Jiaqing Xu

Jiaqing Xu


Research Focus & Metrics

Academic Career Length

4Years (2023-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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20 March 2023 in Sports Medicine
Verified
Journal Article
Open access
PDF file
JXJiaqing Xu
Jiaqing Xu
ATAnthony Turner
Anthony Turner
PCPaul Comfort
Paul Comfort
JHJohn R. Harry
John R. Harry
JMJohn J. McMahon
John J. McMahon
CBChris Bishop
Chris Bishop
Background: The heights obtained during the countermovement jump and drop jump tests have been measured by numerous studies using different calculation methods and pieces of equipment. However, the differences in calculation methods and equipment used have resulted in discrepancies in jump height being reported. Objectives: The aim of this systematic review was to examine the available literature pertaining to the different calculation methods to estimate the jump height during the countermovement jump and drop jump. Methods: A systematic review of the literature was undertaken using the SPORTDiscus, MEDLINE, CINAHL, and PubMed electronic databases, with all articles required to meet specified criteria based on a quality scoring system. Results: Twenty-one articles met the inclusion criteria, relating various calculation methods and equipment employed when measuring jump height in either of these two tests. The flight time and jump-and-reach methods provide practitioners with jump height data in the shortest time, but their accuracy is affected by factors such as participant conditions or equipment sensitivity. The motion capture systems and the double integration method measure the jump height from the centre of mass height at the initial flat foot standing to the apex of jumping, where the centre of mass displacement generated by the ankle plantarflexion is known. The impulse-momentum and flight time methods could only measure the jump height from the centre of mass height at the instant of take-off to the apex of jumping, thus, providing statistically significantly lower jump height values compared with the former two methods. However, further research is warranted to investigate the reliability of each calculation method when using different equipment settings. Conclusions: Our findings indicate that using the impulse-momentum method via a force platform is the most appropriate way for the jump height from the instant of take-off to the apex of jumping to be measured. Alternatively, the double integration method via a force platform is preferred to quantify the jump height from the initial flat foot standing to the apex of jumping.

26 September 2023 in Applied Sciences
Verified
Journal Article
Open access
PDF file
JXJiaqing Xu
Jiaqing Xu
Anthony Nicholas TurnerAnthony Nicholas Turner
Anthony Nicholas Turner
Tom ComynsTom Comyns
Tom Comyns
JHJohn Harry
John Harry
SCShyam Chavda
Shyam Chavda
Chris BishopChris Bishop
Chris Bishop
The kinetic analysis of joint work and joint contribution provides practitioners with information regarding movement characteristics and strategies of any jump test that is undertaken. This study aimed to compare joint works and contributions, and performance metrics in the countermovement jump (CMJ), drop jump (DJ), and countermovement rebound jump CMRJ. Thirty-three participants completed 18 jumps across two testing sessions. Jump height and strategy-based metrics (time to take-off [TTTO], countermovement depth [CM depth], and ground contact time [GCT]) were measured. Two-way analysis of variance assessed systematic bias between jump types and test sessions (α = 0.05). Reliability was evaluated via intraclass correlation coefficient [ICC] and coefficient of variation [CV]. Jump height and strategy-based metrics demonstrated good to excellent reliability (ICC = 0.82–0.98) with moderate CV (≤8.64%). Kinetic variables exhibited moderate to excellent reliability (ICC = 0.64–0.93) with poor to moderate CV (≤25.04%). Moreover, apart from TTTO (p ≤ 0.027, effect size [ES] = 0.49–0.62) that revealed significant differences between jump types, CM depth (p ≤ 0.304, ES = 0.27–0.32) and GCT (p ≤ 0.324, ES = 0.24) revealed nonsignificant trivial to small differences between three jumps in both sessions. Finally, the negative and positive hip and knee works, and positive ankle contribution measured in the CMRJ showed significant differences from the CMJ and DJ (p ≤ 0.048, g ≤ 0.71), with no significant difference observed in other kinetic variables between the three jump actions (p ≥ 0.086). Given the consistent joint works and joint contributions between jump types, the findings suggest that practitioners can utilize the CMRJ as a viable alternative to CMJ and DJ tests, and the CMRJ test offers valuable insights into movement characteristics and training suggestions.

