.

The effects of muscular fatigue on shoulder proprioception.

OBJECTIVE: To assess the influence of muscular fatigue on active and passive shoulder proprioception within the midrange of rotation. DESIGN: A randomized controlled, before-and-after design. SETTING: Neuromuscular research laboratory. PARTICIPANTS: Twenty recreationally active men (mean age, 23.81+/-2.77 years) were randomly assigned to either a control or a fatigue group. Exclusion criteria were any history of upper extremity injury or pathology, cardiovascular disease, or disease affecting the sensory system. INTERVENTION: Shoulder proprioception was assessed by active reproduction of passive positioning (ARPP), active reproduction of active positioning (ARAP), reproduction of passive positioning (RPP), and threshold to detect passive motion (TTDPM). For each test direction, the experimental group performed two bouts of maximal reciprocal concentric isokinetic internal and external contractions at 180 degrees/s until peak torque decreased to 50% of the established maximum voluntary contraction. After two bouts of the fatigue protocol, subjects were randomly assessed for proprioception into internal or external rotation. MAIN OUTCOME MEASURES: The absolute angular error for active and passive proprioception was measured on the Biodex System II Isokinetic Dynamometer (Biodex Medical Inc., Shirley, NY, U.S.A.) and a proprioception testing device, respectively. MAIN RESULTS: A two-factor repeated measures analysis of variance revealed no significant interactions between the experimental and control groups for ARPP, ARAP, RPP, or TTDPM. CONCLUSIONS: Shoulder proprioception was not affected by the short-duration, high-intensity protocol used in this study. This may be due to the lack of an extended recovery period observed with this type of fatigue regimen.

Proprioception of the ankle and knee.

Proprioception and accompanying neuromuscular feedback mechanisms provide an important component for the establishment and maintenance of functional joint stability. Neuromuscular control and joint stabilisation is mediated primarily by the central nervous system. Multisite sensory input, originating from the somatosensory, visual and vestibular systems, is received and processed by the brain and spinal cord. The culmination of gathered and processed information results in conscious awareness of joint position and motion, unconscious joint stabilisation through protective spinal-mediated reflexes and the maintenance of posture and balance. Clinical research aimed at determining the effects of articular musculoskeletal injury, surgery and rehabilitation, on joint proprioception, neuromuscular control and balance has focused on the knee and ankle joints. Such studies have demonstrated alterations in proprioception subsequent to capsulo-ligamentous injury, partial restoration of proprioceptive acuity following ligamentous reconstruction, and have suggested beneficial proprioceptive changes resulting from comprehensive rehabilitation programmes.

The comparative effects of sports massage, active recovery, and rest in promoting blood lactate clearance after supramaximal leg exercise.

OBJECTIVE: To determine the comparative effect of sports massage, active recovery, and rest on promoting blood lactate clearance after maximal anaerobic (supramaximal) leg exercise. DESIGN AND SETTING: A counterbalanced experimental design with repeated measures was used. The repeated measures were the three treatment conditions. The order of the conditions was determined by random assignment to a counterbalanced test sequence. All data were collected in the Human Energy Research Laboratory at the University of Pittsburgh. SUBJECTS: Ten male competitive cyclists volunteered for this investigation. MEASUREMENTS: Serial venous blood samples were drawn and analyzed for blood lactate concentration for each test condition. RESULTS: There were significant main effects for both absolute and relative values of blood lactate concentration between the three treatment groups and across time within groups. CONCLUSIONS: After supramaximal leg exercise, active recovery produced significant decreases in both absolute and relative measures of blood lactate concentration when compared with the sports massage and rest conditions. No significant difference was found between sports massage and rest for either absolute or relative changes in blood lactate concentration.

Effect of whirlpool therapy on the signs and symptoms of delayed-onset muscle soreness.

OBJECTIVE: To determine the efficacy of warm whirlpool, cold whirlpool, and contrast therapy in the treatment of delayed-onset muscle soreness. DESIGN AND SETTING: Subjects performed eccentric contractions of the elbow flexors and received 4 treatments: immediately postexercise and 24, 48, and 72 hours postexercise. Treatments consisted of 24-minute treatments with warm whirlpool, cold whirlpool, contrast therapy, or no treatment. SUBJECTS: Fifty-six sex-matched volunteers from the University of Pittsburgh. MEASUREMENTS: Measurements were taken at 5 assessment times: pre-exercise (0 hours); prior to treatment at 24, 48, and 72 hours postexercise; and at 96 hours postexercise. Dependent variables were degrees of resting elbow flexion, active elbow flexion, and extension; perceived soreness values on a Graphic Pain Rating Scale; and maximal voluntary isometric contraction. A repeated-measures analysis of variance (group by time) and Tukey post hoc analysis were used to determine which treatment groups differed significantly in returning subjects to pre-exercise values. RESULTS: Cold whirlpool and contrast therapy were found to return subjects to baseline values of resting elbow flexion and perceived soreness significantly more than warm whirlpool or no treatment (P < .01). Additionally, warm whirlpool was found to be more effective than no treatment in the return of resting elbow flexion (P < .01). CONCLUSIONS: These results suggest that cold whirlpool and contrast therapy are more effective than warm whirlpool or no treatment in alleviating delayed-onset muscle soreness in the elbow flexors.