Review Question - QID 210183

During aerobic activity, the body's preferred energy substrates are fatty acids and glycogen.

For activities lasting less than 10 seconds, ATP and creatine phosphate are the primary energy sources. Between 1 and 4 minutes, the body utilizes glycogen and lactic acid via both aerobic and anaerobic metabolic pathways. For activities that are primarily aerobic (lasting > 4 minutes), the body primarily utilizes glycogen and fatty acids.

Costill et al. examined the role of dietary carbohydrates in muscle glycogen resynthesis after strenuous running. They determined that increasing amounts of carbohydrate consumption was related with significantly higher muscle glycogen levels 24 hours after strenuous exercise. They also found that complex carbohydrate diets, compared with simple carbohydrate diets, resulted in significantly higher muscle glycogen levels at 48 hours.

Sherman et al. looked at the effect of carbohydrate intake on muscle glycogen levels and performance in aerobic athletes over a 7-day training period. They found that, although a high carbohydrate diet maintained muscle glycogen levels, high carbohydrate diets did not appear to provide a performance benefit over moderate carbohydrate intake in this cohort.

Figure A is a blank diagram demonstrating energy substrates used during exercise as a function of time; illustration A shows the completed diagram.

Incorrect Answers:
Answer 1: A corresponds to ATP and creatine phosphate; D corresponds to muscle glycogen, plasma glucose, and liver glycogen.
Answer 2: B corresponds to muscle glycogen; C corresponds to plasma free fatty acids and adipose tissue triglycerides.
Answer 3: A corresponds to ATP and creatine phosphate; B corresponds to muscle glycogen.
Answer 4: A corresponds to ATP and creatine phosphate; C corresponds to plasma free fatty acids and adipose tissue triglycerides.