Spatiotemporal analysis of 3D kinematic asymmetry in professional cycling during an incremental test to exhaustion.

This study investigated the influence of an incremental exercise on bilateral asymmetry through the spatio-temporal evolution of 3D joint angular displacement, using the Normalized Symmetry Index ([Formula: see text]) and cross-correlation methods. Twelve professional cyclists performed an incremental test to exhaustion, during which motion capture was used. Results revealed a decrease in range of motion between the first and last stages for twelve of the eighteen joint rotations, with the highest impact observed for right hip flexion/extension (61.8 ± 4.7° to 58.8 ± 4.1°, p < 0.05, ES = 0.68). For both stages, significant bilateral differences greater than 10° were observed for hip and knee flexion/extension (p < 0.05, ES>0.90) and ankle and hip internal/external rotation (p < 0.05, ES>0.25). Cross-correlation displayed the lowest pattern similarities for hip abduction/adduction and the highest similarities for knee flexion/extension, ankle plantarflexion/dorsiflexion and hip internal/external rotation. The cross-correlation method showed that the right leg was mostly ahead of time with respect to the left leg, a trend that was accentuated with power output increase. Instantaneous [Formula: see text] fluctuated up to 18% throughout the pedalling cycle, with different behaviour between the power and recovery phases. This study demonstrated the workload effects on side-to-side joint angular pattern similarity.

Professional tennis players' serve: correlation between segmental angular momentums and ball velocity.

The purpose of the study was to identify the relationships between segmental angular momentum and ball velocity between the following events: ball toss, maximal elbow flexion (MEF), racket lowest point (RLP), maximal shoulder external rotation (MER), and ball impact (BI). Ten tennis players performed serves recorded with a real-time motion capture. Mean angular momentums of the trunk, upper arm, forearm, and the hand-racket were calculated. The anteroposterior axis angular momentum of the trunk was significantly related with ball velocity during the MEF-RLP, RLP-MER, and MER-BI phases. The strongest relationships between the transverse-axis angular momentums and ball velocity followed a proximal-to-distal timing sequence that allows the transfer of angular momentum from the trunk (MEF-RLP and RLP-MER phases) to the upper arm (RLP-MER phase), forearm (RLP-MER and MER-BI phases), and the hand-racket (MER-BI phase). Since sequence is crucial for ball velocity, players should increase angular momentums of the trunk during MEF-MER, upper arm during RLP-MER, forearm during RLP-BI, and the hand-racket during MER-BI.

How does the tennis serve technique influence the serve-and-volley?

In tennis, a high ball velocity and a fast run toward the net are key features to successful performance of "serve-and-volley" players. For the serve, tennis players can use two techniques: the foot-up (FU) or foot-back (FB) technique. The aim of this study was to determine if the running time toward the net after the serve and the ball velocity (V(ball)) vary between these two techniques. Moreover we analysed the angular momentum values of the trunk and of the arm holding the racquet. Fifteen expert tennis players performed six successful serve-and-volleys with both techniques. Running time to the net is significantly lower for FB, whereas V(ball) is significantly higher for FU. Trunk and arm angular momentums about the transverse axis are significantly higher with FU before ball impact. A significant correlation (r = 0.81, P < 0.001) exists between changes in the maximal trunk angular momentum and in running time to the net between the two serve techniques. A significant correlation (r = 0.84, P < 0.001) also exists between changes in the maximal trunk angular momentum and in V(ball) between the two serve techniques. According to these results, FB is the best technique for moving as quickly as possible to the net because of a lower trunk angular momentum.

Inverse relationship between percentage body weight change and finishing time in 643 forty-two-kilometre marathon runners.

OBJECTIVE: The purpose of this study was to determine the relationship between athletic performance and the change in body weight (BW) during a 42 km marathon in a large cohort of runners. METHODS: The study took place during the 2009 Mont Saint-Michel Marathon (France). 643 marathon finishers (560 males and 83 females) were studied. The change in BW during the race was calculated from measurements of each runner's BW immediately before and after the race. RESULTS: BW loss was 2.3 ± 2.2% (mean±SEM) (p<0.01). BW loss was -3.1 ± 1.9% for runners finishing the marathon in less than 3 h; -2.5 ± 2.1% for runners finishing between 3 and 4 h; and -1.8 ± 2.4% for runners who required more than 4 h to complete the marathon. The degree of BW loss was linearly related to 42 km race finishing time (p<0.0000001). Neither age nor gender influenced BW loss during the race. CONCLUSIONS: BW loss during the marathon was inversely related to race finishing time in 643 marathon runners and was >3% in runners completing the race in less than 3 h. These data are not compatible with laboratory-derived data suggesting that BW loss greater than 2% during exercise impairs athletic performance. They match an extensive body of evidence showing that the most successful athletes in marathon and ultra-marathon running and triathlon events are frequently those who lose substantially more than 3-4% BW during competition.

