Table 2.

Force-velocity and power output characteristics during maximal and submaximal Ca²⁺ activations

	pCa range	Relative force (P/P4.5)	Vmax (MLs−1)	Force optimum (p/Po)	Absolute power output (μW mg−1)	Peak relative power output (P/Po MLs−1)
Cardiac myocytes (n = 8)	4.5	1.0	1.27 ± 0.43	0.28 ± 0.03	3.24 ± 1.53	0.095 ± 0.026
	5.6–5.4	0.70 ± 0.08	0.83 ± 0.26*	0.30 ± 0.05	1.76 ± 1.09*	0.071 ± 0.022*
	5.7–5.5	0.51 ± 0.06	0.69 ± 0.18*	0.30 ± 0.06	1.08 ± 0.55*†	0.062 ± 0.023*†
	5.8–5.6	0.27 ± 0.06	0.40 ± 0.17*†‡	0.37 ± 0.08*‡	0.49 ± 0.36*†‡	0.050 ± 0.026*†‡
Fast-twitch fibres (n = 6)	4.5	1.0	2.00 ± 0.35	0.25 ± 0.02	11.98 ± 3.76	0.131 ± 0.034
	5.8–5.6	0.74 ± 0.06	0.90 ± 0.27*	0.31 ± 0.04*	5.75 ± 1.98*	0.085 ± 0.024*
	5.9–5.7 0	57 ± 0.07	0.50 ± 0.20*†	0.37 ± 0.04*†	3.61 ± 1.33*†	0.069 ± 0.016*†
	6.0–5.8	0.25 ± 0.05	0.43 ± 0.10*†	0.36 ± 0.06*†	1.14 ± 0.48*†‡	0.055 ± 0.001*†
Slow-twitch fibres (n = 5)	4.5	1.0	0.94 ± 0.41	0.18 ± 0.03	2.70 ± 0.70 0	030 ± 0.003
	5.8–5.6	0.65 ± 0.03	0.43 ± 0.10*	0.23 ± 0.03*	1.27 ± 0.41*	0.021 ± 0.003*
	6.0–5.8	0.50 ± 0.06	0.52 ± 0.23*	0.22 ± 0.05	0.96 ± 0.27*	0.022 ± 0.002*
	6.1–6.0	0.25 ± 0.07	0.40 ± 0.13*	0.24 ± 0.03*	0.54 ± 0.15*†‡	0.022 ± 0.002*

ML, muscle length. Values are means ± s. d.

^*P < 0.05vs.P/P_4.5 = 1.0

^†P< 0.05 vs. P/P_4.5 = 0.70

^‡_P < 0.05 vs.P/P_4.5 = 0.50.