Does acute fatigue negatively affect the lower extremity injury risk profile? A systematic and critical review

Background Acute fatigue is hypothesized to alter injury riskprofiles by affecting intrinsic risk factors (i.e. postural control,hamstring strength). However, no systematic overview existsthat merges the insights of prospective lower extremity injuryrisk profiling with the effect of acute fatigue on functionaltest performance.Objective The objective of this review was to identify theinfluence of acute fatigue on prospectively determined modifiableintrinsic risk factors for lower extremity injuries and todetermine if individual fatigue outcomes should be integratedwithin an athlete centred injury risk profile and preventionstrategies.Design Systematic reviewMethods PubMed (MEDLINE), Web of Science, PEDro, andCochrane Library were searched until 29 May 2019. Studieswere eligible when the study outcomes encompassed intrinsicmodifiable risk factors, an acute fatigue intervention, andincluded healthy athletes or physically active people. Intrinsicmodifiable risk factors were identified through recent systematicreviews and meta-analyses. Referenced original researchpapers were used to determine outcome measures associatedwith increased injury risk.Main Outcome Measurements Acute fatigue effect on theintrinsic modifiable risk factors for lower extremity injuries.Results Forty studies reported acute fatigue effects on modifiablerisk factors, with eight studies matching all criteria fordata-extraction. Acute fatigue can decrease single leg posturalcontrol, decrease ankle joint position sense, decrease isokineticstrength of hamstring and quadriceps muscles and can affectisokinetic H:Q ratios.Conclusions Acute fatigue affects prospective intrinsic modifiablerisk factors, indicating an altered injury risk profile forlateral ankle sprain, patellofemoral pain syndrome and hamstringinjuries when fatigued. Current data does not allowconclusions for non-contact ACL injury risk. Cliniciansshould consider acute fatigue responses as part of injury riskprofiling strategies. Future research should allow for individualfatigability as a relevant injury risk outcome and mergeinsights from athlete centred injury risk profiling and fatigueresearch.