Validity of a squash-specific test of change-of-direction speed

Purpose: We examined the validity and reproducibility of a squash-specific test designed to assess change-of-direction speed. Methods: 10 male squash and 10 male association-football and rugby-union players completed the Illinois agility run (IAR) and a squash change-of-direction-speed test (SCODS) on separate days. Tests were repeated after 24 h to assess reproducibility. The best time from three attempts was recorded in each trial. Results: Performance times on the IAR (TE 0.27 s, 1.8%, 90% CI 0.21 to 0.37 s; LOA −0.12 s ± 0.74; LPR slope 1, intercept −2.8) and SCODS (TE 0.18 s, 1.5%, 90% CI 0.14 to 0.24 s; LOA 0.05 s ± 0.49; LPR slope 0.95, intercept 0.5) were reproducible. There were no statistically significant differences in performance time between squash (14.75 ± 0.66 s) and nonsquash players (14.79 ± 0.41 s) on the IAR. Squash players (10.90 ± 0.44 s) outperformed nonsquash players (12.20 ± 0.34 s) on the SCODS (P < .01). Squash player rank significantly correlated with SCODS performance time (Spearman’s ρ = 0.77, P < .01), but not IAR performance time (Spearman’s ρ = 0.43, P = .21). Conclusions: The results suggest that the SCODS test is a better measure of sport-specific capability than an equivalent nonspecific field test and that it is a valid and reliable tool for talent identification and athlete tracking

The relationship between stiffness, asymmetries and change of direction speed

A thesis submitted to the University of Bedfordshire, in fulfilment of the requirements for the degree of Doctor of PhilosophyChange of direction speed (CODS) is an important determinant of performance in many sports. Greater stiffness of the lower limb should be beneficial to CODS, but this had not been well investigated. The purpose of this thesis was to establish the relationship between vertical stiffness, vertical stiffness asymmetries and CODS, with a view to augmenting CODS performance. The pilot study and studies 1-2 sought to determine the most reliable and ecologically valid method to assess stiffness in athletes required to perform changes of direction. The pilot study reported that the use of ultrasonography to determine Achilles tendon stiffness did not demonstrate appropriate reliability for inclusion in subsequent studies. Coefficients of variation (CVs) in excess of 27% were reported during an isometric plantar flexion task. Study 1 reported that CVs for vertical stiffness were lower when assessed during unilateral drop jumping (~7%) than during bilateral drop jumping (~12%) or bilateral hopping (~14%). Study 2 reported that the expression of vertical stiffness (P = 0.033) and vertical stiffness symmetry angle (P = 0.006) was significantly different across three performance tasks: unilateral drop jumping, bilateral drop jumping and bilateral hopping. Asymmetry percentages between compliant and stiff limbs were 5.6% (P < 0.001; d: 0.22), 23.3% (P = 0.001; d = 0.86) and 12.4% (P = 0.001; d = 0.39), respectively. Given the findings of studies 1 and 2, this thesis demonstrated the reliability and validity of a novel method by which to assess vertical stiffness - the unilateral drop jump. This task was used in subsequent studies to measure vertical stiffness. Study 3 sought to determine if vertical stiffness and vertical stiffness asymmetries influenced CODS performance determined during a 90o cutting task. Multiple regression analyses reported that mean vertical stiffness and asymmetry in jump height explained 63% (r2 = 0.63; P = 0.001) of CODS performance. Study 3 was the first investigation to demonstrate the importance of vertical stiffness to CODS performance. Study 4 sought to determine if acute exercise interventions designed to augment vertical stiffness would improve CODS. Unilateral and bilateral ‘stiffness’ interventions were evaluated against a control condition. CODS performances following the unilateral intervention were significantly faster than control (1.7%; P= 0.011; d = -1.08), but not significantly faster than the bilateral intervention (1.0% faster; P = 0.14; d = -0.59). Versus control, vertical stiffness was 14% greater (P = 0.049; d = 0.39) following the unilateral intervention. Study 4 demonstrated that a novel unilateral ‘stiffness’ intervention improved vertical stiffness and CODS performance. This highlights that the potential applicability of unilateral stiffness interventions in the pre-performance preparation of athletes

Unilateral stiffness interventions augment vertical stiffness and change of direction speed

It has previously been shown that pre-conditioning interventions can augment change of direction speed (CODS). However, the mechanistic nature of these augmentations has not been well considered. The current study sought to determine the effects of pre-conditioning interventions designed to augment vertical stiffness on CODS. Following familiarization, ten healthy males (age: 22 ± 2 years; height: 1.78 ± 0.05 m; body mass: 75.1 ± 8.7 kg) performed three different stiffness interventions in a randomized and counterbalanced order. The interventions were: a) bilateral-focused, b) unilateral-focused, and c) a control of CODS test practice. Vertical stiffness and joint stiffness was determined pre- and post-intervention using a single leg drop jump task. CODS test performance was assessed post-intervention using a double 90o cutting task. Performances following the unilateral intervention were significantly faster than control (1.7%; P = 0.011; d = -1.08), but not significantly faster than the bilateral intervention (1.0% faster; P = 0.14; d = -0.59). Versus control, vertical stiffness was 14% greater (P = 0.049; d = 0.39) following the unilateral intervention and 11% greater (P = 0.019; d = 0.31) following the bilateral intervention; there was no difference between unilateral and bilateral interventions (P = 0.94; d = -0.08). The findings of the current study suggest that unilateral pre-conditioning interventions designed to augment vertical stiffness improve CODS within this experimental cohort

