Petrou M, Clarke S, Morrison K, Bowles C, Dunn M, Yacoub M

Imperial College, National Heart and Lung Institute, London, UK.

BACKGROUND: Skeletal muscle assist (SMA) may be limited by loss of power, slowing of contraction and relaxation, and atrophy of the transformed latissimus dorsi muscle (LD). Clenbuterol (clen), a beta2-adrenergic receptor agonist, was used to improve the performance of trained skeletal muscle in sheep. METHODS AND RESULTS: The following 4 groups were used: A (n=6), untrained controls; B (n=6), left LD progressively transformed toward a slow-twitch and fatigue-resistant phenotype by electrical stimulation over 12 weeks (2.5 to 5 V, 240- microsec pulse duration, 35 Hz, 3 to 6 pulses per burst, and up to 40 bursts per minute); C (n=6), clen-treated (0.5 mg/kg SC) for 12 weeks; and D (n=6), clen+trained. In a terminal experiment, the mobilized LD was wrapped around a rubber aorta of a mock circulation and stimulated to contract 40 times per minute. Group A had an initial mean pressure augmentation (DeltaP) of 24.6 mm Hg and stroke power of 2.28 W/kg, but both fell to <20% of their original values by 15 minutes because of fatigue (P<0.005). Group B was fatigue-resistant, with a DeltaP and stroke power at 60 minutes of 13 mm Hg (70% of initial) and 0.34 W/kg (39% of initial), respectively. The performance of group C was similar to that of controls. In group D, however, the muscles were stronger at all time points than in B, with a DeltaP of 23 mm Hg and stroke power of 2.66 W/kg at 60 minutes (P<0.01). The speeds of contraction (+dP/dt eltaP) and relaxation (-dP/dt eltaP) were significantly greater in group D than B. Protein analyses showed group D to have only a trend toward greater abundance of the fast isoforms of myosin heavy chain and sarcoplasmic reticulum Ca2+-ATPase (P>0.1).
CONCLUSIOINS: Clenbuterol improves the performance of trained skeletal muscle in a model of aortomyoplasty by unknown mechanisms. These findings may have important implications in SMA.

Sounds like it may be a good idea for powerlifters and sprinters...

-Stew

quote:

---

Originally posted by Fonz:
Yes, it can increase muscular performance but
it also interferes with muscular adaptation
to performance.

Godspeed

---

Its true

ice

quote:

---

Originally posted by Stew Meat:
Damn, I forgot... I should have cleared it with Fonz before I posted actual research. Becasue you know how an article that is written by a grade school kid for a term paper caries so much more weight than a scientific controlled study. All because Fonz puts his "blessing" on it.
Another case of Fonz being a dumbass.


-Stew

---