Table 1.
Longitudinal trials using single fiber analysis.
| Andersen, 1994 | Male Sprinters: N = 6 |
Sprint training preparation group, post-competitive season (no comparator) | The training was 2.5–3 h per day, 6 days a week, and consisted of a combination of strength and interval training for 3 months. Strength training was 2.5 days a week and consisted of exercises in the one to eight repetition range with 80–100% of 1 RM. Uphill sprints or interval-running were performed 2.5 days a week. One day was used for jumping exercises or recreational activities, such as basketball. | VL; Biopsies were taken post-3-week deload (which commenced after the track season) and post-intervention period. | Single Fiber Isolation. SDS-PAGE. | Mean changes: MHC I: 10.8% decrease (52.0+/−3.0 to 41.2+/−4.7) MHC I/IIa: 1.2% increase (0.2+/−0.2 to 1.4+/−1) MHC IIa: 17.6% increase (34.7+/−6.1 to 52.3+/−3.6) MHC IIa/IIx: 7.8% decrease (12.9+/−5.0 to 5.1+/−3.1) MHC IIx: 0.2% decrease (0.2+/−0.2 to 0.0) |
| Andersen, 1994 | Male Soccer Players in the Danish National League: N = 14 |
High resistance knee extensor strength training group (ST): N = 8 Control group (no RT): N = 6 |
The training in the ST group was performed for 12 weeks, 3 times a week. Sessions consisted of four sets of eight repetitions of knee extensions using high resistance loads at velocities of 30–50 degrees per second. | VL; Biopsies were taken pre- and post-intervention. | Single Fiber Isolation. SDS-PAGE. | Mean changes: ST Group: MHC I: 3.1% increase (55.6+/−4.7 to 58.7+/−3.2) MHC I/IIa: 1.7% decrease (4.4+/−1.2 to 2.7+/−1.0) MHC IIa: 3.3% decrease (33.1+/−4.9 to 29.8+/−3.8) MHC IIa/IIx: 1.8% increase (6.7+/−3.2 to 8.5+/−2.2) MHC IIx: 0.1% increase (0.2+/−0.2 to 0.3+/−0.2) CTRL Group: All changes less than 3% except: MHC IIa: 6.2% decrease (27.7+/−5.2 to 21.5+/−6.8) MHC IIa/IIx: 3.9% increase (7.7+/−2.8 to 11.6 +/−4.9) |
| Williamson, 2000 | Untrained Older Males: N = 7 |
Progressive resistance training (PRT) (no comparator) | The intervention was 12 weeks in duration, with training sessions 3 times per week. Training consisted of knee extensions at a cadence of 2–3 s for both the concentric and eccentric. The subjects performed three sets; the first two sets were 10 repetitions, and the last set was performed to volitional exhaustion. Nearly 2–3 min of rest was given between sets. All PRT exercise sessions were performed at 80% of one-repetition maximum (1 RM) and reassessed every 2 weeks in order to maintain prescribed intensity. | VL; Biopsies were taken pre- and post-intervention. | Single Fiber Isolation. SDS-PAGE. | The MHC I fiber distribution significantly increased by 10.4% after PRT, whereas the MHC IIa and IIx remained unchanged. Authors speculated the 12-week resistance training protocol might have not been sufficient in length to strengthen and increase the proportion of the denervated/reinnervated fibers often present in untrained older populations; thus, type II fibers would have been adapted at a slower rate than the type I fibers. |
| Williamson, 2001 | Young Untrained: Male: N = 6 Female: N = 6 |
Progressive resistance training (PRT) group of men and women compared (same protocol, no comparator) | Same protocol as Williamson, 2000. | VL; Biopsies were taken pre- and post-intervention. | Single Fiber Isolation. SDS-PAGE. | Refer to Table 2 of Williamson, 2001 for a breakdown of the relative dominance of hybrid single fibers. Mean changes: Total hybrid fibers: 19% decrease in women, 29% decrease in men. MHC IIa increased 24% in men and 27% in women. Very little change in type I in either group. |
| Widrick, 2002 | Untrained Males: N = 6 |
