Hip Angular Velocity Research Articles

Noncircular Chainrings Do Not Influence Maximum Cycling Power.

Noncircular chainrings could increase cycling power by prolonging the powerful leg extension/flexion phases, and curtailing the low-power transition phases. We compared maximal cycling power-pedaling rate relationships, and joint-specific kinematics and powers across 3 chainring eccentricities (CON = 1.0; LOWecc = 1.13; HIGHecc = 1.24). Part I: Thirteen cyclists performed maximal inertial-load cycling under 3 chainring conditions. Maximum cycling power and optimal pedaling rate were determined. Part II: Ten cyclists performed maximal isokinetic cycling (120rpm) under the same 3 chainring conditions. Pedal and joint-specific powers were determined using pedal forces and limb kinematics. Neither maximal cycling power nor optimal pedaling rate differed across chainring conditions (all p > .05). Peak ankle angular velocity for HIGHecc was less than CON (p < .05), while knee and hip angular velocities were unaffected. Self-selected ankle joint-center trajectory was more eccentric than HIGHecc with an opposite orientation that increased velocity during extension/flexion and reduced velocity during transitions. Joint-specific powers did not differ across chainring conditions, with a small increase in power absorbed during ankle dorsiflexion with HIGHecc. Multiple degrees of freedom in the leg, crank, and pedal system allowed cyclists to manipulate ankle angular velocity to maintain their preferred knee and hip actions, suggesting maximizing extension/flexion and minimizing transition phases may be counterproductive for maximal power.

Kinematic Analysis of Back Somersault Pike According to Skill Level in Platform Diving

Objective: The purpose of this study was to investigate kinematic differences in back pike somersault in platform diving according to skill level and to apply the findings to improve performance. Method: Korean divers participating in this study were divided into a skilled group (age: 21.6±4.16 y, height: 1.68±0.03 m, weight: 62.0±3.94 kg, career: 12.6±5.13 y) and a less-skilled group (age: 20.6±2.7 y, height: 1.72±0.05 m, weight: 64.8±6.76 kg, career: 12.2±2.49 y) and an independent t-test was performed to analyze differences between groups at the moment of takeoff. Results: The two groups showed significant differences in displacement and velocity of center of mass (COM), takeoff angle, hip joint angle, knee joint angular velocity, and hip joint angular velocity at the takeoff (p<.05), and significant differences in displacement of COM, hip joint, and ankle joint during flight (p<.05). Conclusion: For a successful back pike, the COM should rise quickly in the vertical direction and the hip joint angle and angular velocity should increase. To improve performance, the back pike turn should be practiced on the ground before an attempt on a 10-m platform, to stretch the ankle and knee joints and enable quick flexion of the hip joint when turning in flight.

Infant intralimb coordination and torque production: Influence of prematurity

The purpose of this study is to investigate changes in leg joint coordination, intersegmental dynamics, and their relation in infants born preterm (PT) during the first months of life. Kicking actions were analyzed of 11 infants born PT at 6 and 15-weeks corrected age (CA) using three-dimensional kinematics and kinetics; results were compared to the kicking actions of 10 infants born full-term (FT). Both groups changed from a predominately in-phase coordination at 6-weeks CA to a less in-phase coordination at 15-weeks CA, however, at 6-weeks CA, infants born PT demonstrated less in-phase coordination of their ankle joints with their hip and knee joints. Between groups and across ages, both groups demonstrated consistent net and partitioned joint torque profiles, however, at 6-weeks CA infants born PT demonstrated more complex patterns of torque components. In both groups, less in-phase hip-knee coordination was associated with reduced active knee muscle torque and increased passive knee torques, however, passive knee torques had a greater influence on the kicks of infants born PT at 6-weeks CA. At 6-weeks CA, infants born PT, compared to FT, generated kicks with less in-phase hip-knee coordination, hip excursion, hip angular velocity, and hip muscle torque impulse. By 15-weeks CA, differences resolved in all variables except hip muscle torque impulse. These results highlight a different trajectory of leg joint coordination and torque production for infants born PT compared to FT.

