Research Summary: The effect of low back pain on trunk muscle size/function and hip strength in elite football players

Brief Summary

The aim of this study was to identify possible relationships between lower back pain (LBP), trunk muscle size and function, and isometric hip muscle strength among football players by examining changes in these between the start and end of preseason. The hypothesis was that players with LBP would demonstrate reduced trunk muscle size and function and reduced hip muscle strength at the beginning and end of the preseason period.
The study used 25 players from a professional football club who were assessed at the start and end of preseason. At the beginning of preseason, players answered a LBP questionnaire. Those with relevant pain history were asked to rate their pain (VAS). Ultrasound imaging was used to measure the cross-sectional area of the multifidus and quadratus lumborum. Activation was assessed by imaging the multifidus, transversus abdominis and internal oblique muscles in a contracted and rested state. A handheld dynamometer tested hip adduction, abduction, flexion, and external rotation. Players were asked to perform one practice rep followed by three maximal efforts. The average of the three efforts was taken and multiplied by the lever arm length to calculate the score in torque.

Alongside the team's on-field sessions, the players underwent an injury prevention program over preseason. This program took place twice weekly and consisted of a ‘gym resistance session’ containing six exercises performed against low - moderate resistance and a ‘core, agility and proprioception session’ which involved body weight, floor-based exercises, balance and SAQ/plyometric drills.

Of the 25 players that started the study, 23 players completed the end-of-preseason testing. 7 players reported lower back pain in the initial questionnaire, and none reported discomfort significant enough to interfere with the training schedule. There was a significant interaction effect for “time” and lower back pain for the cross-sectional area of the multifidus. The most significant increase in cross-sectional area was observed in the 7 players reporting lower back pain at the start of preseason. At the L2 vertebral level, players with lower back pain contracted multifidus more than players without LBP. All other contraction results showed no significance; neither did the effect for time. Isometric hip strength results demonstrated a significant interaction between the dominant kicking leg and lower back pain. Abductors were stronger on the stance leg than the kicking leg in players without LBP. Adductors were stronger on the kicking leg compared with the stance leg in players without LBP. This trend was reversed with the presence of lower back pain. Unfortunately, isometric testing was not repeated at the end of preseason and is a limitation of this study. 

This study demonstrated that LBP was associated with the size of the multifidus muscles at the start of preseason in professional football players. Muscle size was modifiable, and the increase in cross-sectional area was associated with a reduction in pain levels during preseason. 

With the correct interventions, developing the cross-sectional area of multifidus can have a positive impact on LBP in professional football. As a secondary observation, a significant trend was identified in hip isometric strength profiles for those experiencing LBP. The implications of this trend were not explored and would require further research. Reassessment of this isometric strength profile at the end of preseason would have proved extremely valuable to note whether a correction in strength deficiencies had occurred throughout preseason and contributed to the reduction in LBP. 

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If you would like to find out more about how the KT360 can help your organization assess isometric hip strength profiles in your preseason please visit our e-book; A Comprehensive Guide to Preseason Screening in Elite Football. Our staff are also able to assist with the RTU imaging of hip and trunk muscles for the assessment of CSA and motor control should you require assistance in this space.