Review: Body by Science by Doug McGuff, MD

Low and Slow Resistance Training

I have a good friend who is usually ahead of trends, and after we both got into traditional weightlifting around 2016, my friend started questioning the powerlifting-uber-alles ideology of Mark Rippetoe after observing a Youtube video in which Rip, who is too macho to care much about nutrition, make a protein smoothie with orange soda as the primary liquid ingredient*. It’s enough to make you question his judgment in other areas, such as his insistence that the only way a real man trains is with heavy weights on a barbell doing traditional squats and deadlifts.

* It seems like some of the “macho” type approaches serve for many as a rationalization for eating too much with extreme exercise as the permission slip. It can be a net win, though many of these people will eventually get injured. Overweight and strong is still > overweight and idle.

I had my own reasons to question after throwing my back out three times, once with a deadlift, and twice with squats, even after consulting a strength coach approved by Rippetoe. I pushed the weight too high and paid the consequence. Anything more than 200 pounds was risky for my back, even if my legs could handle it. Thankfully, I recovered fully. Nevertheless, I have completely eliminated free weights from my routines to prevent further potential for injury.

Some of us, perhaps, are not meant for extremely heavy compound lifts involving the spine. I can leg press double what I could squat safely, developing my legs without putting my back at risk. I believe some of this may have to do with build. On the old Met-Life ideal weight charts, my elbow breadth places me squarely in the small-framed category for my height. I’ve noticed that the heavy weightlifters invariably have thicker joints, genetically built like bulldogs instead of greyhounds.

Yet resistance training is so beneficial it would be a shame to limit it to those who have the capacity to carry heavy spinal loads or abuse connective tissues. It is particularly helpful for aging and preventing frailty. While I have switched to a Tonal machine for my workouts these days that addresses these concerns, Dr. Doug McGuff, an emergency room physician, and co-author John Little have a prescription in Body by Science that more universally applies regardless of equipment access.

McGuff advocates for a particular form of one-set-to-failure exercise. This approach is highly time efficient and surprisingly demanding. He recommends cycling through the major compound lifts with weights sufficiently light to enable the user to take ten seconds per rep and continue for up to two minutes. Once you get to two minutes, i.e. 12 reps, you up the weight. The extremely slow reps eliminate the effects of momentum, where trainees can “cheat” by pushing hard in a stronger part of the range of motion. This deprives the muscle of constant tension and creates joint stress as the joints have to “catch” this same momentum (at the higher weights enabled by the cheating) when it’s time to reverse the rep.

Further, McGuff claims that the constant tension in the range of one to two minutes is precisely what’s needed to sufficiently tire all four of the major types of muscle fibers, from fast to slow twitch. All of these types use different fuel sources, and only a complete and total failure of all the types adequately depletes these fuel reservoirs in the tissues. In McGuff’s modality, the final 10 seconds or so of the exercise consist of shakily holding the weight in place against gravity after all hope of further movement has been totally expended. McGuff hypothesizes that the body’s being unable to move any of the fiber types, of being temporarily paralyzed by exertion, triggers a deep and threatening adaptive response that overcomes the body’s usual reluctance to invest in additional muscle mass (as much as we’d all like to gain ten pounds of metabolically active muscle, the body still thinks it’s 4000 BC and is hoarding calories for the next famine). Fully depleting all available fuel, especially in the gigantic leg muscles, also reduces insulin resistance hopefully providing for a lower bodyweight set point, making calorie reduction more tolerable with less hunger.

It gets worse. Dr. McGuff further wants you to do almost zero rest between exercises, so at the end of twenty minutes your cardiovascular system will be completely wrecked as well, forced to adapt to higher peak demand, as McGuff leans on the deep literature of HIIT-like exercise improving cardiovascular fitness more effectively than time-consuming endurance aerobics. Strangely, it is the body’s effort to replace anaerobic fuel that makes resistance training so intense - it sees this depletion as a survival threat, so extended cardiovascular benefits come after the workout as it seeks to replenish anaerobic fuel stores. I have to be careful not to weight train before giving blood, because my pulse can be elevated for hours and they won’t let me give if it’s above 100 bpm.

Some studies question the ability of HIIT-type exercises to enhance VO2 max as well as Zone 2 aerobics, which I covered in my review of Outlive by Peter Attia. McGuff, however, cites interesting research showing that VO2 max is rather specific to the muscle, in experiments where participants trained only one leg on a cycle, VO2 max increased only when exercising that leg. Other research seems to contradict this, though. It makes sense that some of the benefit would be specific and some more general, as the heart is a muscle. It seems smart to still include 2-3 hours per week of Zone 2 training, such as a light sport, hiking, or brisk uphill walking on a treadmill.

