Article

Selecting Metrics That Matter: Comparing the Use of the Countermovement Jump for Performance Profiling, Neuromuscular Fatigue Monitoring, and Injury Rehabilitation Testing

Authors:
  • Canadian Sport Institute Calgary/University of Calgary
  • San Antonio Spurs
  • Nucleus of High Performance in Sport - NAR, São Paulo, Brazil
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Abstract

The countermovement jump (CMJ) is one of the most used performance assessments in strength and conditioning. While numerous studies discuss the usability of different metrics in this test, this is often done within the context of a specific aim. However, to our knowledge, no information currently exists providing practitioners with some over-arching recommendations on which metrics to choose when the purpose of using the test differs. This article discusses how the metrics selected to monitor during CMJ testing might differ when aiming to use it as a proxy for athletic performance, as part of neuromuscular fatigue monitoring, or as part of a test battery for return to performance in injured athletes.

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THERE IS A LACK OF STRENGTH AND CONDITIONING RESEARCH INTO THE DEMANDS AND THE SPECIFIC AREAS OF DEVELOPMENT REQUIRED TO OPTIMIZE PERFOR- MANCE AND REDUCE THE RISK OF COMMON INJURIES IN FEMALE NETBALL ATHLETES. NETBALL IS PREDOMINANTLY ANAEROBIC, CHARACTERIZED BY FREQUENT HIGH-INTENSITY MOVEMENTS THAT REQUIRE HIGH LEVELS OF STRENGTH, POWER, AND LOWER LIMB CONTROL. HOWEVER, THERE IS LIMITED RESEARCH IN THE PREPARATION OF FEMALE NETBALL PLAYERS FOR TRAINING AND COMPETITION. IN THIS REVIEW, WE PRESENT THE PHYSIOLOGICAL DEMANDS OF TRAINING AND COMPETITION, COMMON CAUSES OF INJURY, AND STRENGTH AND CONDITIONING TRAINING RECOM- MENDATIONS TO ENHANCE PERFORMANCE AND REDUCE THE LIKELIHOOD OF INJURY IN FEMALE NETBALL PLAYERS.
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In female athletes, bilateral aysmmetry in peak landing forces during the drop jump is associated with anterior cruciate ligament (ACL) injury risk and is proposed as a marker of rehabilitation progression following ACL rupture. Less is known regarding the value of the assessment of these asymmetry in jump tasks in relation to recovery from other lower extremity injuries, particularly in male athletes. To evaluate the association between previous injury and bilateral limb asymmetry in peak ground reaction forces during a countermovement jump (CMJ) and a drop jump (DJ). Retrospective study. Professional football club. 24 first team players. CMJ and DJ performed on two force platforms placed side by side with one foot on each platform. Asymmetry in peak force during the take-off and landing phases of a CMJ countermovement jump in healthy players who either had (INJ) or had not (N-INJ) sustained a non-contact lower extremity injury in the preceding season. Compared to N-INJ, P-INJ mean asymmetry in P-INJ was CMJ takeoff force was 8% higher (CMT-a), in landing force (CML-a) 57% higher, in DJ first landing (DJ1-a) and second landing (DJ2-a) 11% and 31% higher, respectively. None of these differences were significant, but based on Cohen's d, the difference between INJ and N-INJ in CML-a was large (d=0.65), in DJ2-a was moderate (d=0.39) and in CMT-a and DJ1-a was small (d=0.13 and d=0.28, respectively). Our findings suggest that in pro footballers jump landing force asymmetry both in CMJ and DJ may be a marker of residual deficits associated with previous lower extremity injury. Larger studies are needed to confirm these findings and to determine whether these asymmetries may also be a marker of future injury risk.
