The best time to plant a tree was 20 years ago. The second best time is now. –Chinese Proverb We all know that keeping fit as we age is important, but what does this truly mean? Often the focus is on strong muscles, which makes sense – more muscular strength leads to increased stamina and an improved ability to carry out activities of daily living. Until fairly recently, however, the contribution of aerobic capacity (VO2 max, also known as maximal oxygen consumption, or aerobic power) has been less understood. VO2 max is the highest rate at which oxygen can be consumed, or taken in, during exercise. The more oxygen you are able to taken in, the higher your threshold for exercise intensity will be. Picture competitive runners, or even the fit runner passing you on the street – they are working hard yet their breathing is controlled and even. They are able to take nice deep breaths yet still continue to exercise at a fairly high intensity. Contrast this with an unfit person trying to run for the first time – short, raspy, rapid breaths. That person cannot yet supply his muscles with enough oxygen to produce much adensine tryphosphate (ATP) – the energy molecule that is the foundation of everything our bodies are able to do. VO2 max can be compromised by various medical conditions, including heart disease chronic obstructive pulmonary disease, asthma, diabetes, cancer, osteoporosis, and osteoarthritis.
Maximal oxygen consumption is not just a boring subject in exercise physiology– it is critical to the maintenance of functional independence in older adults. Research demonstrates that aerobic power declines steadily in sedentary males by almost half between the ages of 20 and 60 (from about 45 ml/kg/min to 25 ml/kg/min). In females, the decline generally begins at around age 35 and drops by one-third by age 60 (from about 38 ml/kg/min to 25 ml/kg/min). The evidence suggests that older adults whose VO2 max has dropped to about 12-15 ml/kg/min are very challenged to complete the activities of daily living necessary to live autonomously. Seniors who live independently tend to have VO2 max values of at least 18 ml/kg/min for men, and or 15 ml/kg/min for women. An inactive lifestyle can, over the course of years, insidiously chip away at maximal oxygen consumption – rendering independent living a pipe dream. Given that the most prevalent fear in the senior population is losing independence, maintaining sufficient VO2 max is critical in order to avoid and/or delay the move to assisted living or long-term care. The good news is that it is possible to increase maximal oxygen capacity in older adults, just as in younger individuals. In fact, a 12.9% increase can be realized after just 8-10 weeks of training; a 14.1% increase after 12-18 weeks; and a 16.9% increase after 24-52 weeks. Gradually increasing aerobic training can boost the aerobic power of the elderly by at least 10 ml/kg/min, potentially delaying the loss of independence by as much as 20 years. When seniors exercise at a higher intensity, even more dramatic gains are realized. I love this Chinese proverb because it is so, so true. With respect to exercise, it is never too late to start. Every single person, regardless of age or physical condition, can increase their fitness level. Increasing fitness level does not mean running a marathon; it more often means having the ability to be active with grandchildren, have the energy to carry out activities of daily living with ease, and remain independent as time goes on.