Phenotypic plasticity and functional asymmetry in response to grip forces exerted by intercollegiate tennis players

Effects of Grip Style and Contact Point on Force Production in a Tennis Forehand Groundstroke

Modern tennis forehand grip style and ball contact points have evolved to enhance power and topspin. Different grip styles and ball contacts are recommended; however, little data are available to support one over another. Through a quantitative experimental study, we sought to determine which grip style and ball contact point produced the greatest forces at static contact. The continental, eastern, and semi-western forehand groundstroke grips of 100 volunteers were evaluated. Participants stood in three defined positions and applied maximum force against a dynamometer with each grip style. The associations of force produced at contact with the grip style, age, sex, tennis experience, and handedness were evaluated using univariate and multivariate linear mixed-effects regression models separately for early, mid, and late contact, including a random effect for each participant. Force production was significantly greater with eastern grip at early, mid, and late contact than with the other two grips (p < 0.001). Force was greater at early contact with semi-western grip than with continental. Force was also significantly greater for men at early, mid, and late contact (p < 0.001). Participants using an eastern grip were able to generate more force compared to those using a continental or semi-western grip, regardless of the ball contact point. Tennis players currently using other forehand grip styles who want to maximize power production may consider transitioning to an eastern forehand grip. The results of this study may improve tennis instruction and training for beginning and novice players who lack force generation.

Rate of Force Development During a Handgrip Task Is Correlated with the Post-Impact Ball Speed of the Flat Serve

The aim of the present research was to test the hypothesis that rate of force development (RFD) during a handgrip task of the dominant arm in three different positions is associated with maximal post-impact ball speed of flat serve (PIBS). Altogether 23 elite junior boys (aged 14.84 ± 2.47 years; weight 59.51 ± 13.83 kg; height 170.47 ± 16.34 cm) tennis players participated in the study. To assess the maximal voluntary contraction (MVC) and RFD during the task, four handgrip tests and a serve test were applied to estimate PIBS. Spearman's rank correlation showed a significant positive correlation between RFD of dominant arm in each three position and PIBS (r = 0.82-0.86; p < 0.001). A very large, significantly positive correlation was also found between MVC of the dominant arm and PIBS (r = 0.88; p < 0.01). The result of the present study indicated that rapid force generation of muscles in the forearm and wrist may probably play a role in the formation of a stable contact point, and it is in connection with PIBS. It is in contrast to the slow maximal force exertion that much rather characterizes the general strength state of players. Therefore, measurement of the RFD during a handgrip task is suggested in the testing session of the flat serve of junior tennis players.

Electromyography-informed musculoskeletal modeling provides new insight into hand tendon forces during tennis forehand

Lateral epicondylitis, also known as tennis elbow, is a major health issue among tennis players. This musculo-skeletal disorder affects hand extensor tendons, results in substantial pain and impairments for sporting and everyday activities and requires several weeks of recovery. Unfortunately, prevention remains limited by the lack of data regarding biomechanical risk factors, especially because in vivo evaluation of hand tendon forces remains challenging. Electromyography-informed musculo-skeletal modeling is a noninvasive approach to provide physiological estimation of tendon forces based on motion capture and electromyography but was never applied to study hand tendon loading during tennis playing. The objective of this study was to develop such electromyography-informed musculo-skeletal model to provide new insight into hand tendon loading in tennis players. The model was tested with three-dimensional kinematics and electromyography data of two players performing forehand drives at two-shot speeds and with three rackets. Muscle forces increased with shot speed but were moderately affected by racket properties. Wrist prime extensors withstood the highest forces, but their relative implication compared to flexors depended on the player-specific grip force and racket motion strategy. When normalizing wrist extensor forces by shot speed and grip strength, up to threefold differences were observed between players, suggesting that gesture technique, for example, grip position or joint motion coordination, could play a role in the overloading of wrist extensor tendons. This study provided a new methodology for in situ analysis of hand biomechanical loadings during tennis gesture and shed a new light on lateral epicondylitis risk factors.

