Conclusions Our results demonstrate that the existence of a relationship between training load and injury continues to be well supported in the literature and is strongest for subjective internal training load .
The directionality of this relationship appears to depend on the type and timeframe of load measured
Background The relationship between training load and musculoskeletal injury is a rapidly advancing area of research in need of an up date d systematic review .
A step towards understanding the mechanisms of running-related injuries.
OBJECTIVES To investigate the association between training-related characteristics and running-related injury using a new conceptual model for running-related injury generation , focusing on the synergy between training load and previous injuries , short-term running experience or body mass index ( > or < 25 kg m(-2 ) ) . DESIGN Prospect i ve cohort study with a 9-month follow-up . METHODS The data of two previous studies using the same methodology were revisited . Recreational runners ( n = 517 ) reported information about running training characteristics ( weekly distance , frequency , speed ) , other sport participation and injuries on a dedicated internet platform  . Weekly volume ( dichotomized into < 2h and ≥ 2 h ) and session frequency ( dichotomized into < 2 and ≥ 2 ) were the main exposures because they were considered necessary causes for running-related injury . Non-training-related characteristics were included in Cox regression analyses as effect-measure modifiers . Hazard ratio was the measure of association . The size of effect-measure modification was calculated as the relative excess risk due to interaction . RESULTS One hundred sixty-seven runners reported a running-related injury . Crude analyses revealed that weekly volume < 2h ( hazard ratio = 3.29 ; 95 % confidence intervals = 2.27 ; 4.79 ) and weekly session frequency < 2 ( hazard ratio = 2.41 ; 95 % confidence intervals = 1.71 ; 3.42 ) were associated with increased injury rate . Previous injury was identified as an effect-measure modifier on weekly volume ( relative excess risk due to interaction = 4.69 ; 95 % confidence intervals = 1.42 ; 7.95 ; p = 0.005 ) and session frequency ( relative excess risk due to interaction = 2.44 ; 95 % confidence intervals = 0.48 ; 4.39 ; p = 0.015 ) . A negative synergy was found between body mass index and weekly volume ( relative excess risk due to interaction = -2.88 ; 95 % confidence intervals = -5.10 ; -0.66 ; p = 0.018 ) . CONCLUSIONS The effect of a runner 's training load on running-related injury is influenced by body mass index and previous injury . These results show the importance to distinguish between confounding and effect-measure modification in running-related injury research
Conclusions Our results demonstrate that the existence of a relationship between training load and injury continues to be well supported in the literature and is strongest for subjective internal training load .
The directionality of this relationship appears to depend on the type and timeframe of load measured
Background The relationship between training load and musculoskeletal injury is a rapidly advancing area of research in need of an up date d systematic review .