Relationships between kinematics and undulatory underwater swimming performance

ABSTRACTUndulatory underwater swimming (UUS) is one of the major skills contributing to performance in competitive swimming. UUS has two phases– the upbeat is performed by hip extension and knee flexion, and the downbeat is the converse action. The purpose of this study was to determine which kinematic variables of the upbeat and downbeat are associated with prone UUS performance in an elite sample. Ten elite participants were filmed performing three prone 20 m UUS trials. Seven landmarks were manually digitised to calculate eighteen kinematic variables, plus the performance variable– horizontal centre of mass velocity (VCOM). Mean VCOM was significantly correlated with body wave velocity (upbeat r = 0.81, downbeat r = 0.72), vertical toe velocity (upbeat r = 0.71, downbeat r = 0.86), phase duration (upbeat r = −0.79), peak hip angular velocity (upbeat r = 0.73) and mean knee angular velocity (upbeat r = −0.63), all significant at P < 0.05. A multiple stepwise regression model explained 78% of variance in mean VCOM. Peak toe velocity explained 72% of the variance, and mean body wave velocity explained an additional 6%. Elite swimmers should strive for a high peak toe velocity and a fast caudal transfer of momentum to optimise underwater undulatory swimming performance.

Changes in Sprint Kinetics and Kinematics Following Static or Dynamic Stretching

Pre-activity stretching is common practice among athletes, yet a lack of consensus exists as to which type of stretch should be performed. Various types of stretching have been utilized over time, though due to equivocal results in the literature, the criterion for choosing a stretch is often based on familiarity or tradition. PURPOSE: This study aimed to compare the effects of dynamic or static stretching on hip kinetics and kinematics during intermittent sprinting. Variables of interest included hip flexion torque production at baseline, post-stretch and post-sprint, hip angular velocity during the initial swing phase of gait, and sprint times throughout the repeated sprint protocol. METHODS: Participants included 10 male (age 25 ± 2.3 years) and 2 female (age 20 ± 1 years) experienced soccer players recruited from the Las Vegas community. Following written informed consent, participants were asked to report to the University of Nevada, Las Vegas Sports Injury Research Center twice. Each visit consisted of the following: 1) 5-minute treadmill warm up at a preferred pace, 2) baseline hip flexion torque measurements, 3) either a static or dynamic stretch, 4) post-stretch torque measurements, 5) a repeated sprint protocol, and 6) post-sprint torque measurements. Peak hip flexion torque values were analyzed in SPSS using a 2x3 repeated measures factorial ANOVA. Paired t-tests for average sprint time, difference between first and last sprint time, peak instantaneous velocity, and percent phase occurrence of peak velocity were computed with (α=0.05). RESULTS: No statistically significant differences were found for any variable among any level. CONCLUSIONS: A lack of statistical significance may be attributed to a low n and high variability among participants. Additionally, coupled with previous results in the literature, it may suggest that there is not a “one-size-fits-all” approach to pre-activity stretching.

Influence of Compression and Stiffness Apparel on Vertical Jump Performance.

Compression apparel alters both compression of the soft tissues and the hip joint stiffness of athletes. It is not known whether it is the compression elements, the stiffness elements, or some combination that increases performance. Therefore, the purpose of this study was to determine how systematically increasing upper leg compression and hip joint stiffness independently from one another affects vertical jumping performance. Ten male athletes performed countermovement vertical jumps in 8 concept apparel conditions and 1 control condition (loose fitting shorts). The 8 apparel conditions, 4 that specifically altered the amount of compression exerted on the thigh and 4 that altered the hip joint stiffness by means of elastic thermoplastic polyurethane bands, were tested on 2 separate testing sessions (one testing the compression apparel and the other testing the stiffness apparel). Maximum jump height was measured, while kinematic data of the hip, knee, and ankle joint were recorded with a high-speed camera (480 Hz). Both compression and stiffness apparel can have a positive influence on vertical jumping performance. The increase in jump height for the optimal compression was due to increased hip joint range of motion and a trend of increasing the jump time. Optimal stiffness also increased jump height and had the trend of decreasing the hip joint range of motion and hip joint angular velocity. The exact mechanisms by which apparel interventions alter performance is not clear, but it may be due to alterations to the force-length and force-velocity relationships of muscle.

