Technique and timing in women's inward two and one half somersault tuck (405C) and the men's inward two and one half somersault pike (405B) 3 m springboard dives

The purpose of this study was to compare the inward two and one half somersault dive in a tuck position (405C) performed by females (n = 22) and the inward two and one half somersault dive in a pike position (405B) performed by males (n = 24) to determine changes required by females to successfully perform 405B. Key performance variables in inward dives were also compared to those of backward dives. Video data of the dives performed at the 1999 FINA World Diving Cup were captured and digitized to obtain times and postures of the divers at specific events including takeoff and entry. Estimates of flight height and mass-normalised work done on the springboard were obtained from flight times. Some females worked the springboard strongly enough to generate sufficient height and rotation to perform 405B. Males performed 405B comfortably because they achieved better height and rotation than the females. A comparison of backward and inward dives revealed that divers are able to attain greater height in backward dives than inward dives.     

Technique and timing in the women's reverse two and one half somersault tuck (305C) and the men's reverse two and one half somersault pike (305B) 3m springboard dives

The purpose of this study was to compare the reverse two and one half somersault dive in a tuck position (305C) performed by females (n = 24), and the reverse two and one half somersault dive in a pike position (305B) performed by males (n = 21), to determine changes required by females to successfully perform 305B. Key performance variables in reverse dives were also compared to those of forward dives. Video data of the dives performed at the 1999 FINA World Diving Cup were captured and digitised to obtain times and postures of the divers at specific events including hurdle landing, takeoff, and entry. Estimates of hurdle flight height and mass-normalised work done on the springboard were obtained from hurdle and flight times. The males did more work on the springboard to achieve greater height and rotation than females. Females performing 305C had less hip and knee flexion at hurdle landing than males performing 305B and took longer to achieve maximum hip flexion after takeoff from the springboard. To progress from 305C to 305B females need to adjust their techniques to put more energy into the system. Desirable changes include increased height in the hurdle and increased hip and knee flexion prior to hurdle landing. Comparison of results for reverse dives with data previously presented for forward dives indicated that divers are more limited in the number of somersaults and dive position in reverse dives than forward dives despite equivalent or better height in reverse dives than forward dives.     

Diving

The purpose of this study was to compare the reverse two and one half somersault dive in a tuck position (305C) performed by females (n = 24), and the reverse two and one half somersault dive in a pike position (305B) performed by males (n = 21), to determine changes required by females to successfully perform 305B. Key performance variables in reverse dives were also compared to those of forward dives. Video data of the dives performed at the 1999 FINA World Diving Cup were captured and digitised to obtain times and postures of the divers at specific events including hurdle landing, takeoff, and entry. Estimates of hurdle flight height and mass‐normalised work done on the springboard were obtained from hurdle and flight times. The males did more work on the springboard to achieve greater height and rotation than females. Females performing 305C had less hip and knee flexion at hurdle landing than males performing 305B and took longer to achieve maximum hip flexion after takeoff from the springboard. To progress from 305C to 305B females need to adjust their techniques to put more energy into the system. Desirable changes include increased height in the hurdle and increased hip and knee flexion prior to hurdle landing. Comparison of results for reverse dives with data previously presented for forward dives indicated that divers are more limited in the number of somersaults and dive position in reverse dives than forward dives despite equivalent or better height in reverse dives than forward dives.     

Technique and timing in women's backward two and one half somersault tuck (205C) and the men's backward two and one half somersault pike (205B) 3m springboard dives

The purpose of this study was to compare the backward two and one half somersault dive in a tuck position (205C) performed by females (n = 22) and the backward two and one half somersault dive in a pike position (205B) performed by males (n = 27) and by females (n = 6) to determine changes required by females to successfully perform 205B. Video data of the dives performed at the 1999 FINA World Diving Cup were captured and digitised to obtain times and postures of the divers at specific events including maximum depression, takeoff, and entry. Estimates of mass-normalised work done on the springboard were obtained from flight times. Males performed 31% more mass-normalised work on the springboard to gain height than females. Based on the dive scores and the short time to extend and prepare for entry it was concluded that females are not yet able to perform 205B with the same quality as they perform 205C. Females performing backward dives need to adjust their techniques to allow increased work on the springboard to generate height and rotation. Also, faster contraction of the hip flexors may allow them to achieve the tightest position more quickly to complete rotations with more time to prepare for entry.     

