Part 3: Injury Risk Assessing Muscular Endurance and Strength
Given the active nature of military and law enforcement, musculoskeletal injury is a leading cause of disability and time off. Exposure to new physical training programs, coupled with high stress environments, can increase injury risk and may result in a large financial and logistic complications.
During the initial training camp for the military, about 25% of male and 55% of female recruits will experience at least one musculoskeletal injury. Injuries are divided into modifiable and non-modifiable risk factors. Modifiable risk factors include training program, footwear & equipment. Non-modifiable risk factors include gender, age and previous injury history.
In this article we will discuss the research findings that attempted to identify specific tests of muscular strength and endurance that could predict the risk of injury. The majority of studies were in military and law enforcement (male and female) and professional athletes.
The research is based on a total of 45 articles written between 1970 and 2015 that included male and females, between18-65 years old, with reports on physical fitness measures (pushups, setups etc…) and injury exposure (acute, overuse). Injury was defined as the individual being treated by a health care provider.
The majority (69%) of studies were conducted in the military environment, mostly in basic training (61%). The remaining studies were done in professional athletes (13%), collegiate athletes (11%), physical education majors (4%) and FBI trainees (3%).
Pushups
There is strong evidence that pushups are associated with increased injury risk in males.
There is limited evidence that pushups are associated with increased injury risk in females.
Sit-Ups
There is limited evidence for women and moderate evidence in men that poor sit-up scores increase injury risk.
Pull-Ups
There is insufficient evidence to support score on pull-up tasks as a risk factor for injury.
Additional tests of muscular strength
Isokinetic testing: moderate evidence on association of isokinetic muscle strength of the ankle, although direction cannot be definitively determined. Moderate evidence that knee flexion strength is associated with injury.
Isotonic testing: there is limited association that upper, lower or full body isotonic testing can predict injury risk.
Isometric testing: isometric strength testing is moderately associated with injury risk, and the direction of association cannot be stated.
Other tests
Test to failure: Researchers also looked at “tests to failure” like holding a weight, bench pressing, planks, crunch hold and wall-sits. There was a moderate amount of evidence that these tests can predict injury risk.
Composite Fitness scores: there is moderate evidence that fitness scores (a battery of tests including sit-ups, pushups, pull-ups and back extensions) are associated with injury risk, direction cannot be stated.
Summary
It is interesting to note that there were differences in injury risk based on gender and athletic capability. Studies demonstrate differences in risk between genders (pushups and sit ups). Weak upper body and abdominal strength/endurance was predictive of injury in men, but limited in females. Individuals with weaker or very strong lower body strength were at higher risk of injury. It is hypothesized that people with very strong lower bodies may apply themselves more or perhaps engage in more risky behavior when training, thus increasing injury risk. A study of Finnish soldiers that scored in the upper quartiles were 3.5x more likely to experience meniscus injury and 2.6x more likely to sustain an ACL or PCL injury.
Who can benefit from this information? Tactical athletes (SWAT, FBI field agents, police officers), non-combatants such as fire fighters and paramedics, and athletes.