Intense exercise training induces adaptation in expression and responsiveness of cardiac ß-adrenoceptors in diabetic rats.

BACKGROUND: Informations about the effects of intense exercise training on diabetes-induced myocardial dysfunctions are lacking. We have examined the effects of intense exercise training on the cardiac function of diabetic rats, especially focusing on the Langendorff ß-adrenergic responsiveness and on the ß-adrenoceptors protein expression. METHODS: Control or Streptozotocin induced-diabetic male Wistar rats were randomly assigned to sedentary or trained groups. The training program consisted of 8 weeks running on a treadmill (10° incline, up to 25 m/min, 60 min/day) and was considered to be intense for diabetic rats. RESULTS: This intense exercise training amplified the in vivo diabetes-induced bradycardia. It had no effect on Langendorff basal cardiac contraction and relaxation performances in control and diabetic rats. In diabetic rats, it accentuated the Langendorff reduced responsiveness to ß-adrenergic stimulation. It did not blunt the diabetes-induced decrease of ß1-adrenoceptors protein expression, displayed a significant decrease in the ß2-adrenoceptors protein expression and normalized the ß3-adrenoceptors protein expression. CONCLUSIONS: Intense exercise training accentuated the decrease in the myocardial responsiveness to ß-adrenergic stimulation induced by diabetes. This defect stems principally from the ß2-adrenoceptors protein expression reduction. Thus, these results demonstrate that intense exercise training induces specific effects on the ß-adrenergic system in diabetes.

Activity, inactivity and quality of life among Lebanese adolescents.

BACKGROUND: The aim of the present study was to investigate recent overweight and obesity prevalence rates for Lebanese adolescents, and to examine differences in physical activity, screen time (sum of time spent in front of TV, computer, and videogames), and health-related quality of life (HRQOL) for the first time among normal, overweight, and obese adolescents. METHODS: One thousand Lebanese adolescents (14-18 years old) from nine schools participated in the study. Height, weight, physical activity, screen time, and HRQOL variables were assessed using validated self-report questionnaires. RESULTS: A total of 7.8% of boys and 1.75% of girls were obese, and 22.5% of boys and 12.47% of girls were overweight. Normal-weight boys reported higher physical activity scores at health clubs than obese boys. Normal-weight girls reported higher leisure time and total physical activity scores than obese girls. In the normal-weight group, boys reported higher total screen time than girls. Normal-weight boys reported higher physical functioning scores than their obese peers. Normal-weight girls reported higher physical functioning and average HRQOL scores than obese girls. Normal-weight and overweight boys reported higher average HRQOL scores than girls. CONCLUSION: The present study is the first to provide data on physical activity, screen time, and HRQOL among Lebanese adolescents. Despite the need for further research, all those concerned with the pediatric population are urged to develop and implement effective strategies to increase physical activity and improve HRQOL among adolescents based on the present findings.

Body mass index and body fat in Lebanese female adolescents.

OBJECTIVE: The aim of this study is to investigate the relation between body mass index (BMI) and body fat (BF) among Lebanese female adolescents. METHODS: 51 Lebanese females aged 12 to 18 years participated in this study. BMI was calculated as weight/height. Adiposity was measured by dual energy X-ray absorptiometry (DEXA). RESULTS: Correlation coefficient of percent body fat (%BF) with BMI is 0.82. Correlation coefficient of fat mass (BF) with BMI is 0.93. The two linear regression formulas are: %BF = 6.89 + (1.1 *BMI) and BF = - 0.425 + (129 *BMI). CONCLUSION: Correlations of BMI with DEXA measurements were higher with BF than %BF. For a given BMI, Lebanese girls have a higher than expected %BF. Based on the current findings, there may be a need to develop new cutoff points. From a public health perspective, this may considerably increase the prevalence of obesity among Lebanese female adolescents.

Does the Level of Graphical Detail of a Virtual Handball Thrower Influence a Goalkeeper's Motor Response?

