Your body needs energy and different levels of exercise causes your body to use energy sources in different ways. Muscles are fueled by three distinct pathways:

  1. The phosphate system.
  2. The aerobic system or oxygen system
  3. The anaerobic or lactate system

The methods that energy is transported to your muscles are dependent upon the intensity and duration of your paddling. The efficiency of these systems helps determine your paddling endurance capacity.

The following chart illustrates the ways your body gets energy based on the duration of the activity. Longer activities require high amounts of aerobic conditioning and less anaerobic. Whereas shorter activities need more of a balance between the two and short sprints need phosphate system.

Figure 1: Where the fuel comes from for different activity lengths

Figure 1 can be understood by looking at the duration of your activity, say 30 minutes. On the 00:30:00 line you see about 7% of your energy comes from phosphate system, 18% from Anaerobic and the rest, 75%, from Aerobic.

So What?

Good point. Why care? To be well balanced we need to train all 3 systems to make them stronger. This means we need a combination of the following:

  • Phosphate (1 minute sprints, lots of rest)
  • Anaerobic (longer 3-15 minute repetitive sprints)
  • Aerobic (long runs over 30 minutes at high effort).

The trick is to design your training around your goals. If you want to do do sprints, then phosphate and anaerobic is important. If you’re doing longer events then aerobic training needs to be a priority. However all racers need to do sprints at some point in a competition so none of these types of training should be overlooked but you want to proportion them according to your training goals.

Phosphate Training

The phosphate system drives fast muscle contractions. The phosphate system does not use oxygen and due to the few chemical reactions required, it is the fastest pathway for muscle energy. The phosphate system does not use glucose, or produce lactic acid, hence it supplies anaerobic alactic energy. Muscle contractions are controlled locally by adenosine triphosphate (ATP), which is broken down into adenosine diphosphate (ADP) and energy. You’ll see ATP and ADP mentioned often in sports metabolism.

Muscles have an internal store of ATP that can be called upon for short bursts of maximum effort, up to approximately 3 seconds. The phosphate system then kicks in, and can provide energy for maximum effort for another 12 seconds.

The only way to increase and improve your ATP storage and phosphate system response is with hard, short sprints, alternated with periods of complete rest bringing your heart rate near resting rates. Several months of sprint training will increase this capacity by 25% to 50%.

Anaerobic Training

When carbohydrates or glucose are burned in the muscles they produce lactic acid. This waste product has to be processed quickly and efficiently by the liver. The liver has the ability to convert this acid back into glucose for the muscles to use again. Your livers ability to process this lactic acid is known as the lactate threshold. This is often something monitored in professional athletes while they train.

Lactic acid production chokes your anaerobic power over time. Increased muscle acidity, called acidosis, damages the muscle cells and leaks lactate into the blood. Additionally this acid buildup decreases aerobic endurance. Muscle contractions at very high lactate concentrations become more difficult because of a lack of ATP.

Remember that burning pain as you push the last lap on a 1 mile sprint? That wall where everything suddenly starts to feel heavier and heavier is do to the acidosis and lack of ATP or electrolytes (ion depletion). Here’s how muscles get tired: and from the same author how muscles grow via hypertrophia:

Hard anaerobic exercise often requires days for the body recovers sufficiently to regain full aerobic capacity. Without sufficient recovery between bouts of hard anaerobic exercise, both aerobic and anaerobic endurance capacity decrease considerably, leading to a number of problems referred to collectively as over training.

Recovery time, from 24 hours to as much as 96 hours, is necessary after hard anaerobic workouts. A good training program that includes anaerobic intervals, high intensity “threshold” exercise or tempo training, or racing requires recovery time planning to avoid over training effects on the anaerobic system.

  • Resting about 25 minutes to remove half the accumulated blood lactate. Roughly 90% of lactate is removed after about 1 hour of rest.
  • Always cool down. 20 minute light cool-downs following a race or hard workout accelerate the removal of lactate greatly. Almost 90% will be removed in 20 minutes of light easy exercise.

Anaerobic training requires periods of intense workouts in 3 to 15 minute intervals with some recovery time in between.

Aerobic Training

The aerobic system, commonly associated with oxygen and calledthe “oxygen” system, utilizes fats (in particular, triglycerides) and sugar (in particular, glycogen) to fuel your muscles. This conversion produces ATP for your cells us use as energy.

Exercise allows you to train the muscles’ metabolic systems to use energy more economically. The number and density of mitochondria in the muscles increase with proper training, providing more “engines” to burn fat and glucose. This in turn increases the efficiency of the metabolic pathways allowing a well-trained athlete to oxidize fat for a longer time.

The body stores enough carbohydrate in the muscles and the liver to provide about 90 minutes of energy. When your carbohydrate stores are depleted, fat burning increases and the ability to sustain your level of effort decreases – fat oxidation always requires a small amount of carbohydrate to keep contractions full strength. To avoid fading or hitting a wall glycolysis can be extended by having carbohydrate rich drinks or snacks.

  • Always warm up. It takes about 3 minutes before the heart, lungs, and circulatory system fully function, and for the aerobic system to be fully engaged.
  • Recovery time from a predominately long and hard anerobic activity takes up to 48 hours to replenish glycogen in the liver. Muscle glycogen can be replenished in a few hours. Long workouts (2 hours or longer) should be followed by a recovery day of light exercise, or a strength-training day. If you are training for a very long event, it is not uncommon to train 3 hours followed by 5 hours the next day. This helps train your body for partial recovery times like those long events where recovery time is during the race.
  • Aerobic energy levels can be increased. The body adapts to the stress of training and will increase the density of aerobic muscle mitochondria from 3.5% of muscle mass to as much as 5% of muscle mass. Years (3-4) of extensive aerobic training can increase aerobic endurance capacity by approximately 50%.
  • Other changes that occur over time include increased mitochondria which generate most of the chemical energy needed to power the cell’s biochemical reactions along with blood vessel capillary growth for better blood circulation to tissues. So in general when developing aerobic capacity for paddling, you need to paddle with your heart rate in the aerobic zone to focus development in the critical muscle areas for aerobic energy. This is known as training specificity. Cross-training won’t by itself increase paddling aerobic fitness, but it will increase cardio-pulmonary efficiency that is sometimes hard to increase with just paddling alone.