Resistance training (no comparator) | A total of 36 exercise sessions were performed at a frequency of 3 times per week on nonconsecutive days. Exercises for the lower body consisted of squats, knee extension, knee flexion, and calf raise. Upper body exercise consisted of bench press, lat pull down, shoulder press, triceps press, biceps curl, seated row, and abdominal exercise. Three sets of 5–10 of the exercises listed above (divided approximately equally between those targeting the upper and lower body). During all sessions, the training resistance was adjusted so that subjects were able to complete only the specified number of repetitions, plus or minus one repetition. |
VL; Biopsies were taken pre- and post-intervention. | Single Fiber Isolation. SDS-PAGE. | Mean changes: Type I: 0% decrease (42–42) I/IIa: 4% decrease (4–0) IIa: 25% increase (30–55) IIa/IIx: 19% decrease (22–3) IIx: 3% decrease (3–0) |
| Malisoux, 2005 | Untrained Males: N = 8 |
Stretch shortening cycle (SSC) exercise program | SSC exercise training program consisting of 24 sessions was performed 3 times per week for a total of 5228 jumps. Exercises included static jump, vertical countermovement jump, drop jump (height of 40 cm), double-leg triple jump, single-leg triple jump, double-leg hurdle jump, and single-leg hurdle jumps. The participants were instructed to perform all jumps at a maximal effort. The number of jumps was progressively increased during the first 4 weeks such that initial sessions were 20 min long and were 45 min at the end of the training period. | VL; Biopsies were taken pre- and post-intervention. | Single Fiber Isolation. SDS-PAGE. | Mean changes: MHC I: 0.8% decrease (30.0+/−4.9 to 29.2+/−4.1) MHC I/IIa: 3.1% increase (1.9+/−0.5 to 5.0+/−1.4) MHC IIa: 7.2% increase (33.4+/−5.2 to 40.6+/−4.2) MHC IIa/IIx: 4.7% decrease (26.9 +/−1.9 to 22.2+/−4.3) MHC IIx: 4.4% decrease (7.0+/−3.0 to 2.6 +/−1.9) MHC I/IIa/IIx: 0.4% decrease (0.8+/−0.4 to 0.4 +/−0.2) |
| Trappe, 2006 | Relatively Untrained: Male: N = 4 Female: N = 3 |
Marathon Training (no comparator) | The training program was 4 days a week divided into two phases: a 13-week training period (10% increase in running volume per week), followed by a 3-week taper period. Compared with the last week of training (week 13), running volume was reduced by 25% in week 14, 47% in week 15, and 80% the week before the marathon. | Lateral gastrocnemius; Biopsies taken before the 16-week training plan, after 13 weeks of run training, and after 3 weeks of taper and marathon. Single muscle fiber MHC isoform experiments were only conducted before the training program and after the taper. | Single Fiber Isolation. SDS-PAGE. | Mean changes: Type I: 8% increase Type I/IIa: 5% decrease Type IIa: 2% increase Type IIa/x: 4% decrease Type I/IIax: 5% decrease Total hybrids: 11% decrease |
| Luden, 2011 | Novice Runners: Male: N = 3 Female: N = 3 |
Marathon training (no Comparator) | Same protocol as Trappe, 2006. | VL, Biopsies were taken pre-training, following 13 weeks of run training, and again following 3 weeks of reduced training after a marathon (26.2 miles; 42.2 km). These time points are referred to as T1, T2, and T3, respectively. | Single Fiber Isolation. SDS-PAGE. | Soleus: T1 to T3 MHC I: 5.1% increase (71.1+/−6.1 to 76.2+/−4.7) MHC I/IIa: 0.3% decrease (6.4+/−1.7 to 6.1 +/−1.6%) MHC IIa: 4% decrease (21.4+/−4.8 to 17.4+/−3.9) MHC IIa/IIx: 0.8% decrease (1.1 +/−0.8 to 0.3) MHC IIx: Undetectable at both time points. VL: T1 to T3 MHC I: 6% increase (42.6+/−8.6 to 48.6+/−7.1) MHC I/IIa: 3.1% increase (5.1 +/−1.3 to 8.2 +−3.0) MHC IIa: 4.3% decrease (40.1+/−6.8 to 35.8 +/−4.4) MHC IIa/IIx: 5.5% decrease (11.9+/−2.9 to 6.4+/−2.4) MHC IIx: 1% increase (0 to 1+/−1.0 |