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THE ROLE OF TARGET LOCATION ON THE INTERACTION BETWEEN POSTURAL BALANCE MECHANISMS AND END-EFFECTOR PERFORMANCE IN THE TENNIS SERVE
Get PDFThe purpose of this study was to evaluate the relationship between end-effector (tennis racket) performance and postural balance across 4 serving locations. Eleven right-handed experienced tennis players participated in this study. Participants completed 10 successful tennis serves each to 4 serving locations. 12 optoelectronic cameras at 200 Hz (BTS bioengineering, Milan, Italy) were used to collect whole-body kinematic data. Statistical parametric mapping (SPM) with regression was used to identify the relationship between postural balance control (extrapolated centre of mass displacement and changes in arms/trunk angular momentum in forward/backward direction; 1D data) and end-effector performance (maximum racket forward velocity, 0D data) across the four serving locations. The results showed no systematic relationship between postural balance control mechanisms and end-effector performance across 4 different serving locations. It was concluded that serving to different locations likely involves different balance control mechanisms to adjust for target-specific serve technique constraints. For practical application, we found no evidence that balance control and end-effector performance are tightly related within elite tennis serve performance and that these could be trained separately
CLASSIFICATION OF THE DISCUS THROW TECHNIQUE
Get PDFThe purpose of this study is to classify discus throwers based on the velocity components at release and to investigate their throwing biomechanics. Forty-six male discus throwers were classified into 2 groups through cluster analysis. Twenty-two throwers were classified into a horizontal dominant group, while the remaining 24 throwers were classified into a vertical dominant group. There were no significant differences in the throwing distance and resultant release velocity between the groups. The right leg angle at release and the displacement of the centre of gravity (vertical direction) were significantly greater in vertical dominant group. These results indicated the horizontal dominant group drove their right leg forward to increase the horizontal velocity, while the vertical dominant group lifted their body upward direction to increase the vertical velocity
RELIABILITY AND BILATERAL STRENGTH IMBALANCES OF A NEW ISOMETRIC TEST TO IDENTIFY PREVIOUS HAMSTRING STRAIN COMPARED TO ECCENTRIC STRENGTH
Get PDFThe purpose of this study was to investigate the reliability of a novel device in assessing isometric hamstring strength and determine whether isometric and eccentric strength imbalances remain in previously injured Gaelic footballers from the previous season. A total of 70 amateur Gaelic Footballers were tested in the preseason period (January to March 2020) and 45 of these players were tested on two separate occasions no more than 7 days apart to determine the test-retest reliability of the new Isometric hamstring strength assessment approach. The Nordic hamstring exercise was used to determine maximal hamstring eccentric Torque using the Nordbord testing system™. The isometric testing showed a moderate to high reliability ICC (CI 95%) of 0.89 (CI 0.79-0.94) with the typical error of 7.7 % (6.9-9.7%). Those with previous HSI had significantly lower Isometric strength for the involved side when comparing to the non-involved side in terms of Absolute force, Relative force, Absolute Torque, Relative torque (
EXAMINING THE INTRA- AND INTER-DAY RELIABILITY OF THE VALD HUMANTRAK FOR RANGE OF MOTION OF THE SHOULDER IN FIXED- AND FREE-RANGE CONDITIONS
Get PDFThe purpose of this study was to assess the reliability of the VALD HumanTrak system for estimating shoulder range of motion in the sagittal and frontal planes. Intra- and inter-day reliability was assessed during fixed- and free-range shoulder movements. ICC ranged from good to excellent for abduction (0.753 - 0.959) and flexion (0.868 - 0.975) and poor to good for adduction (0.417 - 0.893) and extension (0.443 - 0.757). The VALD HumanTrak can be a reliable tool to estimate shoulder range of motion within the same day and across multiple days
EFFECT OF BLOCK DESIGN ON ROTATIONAL CHARACTERISTICS OF A SWIM START
Get PDFThe purpose of this study was to examine the effect of start block design on the rotational characteristics of a swim start. Seven male and seven female university-level competitive swimmers (21.1±2.1 yrs, 1.79±0.08 m, 75.6±11.8 kg) completed three maximal effort swim starts under each of four conditions, flat block with no kick plate, flat block with a kick plate, inclined block with no kick plate and inclined block with a kick plate. Temporal and kinematic variables and angular momentum were determined for each start using a two-dimensional video analysis. Use of an inclined block significantly reduced block time by 4%, reduced time to 5m by 2.2% and reduced vertical velocity at entry by 4.9% compared to a flat block. Use of a kick plate significantly reduced block time by 3.4%, reduced time to 5m by 3.4%, increased horizontal velocity at takeoff by 3.7%, increased horizontal velocity at entry by 2.7% and increased the body orientation angle at takeoff by 2.7% compared to not using a kick plate. Neither block inclination nor use of a kick plate affected airborne whole body angular momentum. These data support using an inclined block platform and kick plate to improve start performance and suggest that experienced swimmers can adapt the rotational characteristics of their start to different conditions
THE RELATIONSHIP BETWEEN BACKSTROKE SWIMMING SPRINT PERFORMANCE AND LOAD-VELOCITY PROFILES
Get PDFThe study investigated relationships between backstroke sprint swimming performance and variables extracted from load-velocity profiles. Thirteen male swimmers performed 50 m backstroke and semi-tethered swimming with three progressive external loads. From 50 m backstroke, race time (T50m) swimming velocity (v50m), stroke length and frequency were obtained. From semi-tethered swimming, maximum load (L0) and velocity (v0), slope and L0 normalized to body mass (rL0) were computed. Large to very large significant relationships were found between v50m and all variables derived from the load-velocity profiling. Similar relationships were found between T50m and v0, L0 and slope, but not with rL0 (r = -0.530, p = 0.062). These findings indicate that load-velocity profiling is a practical method to predict and assess sprint backstroke performance and swimming velocity, and to assess propulsive force production and velocity capabilities related to backstroke sprint performance
THE COORDINATION VARIABILITY OF ‘TRADITIONAL’ AND ‘SPECIFIC’ SPRINT TRAINING EXERCISES COMPARED TO HIGH SPEED RUNNING.