Diving

The purpose of this study was to compare the backward two and one half somersault dive in a tuck position (205C) performed by females (n = 22) and the backward two and one half somersault dive in a pike position (205B) performed by males (n = 27) and by females (n = 6) to determine changes required by females to successfully perform 205B. Video data of the dives performed at the 1999 FINA World Diving Cup were captured and digitised to obtain times and postures of the divers at specific events including maximum depression, takeoff, and entry. Estimates of mass‐normalised work done on the springboard were obtained from flight times. Males performed 31% more mass‐normalised work on the springboard to gain height than females. Based on the dive scores and the short time to extend and prepare for entry it was concluded that females are not yet able to perform 205B with the same quality as they perform 205C. Females performing backward dives need to adjust their techniques to allow increased work on the springboard to generate height and rotation. Also, faster contraction of the hip flexors may allow them to achieve the tightest position more quickly to complete rotations with more time to prepare for entry.     

The validation and application of Inertial Measurement Units to springboard diving

Inertial Measurement Units (IMUs) may offer an ecologically valid, reliable, and practical method for biomechanical performance analysis. With such potential in mind, Part 1 of this study examined the accuracy of IMUs gyroscopes with an optical system (Cortex 3.3). A calibration formula standardised the IMUs angular velocity output with the optical system. The percentage differences between the two measures = 0.5% (p < 0.05), suggest IMU’s efficacy for application. In Part 2, the aim was to examine and understand how dive flight angular velocity time series plots change and increase according to dive degree of difficulty. With IMUs attached to three competitive divers performing forward somersault dives, dive flight kinematics were assessed. Biomechanically, a 4½ tuck somersault dive differed to lower degree of difficulty dives in terms of: (1) a rotational delay immediately after takeoff (to gain greater vertical translation); (2) increased total time of flight; (3) greater muscle effort to resist increased centrifugal forces produced by the increased angular velocity (1,090 °/s); and (4) greater eccentric control during deceleration allow a safe and vertical entry into the water. IMUs can be effectively utilised and integrated into contexts such as springboard diving for performance analysis and optimisation purposes.     

The application of inertial measurement units and functional principal component analysis to evaluate movement in the forward 3½ pike somersault springboard dive

Based on technological and analytical advances, the capability to more accurately and finitely examine biomechanical and skill characteristics of movement has improved. The purpose of this study was to use Inertial Measurement Units (IMUs) and Functional Principal Components Analysis (fPCA) to examine the role of movement variability (assessed via angular velocity), on 2 divers (1 international level; 1 national) performing the forward 3½ pike somersault dive. Analysis of angular velocity curves during ive-flight identified 5 fPCs, accounting for 96.5% of movement variability. The national diver’s scatter plots and standard deviation of fPC scores illustrated larger magnitudes of angular velocity variability across dive flight. For fPC1 and fPC3, magnitudes of SD variability were 282.6 and 201.5, respectively. The international diver illustrated more consistent angular velocity profiles, with clustering of fPCs scores (e.g., fPC1 & 3 = SD’s of 75.2 & 68.0). To account for lower variability in the international diver, the ability to better coordinate movement sequences and functionally utilise feedback in response to initiation of the somersault position is highlighted. Overall, findings highlight how both IMUs and fPCA can more holistically and finitely examine the biomechanical and skill characteristics of movement sequences with the capability to inform athlete development.     

Hurdle preflight in springboard diving: a case of diminishing returns

Attempts to increase dive height by introducing a period of flight in the final approach step preceding the hurdle of dives from forward and reverse groups were investigated. One study involved 11 collegiate-level divers experienced in both traditional and hurdle preflight techniques. In a second study, dives executed by 9 national-level women were compared. Dives with a hurdle preflight had shorter final approach steps and greater hurdle flight durations. Flight time differences in favor of hurdle preflight techniques diminished from final approach step through hurdle flight to dive flight. Although the collegiate-level divers had longer dive flight times when using a hurdle preflight, it was suggested that the costs of these techniques may outweigh their potential benefits.     

Biomechanical loading of the hip during side jumps by soccer goalkeepers

Abstract

There is a risk of hip injury in dives to the side by soccer goalkeepers. In this study, we assessed hip loading in goalkeepers when performing such dives. The experiments were conducted in a laboratory setting using an in-ground force plate as well as on a grass surface when the athletes were equipped with force sensors. The forces acting on the hip were measured and high-speed video analysis was performed, allowing the investigation of the dive characteristics and techniques. The peak force values recorded in the laboratory setting ranged from 3 to 8 kN, which corresponded to 4.2–8.6 times body weight. The vertical impact velocities reached 3.25 m · s^?1. In the field experiments, a hip loading of 87–183 N · cm^?2 was determined. We found that goalkeepers who perform a rolling motion reduce their hip loading. The data provided by this study add to the biomechanics database and contribute to the establishment of injury criteria. Such information is necessary to develop and implement strategies to help prevent hip injuries.     