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Scanlan, AT, Wen, N, Pyne, DB, Stojanović, E, Milanović, Z, Conte, D, Vaquera, A, and Dalbo, VJ. Power-related determinants of Modified Agility T-test performance in male adolescent basketball players. J Strength Cond Res 35(8): 2248-2254, 2021-Although the Modified Agility T-test (MAT) has been advocated for assessing change-of-direction performance in basketball, the power-related attributes emphasized during the test are unknown. Therefore, the aim of this study was to identify the power-related determinants of the MAT in basketball players. A cross-sectional, descriptive research design was used whereby national- and state-level male adolescent basketball players (n = 24; 17.3 ± 0.5 years) completed a battery of power-related performance tests. The tests administered included the MAT, isometric midthigh pull, 10-m sprint, countermovement jump, 1-step vertical jump, standing long jump, and repeated lateral bound. Associations between performance during the MAT and other tests were quantified, and performance in each test was compared between faster (>50th percentile) and slower (<50th percentile) players in the MAT. The MAT exhibited large correlations (p < 0.05) with standing long jump distance (r = -0.67, R2 = 45%), countermovement jump relative peak force (r = -0.63, R2 = 39%), isometric midthigh pull relative peak force (r = -0.55, R2 = 30%), and 10-m sprint time (r = 0.53, R2 = 28%). The faster group performed better (p < 0.05) during the standing long jump (mean difference; ±90% confidence limits: 0.16; ±0.12 m) and produced greater (p < 0.05) relative peak force during the isometric midthigh pull (2.5; ±2.3 N·kg-1) and countermovement jump (2.1; ±1.8 N·kg-1) than the slower group. The MAT complements other power-related tests used in basketball and stresses basketball-specific, power-related attributes in various movement planes. These data can inform training and testing approaches to optimize change-of-direction performance in basketball.
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Preferential limb function must be sustained through repetitious asymmetrical activities for continuous athletic development and ultimately, optimal athletic performance. As such, the prevalence of limb dominance and between-limb differences are common in athletes. Severe between-limb differences have been associated with reductions in athletic performance and increased injury risk in athletes. However, in the current literature, the terms limb preference and limb dominance have been used interchangeably. Together, these terms include a limb which is subjectively preferred and one that is objectively dominant in one or more performance measures from a variety of athletic tasks. In this review, we 1) discuss reported correspondence between task-specific limb preference and limb dominance outcomes in athletes, 2) provide greater context and distinction between the terms limb preference and limb dominance, and 3) to offer pragmatic strategies for practitioners to assess context-specific limb dominance. A limb which is subjectively preferred is not necessarily objectively dominant in one or more athletic qualities or sport-specific tasks. Further to this, a limb which is objectively superior in one task may not exhibit such superiority in a separate task. Thus, limb preference and limb dominance are both task-specific. As such, we propose that practitioners intentionally select tasks for limb dominance assessment which resemble the most relevant demands of sport. Because limb dominance profiles are inconsistent, we suggest that practitioners increase assessment frequency by integrating limb dominance testing into standard training activities. This will allow practitioners to better understand when changes reflect sport-specific adaptation versus potential performance or injury ramifications.
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Previous research has highlighted a distinct lack of longitudinal data for asymmetry. The aims of the present study were to provide seasonal variation data for the magnitude and direction of asymmetry. Eighteen elite male academy soccer players (under-23) performed unilateral countermovement jumps (CMJ) and unilateral drop jumps (DJ) during pre, mid and end of season time points. Recorded metrics for asymmetry included: jump height and concentric impulse for the CMJ, and jump height and reactive strength index for the DJ. The magnitude of asymmetry showed trivial to small changes throughout the season (CMJ effect size range = -0.43 to 0.05; DJ effect size range = -0.18 to 0.41). However, Kappa coefficients showed poor to substantial levels of agreement for the direction of asymmetry during the CMJ (Kappa = -0.06 to 0.77) and DJ (Kappa = -0.10 to 0.78) throughout the season. These data show that when monitoring asymmetry, the magnitude alone may provide a false impression of consistent scores over time. In contrast, monitoring the direction of asymmetry highlights its task and variable nature, and is suggested as a useful tool for practitioners who wish to monitor asymmetry over the course of a competitive soccer season.