Get PDFThis study aimed to compare specificity of three different resistance training exercises (Back Squat (BS), Bulgarian Split Squat (BSS), and Single-Leg Romanian Deadlift (SL-RDL) compared to high speed running (HSR). Three-dimensional kinematic data were collected from 6 males (age 22.2 ± 1.6 years, height 1.85 ± 0.05 m, mass 77.55 ± 6.50 kg) who completed two sets of six repetitions with two repetitions in reserve for each resistance training exercise and two 10 second treadmill runs at 20 kph (5.56 m/s). Kinematic results from the hip, knee and ankle (max. flexion, max. extension, and range of motion) revealed there was not an exercise that was consistently similar to HSR. Coordination profiling revealed the BS exercise had similarities to HSR across all three joints, however the BSS did show greater specificity at the hip
POTENTIAL INFLUENCE OF FOOTWEAR ON ANKLE INVERSION INJURY RISK DURING LATERAL JUMPS IN OLDER ADULTS
Get PDFThe purpose of this study was to explore the effect of footwear on the ankle inversion and plantar pressure experienced by older females performing change of direction tasks. Eight older female tennis players performed five lateral side jumps and five 180° turns in a running shoe and tennis shoe. Time of peak plantar pressure and peak ankle inversion angle were recorded. Individual differences revealed reduced magnitude and duration of rearfoot loading and increased forefoot loading of two participants in the running shoe compared to the tennis shoe when performing the lateral side jumps. Greater peak inversion angle was also recorded in the running shoe compared to the tennis shoe for these participants. While the cushioning properties of running shoes may be appealing for some older tennis players, wearing running shoes during tennis may increase the risk of incurring an ankle sprain
BAREFOOT RUNNING PRODUCES CHANGES IN FOOT STRIKE PATTERN AND BILATERAL ASYMMETRIES ONLY AS AN ACUTE EFFECT
Get PDFThis study analyzed changes and bilateral asymmetries in Foot Strike Pattern (FSP). Twenty-eight subjects were divided into Barefoot Group (BFGr) (n=16) and Shod Group (SHGr) (n=12), evaluated before (Baseline) and after running for 20 min at 3.1 m·s−1 (Post 20min Running), and at the end of an 8-week running training protocol (Post 8-week Training). Plantar pressures were obtained to calculate Strike Index (SI). Only condition factor (SHGr/BFGr) resulted in significative effect (F=52.45, p=0.00, ƞ2p =0.67). The number of subjects with Forefoot Strike (FFS) and Midfoot Strike (MFS) was always higher in BFGr than SHGr. This difference was higher in Post 20min Running, where BFGr outperformed SHGr by 46 percentage points. BFGr doubled the percentage of asymmetric subjects in Post 20min Running (25% in Baseline to 50% in 20min Running) and returned to Baseline’s value in Post 8-week Training. The shift of FSP towards MFS or FFS and the increase of asymmetries are immediate adaptations caused by barefoot running. However, a training protocol of 8-weeks does not produce maintenance of these modifications
KNEE JOINT LOADING IN JUMP LANDINGS IN DIVERSE CONDITIONS
Get PDFThe purpose of this single case study is to provide an overview on knee joint loading in counter movement jumps using different landing strategies and additional loads. One athlete experienced in jump training performed counter movement jumps and jump landings with additional barbell loads of 0 kg, 20 kg, 40 kg, 60 kg, 80 kg and with variations in landing conditions: “regular”,“soft”, “elevated” and “spotted”. GRF and kinematics were measured, and peak forces, peak knee moments and peak knee powers were determined using inverse dynamics. Different loading conditions and landing conditions lead – as expected – to different knee joint loadings and can therefore be used to specifically control the amount of loading during jump or jump strength training. The most effective in terms of high training loads and low landing joint loading are elevated and spotted landing conditions