Asimetría entre los miembros superiores en jóvenes padelistas de competición

Existe escasa literatura sobre las asimetrías en el pádel, un deporte de naturaleza asimétrica. Para estudiar el desarrollo de asimetrías en este deporte se evaluó, con bioimpedancia, la masa magra de ambos miembros superiores de 96 jugadores de pádel jóvenes y de 76 esquiadores (grupo control) y se calculó el índice de simetría. Los jugadores de pádel tuvieron una asimetría entre ambos miembros superiores mayor que los esquiadores, cuando se consideró toda la muestra (7.2 ± 5 % vs. 1.4 ± 3.2 %; p < 0.001), en jugadores con un estado de madurez negativo (5,7 ± 3,2 % vs. 1,5 ± 3,8 %; p < 0,001) y en aquellos con un estado de madurez positivo (8,3 ± 5,8 % vs. 1,3 ± 2,4 %; p < 0,001). Este estudio revela que el pádel genera asimetrías de masa magra en los miembros superiores, incluso antes de la edad de crecimiento pico.

Relationship between Asymmetries and Functional Autonomy in Older Chilean Adults

The objectives of this study were: (a) to determine asymmetries, both lower limb (LL) and upper limb (UL), in Chilean older adults, and (b) to relate asymmetries to FA in both LL and UL. Forty-one older adults voluntarily participated in this study (mean ± standard deviation [SD]: age 72.0 ± 8.0 years, LL asymmetries 13.78 ± 14.87%, UL asymmetries 10.70 ± 8.85%, FA 40.35 ± 16.26 points). The variables were: (1) asymmetries of LL and UL, assessed through a force platform and handgrip, respectively; (2) FA, assessed through the Latin American Group for Maturity (GDLAM) and the GDLAM index of autonomy (GI) protocol. The relationship between the variables was performed through Spearman's correlation. The analysis showed that 39% of the participants presented asymmetries above 15% in the LL. Likewise, this 39% of older adults presented a lower FA than their peers with asymmetries below 15% in the LL (≤15%: 35.64 ± 12.26 points vs. >15%: 47.69 ± 19.23 points, p = 0.003). The analysis showed a small correlation between LL and GI asymmetries (r = 0.27, p = 0.07) and a small but negative correlation between UL and GI (r = -0.21). The mean values of asymmetries of both LL and UL are within 'normal' parameters. However, several older adults were identified as being at risk. In parallel, older adults who presented a higher level of asymmetries in LL showed a lower level of FA.

Evaluation of Explicit Motor Timing Ability in Young Tennis Players

A crucial ability for athletes playing sports that involve coincidence timing actions is the motor timing ability. The efficiency of perceptual and motor processes underlying the motor timing ability has been related to the motor experience gained in interceptive sports, such as tennis. In the present study, the motor timing ability in young tennis players (TP) and age-matched control participants (CTRL) was compared by means of a synchronization paradigm. Participants were asked to perform finger-opposition movements in synch to a metronome beating 0.5 and 2 Hz in (1) a bimanual coordination test, which compared the performance of the dominant hand with that of the contralateral hand, and (2) a movement lateralization test, which compared the motor performance of the dominant hand during single-hand and bimanual tasks (BTs). The motor performance was evaluated through movement strategy [defined by touch duration (TD), inter-tapping interval (ITI), and movement frequency] and movement accuracy (temporal accuracy defined by the synchronization error and spatial accuracy defined by the percentage of correct touches—%CORR_SEQ). Results showed that motor expertise significantly influences movement strategy in the bimanual coordination test; TD of TP was significantly higher than those of CTRL, specifically at 0.5 Hz. Furthermore, overall ITI values of TP were lower than those of CTRL. Lastly, in the movement lateralization test, the %CORR_SEQ executed with the right dominant hand by TP in the BT was significantly higher than those of CTRL. A discussion about the role of motor expertise in the timing ability and the related neurophysiological adaptations is provided.

