It's not the destination, it's the 'road to load' that matters: a tennis injury prevention perspective

Immunological Response and Match Performance of Professional Tennis Players of Different Age Groups During a Competitive Season

ABSTRACT

Kozłowska, M, Żurek, P, Rodziewicz, E, Góral, K, Żmijewski, P, Lipińska, P, Laskowski, R, Walentukiewicz, AK, Antosiewicz, J, and Ziemann, E. Immunological response and match performance of professional tennis players of different age groups during a competitive season. J Strength Cond Res 35(8): 2255-2262, 2021-We aimed to investigate the effect of physical workloads on immunological response, match performance, and iron metabolism in professional tennis players of different age groups throughout the tournament season and to determine the interdependence of vitamin D status and inflammation. Thirty-eight young, male tennis players with a top national ranking (1-25) participated in this study and were assigned to the following age groups: cadets (CG), juniors (JG), and seniors (SG). Blood samples were collected at the beginning, midpoint, and end of the tournament season to assess the proinflammatory cytokine (tumor necrosis factor-alpha [TNF-α]), anti-inflammatory myokines (interleukin [IL]-6 and IL-10), heat shock proteins (HSP70, HSP27), iron metabolism markers, and vitamin D concentrations. The total number of matches (won and lost) at the national and international events was recorded. The IL-6 and IL-10 concentrations significantly increased across all groups in the middle and end of the tournament season (effect large and very likely). The TNF-α concentration was elevated at the end of the season in CG and SG. The increase in TNF-α concentration corresponded with an increase in hepcidin concentration in these groups. The significant increase in HSP27 concentration was only noticed in SG with normal vitamin D concentrations. In JG and SG, a mild seasonal increase in vitamin D concentration was noted, but still it was insufficient. The immunological response was not affected by the number of tennis matches; however, the anti-inflammatory effect was regulated by higher concentrations of vitamin D. Unexpectedly, most tennis players had vitamin D deficiency. Iron status remained unchanged.

Validity and reliability of a novel monitoring sensor for the quantification of the hitting load in tennis

Wearable sensor systems are a emerging tools for the evaluation of the sport’s activity and can be used to quantify the external workload of the athlete. The main goal of this paper was to evaluate the validity and reliability of the “Armbeep inertial measurement unit” (IMU) sensor both in a closed tennis exercise and in open matchplay. Twentyfour junior tennis players performed a baseline drill and played matches, during which they wore a combined accelerometer and gyroscope sensor. Video footage was concomitantly recorded using a digital video camera. The agreement between the measurements was assessed with the intraclass correlation coefficient (ICC) and the standard error of measurement (SEM). A simple linear regression was used to predict the number of shots registered from the video and from the Armbeep IMU sensor’s data. The number of total forehand and backhand shots during the drill repetitions showed an excellent test and re-test reproducibility (ICC≥0.90). There was a significant relationship between the Armbeep IMU sensor’s number of contacts and the total number of shots (R² = 0.938) which indicated the excellent reliability of the tested Armbeep IMU sensor for those parameters. Considering the accuracy of the total tennis shots and the small magnitude of error for wrist speed and acceleration, the Armbeep IMU sensor appears to be an appropriate on-court tool that can be used to monitor the hitting load during tennis practice and matches.

What Role Do Chronic Workloads Play in the Acute to Chronic Workload Ratio? Time to Dismiss ACWR and Its Underlying Theory

AIM

The aim of this study was to examine the associations between the injury risk and the acute (AL) to chronic (CL) workload ratio (ACWR) by substituting the original CL with contrived values to assess the role of CL (i.e., the presence and implications of statistical artefacts).

METHODS

Using previously published data, we generated a contrived ACWR by dividing the AL by fixed and randomly generated CLs, and we compared these results to real data. We also reproduced previously reported subgroup analyses, including dichotomising players' data above and below the median CL. Our analyses follow the same, previously published modelling approach.