13 December 2023 in Journal of Strength & Conditioning Research
Verified
Journal Article
Closed access
JXJiaqing Xu
Jiaqing Xu
ATAnthony Turner
Anthony Turner
TCThomas M. Comyns
Thomas M. Comyns
SCShyam Chavda
Shyam Chavda
CBChris Bishop
Chris Bishop
Xu, J, Turner, A, Comyns, TM, Chavda, S, and Bishop, C. The countermovement rebound jump: Between-session reliability and a comparison with the countermovement and drop jump tests. J Strength Cond Res 38(4): e150–e159, 2024—The countermovement jump (CMJ) and drop jump (DJ) are widely used jump tests to evaluate an athlete's neuromuscular performance. Nevertheless, conducting both the CMJ and the DJ assessments during one testing session can demand a considerable time investment that practitioners or coaches might not always have available. This study investigated whether the countermovement rebound jump (CMRJ) could be considered a viable alternative to the CMJ and DJ tests, respectively. Thirty-three physically active students volunteered as subjects (age: 27.2 ± 5.9 years, height: 1.78 ± 0.8 cm, body mass: 77.5 ± 11.5 kg), with 18 jumps completed for each subject across 2 testing sessions. The jump height (JH) and strategy-based metrics (time to take-off [TTTO], countermovement depth [CM depth], and reactive strength index [RSI] modified for CMJ and the first jump of the CMRJ; leg stiffness [K leg], ground contact time [GCT], and RSI for DJ and the second jump for the CMRJ) were calculated simultaneously via the impulse-momentum, flight time, double integration, and motion capture methods. All variables were examined by repeated-measures analysis of variance, 2-way random effects model intraclass correlation coefficient (ICC), coefficient of variation (CV), and standard error of measurement, with the significance set at p ≤ 0.05. All 3 jump tests showed good-to-excellent relative reliability (ICC = 0.79–0.98) and good-to-moderate CV (≤9.83), with the only exception being K leg measured during the DJ and in the second jump of the CMRJ assessment (CV ≤ 16.01%). Of all measured metrics, significant differences were only observed regarding TTTO between jumps (p ≤ 0.027, effect size [ES] ≤ 0.49). The comparison of calculation methods indicated that the JH calculated by 4 methods were not significantly different between jump actions (p ≥ 0.254). These findings support the use of the CMRJ as a reliable alternative to the CMJ and DJ tests. However, practitioners should be mindful of using K leg as a metric, whereas practitioners are also advised to allocate sufficient familiarization trials before implementing the CMRJ into their routine test batteries.

31 December 2024 in Strength & Conditioning Journal
Verified
Journal Article
Closed access
JXJiaqing Xu
Jiaqing Xu
ATAnthony Turner
Anthony Turner
MJMatthew J. Jordan
Matthew J. Jordan
TCThomas M. Comyns
Thomas M. Comyns
SCShyam Chavda
Shyam Chavda
CBChris Bishop
Chris Bishop
Rebound jumping is one of the most commonly used movement patterns to assess and monitor fast stretch-shortening cycle (SSC) mechanics, a critical component for rapid movements like sprinting, jumping, and directional changes. This narrative review explores the mechanical and neuromuscular mechanics underlying fast SSC function and critically evaluates the strengths and weaknesses of commonly used testing protocols, including drop jumps and multiple rebound jump tests, along with commonly reported metrics from these tests. By integrating scientific evidence with practical applications, the aim of this review is to guide practitioners in selecting appropriate assessment tools and implementing evidence-based strategies to evaluate fast SSC performance in athletes.