Long-term effects of asymmetrical posture in boxing assessed by baropodometry

BACKGROUND

Asymmetrical posture maintained over long training periods may affect phenotypic plasticity, resulting functional to sporting goal but negative to the locomotor system. Aim of this study was to quantitatively evaluate these long-term effects in competitive boxers.

METHODS

Baropodometric analysis was used to assess 20 competitive boxers and 20 non-sportsmen in upright bipedal posture for 5 s and for 51.2 s with open (OE) and closed (CE) eyes.

RESULTS

The boxers' group (BOX) showed a larger total foot load (TFL) (p=0.022) on the right foot and a larger rearfoot load (RfL) (p=0.011) on the left foot compared to non-sport controls (CTR). Moreover, a larger forefoot load (FfL) (p=0.001) on the right foot respect to left one was found in the BOX group, with the inversion of the RfL to FfL ratio (p=0.001) between two feet, while no significant differences were found in the CTR group. These findings, associated to a significantly larger center of foot angle (COF) in the BOX group, may indicate an anticlockwise rotation of the anatomical structures above the ankle joint of the right hemisoma respect to the left one, that appears to be consistent with the orthodox stance. Eventually, the BOX group showed a larger centre-of-pressure sway area (COPsa) in the OE condition than what measured in the CE and a significant difference in Romberg Index (BOX< CTR).

CONCLUSIONS

The results of this study seem to confirm the theory of neuromuscular plasticity imprinted by the repetitive movements and long-lasting postures. Moreover, competitive boxers show an increase of proprioceptive function and a decrease of visual dependence on the postural control.

Gender Differences in Neuromuscular, Haematological and Urinary Responses during Padel Matches

Research on the acute physiological response to a padel match is limited. The present study aimed to: (a) evaluate neuromuscular, urinary, and hematological responses after simulated padel competition (SC) and (b) analyze possible gender differences. In this study, 28 high-level padel players participated (men = 13, age = 26.83 ± 6.57 years; women = 15, age = 30.07 ± 4.36 years). The following parameters were analyzed before and after SC: neuromuscular (hand grip strength, squat jump (SJ), countermovement jump (CMJ), and Abalakov jump (ABK)), hematological (red blood cells, hemoglobin, and hematocrit), and urinary (pH, specific gravity, microalbuminuria, and red blood cells). Significant gender differences were found in neuromuscular and hematological responses, with men obtaining higher values (p < 0.05). For the SC influence, changes were noted in ABK and microalbuminuria (p < 0.05). The percentages of change in hand grip strength, SJ (height and watts), CMJ (height), and ABK (height) were higher for men than women (p < 0.05). SC negatively influenced the neuromuscular parameters to a greater extent in women. Our results could be related to gender differences in game actions, the temporal structure, and anthropometric and physiological characteristics. Game dynamics and a different organic response between male and female padel playing were confirmed.

International vs. National female tennis players: a comparison of upper and lower extremity functional asymmetries

BACKGROUND

Asymmetries have been reported to negatively impact sport performance. This study examined the magnitude and direction of whole-body functional asymmetry in international versus national female tennis players.

METHODS

Ten internationally and twelve nationally ranked tennis players participated. Upper extremity functional asymmetries (or side-to-side performance differences) were evaluated using handgrip strength, seated shot-put throw and plate tapping. Lower extremity functional asymmetries were determined using the single leg countermovement jump, single leg forward hop test, 6 m single leg hop test, 505 changes of direction (time and deficit), and Y-balance test (anterior, posteromedial, posterolateral). ANOVAs were used to compare the dominant (overall best or fastest result of a specific test) versus non-dominant performance values (best or fastest result of the corresponding extremity) within the internationally versus nationally ranked players. Functional asymmetry magnitudes differences (expressed as a %) were examined using Mann-Whitney U tests. Kappa coefficients examined the consistency as to which extremity performed dominantly across tests.

RESULTS

Significant asymmetries for every upper and lower extremity test were found. The functional asymmetry magnitude was significantly (p=0.020) higher on the single leg forward hop test for the nationally (6.3%) versus internationally ranked players (2.9%). Kappa coefficients showed perfect levels of consistency regarding all upper extremity tests (k=1.00), indicating true limb dominance whereas more variance was found as to which lower extremity performed dominantly across tests (k range=-0.067-0.174).

