Recently I read an article about how even though we may be training at low intensities or heart rate ranges that correlate to "aerobic" work, that does not necessarily mean our muscles are using oxygen to produce ATP (article link: https://justinmoore.home.blog/2019/12/12/why-your-low-intensity-work-may-actually-be-hurting-you/). This is especially true if we typically spend most of our time training for power or strength.
First off when we are training for strength and power it is specific to using mainly the glycolitic and alactic system, not oxygen. Second, when trining for strength and power our nervous system adapts to contracting maximally and producing a lot of tension in the muscle. Due to this adaptation, our muscles tend to contract maximally no matter what the intensity of the demand is required. For example when jogging, the intensity of the movement is very low, so during the stance phase the quad only needs to contract submaximaly for the runner to move efficiently. The benefit of a submaximal contraction is there is minimal tension in the muscle, so deoxygenated blood can leave the muscle and oxygenated blood can enter the muscle without much resistance. The opposite is true for a muscle that is trained to always contract maximally, there is always high levels of resistance for blood to enter and exit the muscle, so typically the muscle has low oxygen saturation. Requiring it to be in a glycolitic state, even when exercise intensity is very low. So I believe this is what happens to most power/strength athletes when they attempt to perform LSD type training sessions.
I watched this happen to my hockey players in pre-season who only lifted during summer. They could not perform continuous submaximal efforts because there body was relying on the glycolitic energy system instead of the aerobic.
The problem this left me with though was how do I decrease the "resistance" in the circulatory system of my strength/power athletes so they can perform submaximal exercise aerobically, without spending to a lot of time developing the aerobic system, which may take away from my athlete strength/power abilities.
After to speaking to Cal Dietz about this predicament, I decided to go with one of his possibles ideas that could be the answer to the problem. He told me in the past when his athlete had gone through supra-maximal isometric phases that he's seen heart rates drop to between 30-35 after two weeks of the training. He believed this happened because he instructed his athletes to hold their breath during the duration of the isometric. He believed holding their breath while producing maximal force to hold position would lead to drastic increases in blood pressure, that would make the circulatory system more elastic. So when the circulatory system is more elastic it can pump more blood per beat at a stronger rate. Which removes the problem of "resistance" or occlusion at the muscle, because with a more elastic circulatory system there is less risk that to much tension in the muscle will prevent oxygenated blood from reaching the muscle.
THE ANSWER HOPEFULLY
With that in mind I decided I to run a test on myself. After performing a 6 week Strength cycle that focus on reps primarily in the time range of 18-30 seconds, so a glycolitic emphasis, I ran myself through an Deload/Aerobic Reboot. I was putting myself through this because whenever I was performing conditioning pieces it felt like it was always lactic, even when I attempted to keep my intensity low. Also I would feel smoked the day after active recovery, which tells me that i was not as aerobic as i though i was for the 40 minute low intensity session. Lastly my Resting Heart Rate was abnormally high, which I usually notice is an indicator that I am not recovering as fast as I'd like to be.
So during my Deload/Aerobic Reboot Week I decided I was going to first perform 3 sets of Overcoming Isometrics (w/ a breath hold) for my all my major multijoint movement patterns everyday (monday-saturday). I did this with the hope that it would improve the elasticity of my circulatory system, so my heart was capable of pumping more blood every beat. Below is how I performed this portion of my training:
1A. Right Split Squat DL OC Iso: 3x10s
1B. Left Split Squat DL OC Iso: 3x10s
1C. BP OC Iso: 3x10s
1D. Bent Over Row OC Iso: 3x10s
Next I performed either 10 minutes of extensive plyometrics or med ball throws for general athleticism purpose, it has nothing to do with my end results.
I followed that though with a 30-50 min Aerobic circuit that was performed via stritly nasal breathing. I base the template of my aerobic circuit off of Cal Dietz becuse I like how it has you constantly switching sides of your body forcing the heart to work harder pumping blood back and forth between muscle groups. One change I made from his typical prescription though was instead of performing one side of the body for 30 seconds of work and 10 seconds of rest, then switching to the other side of the body and doing the same. I did two intervals per exercise alternating back and forth between sides of the body for 15 seconds of work and 5 seconds of rest. the work to rest is the same no matter what protocol you follow, i just believed that peforming 15/5 and switching sides would lead to a more aerobic adaptation by limiting local fatigue and keeping it more global.
Prior to starting this week long cycle my resting heart was on average 56 the previous 7 days. Then over the course of this cycle my heart rate dropped to 45 seven days after starting. This is the lowest resting heart rate I have ever recorded on myself, so to say the least I am very happy with the result. Considering I am competitve CrossFit athlete, conditioning has been a very important component of my training the last 5 years since starting. I have comitted week long cycles to imporving my aerobic fitness in the past but have never had a resting heart rate lower than 49 by the end of the week. this leads me to believe the difference was including the overcoming isometrics with breath holds that Cal recomended. In the future once I am done with my current program I am excited to commit two weeks to this Deload/Aerobic reboot cycle as i have called to see if i can get my resting heart rate into the 30s. Cal has talked about his hockey players being in the 30s following an isometric phase, which isn't shocking considering they are elite professional hockey players.
As i get into my next three week block of my strength cycle I am excited to see how long the effect of this previous week long phase last. The training residuals for aerobic training are said to last roughly 30 days, but i will be keeping a close on eye vie RHR to see for myself.
Also the next time I start a phase similar to the Deload/Aerobic Reboot I am also going to track my blood pressure every morning to see what effect the breath hold isometrics have on that. I would assume my blood pressure would decrease if my circulatory system is more elastic, but at the same time if I have a lower RHR it leads me to think my heart would have to pump more blood every beat which would increae my blood pressure? something i definitely need to look into more because im sure there is a simple answer.
also a friend, nate wells mentioned to that the overcoming isometrics could be improving my heart pulse wave velocity which is something i've never looked into. but he sayd it is related to your blood pressure. he thinks pre and post measurements of blood pressure based on the phase could be a possible way to determine increases in pulse wave velocity.
Lastly i am excited to run a two week phase of this to see how low I can get my resting heart rte to drop. if it does drop into the 30s how that will affect my ability to recover in future phase, which im assuming it would affect it greatly in a positive manner. lower resting heart rate means lower values when i am training at higher intensities than if i were to have a higher resting heart rate.
I am looking forward to updating this next time i have the oppurtunity to run a phase similar to this one which should be in roughly 3 weeks.