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C57BL/6 life span study: age-related declines in muscle power production and contractile velocity.

Graber TG, Kim JH, Grange RW, McLoon LK, Thompson LV - Age (Dordr) (2015)

Bottom Line: We hypothesized and found that power decreased with age not only at P max but also over the load range.Importantly, we found greater age-associated deficits in both power and velocity when the muscles were contracting concentrically against heavy loads (>50 % P 0).The results demonstrate that age-associated difficulty in movement during challenging tasks is likely due, in addition to overall reduced force output, to an accelerated deterioration of power production and contractile velocity under heavily loaded conditions.

View Article: PubMed Central - PubMed

Affiliation: Program in Physical Therapy, Department of Physical Medicine and Rehabilitation, University of Minnesota Medical School, Rm 366A Children's Rehab Center, 426 Church Street SE, Minneapolis, MN, 55455, USA, grab0170@umn.edu.

ABSTRACT
Quantification of key outcome measures in animal models of aging is an important step preceding intervention testing. One such measurement, skeletal muscle power generation (force * velocity), is critical for dynamic movement. Prior research focused on maximum power (P max), which occurs around 30-40 % of maximum load. However, movement occurs over the entire load range. Thus, the primary purpose of this study was to determine the effect of age on power generation during concentric contractions in the extensor digitorum longus (EDL) and soleus muscles over the load range from 10 to 90 % of peak isometric tetanic force (P 0). Adult, old, and elderly male C57BL/6 mice were examined for contractile function (6-7 months old, 100 % survival; ~24 months, 75 %; and ~28 months, <50 %, respectively). Mice at other ages (5-32 months) were also tested for regression modeling. We hypothesized and found that power decreased with age not only at P max but also over the load range. Importantly, we found greater age-associated deficits in both power and velocity when the muscles were contracting concentrically against heavy loads (>50 % P 0). The shape of the force-velocity curve also changed with age (a/P 0 increased). In addition, there were prolonged contraction times to maximum force and shifts in the distribution of the myosin light and heavy chain isoforms in the EDL. The results demonstrate that age-associated difficulty in movement during challenging tasks is likely due, in addition to overall reduced force output, to an accelerated deterioration of power production and contractile velocity under heavily loaded conditions.

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Related in: MedlinePlus

Force-velocity curve changes with age: a/P0 increases with age. a EDL. b SOL. Equation is a simple linear regression of a/P0, which describes the shape of the force-velocity curve, with respect to age of the mouse in months. Each symbol represents the a/P0 of one mouse
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Fig3: Force-velocity curve changes with age: a/P0 increases with age. a EDL. b SOL. Equation is a simple linear regression of a/P0, which describes the shape of the force-velocity curve, with respect to age of the mouse in months. Each symbol represents the a/P0 of one mouse

Mentions: To determine if there was a difference in the shape of the EDL and SOL force-velocity curves, the a/P0 value was evaluated (a: constant from the Hill equation, a/P0: describes the shape of the curve, see “Methods”). There was a downward and leftward shift with advancing age in the EDL (one-way ANOVA: F = 19.1, p < 0.001; Tukey’s HSD: adult vs. elderly p < 0.001; old vs. elderly p = 0.005) (Table 1). In contrast, the SOL curves did not exhibit a significant shift with age between groups (one-way ANOVA: F = 3.401, p = 0.067) (Table 1). Over the life span, however, linear regressions showed an increase in a/P0 with age in both the EDL and SOL, thus demonstrating that the force-velocity curve is altered with age (Fig. 3a, b).Fig. 3


C57BL/6 life span study: age-related declines in muscle power production and contractile velocity.

Graber TG, Kim JH, Grange RW, McLoon LK, Thompson LV - Age (Dordr) (2015)

Force-velocity curve changes with age: a/P0 increases with age. a EDL. b SOL. Equation is a simple linear regression of a/P0, which describes the shape of the force-velocity curve, with respect to age of the mouse in months. Each symbol represents the a/P0 of one mouse
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4401475&req=5

Fig3: Force-velocity curve changes with age: a/P0 increases with age. a EDL. b SOL. Equation is a simple linear regression of a/P0, which describes the shape of the force-velocity curve, with respect to age of the mouse in months. Each symbol represents the a/P0 of one mouse
Mentions: To determine if there was a difference in the shape of the EDL and SOL force-velocity curves, the a/P0 value was evaluated (a: constant from the Hill equation, a/P0: describes the shape of the curve, see “Methods”). There was a downward and leftward shift with advancing age in the EDL (one-way ANOVA: F = 19.1, p < 0.001; Tukey’s HSD: adult vs. elderly p < 0.001; old vs. elderly p = 0.005) (Table 1). In contrast, the SOL curves did not exhibit a significant shift with age between groups (one-way ANOVA: F = 3.401, p = 0.067) (Table 1). Over the life span, however, linear regressions showed an increase in a/P0 with age in both the EDL and SOL, thus demonstrating that the force-velocity curve is altered with age (Fig. 3a, b).Fig. 3

Bottom Line: We hypothesized and found that power decreased with age not only at P max but also over the load range.Importantly, we found greater age-associated deficits in both power and velocity when the muscles were contracting concentrically against heavy loads (>50 % P 0).The results demonstrate that age-associated difficulty in movement during challenging tasks is likely due, in addition to overall reduced force output, to an accelerated deterioration of power production and contractile velocity under heavily loaded conditions.

View Article: PubMed Central - PubMed

Affiliation: Program in Physical Therapy, Department of Physical Medicine and Rehabilitation, University of Minnesota Medical School, Rm 366A Children's Rehab Center, 426 Church Street SE, Minneapolis, MN, 55455, USA, grab0170@umn.edu.

ABSTRACT
Quantification of key outcome measures in animal models of aging is an important step preceding intervention testing. One such measurement, skeletal muscle power generation (force * velocity), is critical for dynamic movement. Prior research focused on maximum power (P max), which occurs around 30-40 % of maximum load. However, movement occurs over the entire load range. Thus, the primary purpose of this study was to determine the effect of age on power generation during concentric contractions in the extensor digitorum longus (EDL) and soleus muscles over the load range from 10 to 90 % of peak isometric tetanic force (P 0). Adult, old, and elderly male C57BL/6 mice were examined for contractile function (6-7 months old, 100 % survival; ~24 months, 75 %; and ~28 months, <50 %, respectively). Mice at other ages (5-32 months) were also tested for regression modeling. We hypothesized and found that power decreased with age not only at P max but also over the load range. Importantly, we found greater age-associated deficits in both power and velocity when the muscles were contracting concentrically against heavy loads (>50 % P 0). The shape of the force-velocity curve also changed with age (a/P 0 increased). In addition, there were prolonged contraction times to maximum force and shifts in the distribution of the myosin light and heavy chain isoforms in the EDL. The results demonstrate that age-associated difficulty in movement during challenging tasks is likely due, in addition to overall reduced force output, to an accelerated deterioration of power production and contractile velocity under heavily loaded conditions.

Show MeSH
Related in: MedlinePlus