CONCLUSIONS

The included female tennis players displayed significant whole-body functional asymmetries. Poor consistency as to which lower extremity performed dominantly across tests warrants individual asymmetry monitoring.

Whole-body morphological asymmetries in high-level female tennis players: A cross‑sectional study

This cross-sectional study aimed to examine the degree of whole-body morphological asymmetries in female tennis players. Data were collected in 19 high-level female tennis players (21.3 ± 3.4 years). Based on anthropometric measurements (upper arm, lower arm, wrist, upper leg and lower leg circumferences as well as elbow and knee widths) and dual x-ray absorptiometry research scans (bone mineral density (BMD), bone mineral content (BMC), lean mass (LM), fat mass (FM) as well as humerus, radio-ulnar, femur and tibia bone lengths), within-subject morphological asymmetries for both upper (dominant vs. non-dominant) and lower (contralateral vs. ipsilateral) extremities were examined. Upper arm (p = 0.015), lower arm (p < 0.001) and wrist circumferences (p < 0.001), elbow width (p = 0.049), BMD (p < 0.001), BMC (p < 0.001), LM (p = 0.001), humerus (p = 0.003) and radio-ulnar bone length (p < 0.001) were all greater in the dominant upper extremity. BMC (p < 0.001) and LM (p < 0.001) were greater in the contralateral lower extremity, whereas FM (p = 0.028) was greater in the ipsilateral lower extremity. This is the first study to report significant side-to-side differences in both upper and lower extremities in high-level female tennis players.

Measurement of scapular medial border and inferior angle prominence using a novel scapulometer: A reliability and validity study

BACKGROUND

Previous studies have proposed various ways to assess scapular dyskinesis. In clinic, assessment tools designed to measure the posterior displacement of the inferior angle of the scapula with reference to the posterior thoracic cage are needed.

OBJECTIVES

A novel scapulometer was developed to measure scapular medial border and inferior angle prominence.

METHODS

A novel scapulometer was designed to measure the distance from the root of the spine (ROS) and the inferior angle (INF) of the scapula to the thorax wall in 29 participants with scapular dyskinesis bilaterally. Two raters measured the ROS and INF distance of the scapula 3 times bilaterally. Intraclass correlation coefficients (ICC) and standard error of measurement (SEM) were calculated to determine the inter-rater and intra-rater reliability. Validity was based on correlations (convergent: ROS and internal/external rotation, and INF and tilt; divergent: ROS/INF and upward rotation of the scapula) using a FASTRAK Polhemus 3-D motion tracking system assessing scapular tilt, internal/external rotation, and upward/downward rotation.

RESULTS

The average ROS and INF displacements were 13.7 ± 5.0 mm and 12.5 ± 6.3 mm, respectively. The results showed excellent intra-rater and inter-rater reliability, with ICC = 0.88-0.99 and 0.95-0.99 (SEM = 0.7-0.8 mm), respectively. Correlations were 0.35/0.19 (convergent validity) and 0.07/0.09 (divergent validity).

CONCLUSIONS

The novel scapulometer has excellent reliability and fair validity to quantify medial border and inferior angle prominence of the scapula. Further research utilizing this instrument is recommended.

Evaluation of Bilateral Asymmetry between Upper Limb Masses in Right-Handed Young Adults of Both Sexes

The study introduced a novel precise method for measurement and calculation of upper arm mass and to assess the difference between masses of upper limbs on the dominant and non-dominant sides of the body of right-handed participants. Forty healthy untrained male ( n = 20; M age = 20.8yr., SD = 1.2) and female ( n = 20; M age = 20.7 yr., SD = 1.3) participants without a history of upper-extremity pathology participated. Kinematic and kinetic data were collected during arm motion. The mass of each arm was calculated. Each participant performed 20 movements with each arm. Most often the dominant arm was more massive than the non-dominant in both sex groups; however, mass was more symmetric for female participants than for male participants. Regression equations related to total body mass were calculated for each arm independently.

