Monday, July 15, 2013

The Metabolic Demands of Various Exercise Protocols

by Doug Dupont


Whether we are athletes or coaches, if we are involved in program design then we need to understand the body's basic processes. If you choose the wrong programs, the results will invariably suffer. For example, many people use resistance training prescriptions for stressing muscle metabolism, which is not as well understood as you may think. Understanding these processes could factor into designing programs for increasing the ability to withstand metabolic stress, such as CrossFit, or programs focused on fatigue avoidance, such as many strength programs and recovery workouts.

In a study this month in the Journal of Strength and Conditioning, researchers sought to learn more about how common workout routines affect muscle metabolism. According to the researchers, these facts were well understood for cardiovascular training, but much less so for resistance training.

In particular, the researchers wanted to study two chemicals that increase with training. The first is ammonium. Ammonium is the product of what’s called the purine nucleotide cycle. This cycle is most active when there is rapid use of both ATP and phosphocreatine. The second is lactate, which signals the depletion of muscle glycogen and dropping pH. Each of these chemicals represents a different energy cycle and responds differently to various training methods, although they are often expressed simultaneously. This was the first time the relationship between these two chemicals has been examined.

The researchers tested three common workout programs, and then measured for ammonium and lactate. The programs ran the gamut, from endurance (2 sets of 20 reps with short rests), to hypertrophy (3 sets of 10 reps with 2 minute rest periods), and on up to strength (5 sets of 5 reps with 3 minute rests). Each program was equalized in terms of work. In other words, although the 5x5 protocol had fewer total reps than the other programs, it used more weight, so the total work load was the same for all three protocols.

Since ammonium increases with heavy resistance because of the demand on ATP, the researchers speculated the strength routine would cause the greatest elevations. Although there was a relationship between ammonium and lactate in all three protocols, the joint chemical response to the protocols was varied enough to indicate that the energy systems involved did respond differently to each program.

That said, the researchers were wrong in their hypothesis. The endurance program caused the greatest levels of both ammonium and lactate. Hypertrophy was in the middle, and strength had the least response. So total volume of repetitions had a more substantial effect on these chemicals than intensity of each rep.

The rest period was another suspected culprit in the results. For each set, the endurance work might not have caused the same metabolic response, but with only 45 seconds of recovery, the researchers hypothesized that ATP and creatine could not recover quickly enough, resulting in elevated ammonium and lactate.

Ultimately, the results aren’t so surprising, but it’s always good to have more academic power behind your plan designs. A light load and short rests are key for working these metabolic systems. For recovery, a light load with longer rest periods would work well. For strength, long rest is ideal to ensure the most consistent heavy lifting. For added muscle, something in between is probably best.

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