Effects of Pedal Speed and Crank Length on Pedaling Mechanics during Submaximal Cycling

ABSTRACTDuring submaximal cycling, the neuromuscular system has the freedom to select different intermuscular coordination strategies. From both a basic science and an applied perspective, it is important to understand how the central nervous system adjusts pedaling mechanics in response to changes in pedaling conditions.PurposeTo determine the effect of changes in pedal speed (a marker of muscle shortening velocity) and crank length (a marker of muscle length) on pedaling mechanics during submaximal cycling.MethodsFifteen trained cyclists performed submaximal isokinetic cycling trials (90 rpm, 240 W) using pedal speeds of 1.41 to 1.61 m·s−1 and crank lengths of 150 to 190 mm. Joint powers were calculated using inverse dynamics.ResultsIncreases in pedal speed and crank length caused large increases knee and hip angular excursions and velocities (P < 0.05), whereas ankle angular kinematics stayed relatively constant (P > 0.05). Joint moments and joint powers were less affected by changes in the independent variables, but some interesting effects and trends were observed. Most noteworthy, knee extension moments and powers tended to decrease, whereas hip extension power tended to increase with an increase in crank length.ConclusionsThe distribution of joint moments and powers is largely maintained across a range of pedaling conditions. The crank length induced differences in knee extension moments, and powers may represent a trade-off between the central nervous system’s attempts to simultaneously minimize muscle metabolic and mechanical stresses. These results increase our understanding of the neural and mechanical mechanisms underlying multi-joint task performance, and they have practical relevance to coaches, athletes, and clinicians.

Is the total vertical ground reaction force time-amplitude profile an invariant during sit-to-stand movements following stroke?

Weight-bearing asymmetry is a common characteristic of post-stroke individuals when executing sit-to-stand (STS) movements. Spontaneously, these individuals put less weight on the affected limb during STS. In healthy subjects, it has been shown that events of the total vertical ground reaction force (VGRF) occurred invariably in sequential order for every individual for different STS conditions. This study aimed to determine whether the total VGRF time-amplitude profile remains similar between healthy and post-stroke individuals executing STS and to examine the bilateral coordination of VGRF in both groups. Eleven individuals with sub-acute stroke (mean (±SD) time post-stroke: 80.4 (±46) days) and nine age-matched healthy volunteers participated in the study. Both groups executed three STS movements from a standard chair, without back support, height adjusted to obtain 90° of knee flexion. They were instructed to stand up at natural speed with their arms raised straight ahead and hands folded. A force plate positioned directly beneath each participant's bare feet allowed recording the VGRF at 50-Hz while kinematics data at the trunk and lower limbs were recorded with a VICON system. The hip angular velocity signal was used to determine STS duration. Non-parametric statistics and intercorrelation functions were used to compare total VGRF characteristics between the two groups and coherence of the VGRF between sides. The stroke group took more time to execute STS (3273 vs. 2467 ms) and their weight distribution was asymmetrical (67.6% vs. 32.4%) compared to healthy group (50.1% vs. 49.9%). The maximal values of total VGRF did not differ between groups (stroke: 123.8% of total body weight (BW) vs. 120.2% BW for healthy group, P = 0.79) as their occurrence (at 35% vs. 36% of STS duration; P = 0.52). The intercorrelation analyses revealed that VGRF were still coordinated in stroke subjects (Correlation coefficient (CC) = 0.83) but lesser than in healthy subjects (CC = 0.94, P = 0.007) with corresponding temporal delays of 100 ms and 78 ms, respectively. As healthy subjects, individuals post-stroke show invariant in STS task realization. Mainly, the maximal total VGRF seems to be an important control parameter regardless of the weight-bearing asymmetry.