The authors investigated how different levels of detail (LODs) of a virtual throwing action can influence a handball goalkeeper's motor response. Goalkeepers attempted to stop a virtual ball emanating from five different graphical LODs of the same virtual throwing action. The five levels of detail were: a textured reference level (L0), a non-textured level (L1), a wire-frame level (L2), a point-light-display (PLD) representation (L3) and a PLD level with reduced ball size (L4). For each motor response made by the goalkeeper we measured and analyzed the time to respond (TTR), the percentage of successful motor responses, the distance between the ball and the closest limb (when the stopping motion was incorrect) and the kinematics of the motion. Results showed that TTR, percentage of successful motor responses and distance with the closest limb were not significantly different for any of the five different graphical LODs. However the kinematics of the motion revealed that the trajectory of the stopping limb was significantly different when comparing the L1 and L3 levels, and when comparing the L1 and L4 levels. These differences in the control of the goalkeeper's actions suggests that the different level of information available in the PLD representations (L3 and L4) are causing the goalkeeper to adopt different motor strategies to control the approach of their limb to stop the ball. Key pointsVirtual reality technology can be used to analyze sport performance because it enables standardization and reproduction of sport situations.Defining a minimal graphical level of detail of a virtual action could decrease the real time calculation of a virtual reality system.A Point Light Display graphical representation of a virtual throwing motion seems to influence the regulation of action of real handball goalkeepers.

Catecholamines and the effects of exercise, training and gender.

Stress hormones, adrenaline (epinephrine) and noradrenaline (norepinephrine), are responsible for many adaptations both at rest and during exercise. Since their discovery, thousands of studies have focused on these two catecholamines and their importance in many adaptive processes to different stressors such as exercise, hypoglycaemia, hypoxia and heat exposure, and these studies are now well acknowledged. In fact, since adrenaline and noradrenaline are the main hormones whose concentrations increase markedly during exercise, many researchers have worked on the effect of exercise on these amines and reported 1.5 to >20 times basal concentrations depending on exercise characteristics (e.g. duration and intensity). Similarly, several studies have shown that adrenaline and noradrenaline are involved in cardiovascular and respiratory adjustments and in substrate mobilization and utilization. Thus, many studies have focused on physical training and gender effects on catecholamine response to exercise in an effort to verify if significant differences in catecholamine responses to exercise could be partly responsible for the different performances observed between trained and untrained subjects and/or men and women. In fact, previous studies conducted in men have used different types of exercise to compare trained and untrained subjects in response to exercise at the same absolute or relative intensity. Their results were conflicting for a while. As research progressed, parameters such as age, nutritional and emotional state have been found to influence catecholamine concentrations. As a result, most of the recent studies have taken into account all these parameters. Those studies also used very well trained subjects and/or more intense exercise, which is known to have a greater effect on catecholamine response so that differences between trained and untrained subjects are more likely to appear. Most findings then reported a higher adrenaline response to exercise in endurance-trained compared with untrained subjects in response to intense exercise at the same relative intensity as all-out exercise. This phenomenon is referred to as the 'sports adrenal medulla'. This higher capacity to secrete adrenaline was observed both in response to physical exercise and to other stimuli such as hypoglycaemia and hypoxia. For some authors, this phenomenon can partly explain the higher physical performance observed in trained compared with untrained subjects. More recently, these findings have also been reported in anaerobic-trained subjects in response to supramaximal exercise. In women, studies remain scarce; the results are more conflicting than in men and the physical training type (aerobic or anaerobic) effects on catecholamine response remain to be specified. Conversely, the works undertaken in animals are more unanimous and suggest that physical training can increase the capacity to secrete adrenaline via an increase of the adrenal gland volume and adrenaline content.

Force-plate based computation of ankle and hip strategies from double-inverted pendulum model.

BACKGROUND: Using statistical characteristics of the centre of pressure displacement or of the ground reaction forces, it is difficult to have quantitative evaluation of the equilibrium strategy employed (ankle or hip). The purpose of this study is to validate a new force-plate based approach that allows to evaluate postural strategies employed through a method based on a double-inverted pendulum model. METHODS: This method allows to compute ankle and hip joint motion only from force plate data and relies on inverse kinematics with the centre of mass considered as the end effector. Furthermore, an index, depending on the covariance between hip and ankle angles, is proposed to quantify the strategy used. To validate the method and the strategy index, we compare the results of our computation to an optical stereophotogrammetry measurement of the angles considered as reference value. FINDINGS: The experiments demonstrate that our method provides acceptable results. The root mean square error between computed and measured hip and ankle angles stands between 4.5 x 10(-3)degrees for ankle angle in static condition and 1.1 x 10(-1) degrees for hip angle in hip forced condition. INTERPRETATION: The main interest of our method for clinicians is that it allows to retrieve the ankle and hip angles only using a simple and widespread device, the force-plate. Moreover, it proposes a new postural index that can be also be computed without videographic systems.

