Increasing Trunk Mass Evokes Lower Extremity Biomechanical Plasticity during Stair Descent

International Journal of Exercise Science 16(1): 942-953, 2023. The purpose of this study was to investigate the influence of simulated changes in body mass on lower extremity joint work and relative joint contributions during stair descent. Ten healthy recreationally active college-age participants performed five stair descent trials in each of five loading conditions: no added load and with an additional 5%, 10%, 15% and 20% of their body weight. Three-dimensional ankle, knee and hip joint powers were calculated using a six degree-of-freedom model in Visual3D (C-Motion Inc., Germantown, MD, USA). Sagittal plane joint work was calculated as the joint power curve integrated with respect to time during the period between initial contact and toe off. Prism 9.0 (GraphPad Inc., San Diego, CA) was used to perform univariate 1 x 5 repeated measures analyses of variance to determine the effect of added mass on absolute and relative joint work values for total and for each lower extremity joint independently. Increasing added mass was associated with greater total lower extremity negative work during the stair descent task (p \u3c 0.001). At the ankle, increasing added mass was associated with increasing magnitudes of negative joint work. Increasing added mass was associated with greater relative contributions of the ankle and reduced knee contributions to total negative lower extremity joint work (p = 0.014 and p = 0.006). The current findings demonstrated increases in ankle joint contributions to total lower extremity work while knee joint contributions to total lower extremity work were reduced in response to increasing added mass

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead

Greater Breast Support Reduces Common Biomechanical Risk Factors Associated with Anterior Cruciate Ligament Injury

To examine the effects of breast support on trunk and knee joint biomechanics in female collegiate athletes during a double-limb landing task.Methods: Fourteen female athletes completed five landings in three different sports bra conditions: no support, low support, and high support. 3D kinematics and ground reaction forces were recorded simultaneously. Visual 3D was used to calculate trunk and knee joint angles and moments. Custom software determined discrete trunk and knee joint variables. A repeated measures analysis of covariance with post-hoc t-tests compared landing biomechanics by condition.Results: Greater breast support was associated with reducation in knee flexion and knee valgus angles as well as increases in knee varus moments. Greater breast support was associated with greater trunk flexion angles at initial contact and greater peak trunk flexion angles.Conclusions: Lower levels of breast support are associated with knee joint and trunk biomechanical profiles suggested to increase ACL injury risk

Greater Breast Support Is Associated With Reduced Oxygen Consumption and Greater Running Economy During a Treadmill Running Task

Introduction: Breast pain is a major barrier to running for women. While breast support through the use of sports bras reduces breast-related discomfort, the effect of breast support on running performance is less understood. Therefore, the purpose of the current study was to evaluate the effect of greater breast support on oxygen consumption and running economy during a treadmill running task. Methods: Fifteen female recreational runners performed a 10-min treadmill running task at their preferred running speed in each of two sports bra conditions: low support and high support. Participants ran on an instrumented treadmill (1,200 Hz, Bertec) while indirect calorimetry was performed using a metabolic measurement system (100 Hz, TrueOne, ParvoMedics). Average VO2 (absolute and relative) from the third to 10th minutes was used to evaluate oxygen consumption. Running economy was calculated as the distance traveled per liter of oxygen consumed. Paired samples t-tests were used to compare mean oxygen consumption and running economy values between breast support conditions. Correlation analysis was performed to evaluate the relationship between breast size and change in running performance. Results: Greater breast support was associated with reductions in absolute (p \u3c 0.001) and relative oxygen consumption (p \u3c 0.001; LOW: 30.9 ± 7.1 ml/kg/min; HIGH: 28.7 ± 6.7 ml/kg/min). Greater breast support was associated with increases in running economy (p \u3c 0.001; LOW: 88.6 ± 29.1 m/L O2; HIGH: 95.2 ± 31.1 m/L O2). No changes in temporospatial characteristics of running were observed including cadence (p = 0.149), step length (p = 0.300) or ground contact time (p = 0.151). Strong positive linear correlations were observed between the change in running performance metrics and breast size (Oxygen Consumption: p \u3c 0.001, r = 0.770; Relative Oxygen Consumption: p \u3c 0.001, r = 0769; Running Economy: p \u3c 0.001, r = 0.807). Conclusions: Greater breast support was associated with reduced oxygen consumption and increased running economy. These findings demonstrate that greater breast support is not only associated with improved comfort but also improved running performance

