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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

Percent reduction in power is correlated with increases in % P0, comparing the elderly to adult. a EDL: There was a −0.26 % reduction in power per unit increase in load (% P0, percentage of maximum force at which power was derived) (R = 0.993). b SOL: There was a percentage decrease of −0.10 (R = 0.810) in power, per unit increase in % P0. Each symbol represents the difference between the mean power production of the entire adult group compared to the entire elderly group. Equation: simple linear regression of percent change in power from adult to elderly (y) as a function of % P0
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Fig5: Percent reduction in power is correlated with increases in % P0, comparing the elderly to adult. a EDL: There was a −0.26 % reduction in power per unit increase in load (% P0, percentage of maximum force at which power was derived) (R = 0.993). b SOL: There was a percentage decrease of −0.10 (R = 0.810) in power, per unit increase in % P0. Each symbol represents the difference between the mean power production of the entire adult group compared to the entire elderly group. Equation: simple linear regression of percent change in power from adult to elderly (y) as a function of % P0

Mentions: The percent reduction in power by the EDL per unit increase in load (% P0) had a linear relationship that amounted to −0.26 % (R = 0.993, p < 0.001). Likewise, the SOL had a percentage decrease of −0.10 (R = 0.810, p = 0.003) in power, per unit increase in % P0 (Fig. 5a, b).Fig. 5


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)

Percent reduction in power is correlated with increases in % P0, comparing the elderly to adult. a EDL: There was a −0.26 % reduction in power per unit increase in load (% P0, percentage of maximum force at which power was derived) (R = 0.993). b SOL: There was a percentage decrease of −0.10 (R = 0.810) in power, per unit increase in % P0. Each symbol represents the difference between the mean power production of the entire adult group compared to the entire elderly group. Equation: simple linear regression of percent change in power from adult to elderly (y) as a function of % P0
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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

Fig5: Percent reduction in power is correlated with increases in % P0, comparing the elderly to adult. a EDL: There was a −0.26 % reduction in power per unit increase in load (% P0, percentage of maximum force at which power was derived) (R = 0.993). b SOL: There was a percentage decrease of −0.10 (R = 0.810) in power, per unit increase in % P0. Each symbol represents the difference between the mean power production of the entire adult group compared to the entire elderly group. Equation: simple linear regression of percent change in power from adult to elderly (y) as a function of % P0
Mentions: The percent reduction in power by the EDL per unit increase in load (% P0) had a linear relationship that amounted to −0.26 % (R = 0.993, p < 0.001). Likewise, the SOL had a percentage decrease of −0.10 (R = 0.810, p = 0.003) in power, per unit increase in % P0 (Fig. 5a, b).Fig. 5

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