Surfing the Waves of the CMJ; Are There between-Sport Differences in the Waveform Data?

Examining Countermovement Jump Strategies Between Women's NCAA Division I Sports

ABSTRACT

Donahue, PT, Peel, SA, Rush, M, McInnis, AK, Littlefield, T, Calci, C, and Brutofsky, T. Examining countermovement jump strategies between women's NCAA Division I sports. J Strength Cond Res 37(10): 2052-2057, 2023-The purpose of this study was to examine countermovement vertical jump performance among female athletes who rely heavily on vertical jump performance within their given sport. Forty-five female athletes representing 3 teams (basketball, volleyball, and beach volleyball) competing at the NCAA Division I level completed 2 maximal effort countermovement jumps (CMJ) using a portable force platform. A 1-way analysis of variance was used to compare groups across each variable. Statistically significant differences were found between the groups regarding propulsive duration and time to takeoff with basketball showing the shortest time and beach volleyball having the longest times ( p < 0.05). In addition, differences were seen in countermovement depth and mean propulsive force between the groups with basketball displaying the smallest countermovement and highest force ( p < 0.05). No differences were seen in jump height and reactive strength index modified. Greater force and shorter durations in basketball athletes versus the low force and long durations in the beach volleyball athletes suggest that sporting backgrounds play a large role in how the CMJ is performed. This information can aid strength and conditioning practitioners in the design of training programs that are sport specific to the strategies used by the athlete.

Identifying Consistent Metrics from the Force-Time Curve of the Countermovement Jump in Combat Fighters and Physically Active Men

We investigated the consistency of metrics obtained from the unweighting, braking, propulsive, and landing phases of the countermovement (CMJ) force-time curve in combat fighters and physically active men. Combat fighters (n=21) and physically actives (n=21) were tested for three days (2-7 days apart). Participants performed four maximal CMJ separated by 1-min for between-day comparisons. From force-time recording, the consistency of 16 CMJ metrics (peak and mean ground reaction forces (GRF), net impulse, and duration from each phase) was investigated using the intraclass correlation coefficient (ICC) and typical error (CVTE). We considered as "consistent" those metrics showing no systematic differences, ICC ≥ 0.75, and CVTE ≤ 10%. We further compared the CVTE between groups and pairs of trials (days). Participants demonstrated more consistency in the braking and propulsive phases, while the unweighting phase did not show any consistent metric. There was no evidence of a learning effect (systematic changes), but analysis appointed more consistency on days 2-3 than on days 1-2 (18 metrics presented lower CVTE while 11 presented higher). We identified braking and propulsive GRF (peak and mean) and propulsive impulse as consistent metrics for combat fighters, while only propulsive impulse for physically actives. The between-group analyses showed that 24 comparisons favored the combat fighters against only five favoring the physically actives. In conclusion, force-time metrics related to jumping strategy, like phase duration, are less consistent than those related to driven forces and jump output, probably because participants changed their jump strategy during testing days.

Muscle-Specific Contributions to Vertical Ground Reaction Force Profiles During Countermovement Jumps: Case Studies in College Basketball Players

ABSTRACT

Kipp, K and Kim, H. Muscle-specific contributions to vertical ground reaction force profiles during countermovement jumps: case studies in college basketball players. J Strength Cond Res 37(7): 1523-1529, 2023-The purpose of this study was to determine muscle-specific contributions to various types of vertical ground reaction force (vGRF) profiles in collegiate basketball players. Players from a men's ( n = 5; height: 1.84 ± 0.14 m; mass: 92.8 ± 11.4 kg) and a women's ( n = 5; 1.71 ± 0.09 m; mass: 80.1 ± 17.6 kg) basketball team completed 3-5 countermovement jumps (CMJ) while motion capture and force plate data were recorded. Muscle-specific contributions to vGRF were calculated through vGRF decomposition analysis. Profiles of vGRF were analyzed based on the presence of unimodal or bimodal peaks during the CMJ. The results showed that the soleus (SOL), gastrocnemii (GAS), vastii (VAS), and gluteus maximus (GMX) muscles all contributed to upward vGRF generation throughout the entire CMJ duration. The contributions were greatest for the SOL (1.78 body weight [BW]), intermediate for the GAS (0.96 BW) and VAS (0.72 BW), and negligible for the GMX (0.11 BW). For unimodal vGRF profiles, SOL contributions coincided with peak vGRF, whereas VAS contributions were stable throughout most of the CMJ. For bimodal vGRF profiles, SOL and VAS contributions explained the presence of the first vGRF peak, whereas GAS and VAS contributions explained the second vGRF peak. Differences between vGRF profiles appear to be the result of distinct force contributions from the VAS muscle, which may have implications for the analysis of vGRF time series data during CMJ testing.

Countermovement Jump and Squat Jump Force-Time Curve Analysis in Control and Fatigue Conditions

ABSTRACT

Hughes, S, Warmenhoven, J, Haff, GG, Chapman, DW, and Nimphius, S. Countermovement jump and squat jump force-time curve analysis in control and fatigue conditions. J Strength Cond Res 36(10): 2752-2761, 2022-This study aimed to reanalyze previously published discrete force data from countermovement jumps (CMJs) and squat jumps (SJs) using statistical parametric mapping (SPM), a statistical method that enables analysis of data in its native, complete state. Statistical parametric mapping analysis of 1-dimensional (1D) force-time curves was compared with previous zero-dimensional (0D) analysis of peak force to assess sensitivity of 1D analysis. Thirty-two subjects completed CMJs and SJs at baseline, 15 minutes, 1, 24, and 48 hours following fatigue and control conditions in a pseudo random cross-over design. Absolute (CMJ ABS /SJ ABS ) and time-normalized (CMJ NORM /SJ NORM ) force-time data were analyzed using SPM 2-way repeated measures analysis of variance with significance accepted at α = 0.05. The SPM indicated a magnitude of difference between force-time data with main effects for time ( p < 0.001) and interaction ( p < 0.001) observed in CMJ ABS , SJ ABS, and SJ NORM, whereas previously published 0D analysis reported no 2-way interaction in CMJ and SJ peak force. This exploratory research demonstrates the strength of SPM to identify changes between entire movement force-time curves. Continued development and use of SPM analysis techniques could present the opportunity for refined assessment of athlete fatigue and readiness with the analysis of complete force-time curves.

