REF-808 · Korhonen et al., 2006 · Journal of Applied Physiology, Vol. · Paper · PubMed

Aging, muscle fiber type, and contractile function in sprint-trained athletes

Blimited evidenceMeasured on trained to elite athletesWritten before October 2026, being re-checked

Vastus lateralis biopsies from 91 male sprinters aged 18-84 were analysed for fibre-type distribution, fibre size and myosin heavy chain (MHC) isoforms; single-fibre specific tension and maximum shortening velocity (V(o)) were measured in 144 fibres from younger (18-33 yr, n = 8) and older (53-77 yr, n = 9) runners, and knee-extensor force-time characteristics in isometric contraction.

With age, type II fibre area fell while type I did not, MHC I rose and MHC IIx fell. Specific tension did not differ with age; V(o) of type I fibres was lower in the older runners, that of type IIa fibres was not. Maximal isometric force and normalised rate of force development declined with age, and rate of force development was associated with MHC II content.

The authors conclude that sprinters show the typical ageing pattern, but their muscle stays at a high level into old age.

Participants

n = 91 male sprinters aged 18-84 yr (biopsies). Single-fibre subset: younger 18-33 yr (n = 8) and older 53-77 yr (n = 9). Competitive level is not given in the abstract.

Protocol

Vastus lateralis biopsies: ATPase histochemistry and SDS-PAGE for fibre-type distribution, cross-sectional area and MHC isoforms.
Single skinned fibres (144): specific tension and maximum shortening velocity V(o).
Knee extensors: isometric force-time characteristics (maximal force, rate of force development).

Key Results

Type I fibre cross-sectional area unchanged with age; type II fibre area reduced (P < 0.001).
MHC I increased (P < 0.01) and MHC IIx decreased (P < 0.05) with age; MHC IIa did not differ.
Specific tension of type I and IIa fibres did not differ between younger and older runners.
V(o) of type I fibres was lower in older runners (P < 0.05); V(o) of type IIa fibres did not differ.
Maximal isometric force (P < 0.001) and normalised rate of force development (P < 0.05) of the knee extensors declined with age; rate of force development was positively associated with MHC II (P < 0.05).
Authors' conclusion: sprint-trained athletes show the typical ageing loss of fast-fibre size, a shift to slower MHC and lower type I V(o), which contributes to the decline in explosive force, but their muscle characteristics are preserved at a high level in the oldest runners.

Practical Application

"I still sprint — why am I losing explosiveness?" — in 91 male sprinters aged 18-84 (biopsies, single fibres and knee-extensor force), fast (type II) fibres shrank, the muscle shifted toward slower myosin and maximal and explosive force fell with age even in sprint-trained men, yet their muscle stayed at a high level into old age.
Expect explosive force to decline with age despite training; judge a masters sprinter by the rate of decline, not by whether it exists.
Inference, not tested here: because the loss sits in fast-fibre size and rate of force development, heavy and explosive strength work is the logical way to defend a masters sprinter's speed; this study compared ages, it tested no training.
Not from this paper; the base's own practice: keep the intensity and widen the recovery gaps in masters training (SYNTH-35).

Limitations

Cross-sectional: age differences, not change within the same athletes over time.
Men only; competitive level and training history are not given in the abstract.
Single-fibre mechanics in small subgroups (8 younger, 9 older).
No untrained comparison group is described in the abstract, so "preserved at a high level" is the authors' judgement.
Written from the abstract and record metadata only (full text not read).
How this entry was checked and changed
Why this level

cross-sectional, n=91 (single-fibre subset n=17)