Biomechanical factors associated with jump height: a comparison of cross-sectional and pre-to-post training change findings

Previous studies investigating the biomechanical factors associated with maximal countermovement jump height have typically utilised cross-sectional data. An alternative but less common approach is to use pre-to-post training change data, where the relationship between an improvement in jump height and a change in a factor is examined more directly. Our study compared the findings of these approaches. Such an evaluation is necessary because cross-sectional studies are currently a primary source of information for coaches when examining what factors to train to enhance performance. The countermovement jump of forty four males was analysed before and after an eight week training intervention. Correlations with jump height were calculated using both cross-sectional (pre-training data only) and pre-to-post training change data. Eight factors identified in the cross-sectional analysis were not significantly correlated with a change in jump height in the pre-to-post analysis. Additionally, only six of eleven factors identified in the pre-to-post analysis were identified in the cross-sectional analysis. These findings imply that: (a) not all factors identified in a cross-sectional analysis may be critical to jump height improvement, and (b) cross-sectional analyses alone may not provide an insight into all of the potential factors to train to enhance jump height. Coaches must be aware of these limitations when examining cross-sectional studies to identify factors to train to enhance jump ability. Additional findings highlight that while exercises prescribed to improve jump height should aim to enhance concentric power production at all joints, a particular emphasis on enhancing hip joint peak power may be warranted

CAN BIOMECHANICAL DIAGNOSTIC PROFILING IDENTIFY THE EFFECTIVENESS OF SPECIFIC TRAINING EXERCISES?

This study investigated the use of a diagnostic and prescriptive pathway that aims to determine the effectiveness of specific training exercises. The model was tested by examining if the effects of drop jump (DJ) training on countermovement jump (CMJ) performance could be explained by the degree to which performance determining factors (PDFs) for the CMJ were overloaded. Participants trained with DJ for 8 weeks yet no change in CMJ performance occurred. Of the 4 CMJ PDFs identified only hip rate of power development was overloaded by the DJ and none were enhanced with training. The results imply that the pathway was effective in identifying whether DJ training would enhance participants CMJ performance. The model could be used to determine if a given exercise would enhance a specific group of athletes prior to initiating training

A Life-Threatening Emergency Exacerbated by Untreated Mental Illness in a Low-Barrier Health Center

Introduction: We report on a patient with untreated severe mental illness who presented with a life-threatening emergency: retained products of conception and hemorrhage. Clinical Findings: A female patient experiencing homelessness developed life-threatening hemorrhage. Her mental illness impaired effective communication and treatment. Clinical Course: The patient presented with fatigue, vaginal bleeding, and known retained products of conception. Her active mental illness complicated the situation as it limited effective communication and treatment due to delusions. She requested only treatment for an infectious cause of her symptoms. She refused most interventions and had a self-directed discharge from the hospital. Throughout this process, we assessed that she understood the implications of declining care, despite her mental illness. After extensive patient-centered and trauma-informed discussions, she accepted medical treatment. Conclusions: This case highlights the importance of patient-centered communication and team-based care during emergencies and refusal of care. Shared decision-making and trauma-informed care are appropriate methods for assessing the capacity of patients with severe mental illness in acute and life-threatening conditions

CHANGES IN HIP FORCE VECTOR AFTER ATHLETIC GROIN PAIN REHABILITATION DURING A RUNNING CUT

The purpose of this study was to examine changes in hip force vectors after successful athletic groin pain rehabilitation. Forty athletes with athletic groin pain that underwent a rehabilitation intervention participated in this study. Hip force magnitude, direction and their combination were examined using a continuous waveform analysis. Hip posterior and medial force at the start and end of the movement decreased following rehabilitation, while superior forces increased (over most of the movement cycle). Findings suggest that athletes with groin pain benefit from a rehabilitation intervention that decreases posterior and medial hip joint forces

Regulation of prostaglandin synthesis and cell adhesion by a tryptophan catabolizing enzyme

