Influence of Self-managed Rehabilitation on Work Efficiency in Active Duty Military With a Knee Injury

Knee injuries associated with intense physical training are one of the most frequent injuries associated with medical encounters for military members. The purpose of this study was to evaluate four approaches to physiotherapy rehabilitation and their effects on work efficiency in active duty military with a knee injury. The four groups included neuromuscular electrical stimulation (NMES), walking with a weighted vest (WALK), combined NMES/Walk, and standard physiotherapy rehabilitation. All groups received standard physiotherapy rehabilitation.We have previously reported that quadriceps muscle strength improved over 18 weeks in the study for the three interventions relative to standard rehabilitation alone. This report presents results from an examination of work efficiency as evaluated during a step test while measuring oxygen utilization.

A randomized controlled trial was conducted, with repeated outcome measures of work efficiency assessed at baseline, 3, 6, 12, and 18 weeks. The sample consisted of 67 active duty service members between the ages of 18 and 50 years with a knee injury. Participants were randomized to one of the four approaches to physiotherapy rehabilitation: (1) NMES was applied to the quadriceps muscle four times per week, for 30 minutes (15 minutes to each leg), consisting of 15 quadriceps muscle contractions per leg; (2) graduated strength walking using a weighted vest (WALK) was for 30 minutes, 3 to 4 days a week; (3) combined NMES with strength walking received both the NMES therapy and the weighted vest walking; and (4) standard physiotherapy consisted of progressive exercise with the number and type of sessions not controlled by the study. All four groups received the standard physiotherapy for a knee injury. The primary outcome was work efficiency, as measured by oxygen utilization during a 2-minute self-paced step test over 18 weeks. The primary analysis used repeated measures, linear mixed-effects models with a random effect for subject.

Both the number of steps performed and gross work efficiency improved during the study for all three intervention groups. For gross work efficiency, standard rehabilitation improved 12%, WALK showed a 19% improvement, NMES increased by 24%, and the NMES/Walk group improved by 40%.

All groups showed improved submaximal exercise efficiency based on oxygen utilization, with the intervention groups showing a greater improvement in work efficiency as compared to standard rehabilitation. Knee injuries can be problematic for active duty members because of reduced mobility leading to deconditioning and associated declines in work efficiency. Rehabilitative programs, including those described in this study, may minimize loss of work efficiency and fitness and promote a quicker recovery.