Influence of a Prolonged Tennis Match Play on Serve Biomechanics.

The aim of this study was to quantify kinematic, kinetic and performance changes that occur in the serve throughout a prolonged tennis match play. Serves of eight male advanced tennis players were recorded with a motion capture system before, at mid-match, and after a 3-hour tennis match. Before and after each match, electromyographic data of 8 upper limb muscles obtained during isometric maximal voluntary contraction were compared to determine the presence of muscular fatigue. Vertical ground reaction forces, rating of perceived exertion, ball speed, and ball impact height were measured. Kinematic and upper limb kinetic variables were computed. The results show decrease in mean power frequency values for several upper limb muscles that is an indicator of local muscular fatigue. Decreases in serve ball speed, ball impact height, maximal angular velocities and an increase in rating of perceived exertion were also observed between the beginning and the end of the match. With fatigue, the majority of the upper limb joint kinetics decreases at the end of the match. No change in timing of maximal angular velocities was observed between the beginning and the end of the match. A prolonged tennis match play may induce fatigue in upper limb muscles, which decrease performance and cause changes in serve maximal angular velocities and joint kinetics. The consistency in timing of maximal angular velocities suggests that advanced tennis players are able to maintain the temporal pattern of their serve technique, in spite of the muscular fatigue development.

Influence of Playing a Prolonged Tennis Match on Shoulder Internal Range of Motion.

BACKGROUND: Shoulder range of motion (ROM) deficits have been identified as an injury risk factor among tennis players. It is well known that shoulder internal rotation deficit increases with age and years of play, but there is a lack of knowledge regarding the influence of a prolonged tennis match on shoulder ROM. PURPOSE: To examine changes in shoulder ROM during a prolonged tennis match. STUDY DESIGN: Descriptive laboratory study. METHODS: Shoulder passive internal and external rotation ROM were measured on 8 male tennis players before, every 30 minutes during, and just after a 3-hour tennis match. Total ROM was calculated as the combination of shoulder internal and external rotations. Ball velocity on the serve was measured with a radar gun before, at midmatch, and just after the match. RESULTS: Decreases in shoulder internal rotation (-20.8°; P = .005), total ROM (-24.6°; P = .001), and serve velocity (-1.8 m/s; P = .002) were observed at the end of the match. No statistically significant difference was observed for shoulder external rotation after the match (P = .460). CONCLUSION: Passive shoulder internal rotation and total ROM are significantly decreased during a 3-hour tennis match. CLINICAL RELEVANCE: The results show that a prolonged tennis match play can modify values of shoulder ROM.

Is physical activity, practiced as recommended for health benefit, a risk factor for osteoarthritis?

In this critical narrative review, we examine the role of physical activity (PA), recreational and elite sports in the development of knee/hip osteoarthritis (OA), taking into account the role of injury in this relationship. The process of article selection was unsystematic. Articles were selected on the basis of the authors' expertise, self-knowledge, and reflective practice. In the general adult population, self-reported diagnosis of knee/hip OA was not associated with low, moderate or high levels of PA. For studies using radiographic knee/hip OA as a primary outcome, the incidence of asymptomatic radiographic OA was higher for subjects with the highest quartile of usual PA than the least active subjects. The risk of incident radiographic knee/hip OA features was increased for subjects with a history of regular sports participation (for osteophyte formation but not joint space narrowing). This risk depended on the type of sport (team and power sports but not endurance and running), and certain conditions (high level of practice) were closely related to the risk of injury. The prevalence of radiographic OA was significantly higher, especially the presence of osteophytes, in former elite athletes than controls. The risk of OA was higher with participation in mixed sports, especially soccer or power sports, than endurance sport. However, the prevalence of clinical OA between former elite athletes and controls was similar, with less hip/knee disability in former athletes. Moderate daily recreational or sport activities, whatever the type of sport, are not a consistent risk factor for clinical or radiographic knee/hip OA. Risk of injury in different sports may be the key factor to understanding the risk of OA related to sport.