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Background The decision as to whether or not an athlete is ready to return to sport (RTS) after ACL reconstruction is difficult as the commonly used RTS criteria have not been validated. Purpose To evaluate whether a set of objective discharge criteria, including muscle strength and functional tests, are associated with risk of ACL graft rupture after RTS. Materials and methods 158 male professional athletes who underwent an ACL reconstruction and returned to their previous professional level of sport were included. Before players returned to sport they underwent a battery of discharge tests (isokinetic strength testing at 60°, 180° and 300°/s, a running t test, single hop, triple hop and triple crossover hop tests). Athletes were monitored for ACL re-ruptures once they returned to sport (median follow-up 646 days, range 1–2060). Results Of the 158 athletes, 26 (16.5%) sustained an ACL graft rupture an average of 105 days after RTS. Two factors were associated with increased risk of ACL graft rupture: (1) not meeting all six of the discharge criteria before returning to team training (HR 4.1, 95% CI 1.9 to 9.2, p≤0.001); and (2) decreased hamstring to quadriceps ratio of the involved leg at 60°/s (HR 10.6 per 10% difference, 95% CI 10.2 to 11, p=0.005). Conclusions Athletes who did not meet the discharge criteria before returning to professional sport had a four times greater risk of sustaining an ACL graft rupture compared with those who met all six RTS criteria. In addition, hamstring to quadriceps strength ratio deficits were associated with an increased risk of an ACL graft rupture.
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The purpose of this study was to determine whether any significant associations were present between lower-body strength and power and the performance of turning and aerial manoeuvres in elite surfing athletes. Eighteen competitive male surfers performed a battery of physical tests (countermovement jump (CMJ), squat jump (SJ), and isometric mid-thigh pull (IMTP)) during a single session, in addition to having their performance of turning and aerial manoeuvres ranked from highest to lowest. Significant associations were identified between turning manoeuvre ranking and; peak force in the CMJ, SJ and IMTP (ρ=-0.737, p<0.01; ρ=-0.856, p<0.01; ρ=-0.683, p<0.01, respectively), as well as, peak velocity and jump height in the CMJ (ρ=-0.560, p=0.02; ρ=-0.529, p=0.02, respectively). No significant associations were identified between aerial manoeuvre ranking and any strength and power variable. These results suggest that surfing athletes that exhibit greater lower-body isometric and dynamic strength, and power also perform higher scoring turning manoeuvres during wave riding.
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Functional testing is used to assess anterior cruciate ligament (ACL) reconstruction rehabilitation, with the goal of symmetric ability. The pattern of change in the uninvolved limb's function during rehabilitation is not established. (1) Involved and uninvolved limb ability increases during rehabilitation, but the uninvolved limb ability increases to a lesser degree. (2) Hop tests will show larger initial asymmetry and will improve the most with rehabilitation. Cohort study; Level of evidence, 3. This was a retrospective case series of 122 patients who underwent ACL reconstruction at our ambulatory surgery center and received multiple postoperative Standard Functional Tests (SFTs) between October 2009 and October 2013. Ten of the 12 individual tests within the SFT battery were analyzed. The patients' earliest and latest SFTs were compared for changes in Limb Symmetry Index (LSI) and absolute function in each limb. We also analyzed the subgroup with SFTs (n = 38) at both 4 and 6 months postoperatively. In all patients with multiple SFTs, involved limb performance increased in all tests except eyes-closed stork. Uninvolved limb performance increased in 4 SFT component tests and decreased in none. LSI significantly improved in 6 tests, all of which also showed involved limb improvement that was significant. Of these 6 tests, 5 showed initial LSI below 90%: single-leg squat, retro step-up, single-leg hop, crossover triple hop, and timed hop. Retro step-up and single-leg hop showed LSI improvements greater than 10 percentage points. In patients with 4- and 6-month data, involved limb performance increased in all tests except single-leg triple hop. Uninvolved limb performance increased in 5 SFT component tests and decreased in none. LSI significantly improved in 4 tests, all of which had initial LSI below 90%, and showed involved limb improvement that was significant. Retro step-up, single-leg hop, and crossover triple hop showed LSI improvements greater than 10 percentage points. During ACL reconstruction rehabilitation, LSI improvements indicated absolute increases in involved limb ability and were not attributable to uninvolved limb deterioration. The single-leg squat, retro step-up, single-leg hop, crossover triple hop, and timed hop are suggested as highly useful tests, since all showed initial LSI below 90%, with significant LSI improvement after rehabilitation. © 2015 The Author(s).