Does long-distance walking improve or deteriorate walking stability of transtibial amputees?

BackgroundFalls are common in transtibial amputees which are linked to their poor stability. While amputees are encouraged to walk more, they are more vulnerable to fatigue which leads to even poorer walking stability. The objective of this study was to evaluate the dynamic stability of amputees after long-distance walking. MethodsSix male unilateral transtibial amputees (age: 53 (SD: 8.8); height: 170cm (SD: 3.4); weight: 75kg (SD: 4.7)) performed two sessions (30minutes each) of treadmill walking, separated by a short period of gait tests. Gait tests were performed before the walking (baseline) and after each session of treadmill walking. Gait parameters and their variability across repeated steps at each of the three conditions were computed. FindingsThere were no significant differences in walking speed, step length, stance time, time of occurrence, and magnitude of peak angular velocities of the knee and hip joint (P>0.05). However, variability of knee and hip angular velocity after 30-minute walking was significantly higher than the baseline (P<0.05) and after a total of 60-minute walking (P<0.05). The variability of lateral sway velocity after 30-minute walking was significantly higher than the baseline (P<0.05). InterpretationThe significant increase in variability after 30-minute walking could indicate poorer walking stability when fatigue was developed, while the significant reduction after 60-minute walking might indicate the ability of amputees to restore their walking stability after further continuous walking.

Bone metabolism against mechanical stress shows differing responses in growth periods and adulthood

1.8± 1.3 cm at P2. In the condition UCon, the COG of all subjects displaced to dominant side at both postures. The hip joint angular velocity of Con was significantly higher than that of UCon in both postures (p< 0.01). Moreover, the jerk cost on an anteroposterior direction and the right and left direction was significantly larger Con than UCon in both postures (p< 0.01). The jerk cost on vertical direction was not significantly difference between Con and UCon in both postures. Conclusion(s): The energy cost influenced the formation of COG trajectory during sit-to-stand motion with asymmetrical foot placement. Implications: Rising from chair in asymmetrical foot placement is useful treatment for involved lower extremity of stroke patients. The results of this study gave the evidence of the treatment.

Reliability of the Turning Point Core Trainer as a Measure of Shoulder Hip Separation Angle, Shoulder Angular Velocity, and Hip Angular Velocity During Volleyball Spiking Actions

Separation of the shoulders and hips is an important contributor for rotational sports such as baseball and golf. Most recent has utilized Motion Capture technology. A new instrument has been developed as a tool to measure separation angle and can also be used to train the core musculature. The primary aim of the current study was to examine the reliability of shoulder hip separation angle (SHSA), shoulder angular velocity (SAV), and hip angular velocity (HAV) as measured using the Turning Point Core Trainer (TP) during volleyball spiking actions. Voluntary participants included 14 collegiate, Division I, female volleyball players from the University of Utah, ranging from 18-30 years of age. Participants completed 10 volleyball spike actions will fastened to the TP. SHSA was calculated at the height of the back swing. Participants were asked to provide maximal velocity during the forward phase thus providing SAV and HAV. Analysis for reliability demonstrated high Cronbach’s alpha coefficients across the 10 SHSA, SAV, and HAV (a =.98; a =.91; a =.94), respectively, indicating excellent internal consistency reliability for the TP. Follow-up research should examine whether or not training female outside hitters to increase SHSA at the top of the back swing, will increase SBV during either DL or DAC spikes. The TP measure of-axial rotation during spiking the internal consistency of the measures was high.

