I have always found this so interesting, everything that scientifically happens in the body, and most importantly I wanted to know how the food we eat, gets turned into energy, allowing for life and movement. Here, I discuss that our body’s ability to generate a muscle contraction is a result of our muscles being involved in the molecular breakdown of the high energy compound called ATP(adenosine triphosphate). This high energy compound is stored in limited quantities in the muscle that rapidly breakdown to provide our bodies with muscular contractions, which the duration of those contractions vary dependent on the type of activity our muscles engage in and the required force generated. This activity is reliant on the metabolic pathway to ensure continual muscle contraction occurs. The three metabolic pathways that provide ATP production in the muscle: First, through the phosphocreatine (PC) breakdown, which provides our supply of stored ADP (adenosine diphosphate) an additional phosphate to create ATP. This limited supply provides the muscle with approximately 5 seconds of intense muscle contraction. Activities that would focus on this energy would be resistance training, sprints, and high intensity intervals. This stage is also referred to as the phosphagen system. If the muscle requires additional contractions, our second energy system would be required to participate, and this is called the glycolysis phase. During this phase, stored glycogen or glucose is broken down to form pyruvate which provides the muscle the necessary phosphate group to continue the ADP to ATP reaction. According to Powers and Howley “The Winning Edge” article, activities would be longer running, such as 400 meter races, 2000 meter rowing, and the similar. In the third stage, the oxidative stage, our muscles are able to generate ATP from the hydrogen removal of our food stuff that occurs in the metabolic pathway of the Krebs cycle. The food stuff of carbohydrates, fats and proteins is broken down by acetyl-CoA to provide the additional phosphate to the ADP to regenerate ATP to the muscle (Powers and Howley, 2012).
Crossfit style workouts make up the mainstay of my exercise program, which typically consist of short bouts of high intensity intervals that typically last 10 to 30 seconds for most exercises. For example, a complete round might consist of 25 burpees, 25 pullups and 25 kettlebell swings, which rest is typically required throughout the round to rebuild adequate supplies of ATP to continue muscle contractions. The second round would be 15 reps and the third round 10 reps. This style of exercise I would complete would be a rest-as-needed to continue additional reps. Referencing The Winning Edge 3.2 by Powers and Howley (2012), given the intensity level of the exercise, the phoshagen would be the primary energy source to create necessary ATP with a secondary glycolysis to complete the muscle contractions for approximately 30 seconds. The exception to this would occur during 2000 meter rows which requires the oxidative system to become approximately 60% of the preferred energy source of muscle contraction. In research conducted by Baumann et al, (2012), female runners that trained in a phosphagen and glycolictic capacity demonstrated a higher capacity to excel in running events that relied primarily on the oxidative energy system. The findings showed that a runner’s ability to regenerate ATP anaerobically provided increased performance in comparison to a runner with similar abilities. This research helped provide additional insight to the benefits those athletes who train for aerobic benefits can obtain additional benefits of ATP production by increasing their anaerobic physiological system. Similar findings were concurred in a study by Laursen’s “Training for intense exercise performance: high intensity or high volume training?” Findings of the study showed that athletes that trained for aerobic events where approximately 75% of the preparation training was utilizing the oxidative energy system performing high volume training, while 10-15% focused on higher intensity activities, which increased their athletic performance and VO2 max by 2-4% (Laursen 2010).
Powers, S., & Howley, E.. (2012). Exercise Physiology: Theory and Application to Fitness and Performance. (8th ed.). New York, NY: McGraw-Hill Companies, Inc.
Laursen, P. B. (2010). Training for intense exercise performance: high-intensity or high-volume training?. Scandinavian Journal Of Medicine & Science In Sports, 201-10.
Baumann, C. W., Rupp, J. C., Ingalls, C. P., & Doyle, J. (2012). Anaerobic Work Capacity’s Contribution to 5-km-Race Performance in Female Runners. International Journal Of Sports Physiology & Performance, 7(2), 170-174.