External Training Load and  the Association With Back Pain in Competitive Adolescent Tennis Players: Results From the SMASH Cohort Study

Johansson F, Gabbett T, Svedmark P, Skillgate E. [published online ahead of print, 2021 Oct 25]. Sports Health. 2021;19417381211051636. doi:10.1177/19417381211051636
Full Text Freely Available

Association Between Spikes in External Training Load and Shoulder Injuries in Competitive Adolescent Tennis Players: The SMASH Cohort Study

Johansson F, Cools A, Gabbett T, Fernandez-Fernandez J, Skillgate E. [published online ahead of print, 2021 Oct 25]. Sports Health. 2021;19417381211051643. doi:10.1177/19417381211051643
Full Text Freely Available

Take-Home Message

Sudden increases in training/match play hours each week – not overall training load – may increase the risk of back pain or shoulder complaints/injuries among adolescent tennis players.


An athlete exposed to excessive external workload (e.g., distance covered, duration, or frequency of training/competition) may be at greater risk for injury. However, it remains unclear if this relationship exists among adolescent tennis players. Understanding the relationship between workload and the most common injuries in young tennis players (low back pain and shoulder injuries) may lead to changes in training or competition schedules that could reduce the risk of injury.

Study Goal

Hence, Johansson and colleagues used data from a longitudinal cohort called SMASH (Shoulder Management and Assessment Serving High Performance) to investigate if accumulated external workload spikes and high or low workload/age ratio were associated with back or shoulder pain.


Competitive tennis players (13 to 19 years) completed weekly surveys for 52 weeks to report back pain, shoulder complaints/injuries, and external workload (i.e., time engaged in match play, tennis practice, and non-tennis training activities). The authors defined a spike as a week when the training/match hours were at least 30% greater than the average number of training/match hours during the previous 4 weeks. Investigators looked at the relationship between the number of external workload spikes and the workload/age ratio to the onset of 1) back pain (pain intensity ≥2/10 in the lower back or the upper back/neck with a pain-related disability) or 2) shoulder complaints (≥20) and injuries (≥40; Oslo Sports Trauma Research Center Overuse Injury Questionnaire).


Investigators found that each external workload spike increased the risk of back pain and shoulder complaints/injury. However, training workload/age ratio was unrelated to back pain or shoulder complaints/injury.


Interestingly, while an adolescent tennis player’s overall training workload had no relationship to shoulder or back complaints, sudden increases in training load did.  Hence, a well-planned training program that limits large increases in external load may be needed to safely develop physical and technical abilities in adolescent tennis players. For example, it would be beneficial to determine if lowering the training hours during weeks with excessive match hours helps reduce the risk of shoulder or back complaints. The authors noted that these results should only be applied to tennis players competing at the regional or national levels. It would be helpful to see if these results apply to other tennis players or athletes in individual sports that may need to compete in multiple competitions during a tournament (e.g., swimmers).

Clinical Implications

Clinicians should educate athletes, coaches, and parents about maintaining a consistent schedule (similar number of match/training hours per week) for adolescent tennis players to reduce the risk for back pain and shoulder complaints. It may be helpful to work with these stakeholders to develop a strategy to monitor how many hours a player is training or competing each week.

Questions for Discussion

Do you track non-sport-related physical activity in athletes? Do you monitor competition duration in events that are not time bound (e.g., volleyball, cricket, softball, baseball)?

Post by: Erin Pletcher
Reviewed by: Jeffrey Driban

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