Sunday, July 9, 2017

Introduction to low load strength training with muscle O2

After 20 years of weight training, my rotator cuff impingement was finally getting the best of me.  I had already tried most non surgical treatments but finally came to the conclusion that the absolute load of the chest press was the culprit.  So my new project was to find a way to optimize lifting lighter loads in order to have similar results in muscle mass and perhaps strength.
Over the years I have read with interest the weight training literature in regards to blood flow restricted techniques (otherwise known as kaatsu) and lower load lifting without restricting cuffs.
Instead of using compression cuffs to impede blood flow, many investigators use low load training, (for example an exercise workout would consist of about 40% of the 1 rep max, 10-15 reps over 30 seconds, rest 30 seconds and repeat for 4 sets total).
The idea behind the above, is to create muscle ischemia by using the muscle itself as the “tourniquet” thereby limiting blood flow instead of using pressure cuffs on the limbs.  The force of the "muscle squeeze" can be sufficient to limit blood flow.  The advantages to this way include: being able to train central muscles not able to be cuffed, safety, less obtrusive looking in public and avoiding costly cuff regulating equipment.
The problem however is that one really does not know for sure if you are achieving reasonable muscle ischemia with the weight lifted, as well as the effects of time under tension, range of motion, rest/work intervals chosen.  In other words, we don't really know the actual muscle oxygen saturation levels as the exercise is taking place.  Studies have shown that the perception of fatigue is not always related to muscle O2, (if at all) so the "no pain no gain" approach is not valid.
Many of the studies done use the concept of a proportion of the one rep maximum as a lifting target. What should you lift if you don’t know your 1 RM?  Is that concept truly valid?  Perhaps one can get good results with 20% of the 1 RM, or maybe you actually need 50%.
Depending on your injury, ability, innate strength it is really hard to know.  

An interesting solution utilizes a portable, inexpensive muscle oxygen sensor to guide the fine tuning and application of the above concepts.  Low cost muscle oxygen sensors are now available that will transmit to many activity watches/smartphones.  My goal in this post is to get a user up and running with this and go through a typical strength training session.  In future posts I hope to go through various aspects of basic science, sports physiology in regards to this technology and how it may help with optimal physical training and performance.  I will also explore endurance sports, especially cycling which is another interest of mine.  But, In my opinion (thus far), the use of this tech in improving your cycling ability is probably limited at best.
The main practical application is in strength training and rehab of injuries where the subject just can’t conventionally train (greater than 70% 1 RM).

The gear:
There are 2 sensors on the market that are mobile units, small and reasonably priced.  The Moxy sensor and BSX Insight.  I have the BSX, reason being it’s a bit smaller, flatter and cheaper than the Moxy.  The Moxy has better software and support.  Both transmit Ant+ (a form of bluetooth) that can be read by many Samsung/Sony android phones as well as Garmin watches (check specs before buying).  The BSX needs to be started via your smartphone, but once it’s transmitting, you do not need the phone and/or can kill the phone app.  You will need to pair the unit with your device and use software to record the data.  Garmin watches running the Moxy Run software app will record and upload the data for you to Garmin’s site.  If you are using an android smartphone, Ipbike will pair and record the data as well.  The data file can then be looked at by software (Golden Cheetah) or uploaded to a 3rd party ( which supports the O2 and total hemoglobin data fields.
My initial setup was:
BSX (about 250$)
Android phone to start the unit (already had one)
Compression garment (variable $)

I use both Garmin Connect and Cycling Analytics to view the data.

Note: make sure you follow the directions to update the BSX firmware if asked when you set it up. Details are at their website.

How to place and use the sensor:
This is a major issue as poor placement, loose sensor contact will give erroneous results.  I initially tried tape, various stretch wraps but finally settled on tight compression garments as the preferred method.  Yes, one could use tape/ stretch wrap to put the sensor on the bicep for example.  But what happens when you switch machines and want a placement elsewhere on the arm.  Even worse, the lats, chest, abdominal areas are not that easy to get a good tight contact with tape.  Using Skins compression longsleeves shirts (or tights on the legs) one can get stable placement and still easily move the sensor around when needed.  The other thing needed is reasonable light shielding to the sensor.  The sensor tech uses light to measure the oxygenated hemoglobin, bright light washes out the led pulses.  Make sure the compression garment is black.  If you are outside, you may even need another black layer (Skins black tights under black bike shorts work fine in the Florida sun).  Indoors, only the black outer layer should be sufficient.