Effect of motor control training on muscle size and football games missed from injury

PURPOSE

This panel-randomized intervention trial was designed to examine the effect of a motor control training program for elite Australian Football League players with and without low back pain (LBP).

METHODS

The outcome measures included cross-sectional area (CSA) and symmetry of multifidus, quadratus lumborum, and psoas muscles and the change in CSA of the trunk in response to an abdominal drawing-in task. These measures of muscle size and function were performed using magnetic resonance imaging. Availability of players for competition games was used to assess the effect of the intervention on the occurrence of injuries. The motor control program involved performance of voluntary contractions of the multifidus and transversus abdominis muscles while receiving feedback from ultrasound imaging. Because all players were to receive the intervention, the trial was delivered as a stepped-wedge design with three treatment arms (a 15-wk intervention, a 8-wk intervention, and a waitlist control who received a 7-wk intervention toward the end of the playing season). Players participated in a Pilates program when they were not receiving the intervention.

RESULTS

The intervention program was associated with an increase in multifidus muscle size relative to results in the control group. The program was also associated with an improved ability to draw-in the abdominal wall. Intervention was commensurate with an increase in availability for games and a high level of perceived benefit.

CONCLUSIONS

The motor control program delivered to elite footballers was effective, with demonstrated changes in the size and control of the targeted muscles. In this study, footballers who received the intervention early in the season missed fewer games because of injury than those who received it late in the playing season.

Screening the lumbopelvic muscles for a relationship to injury of the quadriceps, hamstrings, and adductor muscles among elite Australian Football League players

STUDY DESIGN

Longitudinal observational study.

OBJECTIVES

To examine the relationship between severity of preseason hip, groin, and thigh (HGT) muscle injuries, and lumbopelvic muscle size, asymmetry, and function at the start and end of the preseason.

BACKGROUND

In Australian Rules Football, HGT muscle injuries have the highest prevalence and incidence. Deficits within the lumbopelvic region, such as impaired muscle function and muscle asymmetry, could contribute to injuries in the preseason, and injury could, in turn, affect muscle size and function.

METHODS

MRI examinations were performed on 47 male elite Australian Rules Football players at the start and at the end of the football preseason. The cross-sectional area (CSA) of multifidus, psoas major, and quadratus lumborum muscles was measured, as well as change in trunk CSA due to the function of voluntarily contracting the transversus abdominis muscle. Injuries occurring during each preseason training session were routinely recorded by the club's performance staff.

RESULTS

Analysis of variance indicated that players with more severe preseason HGT injuries (more training sessions missed) had significantly smaller multifidus muscle CSA compared to players with no HGT injury (P = .006). No relationship was found for size or asymmetry of the quadratus lumborum or psoas major muscles, or ability to contract the transversus abdominis muscle through drawing in of the abdominal wall (P>.05). Small multifidus muscle size at L5 predicted 5 of 6 players who incurred a more severe HGT injury.

CONCLUSIONS

An association between multifidus muscle size (relative to age, height, and weight) and preseason injury suggests a way to identify players at risk of severe HGT injuries. This result needs to be replicated in a larger sample before resources are committed to intervention efforts.

Teste de força de preensão manual: análise metodológica e dados normativos em atletas