Behavior of medial gastrocnemius motor units during postural reactions to external perturbations after stroke

ObjectiveThis study investigated the behavior of medial gastrocnemius (GM) motor units (MU) during external perturbations in standing in people with chronic stroke. MethodsGM MUs were recorded in standing while anteriorly-directed perturbations were introduced by applying loads of 1% body mass (BM) at the pelvis every 25–40s until 5% BM was maintained. Joint kinematics, surface electromyography (EMG), and force platform measurements were assessed. ResultsAlthough external loads caused a forward progression of the anterior–posterior centre of pressure (APCOP), people with stroke decreased APCOP velocity and centre of mass (COM) velocity immediately following the highest perturbations, thereby limiting movement velocity in response to perturbations. MU firing rate did not increase with loading but the GM EMG magnitude increased, reflecting MU recruitment. MU inter spike interval (ISI) during the dynamic response was negatively correlated with COM velocity and hip angular velocity. ConclusionsThe GM utilized primarily MU recruitment to maintain standing during external perturbations. The lack of MU firing rate modulation occurred with a change in postural central set. However, the relationship of MU firing rate with kinematic variables suggests underlying long-loop responses may be somewhat intact after stroke. SignificancePeople with stroke demonstrate alterations in postural control strategies which may explain MU behavior with external perturbations.

Relationships between lower-limb kinematics and block phase performance in a cross section of sprinters

This study investigated lower-limb kinematics to explain the techniques used to achieve high levels of sprint start performance. A cross-sectional design was used to examine relationships between specific technique variables and horizontal external power production during the block phase. Video data were collected (200 Hz) at the training sessions of 16 sprinters who ranged in 100 m personal best times from 9.98 to 11.6 s. Each sprinter performed three 30 m sprints and reliable (all intraclass correlation coefficients, ICC(2,3) ≥ 0.89) lower-limb kinematic data were obtained through manual digitising. The front leg joints extended in a proximal-to-distal pattern for 15 sprinters, and a moderate positive relationship existed between peak front hip angular velocity and block power (r = 0.49, 90% confidence limits = 0.08–0.76). In the rear leg, there was a high positive relationship between relative push duration and block power (r = 0.53, 90% confidence limits = 0.13–0.78). The rear hip appeared to be important; rear hip angle at block exit was highly related to block power (r = 0.60, 90% confidence limits = 0.23–0.82), and there were moderate positive relationships with block power for its range of motion and peak angular velocity (both r = 0.49, 90% confidence limits = 0.08–0.76). As increased block power production was not associated with any negative aspects of technique in the subsequent stance phase, sprinters should be encouraged to maximise extension at both hips during the block phase.

The acute effect of stretching on the kinematics of instep kicking in soccer

Some previous research indicates that compared to dynamics stretching, static stretching may inhibit the performance of the instep kick, but the effect of these two modes of stretching on soccer players with differing levels of playing experience is not known. Hence, the purpose of this study was to examine the effects of static and dynamic stretching during pre-exercise warm-up on lower extremity kinematics during soccer instep kicking in less and more experienced players. Twenty-four professional male soccer players (12 less experienced and 12 more experienced players) volunteered to participate. Lower extremity joint kinematics of soccer instep kicking were analyzed after static stretching, dynamic stretching, and no-stretching warm-up protocols. The kinematic variables analyzed were the maximum hip angular velocity and maximum knee angular velocity during the leg acceleration phase, and maximum ball velocity after impact phase. Relative to the no-stretching condition, both less and more experienced players had significantly larger hip angular velocity, knee angular velocity, and ball velocity after dynamic stretching than after static stretching. There were no significant differences in joint angular kinematics and ball velocity data between less and more experienced players after static stretching compared to dynamic stretching. This study suggests that dynamic stretching within warm-ups may be more effective than static stretching as a preparation for the instep kick in soccer players.