RESULTS

The analyses with original data showed effects compatible with higher injury risk for ACWR only (odd ratios, OR: 2.45, 95% CI 1.28-4.71). However, we observed similar effects by dividing AL by the "contrived" fixed and randomly generated CLs: OR 1.95 (1.18-3.52) dividing by 1510 (average CL); and OR ranging from 1.16 to 2.07, using random CL 1.53 (mean). Random ACWRs reduced the variance relative to the original AL and further inflated the ORs (mean OR 1.89, from 1.42 to 2.70). ACWR causes artificial reclassification of players compared to AL alone. Finally, neither ACWR nor AL alone confer a meaningful predictive advantage to an intercept-only model, even within the training sample (c-statistic 0.574/0.544 vs. 0.5 in both ACWR/AL and intercept-only models, respectively).

DISCUSSION

ACWR is a rescaling of the explanatory variable (AL, numerator), in turn magnifying its effect estimates and decreasing its variance despite conferring no predictive advantage. Other ratio-related transformations (e.g., reducing the variance of the explanatory variable and unjustified reclassifications) further inflate the OR of AL alone with injury risk. These results also disprove the etiological theory behind this ratio and its components. We suggest ACWR be dismissed as a framework and model, and in line with this, injury frameworks, recommendations, and consensus be updated to reflect the lack of predictive value of and statistical artefacts inherent in ACWR models.

'In search of lost time': Identifying the causative role of cumulative competition load and competition time-loss in professional tennis using a structural nested mean model

Injury prevention is critical to the achievement of peak performance in elite sport. For professional tennis players, the topic of injury prevention has gained even greater importance in recent years as multiple of the best male players have been sidelined owing to injury. Identifying potential causative factors of injury is essential for the development of effective prevention strategies, yet such research is hampered by incomplete data, the complexity of injury etiology, and observational study biases. The present study attempts to address these challenges by focusing on competition load and time-loss to competition-a completely observable risk factor and outcome-and using a structural nested mean model (SNMM) to identify the potential causal role of cumulative competition load on the risk of time-loss. Using inverse probability of treatment weights to balance exposure histories with respect to player ability, past injury, and consecutive competition weeks at each time point; the SNMM analysis of 389 professional male players and 55,773 weeks of competition found that total load significantly increases the risk of time-loss (HR = 1.05 per 1,000 games of additional load 95% CI 1.01-1.10) and this effect becomes magnified with age. Standard regression showed a protective effect of load, highlighting the value of more robust causal methods in the study of dynamic exposures and injury in sport and the need for further applications of these methods for understanding how time-loss and injuries of elite athletes might be prevented in the future.

Injury rates in recreational tennis players do not differ between different playing surfaces

Objective

The aim of this study was to determine whether there is a difference in the prevalence of tennis injuries between the four most common court surfaces in the Netherlands, including hard court, clay, sand-fill artificial grass and red-sand-fill artificial grass. Natural grass was not included in this study.

Methods

This was a repeated cross-sectional study over 6 months, involving members of the Royal Netherlands Lawn Tennis Association (KNLTB). A monthly questionnaire was sent to a random sample of 20 000 KNLTB members, stratified by their club’s playing surface. The questionnaire included questions on court surface, tennis exposure and physical complaints, using the Oslo Sports Trauma Research Centre questionnaire on health problems.

Results

A total of 3656 (18%) of the 20 000 invited members completed at least one of the monthly questionnaires [mean age 49 years (15)]. A total of 4047 injuries were reported by 1957 respondents. Of these injuries, 3246 (80%) were overuse and 801 (20%) were acute. There were no statistically significant differences in injury prevalence between groups who played primarily on any one of the four court surfaces. However, players who played on multiple surfaces had a higher injury prevalence, particularly of overuse injuries, than those who primarily played on one court surface. Compared with the other court surfaces, there was a higher prevalence of lower limb overuse injuries when playing on hard court.

Conclusion

There is no significant difference in the overall prevalence of injury on clay, hard court, sand-fill artificial grass and red-sand-fill artificial grass.