7 research outputs found
Measurement of resistance exercise force expression
This is the publisher's version, also found at http://ehis.ebscohost.com/ehost/detail?sid=afef5b5e-42ad-4a92-896e-f02e050a2011%40sessionmgr10&vid=1&hid=17&bdata=JnNpdGU9ZWhvc3QtbGl2ZQ%3d%3d#db=s3h&AN=13021242Displacement-based measurement systems are becoming increasingly popular
for assessment of force expression variables during resistance exercise.
Typically a linear position transducer (LPT) is attached to the barbell to measure
displacement and a double differentiation technique is used to determine
acceleration. Force is calculated as the product of mass and acceleration. Despite
the apparent utility of these devices, validity data are scarce. To determine
whether LPT can accurately estimate vertical ground reaction forces,
two men and four women with moderate to extensive resistance training experience
performed concentric-only (CJS) and rebound (RJS) jump squats, two
sessions of each type in random order. CJS or RJS were performed with 30%,
50%, and 70% one-repetition maximum parallel back squat 5 minutes following
a warm-up and again after a 10-min rest. Displacement was measured via
LPT and acceleration was calculated using the finite-difference technique. Force
was estimated from the weight of the lifter-barbell system and propulsion force
from the lifter-barbell system. Vertical ground reaction force was directly
measured with a single-component force platform. Two-way random average-
measure intraclass correlations (ICC) were used to assess the reliability
of obtained measures and compare the measurements obtained via each method.
High reliability (ICC > 0.70) was found for all CJS variables across the loadspectrum.
RJS variables also had high ICC except for time parameters for
early force production. All variables were significantly (p < 0.01) related between
LPT and force platform methods with no indication of systematic bias.
The LPT appears to be a valid method of assessing force under these experimental
conditions
Myosin heavy chain isoform expression: Influence on isointertial and isometric performance
This is the publisher's version, also found at http://ehis.ebscohost.com/ehost/detail?vid=3&sid=c184ec76-77d8-4a98-bb1f-f5bceba902aa%40sessionmgr10&hid=2&bdata=JnNpdGU9ZWhvc3QtbGl2ZQ%3d%3d#db=s3h&AN=19495568Thirty-six healthy men with varying degrees of physical training background performed maximal-effort isometric and isoinertial knee extensor actions, with relative loads equal to 40% and 70% of one-repetition maximum. Force, velocity, and power were derived from force and linear position transducers at 500 Hz. Biopsies were taken from the vastus lateralis and analyzed by SDS-PAGE for relative myosin heavy chain (MHC) content. Relative MHC IIx content was included in a regression model, and explained variance noted. Relative MHC I content was subsequently added to the regression model to determine what, if any, additional variance was explained beyond that of MHC IIx. Results indicated that no relationship ( r = 0.0 to 0.1) exists between the relative expression of MHC isoforms from the vastus lateralis and isometric/isoinertial performance in a population with diverse training backgrounds. Lack of nervous system adaptations in the untrained subjects in the study possibly attenuates the significant relationship between MHC and in-vivo muscle performance previously established in trained populations. ABSTRACT FROM AUTHO
Muscle fiber and performance adaptations to resistance exercise with MyoVive, colostrum or casein and whey supplementationa
This is the publisher's version, also found at http://ehis.ebscohost.com/ehost/detail?sid=ba69ee0d-97cf-4a2c-a1a2-2c26fb60d65c%40sessionmgr13&vid=1&hid=2&bdata=JnNpdGU9ZWhvc3QtbGl2ZQ%3d%3d#db=s3h&AN=10725638To determine the effects of 12 weeks of resistance exercise with MyoVive
and/or colostrum supplementation, 19 male and female recreationally weighttrained
subjects (X ± SE; age = 28.3 ± 6.9 yrs; hgt = 68.2 ± 3.8 cm) were
divided into MyoVive + colostrum (n = 4), MyoVive + casein & whey (n
= 4), colostrum + casein & whey (n = 6), and casein & whey (n = 5) groups.
All groups similarly increased (p < .05) 1 repetition maximum (RM) leg press
(kg; pre = 158.6 ± 12.8, post = 189.3 ± 11.3), body mass (kg; pre = 79.0 ±
3.2, post = 80.7 ± 3.8), and lean body mass (kg; pre = 60.1 ± 3.1, post = 62.2
± 2.8). Increases were observed for peak force (N; all loads), peak velocity
(m.s-1; 70% & 40% 1 RM), and peak power (W; 70% & 40% 1 RM) for all
groups for the leg press exercise, with no differences between groups. When
performance data were adjusted for body mass, lean body mass, lower body
lean mass as determined by DEXA, or % change, no group differences were
observed. Relative (%) fiber type content, cross-sectional areas (mm2), % fiber
type areas, or % myosin heavy chain expression did not change for any
group. These data suggest that MyoVive and colostrum supplementation
have no greater effect on cellular and performance adaptations when compared
to casein and whey protein
Adult Cardiac Progenitor Cell Aggregates Exhibit Survival Benefit Both In Vitro and In Vivo
Background: A major hurdle in the use of exogenous stems cells for therapeutic regeneration of injured myocardium remains the poor survival of implanted cells. To date, the delivery of stem cells into myocardium has largely focused on implantation of cell suspensions. Methodology and Principal Findings: We hypothesize that delivering progenitor cells in an aggregate form would serve to mimic the endogenous state with proper cell-cell contact, and may aid the survival of implanted cells. Microwell methodologies allow for the culture of homogenous 3D cell aggregates, thereby allowing cell-cell contact. In this study, we find that the culture of cardiac progenitor cells in a 3D cell aggregate augments cell survival and protects against cellular toxins and stressors, including hydrogen peroxide and anoxia/reoxygenation induced cell death. Moreover, using a murine model of cardiac ischemia-reperfusion injury, we find that delivery of cardiac progenitor cells in the form of 3D aggregates improved in vivo survival of implanted cells. Conclusion: Collectively, our data support the notion that growth in 3D cellular systems and maintenance of cell-cell contact improves exogenous cell survival following delivery into myocardium. These approaches may serve as a strategy to improve cardiovascular cell-based therapies