Figure 4. Effect of lactic acid or increased CO₂ tension on the relation between steady state tetanic force and [K⁺]_o.

Muscles were incubated at different [K⁺]_o values until a steady force level was obtained. ▪, control muscles, buffer pH 7.4 (n = 4–6); ○, 20 mm lactic acid added, buffer pH 6.82 (n = 8–10); •, CO₂ increased to 50 %, buffer pH 6.72 (n = 8). Data show means and s.e.m. At all [K⁺]_o values above 8 mm, the relative force of the muscles at low pH was significantly higher than in the control muscles at the corresponding [K⁺]_o (P < 0.05).