Today’s post might seem a little all over the place, but it’s goal is lofty as I’m trying to outline some simplistic view of how and why recovery is important, ranging from biomechanics to physiology to how to lift more weight on subsequent sets. Essentially it’s a brain dump. Enjoy the ride.
Recovery is one of those features of training that tends to not get the same level of play that intensity or specific exercises gets in the interwebz and resultantly in the mass media. It’s probably one of the most important aspects of training that people don’t understand thoroughly, and is a major reason a lot of people aren’t seeing the results in the gym they should be seeing with their programs.
Most people think of recovery as kicking back and watching some Sunday football while smashing Cheetos and light beer into their pie hole. While this is a systemic passive recovery modality, it’s not the entire picture of recovery. What about rest periods between sets? What about active recovery? What about the difference in recovery from sprint intervals and long slow duration training? Do powerlifters and spin class enthusiasts have different recovery demands on their systems? Absolutely, and todays post will break down the main bullet points of how and why to recover.
#1: Cardiopulmonary Recovery
When performing hard exercise, or even any exercise for that matter, you’ll see an increase in heart rate. The amount of increase is dependent on the demands on your body to produce energy from oxygen-dependent sources, and as a result when you work at higher intensities your heart rate will go up higher than for easy stuff. The amount of heart rate increase is directly determined by how much oxygen you use to do a specific task.
If you work really hard, you can wind up out-working your bodies ability to bring in and use oxygen, which means it has to switch to a different means of energy production. This point where you body is using more oxygen than it’s taking in is the anaerobic threshold, and a common place a lot of distance or endurance athletes try to train at and around. The higher this is, the more work they can do without getting into an anaerobic state. When in an anaerobic state, you can only last for a few minutes before your body slows things down and makes you recover the difference in oxygen between what you were using and what you can bring in.
The basic premise of interval training is to work in an anaerobic zone for a certain time frame and then recover beneath the anaerobic threshold to be able to recover the oxygen needed for further work.
Once oxygen content in the body is back to taking in more than is being used, you’re ready to go again. This can be a relatively short period of time, a few seconds in really well trained athletes or 30-60 seconds in less trained individuals, and is again dependent on how much oxygen deficit was built up with the anaerobic work. For near maximal work output it could take a few minutes to completely recover the spent oxygen.
Instead of using a timeframe for recovery (ie. 60 seconds), a more specific model to see optimal cardio recovery would be to return to activity when the individuals heart rate is back to within a target based on their starting heart rate. For instance, if my resting heart rate is 70 and my max is 190, the range between these two is 120. I would want my heart rate to recover to within 30-40% of my range (classically called the heart rate reserve) based on the intensity I was working at. For instance, if I’m working at an intensity of about 170 bpm (83% of maximal range) and maintaining for 3-5 minutes, I would recover with very low intensity exercise until my heart rate returned to about 110 bpm (40 beats above resting, or 33% of the total range). This is just one instance, so don’t take it as the entire way of doing things.
Typically, systemic recovery from cardio work, even work done above the anaerobic threshold, is very rapid. The only longer-term recovery need is something called exercise post-oxygen consumption, or EPOC. This is where you continue to need a higher than normal rate of oxygen intake for a few hours after higher intensity work. Most people could realistically get in 2 or more cardio sessions each day if needed and not see any specific detriments to performance or health, as long as they were also getting substrate recovery as well, which is the next section.
#2: Substrate Recovery
The body uses different types of fuel depending on how intense the exercise or activity being done is and how hard it is on the body. Fatty acids are used when the intensity is mind-numbingly low, which is pretty much when you’re sitting or slowly walking around. Essentially, you’re in the “fat burning zone” all day when you’re on the computer. The downside is your body uses this fuel source like a Prius uses unleaded. It sips it slowly, which means it’s a pretty low benefit system if you want to lose body fat.
Glucose is used with higher intensity work, and is broken into slow and fast glycolysis. Slow glycolysis is used when there’s enough oxygen to make your mitochondria earn their keep, and produces a lot of energy from a relatively small energy source. When oxygen utilization exceeds intake (anaerobic), you switch to a fast glycolysis to help meet the demand greater than slow glycolysis. This produces power, but less efficiently and is dependent on the availability of enzymes to make the reaction happen and the build up of metabolic byproducts from anaerobic metabolism that slow everything down and make you hate life during the hard work.
Fatty acids are always around. Unless you’re drowning, oxygen should always be around too, so glucose and fatty acids can be used with pretty much anything in near endless amounts. When the intensity and duration are a little higher, you can wind up running out of glucose, which is why endurance athletes carb load to build a bigger gas tank. When intensity goes up, much like with cardio recovery, you can only manage a higher intensity until you run out of juice or other byproducts get in the way. Once you recover the oxygen and get the byproducts cleared out with your normal circulation, you can go again.
Creatine phosphate is another beast. It’s used with maximal and near-maximal intensity activities, doesn’t need oxygen to work, and produces a sickly inefficient amount of energy per unit compared to fatty acids and glucose. As a result on the intensity and inefficient use, it winds up getting burned out quickly, and takes a fairly long time to recover. For a 10 second maximum intensity bout, it could take about 5 to 10 minutes to completely recover the creatine phosphate to go again, which is dramatically longer when you compare the work to rest ratio for some of the glycolysis intervals.
