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What Happens When You Train 2: Conditioning Exercises

Our final installment in our short blog series on what happens when you train discusses what happens during and after a workout that focuses on conditioning. First, know that the ‘split’ between resistance and conditioning work is artificial.  It helps us understand what’s going on, but there is no such thing as resistance training without a conditioning element, or conditioning workouts without a resistance element.

Related: What Happens When You Train 1: Resistance Exercises

As in resistance work, conditioning work causes changes to your neurological, endocrine, immune, and metabolic systems.  Instead of repeating that information, however, here I’ll discuss what happens to improve your ability to deliver energy to sustain work.

The body really “burns” only one fuel: ATP (adenosine triphosphate).  But we have four ways we can produce ATP.  These are: aerobic lipolysis, aerobic glycolysis, anaerobic glycolysis, and the phosphagenic system.  We’ve covered these in other blogs, so please look at those if this is new to you.  Here, we’re talking about what changes in these systems in response to a workout.

The adaptations you build depend on the stress your workout applied. 

As you finish a workout, you do your cool-down (right?!) to lower your core temperature, return your heart rate to normal, and activate your parasympathetic nervous system (rest and digest).  This tells your subconscious (often referred to as your “body”) that the stressful event that was your workout is now over and it can devote resources to repairing the damage and “supercompensate” to improve your abilities, so you’re more capable of handling that kind of stress again.

The adaptations you build depend on the stress your workout applied.  This is known as the principle of specificity – you adapt to the specific demand placed on you.  Note: CrossFit’s “constantly varied” aspect means exposing you to lots of different demands, to build the broadest possible fitness, as opposed to, say, a runner who wants to run a specific distance as fast as possible.  With four major sources of ATP, we need to discuss these separately.

For extremely short, intense bursts of activity, the phosphagenic energy system (also known as the ATP/CP system) predominates.  It adapts to these stresses by increasing the number of mitochondria you have, which increases amount of ATP and creatine phosphate you can store and burn at any at time.  You also build more of the enzymes that help these reactions occur, ATPase and creatine kinase.  More energy available faster = stronger and faster muscle contractions = improved performance.

Related: Intensity: the Key to Improving Your Physical Fitness

For workouts that really make your lungs and muscles burn, your body responds by improving your glycolytic capabilities – the ability to turn sugar into ATP rapidly without using oxygen in the reaction.  Protein and fat cannot be metabolized without oxygen.  Only carbohydrate can supply energy this way.  This is one reason the system has only limited capacity.  One response is to increase the ability to store carbohydrate, either as glycogen in your muscles or glucose in the blood and liver.  Other responses include increasing the store of enzymes needed to process sugar, the number of mitochondria available for these reactions, the amount of the enzymes and other chemicals needed for the Krebs cycle, which converts the waste product pyruvate into ATP.

For longer workouts, or those with significant rest breaks between efforts (interval work), you respond by improving your ability to turn sugar into ATP with oxygen.  This has similar effects to those discussed immediately above and some additional results.  These include increased mitochondria, improved efficiency of Type I (“slow twitch”) muscle fibers, and faster processing of both lactate to prevent its accumulation and hydrogen ions to prevent that burning sensation associated with fatigue.

If you do our Burn45 class, or take an easy run, bike, or swim, you’ll improve your ability to utilize fat as fuel.  This is because while fat is an extremely rich source of fuel (potentially over 300 ATP’s per fat molecule, depending on its size), the reactions required to convert it to ATP are relatively slow, and can’t provide energy fast enough to power intense work.  Hence the name “Burn45”, and the need to keep the intensity down during it.  After such a workout, your body responds by increasing its ability to perform the series of reactions called “beta oxidation” which prepares a fat molecule to enter the Krebs cycle and “electron transport chain,” both of which result in ATP.

Related: The Importance of Recovery

As with resistance exercise, these responses are subconscious, but they are what we seek when we train.  Our programming is designed to maximize positive responses across these energy systems.  It is important to ensure you (1) work hard frequently in the gym and then (2) allow these systems time and energy to do their work, so you can reap the benefit of your hard work.

Please contact me if you have any questions about how our programming can maximize your fitness gains from your time and effort!

John Bryant

Founder & Head Trainer

john@crossfitslipstream.com