The Effect of External Load on Self Perceived Shoulder and Elbow Function in Competitive Junior Tennis Players
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Competitive junior tennis players undergo rigorous practice schedules and participate in monthly local and sectional tournaments. As a result of this competition, intense training loads are common. Training loads, such as hitting volume, may be related to shoulder and elbow function. The Kerlan-Jobe Orthopaedic Clinic (KJOC) Shoulder and Elbow Score allows players to rate self-perceived shoulder and elbow function. It is reasonable to suggest that training loads may affect a player’s self-perceived shoulder and elbow function when measured using the KJOC. Therefore, the purpose of this research was to determine if absolute and relative training load affects KJOC scores over an 8- month time period in competitive junior tennis players. Eighteen players, 14 males and 4 females, from one tennis academy, were recruited. Each player completed a KJOC prior to the start of data collection, at 4 months, and at 8 months. External load was defined as all training drills and simulation match play taking place between Monday-Friday and is referred to as hitting volume. Hitting volume was collected using a shot tracking sensor. Load was quantified as the sum of all shots (forehand swings, backhand swings, and overhead swings) over the 8-month observational period for each player. In order to quantify absolute load over the 8-month observational period players were categorized into two groups (high and low hitting volume). These groups were determined by calculating the median hitting volume (26,044 shots) for all participants. Players who recorded greater than 26,044 shots were grouped into the high volume (n=9) group while players below were considered low volume (n=9). Relative load was analyzed using the acute:chronic workload ratio (ACWR). Acute workload was determined as the total hitting volume for one week, while a 4-week rolling average hitting represented chronic workload. The acute workload was then divided by the chronic workload to determine the ACWR. Relative load was categorized with 2 groups: group 1 (n=10) acquired an ACWR of greater than 1.5 for more than 20% of the observational period while group 2 (n=10) players acquired an ACWR of less than 1.5 for more than 20% of the observational period. A 2X3 repeated measure ANOVA was used to determine differences in KJOC scores using both absolute and relative load groups. The results of the investigation identified no significant differences between high and low absolute volume groups on KJOC scores (F(1,16)=.12, P=.73, ηp2 =.01) at baseline, 4 months, or 8 months. Additionally, there were no differences in KJOC scores between high and low absolute volume groups (F(1,16)=.11, P=.74, ηp2 =.01). Additionally, the analysis identified no significant differences between high and low relative volume groups on KJOC scores at baseline, 4 months, or 8 months (F(1,16)=.12, P=.74, ηp2 =.01). Additionally, there were no differences in KJOC scores between those who had ACWR greater than 1.5 for more than 20% of the observational period (F(1,16)=.54, P=.47, ηp2 =.03) and those below 1.5. Our results indicate that hitting volume in these junior tennis players may not affect selfperceived shoulder and elbow function over the 8-month study period. It is likely these two variables are still important to risk of injury but appear independent of each another in the study conditions. While our sample size is small making differences difficult to detect, shoulder and elbow function may be driven by a variety of physiological and psychological factors beyond external training load. This was the first study, to the author’s knowledge, to investigate external training load and player perception of shoulder and elbow function in a tennis population.