The effects of spinal manipulation on performance-related outcomes in healthy asymptomatic adult population: a systematic review of best evidence

The effectiveness of spinal manipulative therapy (SMT) for improving athletic performance in healthy athletes is unclear. Assessing the effect of SMT on other performance outcomes in asymptomatic populations may provide insight into the management of athletes where direct evidence may not be available. Our objective was to systematically review the literature on the effect of SMT on performance-related outcomes in asymptomatic adults. MEDLINE, CINAHL, SPORTDiscus, and Cochrane Central Register of Controlled Trials were systematically searched from 1990 to March 23, 2018. Inclusion criteria was any study examining a performance-related outcome of SMT in asymptomatic adults. Methodological quality was assessed using the SIGN criteria. Studies with a low risk of bias were considered scientifically admissible for a best evidence synthesis. We calculated the between group mean change and 95% confidence intervals. Of 1415 articles screened, 20 studies had low risk of bias, seven were randomized crossover trials, 10 were randomized controlled trials (RCT) and three were RCT pilot trials. Four studies showed SMT had no effect on physiological parameters at rest or during exercise. There was no effect of SMT on scapular kinematics or transversus abdominus thickness. Three studies identified changes in muscle activation of the upper or lower limb, compared to two that did not. Five studies showed changes in range of motion (ROM). One study showed an increase lumbar proprioception and two identified changes in baropodometric variables after SMT. Sport-specific studies show no effect of SMT except for a small increase in basketball free-throw accuracy. The preponderance of evidence suggests that SMT in comparison to sham or other interventions does not enhance performance-based outcomes in asymptomatic adult population. All studies are exploratory with immediate effects. In the few studies suggesting a positive immediate effect, the importance of such change is uncertain. Further high-quality performance specific studies are required to confirm these preliminary findings.