Comparing muscle O2 desaturation in training:

In a moment we will look at a couple of strength exercises effects on oxygen saturation, as well as total hemoglobin.  But a couple of thoughts.  There has been a quite a bit study data showing that sensor location placement on the muscle can give very different patterns and degrees of desaturation.  So if you are comparing routines (for example: is a shorter rest between sets helpful, or lighter loads able to desaturate) on different days, the placement may not be identical.  My advice is to do your comparisons without moving the sensor off the muscle.  If you are just monitoring your status/workout, then a bit of variation in O2 sat is not going to matter much.
Another thought relates to the degree of desaturation measured.  These devices are calibrated to a certain skin thickness, muscle depth.  So an area of less thickness (biceps) may read much differently but it does not necessarily mean you are getting a different desaturation.  Also some muscles may just not desat as much as others for various physiological reasons.  Lastly, depending on the exercise, the main target muscle group will desat more than a secondary target.  A good example (for me) is the row: my biceps don’t desat nearly as well as the lats with a low load.  But at high loads (5 RM) both desat well.  This information can be used  to help in adding training routines to the muscles that used to desat well with conventional weights but not so well with low load.
Lastly I do want to add that most if not all studies show that conventional strength training(whether undulating or classic periodization)  is still the way to go for peak results.  If you are nursing an injury, lower loads may not only maintain what you have acquired but help repair your injury (future post).

Much can be written about studies looking at the hormonal changes induced by resistance exercise.
Since the theme here will be aiming for good tissue oxygen desaturation, let me at least show a bit of data supporting that approach.  
A older study was done looking at conventional training (4 reps x 4 sets of 90% 1RM) vs low load (15 reps x 4 sets of 60% 1RM), with 3 min rest between sets.  
Testosterone and growth hormone elevations were stimulated better in the lower load group and appeared to be related to deoxygenation kinetics.

A practical example:
Proof of concept:  Can we get reasonable desat with lower loads on a targeted muscle?
Sensor placement is on my latissimus dorsi, and we are looking at muscle oxygen, total hemoglobin on two different days.  On the first day, I kept the sensor in the same place and did 3 sets of Pulldowns.  The first set was 8 reps (8 RM load), then 10 reps (10 RM load) and lastly the low load slow technique (40% 1 RM--about 1/2 of the 8 RM load- 7 reps over 45 sec).

                    8 reps                        10 reps                                        low load set                              
As you can see the O2 drops are better with the heavier weights, but not by much.  In addition, the area under the curve is probably better with the low load since the set lasts longer.  The total hemoglobin is suppressed more with the heavy load as well, but the low load does have some restriction.  One project is to get better hemoglobin suppression by perhaps restricted range of motion to maximize the muscle pump activity (future post) and prevent blood in flow.

Now a look at 3 sets of low load (different day so the O2 may be a bit different) on the same muscle:

                   Low load                                     low load                              low load                             
My currently used protocol consists of 3 sets, about 40% 1 RM, 45 secs each set, about 7 reps then rest 30-45 secs. I have been looking at shorter/longer rests, fast vs slow motion, range of motion and the above will give you a good result, but I suspect it can be fine tuned further on an individual basis (one reason not to do this type of workout by a “formula”).  In addition, it’s possible that one person may show different patterns of response and do better with an altered protocol. 

An example how little weight is needed with certain muscle groups with proper targeting.
The sensor was on my bicep, the first 3 sets are with 23 lbs, 45 seconds on then 45 second rest x 3 sets, immediately followed by just 13 lbs (to see if the desat was still present) and a last control set back to 23 lbs.

           23 lbs                    23 lbs                  23 lbs                  12 lbs                      23 lbs                 

In comparison, here is the sensor also on the bicep, but doing a row (I picked the row because it has a large discrepancy with muscle activation on the lats vs biceps) at a heavy load- 5 RM:

So no problem with O2 desat with a much heavier load (and a very short time under tension)and good total hemoglobin reduction (muscle squeeze).  There is certainly nothing wrong with doing the heavier weight, but if you are injured/rehabbing, one can "make do" with a light load targeted properly.

But targeting is definitely an issue with lower loads:

Here is the same row machine as above, sensor location also on bicep, but using the light weight protocol:

Poor desat on the biceps with the light load (but would have worked fine using a simple bicep curl at very light weight).  Note also the minimal changes in the total hemoglobin (red) tracing, indicating minimal "squeeze" of the muscle restricting blood flow.

  • Bottom line-be careful where you measure and how you train.  A non targeted muscle may have great desat at high loads but will be "neglected" at low ones. You may need to do extra sets on the less targeted exercise (like the simple curl) to compensate for less spill over when you can't hit the higher weights.

Take away points:

  • Abundant study data indicates that low load resistance training will give good results for muscle mass and strength gains.
  • However low load training is not superior to conventional training in regards to the above.
  • Low load training is aimed at individuals who are unable to lift high loads because of injury, joint disease, surgery post op, age related weakening of connective tissue or perhaps as a variation of periodization protocols.
  • Using a muscle oxygen sensor may help guide low load training for the most optimal results.
  • Knowing the quirks and limitations of the sensor tech is important.
  • In the following pages, real life examples will be reviewed to explore this in more detail...

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A disclaimer.  This is not meant to be medical advice, a substitute for physical therapy but a series of concepts and examples of what can be done.

The author is a fitness enthusiast with an M.D. degree and 20 years of both strength training and cycling experience.

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