[Average height of adolescents in the Dinaric Alps]. / Les Alpes Dinariques : un peuple de sujets de grande taille.

This study contributes to an update of average heights among European populations. Our investigation covering 2705 boys and 2842 girls aged 17 years, shows that, contrary to the general belief, adolescents of the Dinaric Alps are, on average, the tallest in Europe. With an average height of 185,6 cm, they are taller than Dutch adolescents (184 cm on average). Above all, the density of very tall subjects appears to be characteristic of the Dinaric Alps, since 28% measure 190 cm or more in height, as opposed to only 20% in Holland and 1.5% in France. Although our information is not complete, adolescent girls in the Dinaric Alps, with an average height of 171 cm come a close second to girls in Holland.

Overnight urinary cortisol and cortisone add new insights into adaptation to training.

PURPOSE: To examine the effects of training on the HPA axis using two new noninvasive tools: salivary cortisol response to awakening and overnight urinary cortisol and cortisone excretion, and on the sympathoadrenal system using overnight catecholamines excretion. To dissociate the effects of training to those of seasonal hormonal variations, endurance-trained men were compared with sedentary men. METHODS: Nine untrained (UT) men and 10 triathletes were followed during a 10-month season. Clinical (total score of fatigue, total training load, and performances during the competition period) and hormonal parameters (overnight excretion of glucocorticoids and catecholamines, increment of saliva cortisol response to awakening) were measured. RESULTS: Significant seasonal variations in overnight urinary glucocorticoids (decreased in June) and catecholamines (increased in June) concentrations and in saliva cortisol response to awakening were depicted in the two groups. Whereas urinary cortisol excretion was similar between both groups, overnight urinary cortisone excretion was significantly higher in triathletes compared with UT men (ANOVA: training effect: F(2,45) = 9.50, P = 0.0003), suggesting that during a resting day there is a higher inactivation of cortisol into cortisone in highly trained men. Two triathletes developed an overtraining syndrome and presented an increased urinary cortisol/cortisone ratio (>1) due to lower cortisone inactivation compared with the triathlete group. CONCLUSION: : When not taken into account, seasonal variations may induce errors in the interpretation of hormonal variations with training. The increased intracellular inactivation of cortisol during the night in endurance-trained men uncovers subtle changes in HPA function during training. We show in this study the interest of noninvasive biological markers of the activity of the neuroendocrine system to monitor the repercussion of training load during longitudinal follow-up of athletes.

Using virtual reality to analyze links between handball thrower kinematics and goalkeeper's reactions.

This work investigates the design of a new method to evaluate the importance of visual elements taken into account by a handball goalkeeper facing a thrower. Virtual reality was used to design and reproduce standardised situations in a controlled environment. Under such conditions, it was possible to isolate for investigation one visual element in the thrower's gestures. The goalkeeper's movements were recorded in order to compare his reactions to two separate throws where only one visual element was modified. Our systems allowed us to measure and record the effects of small changes in the thrower's movements. With the numerical values we obtained from our results we were able to come up with a scale of significance for each isolated element. These preliminary results look promising for neuroscience, allowing us to better understand the strategies used in duel situations.

Estrogen receptor alpha mRNA in human skeletal muscles.

INTRODUCTION/PURPOSE: To explain the effect of estrogen on skeletal muscle, the presence of estrogen receptor alpha mRNA (ERalpha mRNA) was investigated in human skeletal muscle. METHODS: The highly sensitive technique of nested reverse transcriptase-polymerase chain reaction (nested RT-PCR) was applied on a variety of tissue samples of both sexes: women (deltoid, pectoral, and uterus muscles) (N= 3) and men (deltoid muscle) (N= 3). The total ribonucleic acid was isolated from each tissue sample, reverse transcribed in a thermocycler, and nested PCR was then performed with specific primers. The by-products were analyzed by agarose gel electrophoresis. Internal standard 28S was simultaneously amplified. The ERalpha mRNA level was quantitated by using the ERalpha mRNA/28S mRNA ratio. RESULTS: The expected 204-bp product corresponding to ERalpha was amplified in all tested tissue samples, i.e., deltoid, pectoral, and uterine muscles from women and deltoid muscle from men. The ERalpha mRNA/28S mRNA ratios indicating the receptor expression levels in deltoid muscle from men and women were 0.945 +/- 0.393 (mean +/- SD) (N= 3) and 0.973 +/- 0.136 (mean +/- SD) (N= 2), respectively. CONCLUSIONS: In conclusion, the nested RT-PCR technique identified the presence of transcript encoding ERalpha mRNA in human skeletal muscles. Semi-quantification did not reveal gender difference.

