Table 2.
In vitro skinned muscle fibre characteristics from the legs (quadriceps, Q) and arms (elbow flexors, EF) of healthy young (YG), mobile oldest-old (OM), and immobile oldest-old (OI). Data relative to the three major fibre types (slow, fast IIA, and fast IIA-X) and covering approximately 90% of the fibre population are shown, whereas the minor groups of mixed I-IIA and pure IIX fibres are omitted.
| Q-Leg | EF-Arm | ||||||
|---|---|---|---|---|---|---|---|
| MyHC | I | IIA | IIA-X | I | IIA | IIA-X | |
| YG | N | 27 | 20 | 10 | 20 | 20 | 20 |
| Fo (mN) | 0.399±0.044 | 0.540±0.055 | 0.461±0.024 | 0.274±0.031 | 0.559±0.080 | 0.413±0.020 | |
| CSA (µm2) | 4259±378 | 4770±448 | 4156±792 | 3423±325 | 4046±394 | 3153±339 | |
| Po (mN∙mm−2) | 105±12 | 136±22 | 128±14 | 88±11 | 153±27 | 144±11 | |
| OM | N | 22 | 11 | 10 | 23 | 7 | 10 |
| Fo (mN) | 0.435±0.041 | 0.377±0.064 | 0.561±0.115 | 0.3756±0.031 | 0.411±0.052 | 0.535±0.078 | |
| CSA (µm2) | 5327±598 | 3854±820 | 4834±545 | 4005±333 | 3861±330 | 3827±419 | |
| Po (mN∙mm−2) | 93±13 | 109±12 | 112±14 | 106±13 | 112±16 | 146±23 | |
| OI | N | 20 | 4 | 10 | 22 | 6 | 10 |
| Fo (mN) | 0.557±0.042 | 0.378±0.123 | 0.640±0.075 | 0.305±0.039 | 0.701±0.028* | 0.431±0.065 | |
| CSA (µm2) | 5603±464 | 2939±521 | 3859±403 | 3069±377 | 6499±706* | 4092±783 | |
| Po (mN∙mm−2) | 111±12 | 131±32 | 177±7 | 108±8 | 113±14 | 119±18 | |
Mean ± S.E. N, number of fibres analyzed; CSA, cross sectional area; Fo, maximal isometric force; Po, specific tension; MyHC, myosin heavy chain isoform.
*
significantly different from corresponding values in YG and OM.