Based on this admittedly over-simplistic representation of recovery times, the higher the intensity, the longer the recovery time needed.
For non-anaerobic intensities, recovery is more based on mitigating tissue damage from the workout, refeuling, or changing the activities to something different to kick into a different group of muscles being used.
For the anaerobic intensities, recovery is a little more challenging to nail down. Again, it’s not going to be a set time frame for everyone. Interestingly, a lot of recovery seems to correlate to respiratory rate. When the heart rate drops following exercise, it means there’s oxygen hitting the tissues and balancing things out again, which sends a signal to the heart to slow down. Breathing rate tends to stay elevated for a while after heart rate normalizes, which could give a clue as to how long recovery is needed.
For a completely non-specific method of determining respiration rate recovery, I’ve used 25% of the difference between resting and max respiration rate as a good target. This means if someone breathes 20 times in a minute at rest and 32 times a minute when working really hard, when their breathing rate returns to 24 breaths per minute, it’s time to go again.
This is only when you want maximal power output or speed, like in powerlifting or sprint work. If you’re looking for metabolic conditioning for the purpose of fat loss or sport specific conditioning, I would opt more for heart rate recovery.
#3: Tissue Recovery
This is again intensity dependent, but is more of a macro view of recovery versus micro. Essentially, this looks at how long specific tissues take between training sessions to recover to get back into action again.
Depending on the intensity of activity, specific muscle fibers will work more than others. With lower intensity, you tend to use more type I fibers, which have lower force production capacities but can withstand fatigue much longer and recover very quickly. For higher intensity activities you tend to use more type II fibers, which have faster and greater force production capacities, but fatigue faster and take longer to recover.
The in-set recovery windows are as much for the substrate and oxygen as the contractile properties of the muscles themselves.
Intensity aside, volume is another determinant of recovery. For higher volume workloads, a greater amount of delayed onset muscle soreness and micro damage to the muscle tissue accumulates, which makes you feel like ass about 2 days after the workout, especially if the movements are novel. If the volume is low, the intensity can be very high and recovery will not be much, but once the volume starts creeping up to something akin to a Smolov cycle of hell on wheels, recovery gets compromised to a couple of days before you’re ready to roll at an optimal level.
For the majority of workouts you’ll see in the gym, muscle recovery will be within 2-3 days, sooner if the intensity is lower, even sooner if the volume is relatively mild, and if the workout spreads load throughout the body it can be even sooner, to the point of doing 2 workouts a day without issue. Training experience plays a role in this as well, as more experienced lifters recover from their workouts sooner due to built in mechanisms to speed recovery, like a greater number of satellite cells on the muscles and greater blood delivery into muscles to speed nutrient delivery and waste removal.
With very high intensity workouts, such as max effort lifts, sprint work (real sprint work, not TABATA bastardizations), the determining factor is central nervous system recovery. Essentially, the ability of the brain to send strong and rapid impulses to the muscles begins to degrade with intensity and it can take time to recharge the neurotransmitters that connect the nerve to the muscle, as well as to form the impulses at the level of the brain.
In the hegemony of recovery, neural recovery takes the longest. For repeated bouts of sprints, it could take between 5-10 minutes to be able to replicate the same absolute power output from one set to the next, and if speed or time to cover a certain distance begins to fall by more than 10% it could mean inadequate recovery. For instance, if someone is blazingly fast and can cover a 40 yard dash in 5.0 seconds (we’re not talking combine potentials here just yet), if repeated measures wind up producing 40 yard times at 5.5 seconds or more, recovery periods are either too short or they’re fried and further sets should be stopped.
Full neural recovery can take up to 36 hours in my experience with athletes and also my own training. For the first 3-6 hours, and even sometimes for the first 24 hours, the person can feel like they have the flu. The first hour after the training they may feel really energized and ready to tear into a brick wall, but then it hits them and they don’t feel so hot. It seems like you could set your watch to it for 36 hours.
For this reason, intense workouts shouldn’t be too frequent or in too high of a volume, especially with beginners or novice exercisers.1-2 neural workouts would suffice in a week, as well as 2 low intensity workouts and 2 moderate intensity moderate volume workouts. These could be weight training, cardio, whatever you’re doing, as long as it works to your goals. When possible, try to follow neural workouts with a low intensity “recovery” workout where you just do spinning, walking, etc in order to get blood flowing and to loosen up.
THis little graphs should give a better idea of what recovers faster. The size of the box determines the length of recovery needed, and is in no way measured to be scientifically accurate.
Mental recovery can be pretty fast. Some people want to jump right back into their max weight sets while still breathing hard from their last set! It can be one of the things that stays in a switched on mode or is very difficult to get motivation to train for others. It’s somewhat of an “X-factor” in recovery, which is why it’s to the side.
To determine how fried your nervous system is and whether you’re ready to train, you can look into a heart rate variability measurement device. I’ve used one for a while and it was really interesting to see how it varied based on stress and training.
So what does this all mean? Essentially, the harder you work out and with the more volume, the longer it will take to recover fully to be able to train with similar intensity again. When volume goes up it takes longer for the muscles and substrate to recover, but with lower volumes and stupid high intensities, the recovery will be dependent more on how quickly your nervous system can recover, as your cardio and substrates will recover relatively quickly. However, what we can all agree is that there will be no recovery for Family Guy after they killed off Brian.