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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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Velocity declines with age. a EDL force-velocity curve. b Linear regression of EDL velocity at 60 % P0. See Fig. S1 in the supplement for the other velocities. c SOL force-velocity curve. d Linear regression of SOL velocity at 60 % P0. See Fig. S2 in the supplement for the other velocities. See Table 1 and text for post hoc analysis. Each symbol in b and d in the regression graphs represents a measurement from an individual mouse at the given age. Equation: simple linear regression of velocity (y) as a function of age (x). *p < 0.05, p value from one-way ANOVA. fl/s fiber length per second, % P0 percentage of maximum isometric force, Age age in months
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Fig1: Velocity declines with age. a EDL force-velocity curve. b Linear regression of EDL velocity at 60 % P0. See Fig. S1 in the supplement for the other velocities. c SOL force-velocity curve. d Linear regression of SOL velocity at 60 % P0. See Fig. S2 in the supplement for the other velocities. See Table 1 and text for post hoc analysis. Each symbol in b and d in the regression graphs represents a measurement from an individual mouse at the given age. Equation: simple linear regression of velocity (y) as a function of age (x). *p < 0.05, p value from one-way ANOVA. fl/s fiber length per second, % P0 percentage of maximum isometric force, Age age in months

Mentions: The velocities of contraction under loaded (>0 % P0) conditions showed age-related declines (Fig. 1 and Table 1). In the elderly mice, the extent of reduction in contractile velocities averaged 21 ± 4 % in the EDL (range of 10–34 %) and 24 ± 2 % in the SOL (range of 16–33 %), with no significant difference in the mean decline between the two muscles [Student’s t test comparing % reductions in velocity in elderly mice from 10 to 90 % P0: EDL and SOL; t = −1.1, p = 0.290]. In the old mice, EDL velocities at 30–60 % P0 showed an age-associated reduction compared to the adult. For the old mice, there was slower contraction speed in the SOL compared to the adults from 10 to 80 % P0. Since the old mice were not significantly different from the elderly in contractile velocity, we report herein, for brevity, only the differences in velocity between adult and elderly mice.Fig. 1


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)

Velocity declines with age. a EDL force-velocity curve. b Linear regression of EDL velocity at 60 % P0. See Fig. S1 in the supplement for the other velocities. c SOL force-velocity curve. d Linear regression of SOL velocity at 60 % P0. See Fig. S2 in the supplement for the other velocities. See Table 1 and text for post hoc analysis. Each symbol in b and d in the regression graphs represents a measurement from an individual mouse at the given age. Equation: simple linear regression of velocity (y) as a function of age (x). *p < 0.05, p value from one-way ANOVA. fl/s fiber length per second, % P0 percentage of maximum isometric force, Age age in months
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4401475&req=5

Fig1: Velocity declines with age. a EDL force-velocity curve. b Linear regression of EDL velocity at 60 % P0. See Fig. S1 in the supplement for the other velocities. c SOL force-velocity curve. d Linear regression of SOL velocity at 60 % P0. See Fig. S2 in the supplement for the other velocities. See Table 1 and text for post hoc analysis. Each symbol in b and d in the regression graphs represents a measurement from an individual mouse at the given age. Equation: simple linear regression of velocity (y) as a function of age (x). *p < 0.05, p value from one-way ANOVA. fl/s fiber length per second, % P0 percentage of maximum isometric force, Age age in months
Mentions: The velocities of contraction under loaded (>0 % P0) conditions showed age-related declines (Fig. 1 and Table 1). In the elderly mice, the extent of reduction in contractile velocities averaged 21 ± 4 % in the EDL (range of 10–34 %) and 24 ± 2 % in the SOL (range of 16–33 %), with no significant difference in the mean decline between the two muscles [Student’s t test comparing % reductions in velocity in elderly mice from 10 to 90 % P0: EDL and SOL; t = −1.1, p = 0.290]. In the old mice, EDL velocities at 30–60 % P0 showed an age-associated reduction compared to the adult. For the old mice, there was slower contraction speed in the SOL compared to the adults from 10 to 80 % P0. Since the old mice were not significantly different from the elderly in contractile velocity, we report herein, for brevity, only the differences in velocity between adult and elderly mice.Fig. 1

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