INTRODUÇÃO: Diferentes modalidades esportivas utilizam as mãos como importante seguimento corporal envolvido para o desempenho. Entre essas modalidades destacam-se judô, tênis, vela, remo, boxe, levantamento de peso e outras. A força de preensão manual é exigida nessas modalidades específicas, em que o nível de força gerado pode ser o diferencial no desempenho final. A dinamometria manual é um valioso instrumento a ser utilizado na detecção do talento esportivo, no controle do treinamento e na avaliação de recuperação de lesão. OBJETIVOS: O objetivo deste estudo é fazer uma revisão sobre os principais aspectos metodológicos envolvidos na mensuração da força de preensão manual, utilizando o dinamômetro Jamar®, identificando os aspectos relacionados à validade, confiabilidade, precisão, posição para realização do teste, posição da alça, instruções, número de medidas, período de descanso entre as tentativas, duração do tempo de contração, aquecimento pré-teste. MATERIAIS E MÉTODOS: Foi realizado um levantamento para compor uma base de dados de diferentes modalidades olímpicas: coletivas e individuais. Foi realizada uma pesquisa eletrônica da literatura utilizando as bases de dados MEDLINE, SciELO e LILACS, sendo utilizados os seguintes descritores: força de preensão manual, dinamometria manual e, em inglês, hand, grip, strength, dynamometer, Jamar, norms e reference values. CONCLUSÃO: Os valores de força de preensão manual apresentados pelos atletas diferem de acordo com a modalidade, sexo, peso corporal, nível do atleta, idade e tipo de treinamento. A força de preensão manual deve estar presente nas baterias de testes para identificação de possíveis talentos esportivos.

Força de preensão manual de atletas tenistas avaliada por diferentes recomendações de teste

A avaliação da força de preensão manual (FPM) em tenistas competitivos deve ser realizada devido à assimetria que o jogador pode desenvolver. Para avaliar a FPM, profissionais utilizam dois protocolos diferentes (das Sociedades Americana e Europeia). Os objetivos deste estudo foram comparar a FPM usando a técnica do European Test of Physical Fitness Handbook (Eurofit) e da American Society of Hand Therapists (ASHT), bem como verificar a FPM entre o lado dominante/contralateral e comparar a FPM entre as idades em atletas de tênis da categoria infanto-juvenil. Participaram do estudo 137 tenistas do gênero masculino e 45 do feminino, todos com idade entre oito e 18 anos. Para avaliar a FPM, segundo as recomendações da Eurofit e ASHT, foi utilizado um dinamômetro manual (Jamar). Nenhum dos sujeitos avaliados apresentava qualquer lesão que pudesse comprometer o teste. Os resultados mostram que não há diferença na FPM entre os posicionamentos recomendados pela Eurofit e ASHT para medir a FPM independente do gênero. A curva sigmoide foi a que melhor se adequou para regressão da FPM e idade em ambos os gêneros sendo que para o masculino a FPM tem maior inclinação aos 11 anos, já para o feminino a maior inclinação é aos 10 anos. Além disso, a partir dos 14 anos, o lado dominante dos atletas masculinos apresentou maior FPM que o lado não dominante; contudo, essa assimetria não ocorreu no feminino em qualquer idade até os 18 anos.

The effect of grip size on the hitting force during a soft tennis forehand stroke

Background:

Grip size of a tennis racquet has been reported to influence performance, but clear evidence of a correlation has yet to be established.

Hypothesis:

Hitting force during a soft tennis forehand stroke correlates with grip size.

Study Design:

Controlled clinical study.

Methods:

A total of 40 healthy volunteers (20 men and 20 women) with a mean age of 21.9 years were enrolled. Of the 40 participants, 20 were experienced soft tennis players (10 men and 10 women) and 20 were nonexperienced soft tennis players (10 men and 10 women). Based on racquets with 5 different grip sizes, the hitting force during a soft tennis forehand stroke was measured with a handheld dynamometer. Correlations between 4 factors (sex, experience, grip and pinch strengths, and middle finger length) and hitting force were evaluated with each grip size. Measurements for each factor were repeated, and a 2-way analysis of variance was performed on the obtained data.

Results:

The hitting force was greater for male players than for female players and greater for experienced players than for nonexperienced players (P < .01). Men with large grip and pinch strengths demonstrated an increased hitting force with an increase in grip size. Men who had a long middle finger also demonstrated increased hitting force when grip size increased (P < .05).

Conclusion:

The hypothesis proved accurate for experienced men who had a large grip strength, a large pinch strength, and a long middle finger.

Clinical Relevance:

Large-grip-sized racquets may result in better forehand stroke performance when used by experienced male soft tennis players with a large grip strength, a large pinch strength, and a long middle finger.