Differences in variables of physical fitness and stroke performance by competition level (i.e., elite vs. sub-elite players) have not been systematically investigated yet. Thus, the objective of the systematic review with meta-analysis was to characterize and quantify competition-level dependent differences in physical fitness and stroke performance in healthy tennis players. A systematic literature search was conducted in the databases PubMed, Web of Science, and SportDiscus from their inception date till May 2022. Studies were included if they investigated healthy tennis players and reported at least one measure of physical fitness (e.g., lower extremity muscle power, endurance, agility, speed) or stroke performance (e.g., stroke velocity). Weighted standardized mean differences (SMD) were calculated and reported according to their magnitude. The search identified a total of N = 12,714 records, 16 of which met the inclusion criteria. Competition-level dependent differences in physical fitness and stroke performance were investigated by 11 and 10 studies, respectively. For physical fitness, moderate (lower extremity muscle power: SMD = 0.53; endurance: SMD = 0.59; agility: SMD = 0.54) and small (speed: SMD = 0.35) effects were detected; all in favour of elite tennis players. However, sub-group analyses revealed an influence of players’ age showing higher SMD-values for adult than for young players. Further, a large effect (SMD = 1.00) was observed for stroke performance again in favour of elite tennis players. Lastly, a larger but not significantly different association between physical fitness and stroke performance was observed for elite (r = 0.562) compared to sub-elite (r = 0.372) tennis players. This systematic review and meta-analysis revealed better physical fitness and stroke performances in healthy elite compared to sub-elite tennis players. The greatest differences by competition level were shown in measures of lower extremity muscle power, endurance, and agility. Thus, training programs for sub-elite tennis players should place a special focus on these physical components.

This systematic scoping review aims to summarize findings regarding kinetic, kinematic, and electromyographic analyses of different characteristics (i.e., type/direction and stance style) of the tennis serve and groundstroke. A systematic search of the literature was performed on the databases PubMed, Web of Science, and SportDiscus from their inception date till May 2023. A descriptive analysis of results was conducted. The literature search identified a total of N = 899 records, 23 of which met the inclusion criteria and were analysed in this review. A total of 229 participants aged 18 to 62 years participated in the studies. The studies revealed varying results, ranging from significantly lower/higher values to no significant differences between serve/groundstroke characteristics. These inconsistent results may most likely be attributed to discrepancies in the methodological approach such as players’ age (18–62 years), sex (i.e., men only or both sexes), and performance level (i.e., recreational, intermediate, or advanced) as well as the applied measurement devices (i.e., force plate or pressure-detecting insoles; motion capture system, high-speed video recordings, or IMU sensors) and used outcomes (i.e., measured or estimated force etc.). Future research is needed to provide a comprehensive biomechanical analysis of different serve/groundstroke characteristics. Specifically, it is recommended to compare different tennis serve and groundstroke types/directions and stance styles in female and male age-matched players with diverging performance levels (i.e., recreational, intermediate, advanced) using combined (i.e., kinetic, kinematic, and electromyographic) biomechanical analysis.

Better physical fitness and stroke velocity in healthy elite compared to sub-elite tennis players have been shown in previous studies. However, evidence-based knowledge regarding the effectiveness of athletic training on physical fitness and stroke velocity is currently lacking. Thus, the objective of this systematic review with meta-analysis was to characterize, aggregate, and quantify athletic training effects on measures of physical fitness and stroke velocity in healthy youth and adult tennis players. A computerized systematic literature search was performed in the databases PubMed, Web of Science, and SportDiscus from their inception date to August 2022. Studies were included, among others, if the intervention period lasted a minimum of four weeks and if at least one parameter of physical fitness (i.e., speed, agility, lower-extremity muscle power, upper-extremity muscle power/strength, endurance, balance, flexibility) or stroke performance (i.e., stroke velocity) was tested. Initially, 11,511 articles were identified, after removing duplicates and assessing abstracts and full texts, 24 articles were used to calculate weighted standardized mean differences (SMD). For measures of physical fitness, athletic training resulted in small (speed:SMD = 0.44), moderate (endurance:SMD = 0.61, upper-extremity muscle power:SMD = 0.72; flexibility:SMD = 0.63), and large (agility:SMD = 0.93, lower-extremity muscle power:SMD = 0.88; upper-extremity muscle strength:SMD = 0.90; balance:SMD = 0.88) effects. Further, a large effect (SMD = 0.90) on stroke velocity was detected. The additionally performed sub-analyses showed differences in the effectiveness of athletic training on variables of physical fitness and stroke speed when considering players' age (i.e., youth players: <18 years; adult players: ≥18 years). Precisely, there was a high potential for training-related adaptations in adult players with respect to lower-extremity muscle power, upper-extremity muscle strength, and stroke velocity and in youth players with respect to endurance. Interventions to promote physical fitness and stroke velocity in healthy tennis players revealed varying levels of effectiveness ranging from small to large and these were additionally affected by players' age. Therefore, future studies should investigate modalities to increase training efficacy in youth and adult tennis players, especially for fitness components that showed small- to moderate-sized changes.

