Fitness Part 3: Stamina

Stamina

Having defined our parameters and principles of skill and strength development the final facet of Fitness is stamina. If Strength is our ability to apply force, Stamina is our ability to sustain it.

To further contrast the two categories we can think of strength as being the entire muscle structure performing a task, whereas stamina is governed and developed at the cellular level.

It’s easiest to outline the timeline by which the body accesses and uses energy stored in the body. In doing so we can then use this knowledge to inform our training efforts.

0-10secs

When we first start moving we use fuel stored immediately in the muscle to fuel the contractions. For the first 7-10secs the fuel source most immediately available is ATP and Creatine Phosphate.

Efforts in this domain are likely to be very high power output, sprints or strength sets with long rest periods. This is also why supplementing with Creatine is so effective, it allows us to perform a few extra reps or push for a few extra seconds in these explosive efforts.

Exposing ourselves to this work confers benefits outlined in our previous writing on strength.

10secs-2mins

Once we run out of ATP and Creatine the cells start to use glycogen (Stored carbohydrate). At this stage the system is still in the process of taking in and delivering oxygen to the working muscles, so this stage takes place in the absence of oxygen. The process is fast-acting but only yields a limited amount of energy, acting as a bridge to more sustainable fuelling.

Work at this level of intensity and duration is likely to be higher volume strength sets and short interval repeats resulting in muscle growth and the generation of more enzymes to process carbohydrates in the cell, allowing you to work harder and for longer over time.

2-10mins

As the body takes on and delivers oxygen the next stage of biochemical reactions take place. These still break down carbohydrates for energy but using oxygen as a catalyst for a different metabolic pathway, and while they are less efficient they yield a greater amount of energy.

Workouts targeting this energy system will be short AMRAPS or round for time workouts with lower rep ranges and heavier loading prescriptions.

Adaptations to this kind of work result in yet more development of enzymes and mitochondria), making fuelling this kind of work in future more efficient and effective.

7mins onward

Overlapping the second stage of carbohydrate use, aerobic lipolysis is the long-duration energy source that primarily uses fat as fuel. It is even less efficient than the aerobic use of carbohydrate, but yields yet more energy.

Workouts programmed to target this pathway will be longer AMRAPs of 10mins+ or multiple stage workouts like those programmed on Endurance Wednesdays and Saturdays.

Training at this intensity yields results that are both cellular (Similar to the above developments for carbohydrate use but calibrated for fat burning) and structural; capillaries are formed between muscle fibres and adjacent muscle structures allowing easier access to the bloodstream, making the clearing of waste more effective. In short, this work allows you to recover more effectively both within and between sessions.

Each of these pathways is a chemical reaction with varied outcomes. Any work using creatine as fuel has no metabolic consequence that affects us, it’s a fuel with no exhaust fumes.

Work fuelled with either of the glycolytic engines using carbohydrates as fuel will result in a release of Hydrogen which increases acidity in the muscle. This hydrogen can bond with an enzyme called NAD+ to create NADH, reducing the acidity in the muscle. Eventually all of the NAD+ is is used up and with nowhere to go the hydrogen starts to build up, at which point power output is reduced (Fatigue), signalled via an acute sensation of muscle burning; the more trained you are the greater the amount of NAD+ in the cells, making them more fatigue resistant.

This buildup of acidity (And therefore fatigue) can be further buffered and taken out of the cells via the fat-fuelled aerobic system. Put another way, by training at lower intensities and for longer durations you create a system that can allow you to push harder and for longer in your shorter, higher intensity efforts.

An even more simplified expression of this idea is that higher intensity work (where intensity directly correlates with speed, load, or volume) creates fatigue, while lower intensity work clears fatigue. This is true at every level; at the individual session level your best work will be done by identifying the movements that can be used to clear fatigue vs the movements that will create it, while at the long-term development level you can have sessions that are higher intensity and contrasted with sessions that are deliberately restorative. This last consideration is particularly important for those training more than three times per week.

Knowing all of this can help you make more informed, nuanced decisions in your workouts. If you have heavy deadlifts paired with burpees there’s no way to regulate the load on the bar, so use this as a fatiguing component of the workout and tackle the burpees at a pace that clears the fatigue, allowing you to get straight back to that heavy barbell in the next round. This is far preferable to the “Just go, go, go and see what happens” approach.

The engine is best developed from the bottom up. Take Assault bike pacing as an example. If I find that I hit a wall every time I get on the bike it’s tempting to take an aggressive approach, hammering the pedals at 70+rpm for 30-60secs and then languishing at 45rpm for the remainder of the round. All you’re training yourself to do is burn through your available fuel (Carbs) and then wait for the aerobic system to start burning fat to get you out of the hole. A better approach would be to hold 50-52rpm for the whole session, and then every session for a month, later nudging this range up to 52-54rpm the following month and make that the goal for an extended period.

Refer back to the fuel chart above. Where the depleted glycolytic system meets the ramping up of the aerobic system is “The Valley of Death”. We’ve all experienced it. Fatigue is building up faster than we can clear it and we can’t help but think “Uh oh, what have I done?”. More often than not the story has a happy ending, the aerobic system clears the fatigue to manageable levels and we finish the workout feeling better than that middle section would have liked us to believe.

If we know the aerobic system can’t be rushed into gear then take that into consideration when you start the workout. We often caution you to move at a pace that you feel might be just a little bit too slow for the first five minutes or so. This will preserve the fuel you have long enough to bridge the gap between fuel sources, and is a much better way to train in the long term.

The astute will have gathered that a lot of the vocabulary around stamina finds its roots in nutrition. Ensuring we’re consuming enough carbohydrates and dietary fat to fuel our efforts will amplify our intensity and endurance. This takes our Health and Fitness practice out of the gym and into the world.

More on this in the next one.