Читать книгу Peak Nutrition - Maria Hines - Страница 35

As you age, more than 99 indicators known as biomarkers decline, including muscle mass, reaction time, coordination, memory, and so on. But you can influence a few biomarkers. The primary age-related biomarker is sarcopenia—loss of muscle mass (specifically the fast-twitch type IIa muscle fibers—the ones used during maximum strength, power, or dynamic movements). The result is a loss of strength and power, which can be a real blow for older mountain athletes. This decline may be the result of a decrease in activity because of life changes and priorities. Inactivity can also be caused by prior injury or pain, which can psychologically limit movement. The fear of pain during training is a considerable limiter for folks coming back from an injury. It is an even greater deterrent when you are much older. Don’t let pain stop you from moving. Find a way to move around the pain, and stay as active as you can.

Another age-related biomarker is metabolic rate. Metabolism decreases over time and is dependent on mitochondrial health and thyroid function. Over time, especially if you are inactive, the DNA in your mitochondria gets deleted. Because mitochondria use nutrients and oxygen to generate energy and heat that controls your body temperature, your ability to regulate internal temperature also decreases because of this degradation. In addition, your body fat percentage goes up and your lean body mass decreases. These changes go hand in hand with the loss of muscle mass and decrease in metabolism, which further increases body fat percentage.

As a result of these factors, VO₂ max (an indicator of cardiovascular fitness) decreases because of a decrease in aerobic work and loss of mitochondria. The body reduces its tolerance of varying blood glucose levels, making it harder to level out glucose in the blood, which can lead to diabetes. Blood pressure tends to fluctuate more. Bone density decreases, likely because of inactivity and a reduction in weight-bearing movements. Cholesterol ratios also can become an issue.

What is VO₂ max? It’s an indicator of cardiovascular fitness, essentially how much oxygen you can consume during progressively intense cardio. It is expressed as milliliters of oxygen per kilogram of body weight per minute, or ml/kg/min. The more oxygen you consume, the more ATP the body can generate. (See chapter 6, How Fuel Provides Energy to learn about ATP.)