Knee and ankle position, anterior drawer laxity, and stiffness of the ankle complex.

CONTEXT: Anterior drawer testing of the ankle is commonly used to diagnose lateral ligamentous instability. Our hypothesis was that changing knee and ankle positions would change the stability of the ankle complex during anterior drawer testing. OBJECTIVES: To assess the effects of knee and ankle position on anterior drawer laxity and stiffness of the ankle complex. DESIGN: A repeated-measures design with knee and ankle position as independent variables. SETTING: University research laboratory. PATIENTS OR OTHER PARTICIPANTS: Bilateral ankles of 10 female (age = 19.8 +/- 1.1 years) and 10 male (age = 20.8 +/- 1.2 years) collegiate athletes were tested. INTERVENTION(S): Each ankle complex underwent loading using an ankle arthrometer under 4 test conditions consisting of 2 knee positions (90 degrees and 0 degrees of flexion) and 2 ankle positions (0 degrees and 10 degrees of plantar flexion [PF]). MAIN OUTCOME MEASURE(S): Recorded anterior laxity (mm) and stiffness (N/mm). RESULTS: Anterior laxity of the ankle complex was maximal with the knee positioned at 90 degrees of flexion and the ankle at 10 degrees of PF when compared with the knee positioned at 0 degrees of flexion and the ankle at 10 degrees or 0 degrees of PF (P < .001), whereas ankle complex stiffness was greatest with the knee positioned at 0 degrees of flexion and the ankle at 0 degrees of PF (P < .009). CONCLUSIONS: Anterior drawer testing of the ankle complex with the knee positioned at 90 degrees of flexion and the ankle at 10 degrees of PF produced the most laxity and the least stiffness. These findings indicate that anterior drawer testing with the knee at 90 degrees of flexion and the ankle at 10 degrees of PF may permit better isolation of the ankle capsuloligamentous structures.

The effects of repetitive overhead throwing on shoulder rotator isokinetic work-fatigue.

BACKGROUND: Muscle strength and endurance of the shoulder rotators is important for overhead throwing performance and dynamic glenohumeral stability. Baseball pitching is distinguished as an intermittent activity with explosive, high intensity muscle contractions separated by periods of rest. Rotator cuff muscle performance could acutely decrease due to fatigue associated with bouts of throwing. OBJECTIVE: This study examined the effects of repeated overhead throwing upon isokinetic muscle performance of the shoulder rotators. METHODS: Repeated-measures analyses of vari-ance were used to compare peak torque, total work, and work-fatigue by muscle group, time, and contraction type. Ten collegiate baseball pitchers underwent isokinetic testing of the internal (IR) and external shoulder (ER) rotators one week before and immediately after a throwing protocol of 60 maximal-effort pitches arranged into four innings of 15 pitches per inning. Isokinetic testing consisted of 12 concentric and eccentric repetitions at 300 deg/sec for internal and external rotation of the throwing extremity. RESULTS: The main effect of time and the interaction of muscle group and contraction type were significant for work-fatigue. Post-hoc analysis revealed that subjects had significantly greater eccentric IR work-fatigue (13.3 + 1%) compared to the pre-test (7.3 + 2%). DISCUSSION AND CONCLUSIONS: Throwing-related fatigue affected both muscle groups, especially the IR, which has implications for dynamic glenohumeral stability. Rehabilitation and conditioning programs for competitive baseball pitchers should emphasize eccentric muscle endurance training of the shoulder rotators.