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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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Power declines with age. a EDL. b Linear regression of EDL power at 60 % P0. See Fig. S3 in the supplement for the other regressions. c SOL. d Linear regression of SOL power at 80 % P0. See Fig. S4 in the supplement for the other regressions. 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 power (y) as a function of age (x). *p < 0.05, p value from one-way ANOVA. mN fl/s millinewtons multiplied by fiber lengths per second, % P0 percentage of maximum isometric force, Age age in months
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Fig4: Power declines with age. a EDL. b Linear regression of EDL power at 60 % P0. See Fig. S3 in the supplement for the other regressions. c SOL. d Linear regression of SOL power at 80 % P0. See Fig. S4 in the supplement for the other regressions. 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 power (y) as a function of age (x). *p < 0.05, p value from one-way ANOVA. mN fl/s millinewtons multiplied by fiber lengths per second, % P0 percentage of maximum isometric force, Age age in months

Mentions: Power production declined with age (Table 1, Fig. 4, Figs. S3 and S4). In the elderly mice, the reduction in power averaged 43 ± 3 % in the EDL (range of 33–54 %) and 35 ± 3 % in the SOL (range of 31–39 %), across the loads of 10–90 % P0 but there was no significant difference in percentage power reduction between the two muscles [Student’s t test: t = 2.15, p = 0.052]. In the old mice, the EDL had an overall power reduction of 20 % (mean of all loads) and the SOL averaged 32 % over the higher loads of 60–80 % P0. However, in the old SOL, the decline observed from 10 to 40 % P0 was not significant, so we did not compare the old EDL to the old SOL with respect to the average percent change. Elderly mice had significantly reduced power at 10–80 % P0 (at 90 % P0, p = 0.052) in the EDL, averaging 29 % and ranging from 25 to 41 %, compared to old EDL. In the SOL, the old and elderly power production was not significantly different. In the interest of brevity, we will discuss in depth only the specific differences between the adult and elderly mice.Fig. 4


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)

Power declines with age. a EDL. b Linear regression of EDL power at 60 % P0. See Fig. S3 in the supplement for the other regressions. c SOL. d Linear regression of SOL power at 80 % P0. See Fig. S4 in the supplement for the other regressions. 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 power (y) as a function of age (x). *p < 0.05, p value from one-way ANOVA. mN fl/s millinewtons multiplied by fiber lengths per second, % P0 percentage of maximum isometric force, Age age in months
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Related In: Results  -  Collection

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Fig4: Power declines with age. a EDL. b Linear regression of EDL power at 60 % P0. See Fig. S3 in the supplement for the other regressions. c SOL. d Linear regression of SOL power at 80 % P0. See Fig. S4 in the supplement for the other regressions. 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 power (y) as a function of age (x). *p < 0.05, p value from one-way ANOVA. mN fl/s millinewtons multiplied by fiber lengths per second, % P0 percentage of maximum isometric force, Age age in months
Mentions: Power production declined with age (Table 1, Fig. 4, Figs. S3 and S4). In the elderly mice, the reduction in power averaged 43 ± 3 % in the EDL (range of 33–54 %) and 35 ± 3 % in the SOL (range of 31–39 %), across the loads of 10–90 % P0 but there was no significant difference in percentage power reduction between the two muscles [Student’s t test: t = 2.15, p = 0.052]. In the old mice, the EDL had an overall power reduction of 20 % (mean of all loads) and the SOL averaged 32 % over the higher loads of 60–80 % P0. However, in the old SOL, the decline observed from 10 to 40 % P0 was not significant, so we did not compare the old EDL to the old SOL with respect to the average percent change. Elderly mice had significantly reduced power at 10–80 % P0 (at 90 % P0, p = 0.052) in the EDL, averaging 29 % and ranging from 25 to 41 %, compared to old EDL. In the SOL, the old and elderly power production was not significantly different. In the interest of brevity, we will discuss in depth only the specific differences between the adult and elderly mice.Fig. 4

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