Scoring Bias in Springboard and Platform Diving: A Bayesian Approach to Revision of DD Tables

Abstract

Springboard and platform diving, unlike other sports competitions that use absolute performance measures, relies instead on a panel of judges to assess the aesthetic and technical quality of the athlete's performance. Using data from the 1983 U.S.A. Indoor Diving Nationals, regression analysis was used to determine if there was a statistically significant relationship between degree of difficulty (DD) and scores awarded for a dive. Surprisingly, the analysis revealed that as divers attempted higher degree of difficulty dives, judges became less inclined to award lower scores. Even though the average scores were lower for high DD dives, they were not low enough to compensate for the higher DD rating. Further analysis revealed that the women's competition had less scoring bias towards high DD dives than the men's competition. Even a small amount of scoring bias towards high DD dives is important since typically small total point differences in scores separate the finishing order of divers at a national or international competition. Bayesian analysis, based upon actual diver performance at national and international competitions, is suggested as one method of dealing with the problem of scoring bias towards high DD dives. Using this approach, probability of a score given the DD [P(DD/Score)] is derived from the initially observed P(Scores/DD). Monte Carlo methods can then be used to simulate large numbers of divers performing at each DD level to obtain more precise DD measures for a particular dive.     

Isokinetic imbalance of hip muscles in soccer players with osteitis pubis

Abstract

In this study, we compared the isokinetic torques of hip flexors/extensors and abductors/adductors in soccer players suffering from osteitis pubis (OP), with normal soccer players. Twenty soccer male athletes with OP and 20 normal soccer athletes were included in this study. Peak torque/body weight (PT/BW) was recorded from hip flexor/extensor and abductor/adductor muscles during isokinetic concentric contraction modes at angular velocity of 2.1 rad · s^?1, for both groups. The results showed a significant difference between the normal and OP groups for hip flexors (P < 0.05). The normal group had significant, lower PT/BW value than the OP group for their hip flexors (P < 0.05). The hip flexor/extensor PT ratio of OP affected and non-affected limbs was significantly different from that of normal dominant and non-dominant limbs. There were no significant differences between the normal and OP groups for hip extensor, adductor and abductor muscles (P > 0.05). Regarding the hip adductor/abductor PT ratio, there was no significant difference between the normal and OP groups of athletes (P > 0.05). The OP group displayed increase in hip flexor strength that disturbed the hip flexor/extensor torque ratio of OP. Therefore, increasing the hip extensor strength should be part of rehabilitation programmes of patients with OP.     

Beneficial effect of enriched air nitrox on bubble formation during scuba diving. An open-water study

Bubble formation during scuba diving might induce decompression sickness.

This prospective randomised and double-blind study included 108 advanced recreational divers (38 females). Fifty-four pairs of divers, 1 breathing air and the other breathing nitrox28 undertook a standardised dive (24 ± 1 msw; 62 ± 5min) in the Red Sea. Venous gas bubbles were counted (Doppler) 30–<45 min (early) and 45–60 min (late) post-dive at jugular, subclavian and femoral sites.

Only 7% (air) vs. 11% (air28®) (n.s.) were bubble-free after a dive. Independent of sampling time and breathing gas, there were more bubbles in the jugular than in the femoral vein. More bubbles were counted in the air-group than in the air28-group (pooled vein: early: 1845 vs. 948; P = 0.047, late: 1817 vs. 953; P = 0.088). The number of bubbles was sex-dependent. Lastly, 29% of female air divers but only 14% of male divers were bubble-free (P = 0.058).

Air28® helps to reduce venous gas emboli in recreational divers. The bubble number depended on the breathing gas, sampling site and sex. Thus, both exact reporting the dive and in particular standardising sampling characteristics seem mandatory to compare results from different studies to further investigate the hitherto incoherent relation between inert gas bubbles and DCS.     

