PHYSIOLOGY 101

Whether we are walking, hiking, running, climbing, snowshoeing, or skiing we are creating movement through muscular contractions. The strength and speed with which we get our muscles to contract determines how quickly we move and determines how well we are able to control those movements. How long we can keep contracting these muscles to power our movements is based on several factors:


  • How much fuel we have available to create the energy we need

  • How much oxygen we are able to get to our muscle cells to enable energy production

  • How many muscle fibers we have to utilize and can rotate into action, and...

  • How efficiently we are able to utilize the fuel and oxygen we do have to continue to power our movements


The primary training goal should be to create a base level of fitness that enables your muscles to contract with controlled strength and power for the duration you need for your activity. We also want the ability to contract our muscles for short powerful bursts when needed.

So how do we get there?


Fuel our body so it can create the energy it needs. Two primary sources of fuel:

      • Carbohydrates – these foods are broken down into glucose

      • Fat – these foods are broken down into triglycerides and fatty acids

      • Only 5-10% of protein is used for energy because it is needed elsewhere, such as recovery and rebuilding our muscles after a strenuous workout


The food we eat needs to get transformed into an energy molecule known as adenosine triphosphate (ATP) and this is done via our metabolic pathways.


Train so our body becomes more efficient at creating this energy. Our energy comes from two basic metabolic pathways:


      • Aerobic - This energy pathway requires oxygen and is the alpine athlete’s engine and is the most critical.

        • The bulk of our aerobic energy (ATP) comes from little power houses in our cells known as mitochondria and the enzymes found in them. These enzymes exist to help produce energy from the food we eat to build the ATP molecules we need for energy

        • Slow process – it takes about 10 chemical reactions to break down our fuel into ATP, but it can create 38 ATP from each fuel molecule and can continue for longer durations to allow for hours or days of continuous movement

        • How fast our body can create ATP using this process determines (and limits) our aerobic work capacity. Faster ATP production equals increased endurance and speed

        • Highly trainable. Training aerobically at lower intensities for longer durations increases this ability by increasing the numbers of mitochondria in your cells as well as increasing the amount of enzymes you have available


      • Anaerobic - This energy is created outside of our mitochondria and does not rely on the same enzymes or process as aerobic energy.

        • Still creates ATP, but does so from a different fuel molecule – glycogen. This is a molecule that our muscles store and has a limited supply

        • Fast process – this pathway can create ATP very quickly, but only for a limited amount of time. This allows for greater energy and power – faster speeds. Sprinters use this pathway at the beginning or for the entirety of their race depending on the length

        • Not ideal for endurance athletes. Creates a build-up of lactate and leads to muscle fatigue very quickly


Train so our heart can deliver more oxygen to our muscles when they need it:


  • Strengthening our heart with endurance exercise

  • Training will increase the number of capillaries in your muscle tissue allowing more oxygen to be delivered


Train the muscle fibers you need. There are three basic types of muscle fibers: slow twitch (ST), fatigue-resistant fast twitch (FTa), and fast twitch (FTb). ST fibers are predominantly used in endurance sports. Climbing and backpacking primarily use these ST muscle fibers – so this is where most of your training should focus.


Efficient use of fuel and oxygen comes from proper training and eating. There are no short cuts.