The Relationship Between Training Load and Injury in Athletes:
A Systematic Review
Eckard et al completed a systematic review of the literature regarding training load management and musculoskeletal injury risk.
As usual, it is important we define our terms for these discussions. The authors define training load as follows, “Training load is defined as the cumulative amount of stress placed on an individual from single or multiple training sessions over a period of time.”
There are several ways to measure training load: 1. Internal
2. External
3. Absolute
4. Relative
External training load is defined as, “any external stimulus applied to an athlete independent of their internal characteristics.” Examples: distance, matches played, pitches thrown or in the case of the strength athlete – load on the barbell.
Internal training load is the quantification of “an athlete’s response to an external load”. There are two broad categories of internal training load: 1) Subjective Measures and 2) Objective Measures.
Examples of subjective internal training load = session RPE (sRPE) or RPE for a given set or exercise. Another example for the strength based athlete would be Reps in Reserve (RIR).
Examples of objective internal training load = non-reported measurements by the athlete such as heart rate (HR) and/or blood lactate.
Absolute training load = “summation of load values over a given period”.
Relative training load = loads “that take into account ‘the rate of load application, history of loading, or fitness level of the athlete’”. Relative loads typically express variation in loads between two time periods.
Examples: Acute:Chronic Workload ratio. Acute for a team-based athlete typically includes the summation of the prior week of training load (sRPE x minute of training) and the chronic training load equals the average of the prior 3-4 weeks of training load.
Now that we’ve defined terms, what did the study find?
57 articles were included in the data synthesis.
The authors concluded:
“Finally, the evidence for a relationship between training load and injury in competitive athletes has been substantially strengthened in the past 2 years and continues to be strongest for sRPE and the ACWR. The shape and direction of the load–injury relationship varies across studies and may depend on the type and timeframe of load examined.”
Previously the stance was there was emerging evidence demonstrating a relationship between training load and musculoskeletal injury. However with this new review by Eckard et al, there is sufficient evidence to state, “Together, these studies have contributed meaningfully to the literature by strengthening the evidence for a relationship between training load and injury risk, and have led us to conclude that the evidence for the existence of this relationship has shifted from emerging to established.”
Go read this article in its entirety because there is some nuance to the discussion.