Progressive submaximal effort hamstring muscle endurance is reduced after reconstruction of the anterior cruciate ligament.

BACKGROUND: Endurance capability in the muscles controlling the knee is poorly understood post anterior cruciate ligament (ACL) reconstruction, despite many sporting activities requiring notable muscle endurance. The hamstring muscles, when active, provide important anatomical support to protect the reconstructed graft. In the absence of good hamstring endurance, fatigue may predispose individuals to re-injury. OBJECTIVE: To assess whether ACL reconstruction (ACLR) with a hamstring graft leads to reduced hamstring endurance 9-13 months post-surgery. STUDY DESIGN: A cross-sectional inter-limb comparison study was undertaken with participants 9-13 months after an ACLR with a hamstring graft, and a group of age, sex, and activity-matched controls. There were 22 participants in each group. METHOD: Submaximal hamstring endurance was measured using a progressive fatigue test on an isokinetic dynamometer at a joint angular velocity of 120°/second. The dependant variable was the maximum number of repetitions performed. Statistical comparisons were made across injured, uninjured and control group limbs. RESULTS: There was a significant (p < 0.05) deficit in hamstring endurance observed between the injured leg (mean: 111 repetitions, SD 49) and uninjured leg (mean: 136 repetitions, SD 67) of the ACL group, but not between the uninjured and control group legs (mean: 124 repetitions, SD 50). CONCLUSION: The 18% deficit in submaximal hamstring endurance across the ACL-reconstructed individual's limbs is indicative of a notable loss in muscle performance at 9-13 months post-surgery. These results provide initial evidence for supporting further research examining the inclusion of hamstring endurance training in ACL rehabilitation programmes post-surgery.

Feasibility, criterion validity and retest reliability of exercise testing using the Astrand-rhyming test protocol with an adaptive ergometer in stroke patients.

PURPOSE: (i) to establish feasibility of the Astrand-Rhyming submaximal protocol using the adaptive ergometer in healthy participants, (ii) to test feasibility of this protocol in stroke patients, (iii) to identify clinical characteristics of stroke patients which limit testing, (iv) to establish criterion validity of V·O(2 steady state) ergometry data against the gold standard open-circuit spirometry measure and, lastly, (v) to test-retest reliability of the data generated by the test protocol. METHODS: A descriptive, cross sectional study design was implemented. Ten healthy participants (5 men, mean age 32 ± 6.6 y) and 20 chronic stroke patients (14 men, mean age 61.0 ± 11.6 y; mean months since stroke, 65.6 ± 34.4 y) took part in this study. Independent t-tests, Mann Whitney U tests and chi-square test identified characteristics of those who failed to successfully complete the protocol. Interclass correlation coefficients (ICCs) tested criterion validity and test-retest reliability. RESULTS: No adverse events occurred. All healthy participants (100%) complied with the test protocol and estimation of V·O(2max). 90% of stroke patients completed the test, with V·O(2max) estimated in 35% (7 / 20) stroke patients. Age and beta-blocker medication demonstrated statistical significance as barriers to the test protocol at p = 0.04 and p = 0.03, respectively. Criterion validity established by comparison with breath-by-breath gas analysis was excellent (ICC 0.93). Retest reliability of V·O(2max), steady-state V·O(2) and oxygen pulse had ICCs of 0.94, 0.96 and 0.97, respectively. CONCLUSIONS: The Astrand-Rhyming test protocol and MOTOmed Viva2 adaptive ergometer were feasible in healthy participants. The protocol was not feasible for V·O(2max) estimation for the majority of stroke patients based on heart rate response. The adapted steady state VO2 measures used however were feasible and had strong relationship to actual VO2 consumption. Criterion validity and retest reliability of test data were excellent.