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Volume 41 (2024): Issue 4 (Oct 2024)
Countermovement Jump and Isometric Strength Test–Retest Reliability in English Premier League Academy Football Players
Matthew Springham, Nav Singh, Perry Stewart, Jordan Matthews, Ian Jones, Charlie Norton-Sherwood, Dominic May, Jamie Salter, Anthony J. Strudwick, and Joseph W. Shaw
Purpose: To examine the test–retest reliability of countermovement jump (CMJ) and isometric strength testing measures in elite-level under-18 and under-23 academy football players. Methods: A total of 36 players performed 3 maximal CMJs and isometric abductor (IABS), adductor (IADS), and posterior chain (IPCS) strength tests on 2 separate test days using dual force plates (CMJ and IPCS) and a portable strength testing device (IABS and IADS). Relative (intraclass correlation coefficient) and absolute (coefficient of variation, standard error of the measurement, and minimal detectable change [MDC%]) reliabilities for 34 CMJ, 10 IABS, 10 IADS, and 11 IPCS measures were analyzed using between-sessions best, mean, and within-session methods. Results: For all methods, relative reliability was good to excellent for all CMJ and all IADS measures and poor to good for all IABS and IPCS measures. Absolute reliability was good (ie, coefficient of variation < 10%) for 27 (best) and 28 (mean) CMJ variables and for 6 (IABS and IADS) and 2 (IPCS) isometric measures. Commonly used CMJ measures (jump height, eccentric duration, and flight-time:contraction-time ratio) had good to excellent relative reliability and an MDC% range of 14.6% to 23.7%. Likewise, commonly used isometric peak force measures for IABS, IADS, and IPCS had good to excellent relative reliability and an MDC% range of 22.2% to 26.4%. Conclusions: Commonly used CMJ and isometric strength measures had good test–retest reliability but might be limited by their MDC%. Rate-of-force-development measures (for all isometric tests) and impulse measures (IPCS) are limited by poor relative and absolute reliability and high MDC%. MDC% statistics should be considered in the context of typical responsiveness.
Volume 19 (2024): Issue 10 (Oct 2024)
Volume 32 (2024): Issue 5 (Oct 2024)
Volume 40 (2024): Issue 5 (Oct 2024)
Volume 21 (2024): Issue 10 (Oct 2024)
Volume 46 (2024): Issue 5 (Oct 2024)
Longitudinal Analysis of Race-Management Strategies in a World-Class 200-m Freestyle Swimmer: A Case Study
Camille Loisel, Robin Pla, and Ludovic Seifert
Purpose: To investigate race-management strategies over a longitudinal case study of one of the world’s best female swimmers of the 200-m freestyle to understand if only 1 race-management strategy allowed her to succeed or whether several profiles have been used over the 8 years of analysis. Methods: Different race-management strategies within and between 50-m laps emerged from cluster analysis. To better explain race management, additional characteristics described the level of adversity, the level of competition, the performance outcome, and the type of race. Results: Two strategies of race management between laps have been used, and both allowed her to succeed in her career. The first was characterized by a fast start and a greater decrease of the speed between laps, whereas the second exhibited a more stable speed management. When those strategies were examined in relation to the level of competition and the level of adversity, it appeared that the first strategy was used more in international competitions and associated with higher time intervals between the studied swimmer and the direct rivals, while the second one was used more in national competitions and associated with lower time intervals. Conclusions: Findings suggested that this top elite swimmer did not adhere to a single “ideal” race-management strategy. Instead, she demonstrated flexibility and the ability to adapt her race management to contextual factors throughout her career, effectively controlling adversity. This highlights the importance of including adversity analysis in race-management studies.
Volume 28 (2024): Issue 4 (Oct 2024)
Do Experienced Adolescent Competition Dancers Alter Landing Kinematics and Kinetics for Split Leaps or Center Leaps After Fatigue?
Zoie R. Mink and Amanda Esquivel
Most injuries that dancers sustain are to the lower extremities, specifically the foot and ankle region. Numerous potential risk factors have been examined for dancer injuries such as technical mistakes and fatigue. The purpose of this study was to compare landing kinematics and kinetics during jumps that are common in dance pre and postfatigue. Ten adolescent advanced level dancers participated in this study. Subjects completed 3 split leaps and 3 center leaps before and after a fatigue protocol performed on a stationary bike. Live motion capture was used to record landing kinematic and kinetic data. Results of this study showed a significant increase in ankle eversion and external rotation angles for center leaps from pre- to postfatigue protocol (P = .020 and P = .020, respectively) as well as significant increases in ankle eversion and knee adduction moments for center leaps (P = .020 and P = .036, respectively). These results show that after a fatigue protocol, there are changes to the kinematics of dancers that may make them more susceptible to ankle injury.