Effect of training on beta1 beta2 beta3 adrenergic and M2 muscarinic receptors in rat heart.

OBJECTIVE: Physical training is known to alter several cardiovascular parameters. These adaptations are for a great part linked to an alteration of the myocardial responses to its autonomic nervous regulation. To further explain the parasympathetic and catecholamine effects, we hypothesized that endurance training could modify rat myocardial beta1, beta2, beta3 adrenoreceptors (AR) and M2 muscarinic cholinergic receptor (AchR) densities. METHODS: Two groups of adults female Wistar rats were studied: controls (C) (N = 7) and trained (T) (N = 9). An 8-wk treadmill training protocol was performed, 5 d x wk and of 1 h x d. At the end of the training session, left ventricle and atria muscle were isolated and weighed. Then, quantification of beta1, beta2, beta3 AR and M2 AchR was performed using Western blot analysis. RESULTS: M2 AchR densities were not modified in left ventricle or in atria by training (respectively, 100 +/- 22%, C vs 101 +/- 14%, T and 100 +/- 23%, C vs 119 +/- 30%, T). Concerning the left ventricle beta AR isoforms, beta1AR density was decreased in T (80 +/- 10% T vs 100 +/- 14% C, P = 0.01), beta2AR was unaltered (102 +/- 12%, T vs 100 +/- 17%, C), and beta3 AR density was increased in T (139 +/- 38% T vs 100 +/- 15% C; P < 0.05). CONCLUSIONS: Our results show for the first time that in female rats an 8-wk treadmill training protocol alters specifically the left ventricle beta AR isoforms densities but not the M2 AchR one. These results could explain some of the beneficial cardiovascular adaptations of the physically trained heart.

Does training have consequences for the walk-run transition speed?

A number of authors when studying the walk-run transition phenomenon focused either on the mechanical or energy expenditure whilst only a few used both parameters concurrently. Moreover the literature demonstrates that the contribution of these variables changes along with the level and method of training. Consequently the purpose of this study is to find, by analyzing concurrently these two variables, if the walk-run transition speed is linked to the type of training. To this end we calculated two theoretical transition speeds: one based on the metabolic energy expenditure St(1) and the second one based on the internal work St(2). Subjects were divided into three groups (untrained, sprint and endurance-trained men) who were required to walk and run on a treadmill at increasing speeds. Firstly we show that the relationship between St(1) and St(2) differs depending on the groups. Sprinters have a significantly lower St(2) than St(1) whereas the opposite is found for untrained subjects. We also show that the transition speed is linked to the subject's type of training. To conclude it seems that acquiring running techniques through specific training has consequences for the walk-run transition phenomenon.

Energy flow analysis during the tennis serve: comparison between injured and noninjured tennis players.

BACKGROUND: Energy flow has been hypothesized to be one of the most critical biomechanical concepts related to tennis performance and overuse injuries. However, the relationships among energy flow during the tennis serve, ball velocity, and overuse injuries have not been assessed. PURPOSE: To investigate the relationships among the quality and magnitude of energy flow, the ball velocity, and the peaks of upper limb joint kinetics and to compare the energy flow during the serve between injured and noninjured tennis players. STUDY DESIGN: Case-control study; Level of evidence, 3. METHODS: The serves of expert tennis players were recorded with an optoelectronic motion capture system. The forces and torques of the upper limb joints were calculated from the motion captures by use of inverse dynamics. The amount of mechanical energy generated, absorbed, and transferred was determined by use of a joint power analysis. Then the players were followed during 2 seasons to identify upper limb overuse injuries with a questionnaire. Finally, players were classified into 2 groups according to the questionnaire results: injured or noninjured. RESULTS: Ball velocity increased and upper limb joint kinetics decreased with the quality of energy flow from the trunk to the hand + racket segment. Injured players showed a lower quality of energy flow through the upper limb kinetic chain, a lower ball velocity, and higher rates of energy absorbed by the shoulder and elbow compared with noninjured players. CONCLUSION: The findings of this study imply that improper energy flow during the tennis serve can decrease ball velocity, increase upper limb joint kinetics, and thus increase overuse injuries of the upper limb joints.