Kinematic and kinetic analysis of the goalkeeper’s diving save in football

Kinetics and full body kinematics were measured in ten elite goalkeepers diving to save high and low balls at both sides of the goal, aiming to investigate their starting position, linear and angular momentum, and legs' contribution to end-performance. Our results showed that goalkeepers adopted a starting position with a stance width of 33 ± 1% of leg length, knee flexion angle of 62 ± 18° and hip flexion angle of 63 ± 18°. The contralateral leg contributed more than the ipsilateral leg to COM velocity (p < 0.01), both for the horizontal (2.7 ± 0.1 m·s^?1 versus 1.2 ± 0.1 m·s^?1) and for the vertical component (3.1 ± 0.3 m·s^?1 versus 0.4 ± 0.2 m·s^?1). Peak horizontal and peak angular momenta were significantly larger (p < 0.01) for low dives than for high dives with a mean difference of 55 kg·m·s^?1 and 9 kg·m²·s^?1, respectively. In addition, peak vertical momentum was significantly larger (p < 0.01) for high dives with a mean difference between dive heights of 113 kg·m·s^?1. Coaches need to highlight horizontal lateral skills and exercises (e.g. sideward push-off, sideward jumps), with emphasis on pushing-off with the contralateral leg, when training and assessing goalkeeper’s physical performance.     

How does buoyancy affect performance during a 200m maximum front crawl swim?

We investigated the rotational effect of buoyant force around the body’s transverse axis, termed buoyant torque, during a 200m front crawl maximal swim. Eleven male swimmers of national or international level participated. One stroke cycle (SC) for each 50m was recorded with two above and four below water cameras. The following variables were analysed: swimming velocity; absolute and normalised buoyant force; minimum, average and maximum buoyant torque; SC and arm recovery times. The average value of buoyant torque was higher in the first 50m (14.2 ± 4.5Nm) than in the following 150m (9.3 ± 4.1Nm~10.9 ± 4.5Nm) and was directed to raise the legs and lower the head throughout the race. The change in its magnitude seemed to be linked to the shorter time spent proportionally in arm recovery (first 50m: 27.6% of SC time; next 150m: 23.3–24.4% of SC time). Most swimmers had periods of the SC where buoyant torque was directed to sink the legs, which accounted to 10% of SC time in the first 50m and about twice this duration in the next 150m. These periods were observed exclusively at some instances when the recovering arm had entered the water while the opposite arm was still underwater.     

Comparison of lower limb kinetics during vertical jumps in turnout and neutral foot positions by classical ballet dancers

The purpose of this study was to investigate the effect of hip external rotation (turnout) on lower limb kinetics during vertical jumps by classical ballet dancers. Vertical jumps in a turnout (TJ) and a neutral hip position (NJ) performed by 12 classical female ballet dancers were analysed through motion capture, recording of the ground reaction forces, and inverse dynamics analysis. At push-off, the lower trunk leaned forward 18.2° and 20.1° in the TJ and NJ, respectively. The dancers jumped lower in the TJ than in the NJ. The knee extensor and hip abductor torques were smaller, whereas the hip external rotator torque was larger in the TJ than in the NJ. The work done by the hip joint moments in the sagittal plane was 0.28 J/(Body mass*Height) and 0.33 J/(Body mass*Height) in the TJ and NJ, respectively. The joint work done by the lower limbs were not different between the two jumps. These differences resulted from different planes in which the lower limb flexion–extension occurred, i.e. in the sagittal or frontal plane. This would prevent the forward lean of the trunk by decreasing the hip joint work in the sagittal plane and reduce the knee extensor torque in the jump.     

Effect of different velocity loss thresholds during a power-oriented resistance training program on the mechanical capacities of lower-body muscles

This study compared the effects of two velocity loss thresholds during a power-oriented resistance training program on the mechanical capacities of lower-body muscles. Twenty men were counterbalanced in two groups (VL10 and VL20) based on their maximum power capacity. Both groups used the same exercises, relative intensity and repetition volume, only differing in the velocity loss threshold of each set (VL10: 10% vs. VL20: 20%). Pre- and post-training assessments included an incremental loading test and a 15-m linear sprint to assess the force- and load-velocity relationships and athletic performance variables, respectively. No significant between-group differences (P > 0.05) were observed for the force-velocity relationship parameters (ES range = 0.15–0.42), the MPV attained against different external loads (ES range = 0.02–0.18) or the 15-m sprint time (ES = 0.09). A high between-participants variability was reported for the number of repetitions completed in each training set (CV = 30.3% for VL10 and 29.4% for VL20). These results suggest that both velocity loss thresholds induce similar changes on the lower-body function. The high and variable number of repetitions completed may compromise the velocity-based approach for prescribing and monitoring the repetition volume during a power-oriented resistance training program conducted with the countermovement jump exercise.     