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STATISTICAL ANALYSIS IS CRUCIAL TO THE ROLE OF STRENGTH AND CONDITIONING, AND COACHES SHOULD BE ABLE TO IDENTIFY WHETHER THEIR DATA ARE RELIABLE AND OBJECTIVELY DETERMINE DIFFERENCES AND RELATIONSHIPS. THESE ANALYTICAL SKILLS ARE CENTRAL TO OUR ABILITY OF UNCOVERING TRENDS AND ASSOCIATIONS, MAKING PREDICTIONS AND ASSESSING THE EFFICACY OF TRAINING PROGRAMS. THIS ARTICLE REVIEWS STATISTICAL TESTS AVAILABLE THROUGH MICROSOFT EXCEL, COVERING RELIABILITY (THROUGH THE COEFFICIENT OF VARIATION), THE SMALLEST WORTHWHILE CHANGE (I.E., THE FIRST MEANINGFUL DIFFERENCE IN SCORES), EFFECT SIZES (I.E., THE MAGNITUDE OF CHANGE BETWEEN PERFORMANCE SCORES), AND RELATIONSHIPS (I.E., CORRELATIONS).
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Purpose: To assess the relationships between player characteristics (including age, playing experience, ethnicity, and physical fitness) and in-season injury in elite Australian football. Design: Single-cohort, prospective, longitudinal study. Methods: Player characteristics (height, body mass, age, experience, ethnicity, playing position), preseason fitness (6-min run, 40-m sprint, 6×40-m sprint, vertical jump), and in-season injury data were collected over 4 seasons from 1 professional Australian football club. Data were analyzed for 69 players, for a total of 3879 player rounds and 174 seasons. Injury risk (odds ratio [OR]) and injury severity (matches missed; rate ratio [RR]) were assessed using a series of multilevel univariate and multivariate hierarchical linear models. Results: A total of 177 injuries were recorded with 494 matches missed (2.8±3.3 matches/injury). The majority (87%) of injuries affected the lower body, with hamstring (20%) and groin/hip (14%) most prevalent. Nineteen players (28%) suffered recurrent injuries. Injury incidence was increased in players with low body mass (OR=0.887, P=.005), with poor 6-min-run performance (OR=0.994, P=.051), and playing as forwards (OR=2.216, P=.036). Injury severity was increased in players with low body mass (RR=0.892, P=.008), tall stature (RR=1.131, P=.002), poor 6-min-run (RR=0.990, P=.006), and slow 40-m-sprint (RR=3.963, P=.082) performance. Conclusions: The potential to modify intrinsic risk factors is greatest in the preseason period, and improvements in aerobic-running fitness and increased body mass may protect against in-season injury in elite Australian football.
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The neuromechanical determinants of sprint running performance have been investigated in team sports athletes and non-elite sprinters. The aim of this study was to quantify the relationships between kinetic and performance parameters, obtained in loaded and unloaded vertical and horizontal jumps, and sprinting in elite athletes. Twenty-two sprinters performed squat jumps, countermovement jumps, horizontal jumps and jump squats with different loads on a force platform, in addition to a 50-m sprint. Results indicated that jumping height and distance in vertical and horizontal jumps are more strongly correlated (R ≈ 0.81) to sprinting speed than the respective peak forces (R ≈ 0.36). Furthermore, the optimum load generating the maximum power in the jump squat is also highly correlated to sprint performance (R ≈ 0.72). These results reveal that vertical and horizontal jump tests may be used by coaches for assessing and monitoring qualities related to sprinting performance in elite sprinters.