When a sedentary individual begins a weight training program, what are the initial strength gains mainly a result of? Neural adaptations What laboratory founded in the United States in 1927 has been the most influential in terms of having an impact on the field of exercise physiology? Harvard Fatigue Laboratory What is the functional unit of a muscle fiber? Sarcomere What is the function of the T-tubules? Carry the action potential deep (transversely) into the muscle cell The _____ motor neuron innervates skeletal muscle fibers and stimulates muscle contraction Alpha-motor neuron What protein blocks the myosin binding site on actin at rest in skeletal muscle? Tropomyosin Which muscle fiber type is most fatigue resistant? Type 1 What type of muscle contraction is characterized by muscle shortening? Concentric What metabolic pathway predominates in producing ATP during a 100 meter (~10 second in duration) sprint? PCr What metabolic pathway is primarily responsible for producing ATP during a half mile run (~2-3 minutes of exercise)? Glycolysis (Anaerobic) What metabolic pathway is responsible for producing ATP during a marathon (26.2 miles, ~4 hours)? Oxidative phosphorylation (Aerobic) What enzyme catalyzes the reaction that transfers a phosphate from phosphocreatine to ADP, thereby form ATP and creatine? Creatine kinase What is pyruvate converted to under conditions of low oxygen (anaerobic)? Lactic Acid What is the one molecule that all substrates are converted to before they enter the Krebs Cycle? Acetyl-CoA Which structure is responsible for the salatory conduction (speeding up of an action potential) characteristic of a neuron? Myelin sheath What part of a neuron is responsible for releasing neurotransmitters? Axon terminal