Geneau, MC, Carey, DL, Gastin, PB, Robertson, S, and James, LP. Classification of force-time metrics into lower-body strength domains. J Strength Cond Res 38(9): 1561–1567, 2024—The purpose of this study was to classify force-time metrics into distinct lower-body strength domains using a systematic data reduction analysis. A cross-sectional design was used, whereby competitive field sport athletes ( F = 39, M = 96) completed a series of drop jumps, squat jumps, countermovement jumps (CMJs), loaded CMJs, and 2 isometric tasks on portable force platforms, resulting in a total of 285 force-time performance metrics. The metrics were split into 4 test “families” and each was entered into a sparse principal component analysis (sPCA) model. A single metric from each component of each family-specific sPCA were selected based on the loading, reliability, and simplicity of the metric and entered into a second sPCA that included metrics across all tests. The final sPCA revealed 7 principal components each containing 2 metrics and explained a total of 53% variance of the dataset. The final principal components were interpreted as 7 lower-body strength domains: (a) dynamic force, (b) dynamic timing, (c) early isometric, (d) maximal isometric, (e) countermovement velocity, (f) reactive output, and (g) reactive timing. The findings demonstrate that a total of 7 metrics from a drop jump, CMJ, and isometric test can be used to represent ∼50% of variance in lower-body strength performance of field sport athletes. These results can help guide and simplify the lower-body strength diagnosis process in field sport athletes.

Purpose: Ice hockey is a team invasion sport characterized by repeated high-intensity skating efforts, technical and tactical skill, physical contact, and collisions requiring considerable levels of muscular strength. The purpose of this study was to evaluate the relationships between lower-body vertical force–time metrics and skating qualities in subelite female ice hockey players. Methods: A cross-sectional cohort design was employed utilizing 14 athletes (body mass = 66.7 [1.8] kg; height = 171.6 [6.2] cm; age = 21.1 [1.7] y). The relationships between metrics of lower-body strength collected from a drop jump, squat jump, countermovement jump, loaded countermovement jump, and an isometric squat and 4 skating qualities collected from a linear sprint, repeated sprint test, and a multistage aerobic test were evaluated. Results: The regression models revealed a positive relationship between relative peak force in the isometric squat and skating multistage aerobic test performance (r ² = .388; P = .017) and a positive relationship between repeated-sprint ability and eccentric mean force during the loaded countermovement jump (r ² = .595; P = .001). No significant relationships were observed between strength metrics and skating acceleration or maximal velocity. Conclusions: These data suggest that skating ability is most affected by relative isometric strength in female ice hockey players. It is recommended that practitioners focus training on tasks that improve relative force output. It is also recommended that isometric relative peak force be used as a monitoring metric for this cohort.

Maximal strength of the lower body is important for many athletic tasks and demands. Lower body extensor strength, defined as maximal expressions of force in the vertical plane, can be measured in several different ways, using a wide range of tests and metrics. Although there have been investigations into the interrelationships between lower body strength and force measures, there is no known analysis or synthesis of these data that focuses on classifying variables into groups based on statistical similarity and/or distinction. This information is important to consider in an environment where many measurement options exist for diagnosing lower body characteristics. Understanding the overlap and distinction of these analysis methods and metrics will inform parsimonious, yet comprehensive, assessment of the lower body. It was therefore the purpose of this review to explore and summarize the commonality (i.e., r, R ² , component loading) between metrics from weightbearing, multi-joint lower body strength tests that are presented in the current literature, with the aim to group metrics into distinct domains of strength expression. The results of this review suggest that five unique domains of lower body extensor strength are present in athletes and trained populations: 1) reactive dynamic, 2) unloaded dynamic, 3) loaded dynamic, 4) early isometric, and 5) maximal isometric. Despite these findings, there are considerable limitations and gaps in the literature, and it is suggested that additional empirical investigations be conducted to better understand this concept of lower body strength domains.

Geneau, MC, Carey, DL, Gastin, PB, Robertson, S, and James, LP. A comparison of strength dimensionality across senior and pathway field sport athletes. J Strength Cond Res XX(X): 000–000, 2026—The aim of this study was to investigate the dimensionality and classification of lower-body strength metrics among senior and pathway male and female field sport athletes. One hundred and eighty trained Australian rules football, soccer, and field hockey athletes completed a series of drop jumps, squat jumps, countermovement jumps, countermovement jumps with 60% body mass, isometric squats, and isometric midthigh pulls. Principal component analysis (PCA) and sparse-PCA were used to reduce and classify the 215 force-time metrics from these tests into unique domains of strength. The dimensionality and classification results were then compared between athlete subgroups: senior male and senior female, and senior male and pathway male. To account for 70% of the variance in the data set, 8 principal components were required in the senior male data, 12 in the senior female data, and 9 in the pathway male data, indicating differences between variable relationships across populations. The orientation of the top 4 principal component vectors was consistent across athlete groups. Finally, metric selection identified 4 common strength domains in senior male and female athletes, with 2 also present in the pathway group. These findings highlight the importance of considering athlete developmental level when selecting strength tests and further supports the discovery of strength domains in senior field sport athletes. This study contributes to targeted and effective lower-body strength assessment for field sport athletes.

Despite overwhelming evidence for the physiological and biomechanical benefits of strength training in adolescent girls, there remains a prominent gap in participation due to sociological factors and exposure to correct practices. Using a mixed-methods approach, this pilot study explored the effectiveness of a 5-day program designed to introduce adolescent girls to strength training, aiming to observe whether a 5-day program could improve movement competency, confidence, and perceptions toward strength training. Twelve girls (age = 15.2 ± 0.9 years) were recruited from a 5-day strength training program. This program focused on six key movement patterns, which were instructed, explored, and applied in the strength training environment. Movement competency was evaluated pre-, post-, and 1 month after the program. Perceptions of confidence and participation were evaluated using surveys (at each time point) and focus group discussions postprogram. Participants’ movement competency significantly improved from pre- to postprogram and was maintained 1 month after ( p < .001). The program was effective in developing participants’ confidence, and they reported enjoying the program, which positively influenced their intentions to engage in subsequent strength training. Focus group discussions indicated that social connections across family, friends, and sport would support ongoing strength training uptake, yet the lack of normalized strength training for girls/women may negatively impact adherence. Overall, results lend considerable support for 5-day programs aimed at introducing adolescent girls to strength training, showing an immediate impact on movement quality and perceived confidence and potentially contributing to ongoing participation in strength training.

Background/Objectives: This study evaluated the differences in force–time characteristics of different incrementally loaded countermovement jumps (CMJs) and assessed their relationship to one-repetition maximum (1-RM) back squat performance. Methods: Nineteen resistance-trained males participated in this cross-sectional study, performing CMJs under six conditions (0%, 20%, 40%, 60%, 80%, and 100% body mass) followed by a 1-RM back squat. Multiple regression models were used to evaluate the relationship between discrete CMJ metrics (net concentric impulse, net concentric mean force, eccentric duration) with 1-RM values. Additionally, one-dimensional statistical parametric mapping (SPM) was used to evaluate the intact force–time curve between jump conditions. Results: The multiple regression models explained 53–66% of the variance in 1-RM squat performance, which was greatest under the 80% body mass condition. One-dimensional SPM analysis revealed significant differences in force–time curves across all loading conditions. Conclusions: These findings demonstrate that metrics from a loaded CMJ explained up to 66% of variance in the 1-RM back squat, suggesting the two tests are independent measures of strength. Further, each loaded jump condition elicited unique force-time curves, suggesting that each load requires a different neuromuscular technique.