Rall J A, Schottelius B A
J Gen Physiol. 1973 Sep;62(3):303-23. doi: 10.1085/jgp.62.3.303.
Comparative energetics of chicken latissimus dorsi muscles, tonic anterior (ALD) and phasic posterior (PLD), were investigated by measuring initial heat production. Heat components were analyzed in terms of the equation: E = A + W + alpha(F)(DeltaL) + f(P, t) As the muscles were stretched by increments, heat produced in isometric twitches and tetani decreased in a linear fashion. Two processes are involved: one tension independent, the activation heat, or A; and the other tension dependent, W(i) + alpha(F)(DeltaL) + f(P, t). In twitches, A, per unit tension, is equivalent in the PLD and ALD. Tension-dependent heat, per unit tension, is greater in the PLD due to W(i); but tension-time-related heat, f(P, t), per unit tension, is similar in both muscles. In tetanic contractions, differences in A and f(P, t), per unit tension, are attributed to the greater V(max) in the PLD. The differences in the energetics of isometric contractions in the PLD and ALD, therefore, can be explained by inherent differences in tension development, compliance, and myosin and reticular ATPase activities. Data from isotonic twitches were quantified by means of the equivalent tension technique. Both muscles exhibited an extra heat associated with shortening, alpha(F)(DeltaL). In the PLD, the ratio alpha(F)/P(ot) is greater; it is load independent and (1/2) the value of a/P(o) in both muscles. Enthalpy efficiency, W(e) + W(i)/E, is comparable in both muscles. A Fenn effect is observed only when isotonic energy liberation is compared to a decreasing isometric energy expenditure base line.
通过测量初始产热，研究了鸡背阔肌的比较能量学，即强直性前侧（ALD）和相位性后侧（PLD）肌肉。根据方程(E = A + W + \alpha(F)(\Delta L) + f(P, t))分析热成分。随着肌肉逐步被拉伸，等长收缩抽搐和强直收缩中产生的热量呈线性下降。这涉及两个过程：一个与张力无关，即激活热，或(A)；另一个与张力有关，即(W(i) + \alpha(F)(\Delta L) + f(P, t))。在抽搐中，单位张力下的(A)在PLD和ALD中相等。由于(W(i))，单位张力下与张力相关的热在PLD中更大；但单位张力下与张力 - 时间相关的热(f(P, t))在两块肌肉中相似。在强直收缩中，单位张力下(A)和(f(P, t))的差异归因于PLD中更大的(V_{max})。因此，PLD和ALD中等长收缩能量学的差异可以通过张力发展、顺应性以及肌球蛋白和网状ATP酶活性的内在差异来解释。等张抽搐的数据通过等效张力技术进行量化。两块肌肉都表现出与缩短相关的额外热量(\alpha(F)(\Delta L))。在PLD中，(\alpha(F)/P_{ot})的比值更大；它与负荷无关，是两块肌肉中(a/P_{o})值的((1/2))。两块肌肉的焓效率(W(e) + W(i)/E)相当。只有当将等张能量释放与下降的等长能量消耗基线进行比较时，才会观察到芬恩效应。