BACKGROUND: The tryptophan catabolizing enzyme, indoleamine 2,3, dioxygenase (IDO) is one of two mammalian enzymes, which can catabolize the rarest essential amino acid, tryptophan. IDO is inducible by cytokines such as interferon-γ and plays a role in inflammation and maternal tolerance of fetal allografts, although its exact mode of action is unclear. Therefore, we investigated the circumstances under which IDO is expressed in vitro together with the effects of overexpression of IDO on the growth and morphology of cells. RESULTS: Overexpression of IDO in the murine macrophage cell line RAW 264.7 and the murine fibrosarcoma cell line MC57, resulted in the growth of macroscopic cell foci, with altered cell adhesion properties. The expression of IDO was also detected during adhesion of wild type, nontransfected cells in tissue culture to standard cell growth substrates. Inhibition of this expression, likewise resulted in alterations in cell adhesion. Overexpression of IDO or inhibition of endogenous IDO expression was accompanied by changes in metalloproteinase expression and also in the expression and activity of the cyclooxygenase enzymes. In the case of RAW cells, IDO effects on cell growth could be reversed by adding back prostaglandins. CONCLUSIONS: These results suggest that catabolism of the rarest essential amino acid may regulate processes such as cell adhesion and prostaglandin synthesis

Identification of movement strategies in vertical jumps

The primary aim of this study is to compare the ability of three commonly used clustering techniques to identify movement strategies within countermovement jumps. A secondary aim is to interpret the identified movement strategies. A hierarchical, k-means using non- and normalized subject scores and an Expectation-Maximization approach using normalized subject scores were examined. The ability to identify movement strategies was measured using the r2-value of a regression model to describe jump height. Clusters of the best clustering solution were examined for differences. Hierarchical clustering utilizing normalized subject scores to generate 4 clusters appears to be the most suitable technique. The generated clusters demonstrated clear defining characteristics

Classification of continuous vertical ground reaction forces

The aim of this study is to assess and compare the performance of com- monly used hierarchical, partitional (k-means) and Gaussian model-based (Expectation-Maximization algorithm) clustering techniques to appropriately identify subgroup patterns within vertical ground reaction force data, using a continuous waveform analysis. In addition, we also compared the perfor- mance across each technique using normalized and non-normalization input scores. Both generated and real data (one hundred-and twenty two verti- cal jumps) were analyzed. The performance of each cluster technique was measured by assessing the ability to explain variances in jump height using a stepwise regression analysis. Only k-means (normalized scores; 82 %) and hierarchical clustering (normalized scores; 85 %) were able to extend the ability to describe variances in jump height beyond that achieved using the group analysis (i.e. one cluster; 78 %). Further, our findings strongly indicate the need to normalize the input data (similarity measure) when clustering. In contrast to the group analysis, the subgroup analysis was able to iden- tify cluster specific phases of variance, which improved the ability to explain variances in jump height, due to the identification of cluster specific predictor variables. Our findings therefore highlight the benefit of performing a subgroup analysis and may explain, at least in part, the contrasting findings between previous studies that used a single group level of analysis

What are we measuring? : A review of metrics used to describe biodiversity in offsets exchanges

Peer reviewe

IDENTIFICATION OF MOVEMENT STRAGEGIES IN VERTICAL JUMPS

The primary aim of this study is to compare the ability of three commonly used clustering techniques to identify movement strategies within countermovement jumps. A secondary aim is to interpret the identified movement strategies. A hierarchical, k-means using nonand normalized subject scores and an Expectation-Maximization approach using normalized subject scores were examined. The ability to identify movement strategies was measured using the r2-value of a regression model to describe jump height. Clusters of the best clustering solution were examined for differences. Hierarchical clustering utilizing normalized subject scores to generate 4 clusters appears to be the most suitable technique. The generated clusters demonstrated clear defining characteristics

Performance related factors in countermovement jumps: identified using a continuous subgroup analysis approach

The aim of this study was to examine the benefit of utilizing a subgroup analysis design over a single group analysis design, and determine if performance related factors differ across individuals in countermovement jumping. Joint kinematics and kinetics were used to cluster 122 individuals into four groups, based on their movement strategy. The ability to describe jump height across a single group and subgroup analysis design was assessed to measure the performance of both analysis designs, and performance related factors were identified across the generated clusters. Findings highlight a greater ability of the subgroup analysis design to describe jump height, indicating a benefit of utilizing a subgroup analysis. This is supported by the performance related factors identified, which differed across individuals