A kinematic analysis of the Thai boxing clinch

The purpose of the study was to investigate the kinematics between the double collar-tie and double underhook Thai Boxing clinching positions. Ten amateur mixed martial arts athletes executed six knee strikes for both clinching positions with their dominant limb directed towards a target. A standard two-dimensional video motion analysis was conducted, and the results showed a statistical significant difference at the hip joint angle and the angular acceleration of the knee and ankle. Within both clinching positions, there was a statistically significant correlation between the hip and knee joint angles, hip and knee angular velocities, and hip angular acceleration. Between both clinching positions, there was a statistically significant correlation at the knee joint angle, knee angular velocity, and hip angular acceleration. This study demonstrates the importance of the hip and knee joint movements in both clinching positions, which implies the applications of strength training and flexibility at these joints for sports performance and injury prevention. It is suggested that future studies analyzing the non-dominant leg are warranted to fully understand the Thai Boxing clinch.

Kinematic analysis of a side volley in soccer

The purpose of this study was to analyze kinematic variables of side volley in elite soccer players, as well as examining kinematic variables adjustment in relation to the change of velocity and height of incoming ball. Thirty professional soccer players participated in this study. The experimental protocol implied kicking the ball towards the subject at three different velocities and three different heights. The analysis included a total of the following seven dependent variables: Maximum linear velocity of the foot, the knee and the hip (V_FOOT_max, V_KNEE_max, V_HIP_max), Maximum knee and hip joint angular velocities (W_KNEE_max, W_HIP_max), Distance between the foot and the hip at impact with the ball (D_hip.foot_tk), and Angle between the shoulder and hip axis and the hip and foot axis at impact with the ball (α_SHF_tk). Also, for the purpose of descriptive kinematic analysis, the variables of changed angles and hip and knee joint angular velocities were used in different phases of side volley performance, as well as the variables of changed linear velocity of the foot, the knee and the hip. The variables of side volley kinematics were measured with the 3D kinematic analysis system (Qualisys). The effects of the ball height and velocity, and their interaction, on dependent kinematic variables were tested by using the statistical method of two-way analysis of variance with repeated measures (two-way ANOVA). The velocity and height of the incoming ball had a significant effect on V_ FOOT_max in the sense that, as ball velocity grew, V_FOOT_max increased as well, while as ball height increased, V_FOOT_max dropped. A similar effects of the ball velocity and ball height was observed for V_ HIP_max, but is observed only a tendency towards statistical significance. Also, it was observed that increased speed of the incoming ball affected increase of D_hip.foot_tk, as well as α_SHF_tk, while values of W_HIP_max were decreased. The statistical analysis revealed that changes in the mechanical conditions in which side volleys were performed such as a different velocity/height of the incoming ball affected the modulation of the velocity of the farthermost proximal and distal ends of the kinetic chain/hip and foot joints, while the knee joint function was primarily to fine-tune the distance between the subjects' position and the ball.

이단 평행봉 차오르기 동작의 운동학적 분석

The purpose of this study was to analyze the kinematic variables of glide kip motion on the uneven bars through a two-dimensional cinematography. Three expert female gymnastics players were involved in the data gathering process. The followings were concluded according to the results. The arm, trunk and leg segments were fully extended throughout the kip movement. The whole body center of gravity showed the biggest changes during 66 to 87% of the kip motion. During the kip phase, the horizontal displacement of the leg was greater than the vertical displacement the leg. Glide kip motion should be done in orders of upward movement of leg, forward movement of leg, upward movement of trunk and forward movement of trunk segment. It was found that trunk segment and hip joint movements showed bigger changes than those of leg segment and shoulder joint in the glide kip motion. The largest angular velocity of hip joint was shown in the middle of the kip Phase. In conclusion, effective kip movement could be resulted when the trunk was displaced posterior-upward direction with fast hip joint extension after the leg segment was elevated upward and thrusted forward in advance.

