Association Between Running Shoe Characteristics and Lower Extremity Injuries in United Stated Military Academy Cadets.
Helton GL, Cameron KL, Zifchock RA, Miller E, Goss DL, Song J, Neary MT. Am J Sports Med. 2019 Sept. https://doi.org/10.1177/0363546519870534 [Epub ahead of print]
Text Freely Available
Cadets wearing exercise shoes with a mild-to-moderate rigidity experienced fewer exercise-related injuries when compared to minimal rigidity. Likewise, shoes with a mild to moderate heel height reduced the risk of injury compared to minimal heel heights.
Running is a popular form of physical activity and is the primary form of endurance training among United States military personnel. Running accounts for 50% of all exercise- and sports-related injuries in the Army. It is important for healthcare providers to identify modifiable risk factors for running-related musculoskeletal injuries – such as shoe characteristics – to help prevent these injuries. Specifically, heel height, which provides cushion, and torsional stiffness, which provides flexibility or motion control, are two shoe characteristics that have received little attention regarding the risk of injury. Therefore, the researchers evaluated the relationship between lower extremity injuries and shoes’ heel height or torsional stiffness in U.S. Military Academy Cadets enrolled in basic training. The researchers tested 827 cadets during their first week of basic training and followed them for 9 weeks. Cadets never received standard shoes to wear. Instead, they were instructed to bring “relatively new shoes that have been broken in but not worn out.” The study team measured shoe characteristics with a custom device during the initial testing. The study team assumed these shoes would be worn throughout training. The research team then monitored the cadets for injuries, which they defined as occurring during basic training and resulting in at least 3 days of limited physical activity. Further, they defined an overuse injury as those with a gradual onset secondary to running or marching (repetitive microtrauma). Baseline data also included age, sex, height, body mass index, ethnicity, injury history, foot strike pattern, and foot posture index. The authors divided each shoe characteristic into minimal, mild, moderate, and extreme ranges. Further, torsional stiffness was broken down into medial and lateral rotations.
The researchers reported that about 18% of cadets had a lower extremity injury, and most (59%) were chronic in nature. Neither foot strike pattern nor foot posture index related to injury onset. Cadets wearing shoes with moderate lateral-torsional stiffness were ~50% less likely to incur any lower extremity injury or an overuse injury compared to those wearing shoes with minimal lateral-torsional stiffness. Further, individuals wearing mild or extreme lateral torsion were about 40% less likely to sustain an injury compared to those wearing shoes with minimal stiffness. Similarly, shoes with a mild or moderate heel height were 51% and 40%, respectively, less likely to sustain an injury compared to those wearing shoes with minimal heel height. No other shoe characteristics related to injury risk.
The authors of this study recommended that military cadets reporting for basic training should wear shoes with a mild to moderate lateral-torsional stiffness with an appropriate heel height (2.2 to 2.8 cm) to prevent injuries that are sustained during running or marching. Basic training performed by military cadets is a unique form of training and therefore requires a unique standard for shoe characteristics. Furthermore, the claim that mild to moderate torsional stiffness and moderate heel height reduce injury risk in cadets may not be applicable to most runners. Although the results of this study are highly promising, an underlying shoe characteristic that should not be ignored is the individual’s comfort. Heel height, motion control, and durability are all important in reducing impact forces and plantar pressures. The current recommendation is to find a shoe in between the extremes of torsional stiffness and heel height. The reported shoe characteristics in this study fall in between the minimalist and maximalist thresholds and the authors recommend advising patients in training environments like the military to avoid the extreme ends of lateral-torsional stiffness and heel height.
Questions for Discussion
Do you provide running shoe recommendations to all of your patients, or only those with a current or previous injury? What is the most important running shoe characteristics to consider when providing a recommendation to your patients?
Written by: Danielle M. Torp
Reviewed by: Jeffrey Driban