Maximize Your Cardio Program Part 1: Cellular Adaptations
This four part series of articles addresses the different adaptations that occur in the body as a result of four different levels of cardiovascular conditioning. When you understand how the different energy systems in your body work, you will be able to manipulate type, volume and intensity of your cardiovascular program to achieve optimum results and avoid plateaus, boredom, and injury. For example, a session that stresses VO2max improvement will not necessarily optimize increases in aerobic enzyme activity within the cells. Different volumes and intensities of cardiovascular exercise produce different results. This series of articles examines the volume and intensity of exercise required to achieve cellular adaptations, increased lactate threshold, increased aerobic (VO2max) capacity, and increased speed and economy beginning with cellular adaptation training.
From your first workout through your 10,000th workout and beyond, you accelerate your body’s energy producing mechanisms at the cellular level. Exercising muscle cells demand increased blood supply and increased efficiency in their production of energy. The density of capillaries surrounding muscle cells increases to bring more nutrient rich blood to exercising muscles. The muscle cells increase the number, size, and distribution of mitochondria (sites of aerobic metabolism) within the cells to meet energy needs. Furthermore, the muscle cells increase enzyme activity, or chemicals that aid energy production. This increased energy production is a chronic adaptation to regular exercise. It occurs gradually over time as you continually challenge your body’s capacity to work.
Fortunately, these desirable cellular adaptations do not require high intensity exercise. Furthermore, increasing your intensity might produce more fatigue depending on your volume, but it will not necessarily stimulate greater cellular adaptations. You can achieve significant cellular adaptations working at a pace of about 70% of your VO2max. Your VO2max is the maximum volume of oxygen your body uses per minute to produce energy. You do not need to precisely measure your VO2max to determine when you reach 70% of your VO2max. This level is called “conversational.” In other words, you should be able to speak a couple of sentences clearly at this level of exercise. This is the level you would use for warm ups, cool downs, long sessions and recovery sessions. The length of a “long” session depends on your fitness level and goals but typically means more than 30 minutes of steady, continuous activity. Recovery sessions usually are about 30 to 40 minutes of steady, continuous activity.
If you simply want to maintain your current cardiovascular fitness level, decrease your risk of developing chronic diseases or increase your volume of work at your current level, your cardiovascular program could primarily consist of easy sessions at 70% VO2max. Because of the many benefits resulting from the 70% VO2max level of conditioning, this type of training is often called “base conditioning.” It produces a consistent, baseline level of fitness from which you could build greater volume and intensity. It strengthens the ligaments and tendons supporting exercising bones and muscles to prepare the joints for increased work. Endurance athletes train at this level for weeks and months before introducing higher intensity work. Easy sessions train endurance athletes to maintain a desired pace throughout a race and stay competitive through the middle of the race.
However, to increase the amount of oxygen your body can absorb, convert to energy, and burn more calories, you will need to work at higher intensities. Similarly, endurance athletes who want to sprint at the end of a race or climb hills without excessive fatigue need to incorporate higher intensity training into their program. The next article will discuss the next intensity level of cardiovascular training: your lactate threshold where you stress your body’s ability to produce energy via aerobic pathways. You will learn what the burning sensation in your muscles mean and how to increase your capacity to work longer or harder before feeling uncomfortable.
Daniels, Jack. “Incorporating Sport-Specific Skills into Conditioning: Distance Running,” within High-Performance Sports Conditioning, Bill Foran ed., Human Kinetics, Inc. 2001.