Postural stability and ankle sprain history in athletes compared to uninjured controls

BackgroundDiminished postural stability is a risk factor for ankle sprain occurrence and ankle sprains result in impaired postural stability. To date, ankle sprain history has not been taken into account as a determinant of postural stability, while it could possibly specify subgroups of interest. MethodsPostural stability was compared between 18 field hockey athletes who had recovered from an ankle sprain (mean (SD); 3.6 (1.5) months post-injury), and 16 uninjured controls. Force plate and kinematics parameters were calculated during single-leg standing: mean center of pressure speed, mean absolute horizontal ground reaction force, mean absolute ankle angular velocity, and mean absolute hip angular velocity. Additionally, cluster analysis was applied to the ‘injured’ participants, and the cluster with diminished postural stability was compared to the other participants with respect to ankle sprain history. FindingsMANCOVA showed no significant difference between groups in postural stability (P=0.68). A self-reported history of an (partial) ankle ligament rupture was typically present in the cluster with diminished postural stability. Subsequently, a ‘preceding rupture’ was added as a factor in the MANCOVA, which showed a significant association between diminished postural stability and a ‘preceding rupture’ (P=0.01), for all four individual parameters (P: 0.001–0.029; Cohen's d: 0.96–2.23). InterpretationDiminished postural stability is not apparent in all previously injured athletes. However, our analysis suggests that an (mild) ankle sprain with a preceding severe ankle sprain is associated with impaired balance ability. Therefore, sensorimotor training may be emphasized in this particular group and caution is warranted in return to play decisions.

A twenty-segment kinematics and kinetics model for analysing golf swing mechanics

The golf swing is a complex, multi-planar, three-dimensional (3D) motion sequence performed at very high speeds. These properties make biomechanical analysis of the golf swing difficult. Hence, the aim of this study was to develop a computer model of the golf swing capable of calculating a diverse range of 3D kinematics and kinetics values based on motion analysis data collected in the laboratory. Five golfers performed six swings in the field of view of eight Falcon High Speed Resolution cameras (240 Hz), which captured the movements of 56 markers placed on the golfers and their clubs, resulting in marker trajectories that were processed into linear xyz-coordinates using the Eva Motion Analysis system. To perform the kinematics and kinetics calculations, a 20-segment rigid body model of the human body was designed in the Mechanical Systems Pack, connecting the segments by a selection of linear and spherical constraints, resulting in a system of segments with 58 degrees of freedom, with the constraint equations of motion calculated by the Newton–Lagrangian iteration method. The model allowed for the derivation of segmental sequencing, separation angles, segmental planes of motion, segmental velocity contributions, joint torques and muscle powers. The preliminary data suggest that such an integrated kinematics and kinetics analysis is necessary to understand the mechanical complexity of golf swing. Even with the small sample size analysed in this study, some interesting trends were found, such as certain violations of the classical proximal-to-distal sequencing scheme, differing swing plane and club head trajectories in the backswing and downswing phases, minimal hip angular velocity contribution to the ball at impact, concentric and eccentric muscle powers in the downswing phase, and increased lumbar loading factors from the mid-downswing phase to ball impact.

The effect of leg preference on postural stability in healthy athletes

In research regarding postural stability, leg preference is often tested and controlled for. However, leg preference may vary between tasks. As athletes are a group of interest for postural stability testing, we evaluated the effect of five leg preference tasks categorization (step up, hop, ball kick, balance, pick up) on single-leg postural stability of 16 field hockey athletes. The ‘center of pressure speed’ was calculated as the primary outcome variable of single-leg postural stability. Secondary variables were ‘mean length of the GRF vector in the horizontal plane’, ‘mean length of the ankle angular velocity vector’, and ‘mean length of the hip angular velocity vector’, as well as the separate outcomes per degree of freedom. Results showed that leg preference was inconsistent between leg preference tasks. Moreover, the primary and secondary variables yielded no significant difference between the preferred and non-preferred legs, regardless of the applied leg preference task categorization (p>0.05). The present findings do not support the usability of leg preference tasks in controlling for bias of postural stability. In conclusion, none of the applied leg preference tasks revealed a significant effect on postural stability in healthy field hockey athletes.