Physical characteristics underpinning lunging and change of direction speed in fencing

Lunge velocity (LV) and change of direction speed (CODS) are considered fundamental to success during fencing competitions; investigating the physical characteristics that underpin these is the aim of this study. Seventy fencers from the British Fencing National Academy took part and on average (± SD) were 16.83 ± 1.72 years of age, 178.13 ± 8.91 cm tall, 68.20 ± 9.64 kg in mass and had 6.25 ± 2.23 years fencing experience. The relationship between anthropometric characteristics (height, arm-spam and adductor flexibility) and measures of lower-body power (bilateral and unilateral countermovement jump height and reactive strength index) were examined in their ability to influence LV and CODS. In testing the former, fencers lunged (over a self-selected distance) to and from a force plate, where front leg impact and rear leg propulsive force was quantified; the lunging distance was divided by time to establish LV. CODS was measured over 12 m involving shuttles of between 2 and 4 m. Results revealed that LV and CODS averaged at 3.35 m/s and 5.45 s respectively and in both cases, standing broad jump was the strongest predictor (r = 0.51 and -0.65 respectively) of performance. Rear leg drive and front leg impact force averaged at 14.61 N/kg and 3-times bodyweight respectively, with single leg jumps revealing an asymmetry favoring the front leg of 9%. In conclusion, fencers should train lower-body power emphasizing horizontal displacement, noting that this seems to offset any advantage one would expect fencers of a taller stature to have. Also, the commonly reported asymmetry between legs is apparent from adolescence and thus also requires some attention

Postactivation potentiation and change of direction speed in elite academy rugby players

This study investigated the effect of preceding pro-agility sprints with maximal isometric squats to determine if postactivation potentiation (PAP) could be harnessed in change of direction speed. Sixteen elite under-17 rugby union players (age: 16 +/- 0.41yrs; body mass: 88.7 +/- 12.1kg, height: 1.83 +/- 0.07m) from an Aviva Premiership rugby club were tested. Subjects performed a change of direction specific warm-up, followed by two baseline pro-agility tests. After 10 minutes recovery, 3 x 3-second maximal isometric squats with a 2 minute recovery between sets were completed as a conditioning activity (CA) on a force plate where peak force and mean rate of force development over 300 milliseconds were measured. The pro-agility test was repeated at set time intervals of 1, 3, 5 and 7 minutes following the CA. Overall pro-agility times were significantly slower (p < 0.05) at 1-minute post-CA compared to the baseline (3.3%), with no significant differences occurring at 3, 5 or 7 minutes post-CA. Therefore, it appears that performing multiple sets of maximal isometric squats do not enhance pro-agility performance

Associations between Relative Power on Different Measures of Change of Direction Speed

Change of direction speed (CODS) is an important characteristic for successful athletic performance in most sports. However, it stands to reason that different CODS tests may have different athletic attributes that influence success on these assessments. PURPOSE: The purpose of this study was to examine the relationships between relative power and two different measures of CODS. METHODS: Data from 39 NCAA division I (age: 20.1 ± 1.2yrs; height: 164.9 ± 6.5cm; body mass: 63.8 ± 7.8kg) and 18 NCAA division II (age: 19.3 ± 1.2yrs; height: 165.7 ± 5.7cm; body mass: 63.3 ± 6.3kg) women’s soccer teams was collected and analyzed for this study. The 505-agility test (505) and modified T-test (Mod T) were performed on a turf/grass soccer field following a standardized dynamic warm-up. Data was analyzed using IBM SPSS statistics (Version 24.0; IBM Corporation, New York, NY). Person’s correlation coefficient was used to relate relative power to the 505 and Mod T. Linear regression analysis was completed to determine the influence of relative power on the different measures of CODS. RESULTS: A significant large correlation was found between relative power and 505 (r = -0.714, p = 0.0001), but not Mod T (r = 0.259, p = 0.059). Furthermore, regression analysis revealed 51% of the variance in 505 was explained by relative power (p = 0.0001). In comparison, only 7% of the variance in Mod T was explained by relative power (p = 0.059). CONCLUSION: The results of this study reveal a stronger relationship between relative power to 505 performance, but not Mod T. This may be explained by the nature of the tests themselves. Based on the need for greater hip and knee flexion when performing the 505 test in contrast to the Mod. T, it appears that greater lower-body power may significantly impact performance on this measure. This suggests that measures of COD that require less hip and knee flexion may be more reliant on foot speed and quickness. When assessing CODS, strength and conditioning professionals should consider multiple measures of CODS to determine the ability of an athlete to change direction when performing sport-specific tasks