The role of shoe design on the prediction of free torque at the shoe–surface interface using pressure insole technology

The goal of the current study was to expand on previous work to validate the use of pressure insole technology in conjunction with linear regression models to predict the free torque at the shoe–surface interface that is generated while wearing different athletic shoes. Three distinctly different shoe designs were utilised. The stiffness of each shoe was determined with a material’s testing machine. Six participants wore each shoe that was fitted with an insole pressure measurement device and performed rotation trials on an embedded force plate. A pressure sensor mask was constructed from those sensors having a high linear correlation with free torque values. Linear regression models were developed to predict free torques from these pressure sensor data. The models were able to accurately predict their own free torque well (RMS error 3.72 ± 0.74 Nm), but not that of the other shoes (RMS error 10.43 ± 3.79 Nm). Models performing self-prediction were also able to measure differences in shoe stiffness. The results of the current study showed the need for participant–shoe specific linear regression models to insure high prediction accuracy of free torques from pressure sensor data during isolated internal and external rotations of the body with respect to a planted foot.     

The sidestep cutting manoeuvre requires exertion of lumbosacral lateral flexion torque to avoid excessive pelvic obliquity

During sidestep cutting, the pelvis is supported only on one side; this affects the athlete’s posture. This study investigated the mechanism to avoid excessive pelvic obliquity during sidestep cutting. Ten physically active men performed sidestep cutting with maximal effort, and we captured the kinematics and kinetics with force platforms and an eight-camera motion capture system. Our results indicated that the stance hip exerted little abduction torque; however, lumbosacral lateral flexion torque was exerted towards the free-leg side (peak value: 3.39 ± 0.91 N m/kg). Although bilateral hip joint forces acted to drop the free-leg side of the pelvis, the net torque around pelvic elevation/drop axis was nearly zero during the entire stance phase and the change in the angular momentum around the pelvic elevation/drop axis from touchdown to toe-off was negligible (?0.004 ± 0.003 N m s/kg). The integrated components of lateral flexor for elevating the free-leg side of the pelvis (0.220 ± 0.072 N m s/kg) were significantly larger than any other integrated components, which were all negligible (<0.010 N m s/kg). Thus, sidestep cutting requires the lumbosacral lateral flexion torque exertion to neutralise the passive action that drops the free-leg side of the pelvis.     

Acute and sub-acute effects of repetitive kicking on hip adduction torque in injury-free elite youth soccer players

Abstract

Hip adduction strength is important for kicking and acceleration in soccer players. Changes in hip adduction strength may therefore have an effect on soccer players’ athletic performance. The purpose of this study was to investigate the acute and sub-acute effects of a kicking drill session on hip strength, concerning isometric hip adduction, abduction and flexion torque of the kicking leg and the supporting leg. Ten injury-free male elite soccer players, mean ± s age of 15.8 ± 0.4 years participated. All players underwent a specific 20 min kicking drill session, comprising 45 kicks. The players were tested the day before, 15 min after and 24 h after the kicking drill session by a blinded tester using a reliable test procedure. The isometric hip-action and leg-order were randomized. For the kicking leg, hip adduction torque increased from 2.45 (2.19–2.65) Nm ? kg^?1, median (25th–75th percentiles), at pre-kicking to 2.65 (2.55–2.81) Nm ? kg^?1 (P = 0.024) 24 h post-kicking. This may have implications for the soccer player’s ability to maximally activate the hip adductors during kicking and acceleration, and thereby improve performance the day after a kicking drill session.     

The hip control test is a valid and reliable measure of hip neuromuscular control

Abstract

Insufficient hip neuromuscular control may contribute to non-contact sport injuries. However, the current evaluative test of hip neuromuscular control, the single-leg squat, requires hip abductor muscle strength to complete. The purpose of this study was to develop the hip control test (HCT) and determine the test’s reliability and construct validity. Nineteen healthy adults visited the laboratory twice. The HCT is a 10-s test of reciprocal toe-tapping accuracy. Both automated and manual HCT ratings were recorded simultaneously during each visit. Additionally, eccentric hip abductor torque was measured. HCT reliability was assessed with intra-class correlation coefficients (ICC). Agreement between automated and manual ratings was determined with Bland–Altman plots. Construct validity was established if HCT performance significantly decreased with a secondary cognitive task (p < 0.05). Bivariate regression determined the relationship between HCT performance and eccentric hip abductor torque. Automated and manual HCT ratings both had moderate reliability (ICC = 0.72) and yielded similar results (limits of agreement = ?1 to 2 taps). The HCT had construct validity (p = 0.001), and no correlation with hip abductor muscle strength (r = 0.213). Thus, the HCT is a reliable and valid test. The HCT is simple to administer and measures hip neuromuscular control separately from strength.