23 October 2023 in Symmetry
Verified
Journal Article
Open access
PDF file
JXJiaqing Xu
Jiaqing Xu
Matthew JordanMatthew Jordan
Matthew Jordan
SCShyam Chavda
Shyam Chavda
Anthony Nicholas TurnerAnthony Nicholas Turner
Anthony Nicholas Turner
Chris BishopChris Bishop
Chris Bishop
This study aimed to investigate the test–retest reliability of three bilateral jump tests to assess asymmetry and determine the consistency of both the magnitude and direction of asymmetry between two testing sessions. Thirty-three participants performed the countermovement jump (CMJ), drop jump (DJ), and countermovement rebound jump (CMRJ—jump 1: CMRJ1; jump 2: CMRJ2) over two sessions. Inter-limb asymmetry was calculated for kinetic metrics, including the mean propulsive force, net braking impulse, and net propulsive impulse. Test reliability was computed using intraclass correlation coefficients (ICC), coefficients of variation (CV), and standard error of measurement. Furthermore, analysis of variance was used to determine the systematic bias between jump types and sessions. Kappa coefficients were utilised to assess the consistency of asymmetry favouring the same limb. Results showed poor to excellent reliability for all jump tests between sessions (ICC range = 0.19–0.99, CV range = 2.80–11.09%). A significantly higher magnitude of asymmetry was revealed for the net braking impulse during the DJ compared to the CMRJ2 (p ≥ 0.014, g ≤ 0.53). When computing the direction of asymmetry between test sessions, Kappa coefficients revealed that levels of agreement were substantial (Kappa = 0.63–0.70) for the CMJ, moderate to almost perfect (Kappa = 0.59–0.94) for the CMRJ1, moderate to almost perfect (Kappa = 0.58–0.81) for the DJ, and slight to moderate for the CMRJ2 (Kappa = 0.19–0.57). These results underscore the variable nature of both the magnitude and direction of asymmetry during jump testing. Thus, practitioners should carefully choose evaluation methods and metrics characterised by low variability to ensure robust asymmetry assessments.

26 April 2024 in Applied Sciences
Verified
Journal Article
Open access
PDF file
JXJiaqing Xu
Jiaqing Xu
Anthony Nicholas TurnerAnthony Nicholas Turner
Anthony Nicholas Turner
Tom ComynsTom Comyns
Tom Comyns
SCShyam Chavda
Shyam Chavda
Chris BishopChris Bishop
Chris Bishop
This study investigates the associations between countermovement rebound jump (CMRJ) performance metrics and various independent measures of athletic performance, including the isometric mid-thigh pull (IMTP), 20 m linear sprint, and 505 change-of-direction (COD) speed tests. Pearson’s correlations were used to analyse the relationship between the CMRJ measures with athletic performance, with significance being set at p ≤ 0.006. Results showed large significant positive relationships between IMTP peak force and force at 300 milliseconds with the first jump height of the CMRJ (JH-1, r = 0.54 to 0.55, p ≤ 0.002). Additionally, inverse relationships were observed between reactive strength index modified (RSImod) and reactive strength index (RSI) with 20 m sprint total and split times (r = −0.55 to −0.66, p ≤ 0.001), and the 10 m and total sprint times were significantly correlated with JH-1 (r = −0.54, p = 0.003), indicating that greater vertical explosive power and reactive strength are associated with faster sprint performance. Finally, a significant inverse relationship was identified between CMRJ metrics (two JH values and RSImod) and 505 COD times in both the left and right sides (r = −0.51 to −0.68, p ≤ 0.006). These findings suggest that CMRJ performance metrics are valuable indicators of lower-limb explosive force production, with a strong link to both linear sprint and COD performance. The finding underscores the importance of including CMRJ assessments in athletic performance evaluations due to their dual assessment capacity of slow and fast stretch–shortening cycle mechanics.