Compared to force-plates, pressure-detecting insoles have the advantage that vertical ground reaction force (vGRF) can be estimated under field rather than laboratory conditions. However, the question arises whether insoles also provide valid and reliable results compared to a force-plate (i.e., the gold standard). The study aimed to investigate the concurrent validity and test–retest reliability of pressure-detecting insoles during static and dynamic movements. Twenty-two healthy young adults (12 females) performed standing, walking, running, and jumping movements while simultaneously collecting pressure (GP MobilData WiFi, GeBioM mbH, Münster, Germany) and force (Kistler^®) data twice, 10 days apart. Concerning validity, ICC values showed excellent agreement (ICC > 0.75), irrespective of the test condition. Further, the insoles underestimated (mean bias: −4.41 to −37.15%) most of the vGRF variables. Concerning reliability, ICC values for nearly all test conditions also showed excellent agreement, and the SEM was rather low. Lastly, most of the MDC_95% values were low (≤5%). The predominantly excellent ICC values for between-devices (i.e., concurrent validity) and between-visits (i.e., test–retest reliability) comparisons suggest that the tested pressure-detecting insoles can be used under field-based conditions for a valid and reliable estimation of relevant vGRF variables during standing, walking, running, and jumping.

Fatigue is a multifactorial phenomenon involving central and peripheral mechanisms that could negatively affect performance-related measures in tennis players. The aim of this systematic review and meta-analysis was to quantify the effects of fatigue on physiological (e.g., blood lactate, heart rate), physical fitness (e.g., explosive muscle strength, speed), and stroke performance (e.g., stroke velocity or accuracy) related parameters in healthy tennis players and to provide insight into training and recovery strategies. A systematic literature search of PubMed, Web of Science, and SportDiscus identified studies that examined effects of fatigue in tennis. Inclusion criteria required that studies were conducted with healthy participants, applied fatigue-inducing interventions, and used pre-/post-test designs measuring physiological, physical, or stroke performance related parameters. Effect sizes were calculated using weighted standardized mean differences (SMD) to assess the impact of fatigue. The search identified a total of N = 642 records. Eighteen trials (318 tennis players) were included. Fatigue evoked large to moderate negative effect on physiological (SMDw = −4.19), physical fitness (SMDw = −0.74), and stroke performance (SMDw = −0.60) related parameters. The larger negative effects of fatigue on physiological and physical parameters compared to stroke performance-related outcomes indicate the importance of targeted recovery strategies (e.g., hydration, nutrition or cold baths). For stroke performance, non-fatigued states are recommended for learning new skills, while practice under fatigued conditions may help to maintain biomechanical efficiency during prolonged games.

There is evidence that height-induced postural threat leads to detrimental effects on walking performance. However, little is known about how the additional restriction of stabilizing arm movements affects gait and emotional state outcomes. The purpose was to investigate how the restriction of arm movement affects subjective and objective balance-related measures during walking at or above ground-level. Twenty-two healthy young adults (11 males, 11 females; mean ± SD age; 24.4 ± 4.9 years) walked five meters at self-selected speed on ground-level (no threat) and 80 cm above ground-level (threat) with free and restricted arm movement. Emotional state outcomes were quantified by assessing self-reported balance confidence, fear of falling, perceived instability, and conscious balance processing. Walking outcomes (i.e., gait velocity, cadence, step time, normal impulse) were calculated using pressure-detecting insoles. Irrespective of arm movement condition, height-induced postural threat evoked a decrease in balance confidence and increases in fear of falling, perceived instability, and conscious balance processing as well as deteriorations in walking outcomes (i.e., decrease in gait speed and cadence; increase in step time and normal impulse). For balance confidence and step time, the threat-induced impairments were further amplified when arm movements were restricted. The strengthening of the height-induced deteriorations in emotional state (balance confidence) and walking (step time) outcomes due to the restriction of the arm movements emphasizes the importance of stabilizing, free arm movements ('upper body strategy') for dynamic postural control.