Skeletal muscles respire anaerobically for the first 45 to 90 seconds of moderate-to-heavy exercises because the cardiopulmonary system requires this amount of time to sufficiently increase the oxygen supply to the exercising muscles. If exercise is moderate, aerobic
Test Yourself Before You Continue
1. Explain how graded contractions and smooth, sustained contractions can be produced in vitro and in vivo.
2. Distinguish among isotonic, isometric, and eccentric contractions, and describe what factors determine if a contraction will be isometric or isotonic.
4. Describe the relationship between the resting muscle length and the strength of its contraction.
Plasma free fatty acids
Figure 12.21 Muscle fuel consumption during exercise. The relative contributions of plasma glucose, plasma free fatty acids, muscle glycogen, and muscle triglycerides to the energy consumption of exercising muscles. These are shown during mild exercise (25% of VO2 max), moderate exercise (65% of VO2 max), and heavy exercise (85% of V^ max). Data for heavy exercise performed at 90 to 120 minutes are not available.
respiration contributes the major portion of the skeletal muscle energy requirements following the first 2 minutes of exercise.
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.