STRENGTH | MUSCLE – MUSCLE FIBRE TYPE – AGING


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LONG TERM HIGH LEVEL EXERCISE PROMOTES MUSCLE RE-INVERVATION – 2014


AGING MUSCLE
– Denervation contributes to atrophy, immobility accelerates the process
LONG-TERM PHYSICAL ACTIVITY PROMOTES RE-INNERVATION OF MUSCLE FIBERS
– Decades of high-level exercise allow the body to adapt to age-related denervation by saving otherwise lost muscle fibers through selective recruitment to slow motor units
– These effects on size and structure of myofibers may delay functional decline in late aging


MUSCLE FIBER TYPE & MUSCLE MASS, STRENGTH & METABOLIC SYNDROME – 2014


FIBER TYPE MAY BE IMPORTANT FOR
– Age-related loss of muscle mass and strength
– Increased prevalence of Metabolic Syndrome in elderly subjects


TYPE 2 MUSCLE FIBER & DECLINE IN MUSCLE MASS WITH AGING – 2013


METHODS
– Quadriceps muscle Cross Sectional Area (CSA) and type I and type II muscle fiber size were measured in:
(1) young (n = 25; 23 ± 1y)
(2) older men (n = 26; 71 ± 1y)
– the older subjects performed 6 months of resistance type exercise training
RESULTS
(1) Quadriceps CSA was substantially smaller in older vs. young men; 68 ± 2 vs 80 ± 2 cm2
(2) Type II muscle fiber size was substantially smaller in the elderly vs the young (29%), with a tendency of smaller type I muscle fibers
(3) Differences in type II muscle fiber size fully explained differences in quadriceps CSA between groups
(4) Resistance Training increased type II muscle fiber size by 24 ± 8%, explaining 100 ± 3% of the increase in quadriceps muscle CSA
CONCLUSION
(1) Reduced muscle mass with aging is mainly attributed to smaller type II muscle fiber size and, as such, is unlikely accompanied by substantial muscle fiber loss
(2) The increase in muscle mass following prolonged resistance type exercise training can be attributed entirely to specific type II muscle fiber hypertrophy


FIBER TYPING IN AGING MUSCLE – 2013


INTRODUCTION/PURPOSE
(1) Fast-twitch muscle fibers are preferentially impacted in aging muscle
(2) We hypothesize that this is not valid when aging muscle atrophy becomes severe
(3) Reevaluate the notion of preferential FT fiber involvement in aging muscle, particularly at ages where muscle atrophy becomes severe and most likely to have clinical impact
CONCLUSIONS
(1) Previous assertions of a preferential fast fiber effect in aging muscle are not valid when muscle atrophy becomes most severe
(2) Therapeutic strategies for treating this problem need to consider the atrophy of both slow and fast fibers to have optimal impact


MUSCLE POWER FAILURE IN MOBILITY-LIMITED OLDER ADULTS – 2011


– Impairments in rate of neuromuscular activation and reductions in muscle quality contribute to muscle power deficits and mobility limitations


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