Lower Back Injury
Conditions
Keywords
low back muscular strength and endurance
Brief summary
The investigators will conduct a controlled clinical trial with U.S. Army soldiers training to become combat medics. The purpose of this study is to determine if a 11-week, high intensity exercise program targeting the low back muscles using specialized equipment will result in a 25% increase in low back muscular strength and endurance compared with a lower intensity general core stability exercise.
Detailed description
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 11-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 (strengthening exercise) 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 active comparator control group (stabilization exercise) will perform 5 minutes of low intensity core stabilization exercises on the floor. Interventions will be carried out 1X/week for 11 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 11-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.
Interventions
OTHERLumbar ext. high intensity progressive resistance exercise
1 active set of 1 exercise, 1x/week, 11 weeks
OTHERLow intensity core stabilization exercise
1 set of 5 exercises, 1x/week, 11 weeks
Sponsors
Brooke Army Medical Center
University of South Florida
Study design
Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
PREVENTION
Masking
SINGLE (Outcomes Assessor)
Eligibility
Sex/Gender
ALL
Age
18 Years to 35 Years
Healthy volunteers
Yes
Inclusion criteria
* Age 18-35 years * Active duty soldiers in the US Army training to become combat medics at Fort Sam Houston
Exclusion criteria
* Cardiovascular contraindications to resistance exercise as identified by history and physical examination * Orthopedic contraindications to resistance exercise as identified by history and physical examination * History of systemic inflammatory disease or spinal surgery * Low back pain intensity \> mild * Disability \>= 50% on the Roland Morris Disability Questionnaire * Currently receiving care for spinal pain disorder/injury * Currently disabled due to spinal pain disorder/injury * Currently diagnosed with or receiving treatment for a psychological or psychiatric disorder * Currently performing progressive resistance exercises for the lumbar extensor muscles other than those included in standard for military fitness programs * Active workers' compensation or personal injury case * Pregnant * Simultaneously enrolled in another biomedical clinical trial * Drug or alcohol abuse within the past year * Any other condition, which in the opinion of the investigators or military medical authority, would put the candidate at increased safety risk or otherwise make the candidate unsuitable for this study * Unable or unwilling to complete the study procedures
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Isometric Lumbar Extension Muscular Strength at 11 Weeks | 11 weeks | Isometric lumbar extension muscular strength (torque - Nm) as assessed by a validated physical performance test on the lumbar dynamometer |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Isometric Core Muscular Endurance at 11 Weeks | 11 weeks | Isometric core muscular endurance as assessed by a validated physical performance test (prone static plank test) |
| Dynamic Lumbar Extension Muscular Endurance at 11 Weeks | 11 weeks | Dynamic lumbar extension muscular endurance (# repetitions at 50% peak torque) as assessed by a validated physical performance test on the lumbar dynamometer |
Countries
United States
Participant flow
Recruitment details
Recruitment, enrollment, baseline assessments, and randomization procedures were completed during June 2012 through May 2013 at Fort Sam Houston, TX.
Pre-assignment details
Assessed for eligibility: n = 698. Consented: n = 645. Deemed eligible to participate, completed baseline assessments for primary outcome, and randomized: n = 582. Reasons for ineligibility: declined to participate (n = 43), did not meet inclusion criteria (n = 28), and other or unknown reasons (n = 45).