Maximal Strength in Relation to Force and Velocity Patterns During Countermovement Jumps

Maximal strength is important for the performance of dynamic athletic activities, such as countermovement jumps (CMJ). Although measures of maximal strength appear related to discrete CMJ variables, such as peak ground reaction forces (GRF) and center-of-mass (COM) velocity, knowledge about the association between strength and the time series patterns during CMJ will help characterize changes that can be expected in dynamic movement with changes in maximal strength.

PURPOSE

To investigate the associations between maximal strength and GRF and COM velocity patterns during CMJ.

METHODS

Nineteen female college lacrosse players performed 3 maximal-effort CMJs and isometric midthigh pull. GRF and COM velocity time series data from the CMJ were time normalized and used as inputs to principal-components analyses. Associations between isometric midthigh pull peak force and CMJ principal-component scores were investigated with a correlational analysis.

RESULTS

Isometric midthigh pull peak force was associated with several GRF and COM velocity patterns. Correlations indicated that stronger players exhibited a GRF pattern characterized by greater eccentric-phase rate of force development, greater peak GRF, and a unimodal GRF profile (P = .016). Furthermore, stronger athletes exhibited a COM velocity pattern characterized by higher velocities during the concentric phase (P = .004).

CONCLUSIONS

Maximal strength is correlated to specific GRF and COM velocity patterns during CMJ in female college lacrosse athletes. Since maximal strength was not correlated with discrete CMJ variables, the patterns extracted via principal-components analyses may provide information that is more beneficial for performance coaches and researchers.

Development of evidence-based classification for para surfers with physical impairments: A narrative review

The sport of competitive para surfing is growing internationally without established classification procedures. A classification structure is essential for equitable sport competition and worldwide sport progression. This narrative review summarizes the existing knowledge on Paralympic classification and surfing biomechanics. Its primary purpose is to describe the development of an evidence-based para surfing classification structure that follows the International Paralympic Committee (IPC) Classification Code. Two databases-PubMed and Google Scholar-were searched for three themes: "Paralympic classification", "performance determining factors in surfing", and "impact of impairments on surf performance". The IPC Classification Code and IPC regulations were obtained from the IPC website and official publications. Seventy-six relevant articles were utilized to guide the design of this preliminary para surfing classification structure. A conceptual framework on athlete characteristics, adaptive sport characteristics, and use of equipment is presented to build the essential knowledge base for continual growth of para surfing. This classification structure and conceptual framework will support para surfing sport expansion and help pave the way for its inclusion in the Paralympic Games.

Analyses of Countermovement Jump Performance in Time and Frequency Domains

This study aimed to analyze counter-movement jump (CMJ) performance in time and frequency domains. Fortyfour Division I American football players participated in the study. Kinetic variables were collected from both dominant and non-dominant legs using two force plates. Normalized peak power, normalized net impulse, and normalized peak force significantly correlated with jump height (r = .960, r = .998, r = .725, respectively with p < .05). The mean frequency component was significantly correlated with CMJ performance (r = .355 with p < .05). The reliability of the frequency variables was higher than the time domain variables. Frequency domain variables showed weaker correlations with jump height compared with time domain variables. Frequency domain analysis provides frequency components, which represent the rate of energy transmission from the eccentric phase to the end of the push-off phase. Frequency component information may provide additional information for the analyses of CMJ performance for athletes.

Classification of Soccer and Basketball Players' Jumping Performance Characteristics: A Logistic Regression Approach

This study aimed to examine countermovement jump (CMJ) kinetic data using logistic regression, in order to distinguish sports-related mechanical profiles. Eighty-one professional basketball and soccer athletes participated, each performing three CMJs on a force platform. Inferential parametric and nonparametric statistics were performed to explore group differences. Binary logistic regression was used to model the response variable (soccer or not soccer). Statistical significance (p < 0.05) was reached for differences between groups in maximum braking rate of force development (RFD_Dmax, U₇₉ = 1035), mean braking rate of force development (RFD_Davg, U₇₉ = 1038), propulsive impulse (IMP_U, t₇₉ = 2.375), minimum value of vertical displacement for center of mass (S_BCMmin, t₇₉ = 3.135), and time difference (% of impulse time; Δ_Τ) between the peak value of maximum force value (F_Umax) and S_BCMmin (U₇₉ = 1188). Logistic regression showed that RFD_Davg, impulse during the downward phase (IMP_D), IMP_U, and Δ_Τ were all significant predictors. The model showed that soccer group membership could be strongly related to IMP_U, with the odds ratio being 6.48 times higher from the basketball group, whereas RFD_Davg, IMP_D, and Δ_Τ were related to basketball group. The results imply that soccer players execute CMJ differently compared to basketball players, exhibiting increased countermovement depth and impulse generation during the propulsive phase.