McGuff makes the case, however, of not overdoing intense aerobic exercise such that the body cannot recover, especially if stacked with weight training. He cites research showing the terrible health outcomes of people in the ultramarathoner community, including increased risks of cancer and diabetes despite being much leaner than the general population. Exercise is medicine, and there is an optimal dosage. Most people don’t do enough, but some fitness enthusiasts become addicted to the high, do too much, and harm their bodies.

McGuff calls his moderate approach high-intensity training.

Advantages

• Extreme time efficiency

• Very low risk of injury. As I get older, it’s all about “live to train another day” and avoiding injuries which will stall out gains and make me depressed from not being able to work out… The risk is all too real. I see young men blowing out ACL’s playing basketball and Ultimate Frisbee. I see so many people getting injured from CrossFit and other extreme modalities that this is the type of strength training I would most heartily recommend to others, especially those in and past middle age or with injuries or chronic pain. The older you are, the more being laid up with an injury will cause accelerated sarcopenia and make recovering to the previous level of strength more difficult.

• Better recovery. McGuff’s approach seems to produce more muscle fatigue and less overall fatigue and joint soreness. I find I can recover more quickly from single-set workouts as opposed to multiple sets to failure, which means I can work out more often. McGuff claims once every seven days is sufficient for most, but I find I can split heavy compound lifts and isolation exercises into an A and B rotation, and hit that three times a week. With less volume on any given day, I can still work out three days per week, which is helpful for managing my personal psychology as opposed to overtraining or working out only two days per week. Eventually, though, I may have to slow down, as McGuff cautions. Beginners can often work out several times per week and see consistent gains. The stronger we become, the longer it takes to recover from a workout stimulus sufficient to move the needle. The repair systems of the body do not scale linearly with muscle size and strength.

Disadvantages

• The level of intensity required, and the data necessary to track, probably means most people need a personal trainer to best implement this technique. Regardless of modality, gaining muscle mass requires lifting more weight over time, and a good trainer is super helpful in providing accountability for maximum effort to effectuate actual progress. Several practitioners are out there in major metro areas, some under the “Super Slow” certification and others as “The Perfect Workout” (the latter also does virtual training with home equipment and body weight exercises). Many of these gyms feature Nautilus equipment, which I knew about but didn’t properly appreciate. The inventor of Nautilus, Arthur Jones, designed each machine to have an asymmetrical cam with varying diameter corresponding to the relative strength of the muscle movement through the range of motion. This enables the use of heavier weight and constant tension upon the muscle regardless of angle. It’s a standard part of McGuff’s toolkit, though results can be gotten without it. The gym at my first corporate job, JNJ’s Ethicon plant in San Angelo, Texas, featured Nautilus equipment and I put on a lot of muscle while using it (and met my future wife while out there) without quite knowing why. I now use a Tonal, which eliminates the need for extremely slow reps through momentum-free electromagnetic resistance and can also, with its Smart Flex feature, vary that resistance, like Nautilus, through the range of motion based on the power curve it detects in the first few reps of the movement.

• I’m a bit skeptical of the claims of this being the “best” way to workout, because the literature seems to indicate a lot of agnosticism is appropriate. Almost anything working to near failure is going to produce about the same results, but this is the one least likely to injure anyone, and the time efficiency means it’s probably easier to incorporate without excuses. It may be best in the sense of return on investment and risk/reward only, not absolute return, and McGuff supplies this caveat in the book. For someone with exceptional genetics, very young men in their physical prime, or those taking supernormal levels of exogenous testosterone, a more extreme modality (e.g. 4-5 sets to failure, 4-5 days a week) may produce better absolute gains. Nevertheless, we’re all going to get older and age out of anything more demanding. McGuff’s modality does seem best for those with the most to gain from strength training. Hitting a 300-lb bench press PR does less at the margin for a young guy than avoiding falls does for the elderly.

Lately, Dr. McGuff has been endorsing ARX equipment, which are $40,000+ high-tech robots that implement his theories in the most extreme way possible, including 2-3x resistance on eccentrics to completely fatigue muscles past conventional failure. I like spending money on workout equipment, so I’m tempted as their well-targeted ads currently fill up my Twitter feed. Their UI is not nearly as consumer-friendly as Tonal’s, which is why they’re typically marketed for private trainers to use with clients, but ARX is only available in a select number of gyms in major metros. If I thought such a gym could at least break even on marginal costs and depreciation, it might be worth it to me to make one available locally and risk the startup capital cost.