Figure 2. Effects of chronic clenbuterol treatment on intact muscle contractile properties.

A, Effects of clenbuterol (CLB) treatment for 21 days on EDL maximal isometric tension. Left graph, P₀: maximal isometric tetanic tension, in mN; Right graph, sP₀ specific maximal isometric tetanic tension, in N/cm². * p<0.05 compared to controls (CTR, untreated animals). B, Recordings show the decrease in tension resulting from the fatigue protocol in control EDL muscles (CTR) in which T_lim was almost 50 s and in clenbuterol treated EDL muscles (CLB) in which T_lim was about 34 s. Black dashed lines represent the maximal force and 50% of the initial force. The grey dashed line in the CLB panel represents 50% of the initial force of CTR for comparison. C, Mean ± SEM of the T_lim values/group (n = 15 for CTR; n = 22 for CLB). * p<0.05 compared to CTL.