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The world of exercise can feel like a confusing place, especially if you are struggling to see the kinds of changes you were hoping for when you started your fitness routine. When we sit down with clients who may be frustrated and looking for answers, we tend to always end up discussing how strength training actually works and how to do it correctly. So we thought this would be a great topic for this episode of the podcast/newsletter.
To truly grasp how strength training works, we feel it is beneficial to understand energy systems (or how our body makes energy). The energy that our body makes is called ATP. This is made essentially in 3 ways. The first is through a system known as the Creatine Phosphate system. This is energy made very quickly (basically instantaneously) through a stored form of energy in your muscle that your body can access when you need to produce energy quickly, such as when you are sprinting or lifting something heavy. You don’t have a lot of this energy as it will burn out in about 8-10 seconds, but you can access it quickly.
The second is through a process called Glycolysis. This is when your cells turn glucose into ATP. This again doesn’t make a lot of ATP, but you can produce more than the Creatine Phosphate system, as this energy can keep you going for about 27 seconds. These first two systems do not require oxygen to produce their energy, are used during intense exercise/activity, and require several minutes to replenish before they can be used again.
The third system is known as aerobic metabolism. This is the system that can produce a lot of energy, but requires oxygen to do it. It is very efficient, but is not available during very intense exercise. So basically, your body can change how it is making it’s energy depending on what you are doing in the moment. Sitting around or walking, you are using primarily aerobic metabolism. Running for your life from a grizzly bear, you are using Creatine Phosphate and Glycolysis.
To bring things full circle, we then begin discussing fast twitch and slow twitch muscle fibers. So your muscles are either fast twitch or slow twitch by nature (actually most muscles are a combination of both, but each muscle tends to have more of one kind than the other). Fast twitch are typically bigger and produce more force/power. Slow twitch produce less force/power, but can contract for much longer. This is because slow twitch muscle fibers primarily run on aerobic metabolism. Fast twitch are more Creatine Phosphate and Glycolysis.
When you go to lift a weight, your body will recruit the slow twitch muscle fibers first and then ramp up to the fast twitch fibers if needed if the weight is heavy enough. If you are not approaching failure when lifting weights, it is possible you are not adequately stimulating fast twitch muscle fibers. This is not ideal for a variety of reasons. First, as you age if you are not using fast twitch muscle fibers, you loose them. The same is not true for slow twitch. Fast twitch muscles are better suited for growth and glucose disposal as well, so stimulating them is important.
In order to do this, be sure to be lifting with high enough intensity. This means lifting in a way that you get to a point where you could maybe only do 1-2 more reps before hitting failure. Then allow yourself rest before doing the next set, this will allow replenishment of the fast twitch muscle fibers. Try to hit 10 sets total per muscle group per week. This is a great start for most people.
Simplified Takeaways…
You make energy differently depending on how quickly you need it.
Fast twitch muscle fibers make energy quickly, but fatigue quickly
Slow twitch muscle fibers make energy more slowly, but can make a lot of it and do not fatigue quickly.
Fast twitch muscle fibers will decrease with age if not used. The same is not true for slow twitch.
It is possible to be lifting weights, but not adequately stimulating fast twitch muscle fibers.
This could result it not seeing the progress you would like to see.
To avoid this, lift weights in a way in which you approach failure (usually getting to within 1-2 reps of not being able to do another rep).
Try to do 10 sets per muscle group per week as a good start.
Further Reading…
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