Participants by arm
| Arm | Count |
|---|---|
| Strengthening Exercise Lumbar ext. high intensity progressive resistance exercise | 298 |
| Stabilization Exercise Low intensity core stabilization exercise | 284 |
| Total | 582 |
Withdrawals & dropouts
| Period | Reason | FG000 | FG001 |
|---|---|---|---|
| Overall Study | academic reason | 4 | 1 |
| Overall Study | changed companies | 20 | 34 |
| Overall Study | discharged from US Army | 3 | 4 |
| Overall Study | invalid follow-up strength data | 1 | 4 |
| Overall Study | on profile | 9 | 5 |
| Overall Study | other/unknown | 28 | 17 |
| Overall Study | Withdrawal by Subject | 3 | 2 |
Baseline characteristics
| Characteristic | Stabilization Exercise | Strengthening Exercise | Total |
|---|---|---|---|
| Age, Continuous | 21.5 years STANDARD_DEVIATION 3.6 | 21.8 years STANDARD_DEVIATION 3.8 | 21.7 years STANDARD_DEVIATION 3.7 |
| Dynamic Lumbar Extension Muscular Endurance | 22.0 repetitions STANDARD_DEVIATION 8 | 21.8 repetitions STANDARD_DEVIATION 7.7 | 21.9 repetitions STANDARD_DEVIATION 7.9 |
| Isometric Core Muscular Endurance | 172.8 seconds STANDARD_DEVIATION 64.1 | 169.0 seconds STANDARD_DEVIATION 62.4 | 170.8 seconds STANDARD_DEVIATION 63.2 |
| Isometric Lumbar Extension Muscular Strength | 271.7 Nm STANDARD_DEVIATION 92.8 | 275.4 Nm STANDARD_DEVIATION 87 | 273.7 Nm STANDARD_DEVIATION 89.9 |
| Race/Ethnicity, Customized American Indian | 5 participants | 3 participants | 8 participants |
| Race/Ethnicity, Customized American Indian, Asian, Hispanic, White/Cau | 0 participants | 1 participants | 1 participants |
| Race/Ethnicity, Customized American Indian, Black/African American, White/Cau | 0 participants | 1 participants | 1 participants |
| Race/Ethnicity, Customized American Indian, White or Caucasian | 2 participants | 3 participants | 5 participants |
| Race/Ethnicity, Customized Asian | 14 participants | 12 participants | 26 participants |
| Race/Ethnicity, Customized Asian, Black/African American, Hispanic, White/Cau | 0 participants | 1 participants | 1 participants |
| Race/Ethnicity, Customized Asian, Black or African American, Other | 0 participants | 1 participants | 1 participants |
| Race/Ethnicity, Customized Asian, Hispanic | 1 participants | 0 participants | 1 participants |
| Race/Ethnicity, Customized Asian, Pacific Islander | 1 participants | 0 participants | 1 participants |
| Race/Ethnicity, Customized Asian, White or Caucasian | 1 participants | 3 participants | 4 participants |
| Race/Ethnicity, Customized Black or African American | 26 participants | 27 participants | 53 participants |
| Race/Ethnicity, Customized Black or African American, Hispanic | 0 participants | 1 participants | 1 participants |
| Race/Ethnicity, Customized Black or African American, White or Caucasian | 3 participants | 0 participants | 3 participants |
| Race/Ethnicity, Customized Hispanic | 41 participants | 46 participants | 87 participants |
| Race/Ethnicity, Customized Hispanic, White or Caucasian | 2 participants | 2 participants | 4 participants |
| Race/Ethnicity, Customized Other/unknown | 10 participants | 6 participants | 16 participants |
| Race/Ethnicity, Customized Other, White or Caucasian | 0 participants | 1 participants | 1 participants |
| Race/Ethnicity, Customized Pacific Islander | 4 participants | 2 participants | 6 participants |
| Race/Ethnicity, Customized Pacific Islander, White or Caucasian | 2 participants | 0 participants | 2 participants |
| Race/Ethnicity, Customized White or Caucasian | 172 participants | 188 participants | 360 participants |
| Region of Enrollment United States | 284 participants | 298 participants | 582 participants |
| Sex: Female, Male Female | 68 Participants | 67 Participants | 135 Participants |
| Sex: Female, Male Male | 216 Participants | 231 Participants | 447 Participants |
Adverse events
| Event type | EG000 affected / at risk | EG001 affected / at risk |
