Reduction of Risk for Low Back Injury in Theater of Operations

• Change from baseline in Isometric lumbar extensor muscular strength at 12 weeks [ Time Frame: 12 weeks ] [ Designated as safety issue: No ]
  Isometric lumbar extensor muscular strength (torque) as assessed by a validated physical performance test on the lumbar dynamometer.
  
  

• Change from baseline in endurance as measured through physical performance tests at 12 weeks [ Time Frame: 12 weeks ] [ Designated as safety issue: No ]
  Secondary measures include dynamic lumbar extension endurance, isometric trunk extension endurance, dynamic trunk extension endurance, and isometric core stability muscular endurance by validated physical performance tests.
  
  

Background Low back injury is responsible for the largest percentage of non-battle injuries in the theater of operations and is a large contributor to non-expiration of active service attrition in the US Armed Forces. Weakness and poor endurance of the back muscles are associated with low back injury. Targeted, high intensity exercise approaches using specialized equipment to develop the strength and endurance of the "weak link" muscle group (the lumbar extensors) have been shown to reduce risk for low back injury in high-risk civilian workers, but have not been widely implemented in military settings.

Objective/Hypothesis Specific Aim: In a controlled clinical trial, the investigators will assess the effectiveness of a high intensity progressive resistance exercise training program targeting the lumbar extensors to improve lumbar extensor muscular strength and endurance in US Army soldiers.

Hypothesis: A high intensity progressive resistance exercise for the lumbar extensors will result in a 25% increase in lumbar extensor muscular strength and endurance compared with control following the 12-week intervention.

Study Design A mixed methods, two-arm, controlled clinical trial with cluster randomization will be conducted. The sampling frame will be soldiers training to become combat medics from one domestic US Army base. Soldiers will be randomly assigned (by platoon) to one of two interventions - experimental or control. All participants at a given platoon will receive the same intervention and all interventions will be carried out at the US Army base, in addition to the soldiers' usual physical fitness training program. Participants randomized to the experimental group will perform lumbar extensor muscle progressive resistance exercise using standardized protocols. Exercise training will consist of 1 set of high intensity, progressive resistance exercise for lumbar extensors on specialized equipment. Participants in the control group will perform 5 minutes of low intensity core stabilization exercises on the floor. Interventions will be carried out 1X/week for 12 weeks. Outcome measures that will be utilized to test the hypothesis of Aim 1 include validated physical fitness tests for lumbar extension muscular strength and endurance. Fitness tests will be conducted at baseline and following the 12-week intervention period.

Relevance Soldiers preparing for deployment are in need of advanced technology to help improve and optimize the functional capacity of the lumbar extensor muscles. Assuming positive results from this study and confirmatory trials, implementation of this targeted exercise protocol will maximize resilience in soldiers at high risk for low back injury, thereby helping them become more physically fit to counteract the extreme physical demands required in combat.