Ground reaction force profiles during inclined running at iso-efficiency speeds

While running provides an accessible form of cardiovascular stimulus, many runners report lower extremity musculoskeletal injuries. Additionally, runners who develop overuse injuries, such as tibial stress fractures, also have higher loading rates (LR) and impact forces. Purpose: Therefore, the purpose of this study was to investigate how uphill treadmill running at iso-efficient speeds (IES; a speed-incline combination having the same metabolic intensity as level running) influences impact LR, and peak vertical ground reaction forces (GRF). Methods: Eleven collegiate distance runners completed 3 experimental running conditions (0%, 4%, and 8% treadmill inclination). During each running condition, the metabolic intensity was controlled by implementing an IES for each runner. Results: All variables of interest were significantly reduced as treadmill incline increased (0% \u3e 4% \u3e 8%). Conclusion: Incline running is more metabolically demanding compared to level running at the same speed. But, if speed is controlled to maintain metabolic output, runners could decrease LR and peak vertical GRF while achieving the same metabolic training stimulus as level running

Greater Breast Support Alters Trunk and Knee Joint Biomechanics Commonly Associated With Anterior Cruciate Ligament Injury

Objective: The female breast is a passive tissue with little intrinsic support. Therefore, women rely on external breast support (sports bras) to control breast motion during athletic tasks. Research has demonstrated that lower levels of breast support are associated with altered trunk and pelvis movement patterns during running, a common athletic task. However, no previous study has identified the effect of sports bra support on movement patterns during other athletic tasks including landing. Therefore, the purpose of this study was to examine the effects of breast support on trunk and knee joint biomechanics in female collegiate athletes during a double-leg landing task. Methods: Fourteen female collegiate athletes completed five double-leg landing trials in each of three different sports bra conditions: no support, low support, and high support. A 10-camera motion capture system (250 Hz, Qualisys, Goteburg, Sweden) and two force platforms (1,250 Hz, AMTI, Watertown, MA, USA) were used to collect three-dimensional kinematics and ground reaction forces simultaneously. Visual 3D was used to calculate trunk segment and knee joint angles and moments. Custom software (MATLAB 2021a) was used to determine discrete values of dependent variables including vertical breast displacement, knee joint and trunk segment angles at initial contact and 100 ms post-initial contact, and peak knee joint moments. A repeated measures analysis of covariance with post-hoc paired samples t-tests were used to evaluate the effect of breast support on landing biomechanics. Results: Increasing levels of breast support were associated with reductions in peak knee flexion (Right: p = 0.008; Left: p = 0.029) and peak knee valgus angles (Right: p = 0.011; Left: p = 0.003) as well as reductions in peak knee valgus moments (Right: p = 0.033; Left: p = 0.013). There were no changes in peak knee extension moments (Right: p = 0.216; Left: p = 0.261). Increasing levels of breast support were associated with greater trunk flexion angles at initial contact (p = 0.024) and greater peak trunk flexion angles (p = 0.002). Conclusions: Lower levels of breast support are associated with knee joint and trunk biomechanical profiles suggested to increase ACL injury risk

Metabolic stress and cancer: is autophagy the common denominator and a feasible target?

Objectives: Autophagy facilitates the degradation of proteins or organelles into recyclable molecules, which are released into the cell to foster cell survival under energetic stress. Furthermore, autophagy has been associated with cancer cell survival and chemoresistance, and as such, it is an area of increasing interest. As autophagic activity and its regulation are related to metabolism and energy stress,it is critical to elucidate the exact molecular mechanisms that drive it. Key findings: Cancer is recognised to have specific metabolic changes, which include the switch from oxidative phosphorylation to glycolysis. Although the exact rationale is yet to be determined, it is proposed to limit hypoxic stress and generate substrates for biosynthesis. The various forms of energetic stress including hypoxia, glucose and amino acid deprivation have been reviewed in relation to their effect on autophagy and certain key molecules identified to date. These key molecules, which include AMP-activated protein kinase, mammalian target of rapamycin complex 1, adenosine triphosphate and reactive oxygen species, are all implicated as key stimuli of autophagic activity, as will be discussed in this review. Summary: These findings indicate that autophagic regulation could be a means to better cancer treatment