|---|---|---|
| deaths Total, all-cause mortality | — / — | — / — |
| other Total, other adverse events | 6 / 298 | 1 / 284 |
| serious Total, serious adverse events | 0 / 298 | 0 / 284 |
Outcome results
Primary
Isometric Lumbar Extension Muscular Strength at 11 Weeks
Isometric lumbar extension muscular strength (torque - Nm) as assessed by a validated physical performance test on the lumbar dynamometer
Time frame: 11 weeks
Population: Adjusted (by baseline score) isometric lumbar extension muscular strength in Nm (mean ± SE) at follow-up
| Arm | Measure | Value (MEAN) | Dispersion |
|---|---|---|---|
| Strengthening Exercise | Isometric Lumbar Extension Muscular Strength at 11 Weeks | 310.2 Nm | Standard Error 6.1 |
| Stabilization Exercise | Isometric Lumbar Extension Muscular Strength at 11 Weeks | 282.7 Nm | Standard Error 6.1 |
Comparison: For the primary hypothesis, differences at follow-up between the two groups on lumbar extension muscular strength (Nm) were analyzed using linear mixed-effects regression models, accounting for the effects of cluster (platoon) and adjusting for baseline measures. The linear mixed-effects model treats the data as two levels (level 1 for individuals, level 2 for clusters), while also taking into account between-cluster variation.p-value: 0.001Mixed Models Analysis
Secondary
Dynamic Lumbar Extension Muscular Endurance at 11 Weeks
Dynamic lumbar extension muscular endurance (# repetitions at 50% peak torque) as assessed by a validated physical performance test on the lumbar dynamometer
Time frame: 11 weeks
Population: Adjusted (by baseline score) isometric core muscular endurance in seconds (mean ± SE) at follow-up. Differences in sample sizes for this outcome (compared with primary outcome) are due to invalid test data for this outcome (n = 11 stabilization arm; n = 18 strengthening arm).
| Arm | Measure | Value (MEAN) | Dispersion |
|---|---|---|---|
| Strengthening Exercise | Dynamic Lumbar Extension Muscular Endurance at 11 Weeks | 24.6 repetitions | Standard Error 1 |
| Stabilization Exercise | Dynamic Lumbar Extension Muscular Endurance at 11 Weeks | 21.9 repetitions | Standard Error 1 |
Comparison: For the primary hypothesis, differences at follow-up between the two groups on core muscular endurance (seconds) were analyzed using linear mixed-effects regression models, accounting for the effects of cluster (platoon) and adjusting for baseline measures. The linear mixed-effects model treats the data as two levels (level 1 for individuals, level 2 for clusters), while also taking into account between-cluster variation.p-value: 0.021Mixed Models Analysis
Secondary
Isometric Core Muscular Endurance at 11 Weeks
Isometric core muscular endurance as assessed by a validated physical performance test (prone static plank test)
Time frame: 11 weeks
Population: Adjusted (by baseline score) isometric core muscular endurance in seconds (mean ± SE) at follow-up. Differences in sample sizes for this outcome (compared with primary outcome) are due to invalid test data for primary outcome (n = 4 stabilization arm; n = 1 strengthening arm), and incomplete data for this outcome (n = 1 stabilization arm).
| Arm | Measure | Value (MEAN) | Dispersion |
|---|---|---|---|
| Strengthening Exercise | Isometric Core Muscular Endurance at 11 Weeks | 161.4 seconds | Standard Error 7.2 |
| Stabilization Exercise | Isometric Core Muscular Endurance at 11 Weeks | 160.2 seconds | Standard Error 7.2 |
Comparison: For the primary hypothesis, differences at follow-up between the two groups on core muscular endurance (seconds) were analyzed using linear mixed-effects regression models, accounting for the effects of cluster (platoon) and adjusting for baseline measures. The linear mixed-effects model treats the data as two levels (level 1 for individuals, level 2 for clusters), while also taking into account between-cluster variation.p-value: 0.871Mixed Models Analysis