Ice bath before exercise increases performance
Summary
Mitochondria in your muscle cells convert glucose & triglycerides (fats) in your bloodstream into the mechanical energy that moves your muscles.
Heat production during the energy conversion can damage mitochondrial DNA.
Fatigue is one way your body protects mitochondria from damage.
Cooling your body prior to exercise will increase peak power performance of your muscles & postpone fatigue.
How to boost peak muscle power by more than 20%
Over fifteen years of research at Stanford University was confirmed by a single email I got from Mike Pullano of ARX Fitness in Austin TX.
Mike is in a unique position within the fitness community because his ARX machines are unlike any other. Rather than working by constant resistance (like a barbell), ARX works by constant velocity. That is, displacement sensors control the position of the load plate over time, while a computer adapts resistance to match the force applied by the athlete.
Built-in software records force applied to provide real-time feedback and create an archival record of the quality of the workout. In other words, no one in the world gets more data on their workout performance than Mike's ARX customers.
After we installed a Morozko Pro ice bath at ARX headquarters, this is what Mike wrote to tell me:
For the past year, I've hosted 30+ friends at the ARX headquarters on Sundays. I open the facility to them and give them access to ARX, Biocharger, Neufit Neubie, Joovv, and now the Morozko Forge ice bath. Some people have months and months of data to compare to. After a few weekends of having the ice bath, multiple friends brought me over to the ARX machines to ask me why they saw a MASSIVE increase (5-18%) in their numbers out of the blue? The answer? They all did the cold tub PRIOR to the ARX workout. This scenario continues to play out each week and I'm convinced that doing the tub BEFORE an ARX workout is a good idea.
Joe Rogan has noticed the same thing.
Joe Rogan explains his new precooling practice to David Goggins, on the Joe Rogan Experience podcast.
Heat extraction
Mike was noticing the same phenomenon measured by Stanford scientists Dennis Grahn, PhD and Craig Heller, PhD. In a series of experiments dating back almost 20 years (e.g., Grahn et al. 2005) they discovered that extracting heat from the palms of working athletes increases performance by postponing fatigue. One study of intermittent cooling during rest/recovery periods between sets measured a 40% and 144% improvements in bench press and pull up work volumes (Grahn et al. 2012).
While scientists have known for decades that cold therapy improves exercise performance in heat-sensitive subjects like those suffering from multiple sclerosis, Grahn & Heller were the first to perfect a percooling (during workout) protocol for accomplished athletes.
However, their technique is complicated.
The problem is that not all areas of the skin are efficient for heat extraction. For example, the chest, back, and legs are inefficient locations through which to cool the body. The anatomy of the palms is particularly well suited for heat extraction, except for the fact that application of cold packs to the hands can cause vasoconstriction, slowing blood flow and impeding cooling.
To overcome the vasoconstriction effect, Grahn & Heller designed a device that accelerates cooling by applying a vacuum to promote blood flow at moderate (not freezing) temperatures. When researchers in the United Kingdom recently attempted to reproduce results without the vacuum and colder temperatures, they failed to observe any performance enhancement (McMahon et al. 2022).
So for palm cooling, the vacuum is critical.
But what about whole body?
Fatigue protects mitochondria from damage
It has long been a mystery to me why our bodies should experience fatigue. Although exercise science is aware of some phenomena, such as lactic acid build up in muscles, this doesn't explain cognitive fatigue, nor what evolutionary biological advantage might be served by exhaustion. However, I've recently learned that mitochondrial disorders are implicated in chronic fatigue syndrome (Maksoud et al. 2021) and that's led me to become more interested in metabolic theories of fatigue. For example, some scientists suggest mitochondria are the limiting factor on our capacity to perform work during exercise (Lavorato et al. 2018).
Consider the case of a 28-year old man who suffered from exercise intolerance -- i.e., "lifelong the inability to exercise" (Bromham et al. 2003). Even brief periods of exertion, like running a few steps, left him in a state of fatigue that ordinary rest could not remedy. He was otherwise healthy and presented something of a mystery to medical science until doctors discovered that his mitochondrial DNA was missing a critical gene. That is, the source of his incurable fatigue was mitochondrial disorder (Schwarz & Vissing 2002).
His extreme case reinforces the hypothesis that exercise fatigue is due to limits in mitochondrial function.
Exercise presents two problems to the human body: 1) obtaining enough energy to carry out the will to keep going, and 2) protecting the body from overheating.
The first problem is easier to solve than the second, given the ability of our bodies to mobilize white fat reserves to fuel our metabolism. More of us have plenty of excess energy stores and would be glad to get rid of them.
However, the second problem is more complex.
As exercise warms the human body, several mechanisms begin that will protect us from the damage of overheating (hypertrophy). The first of these is sweat, which cools the skin by evaporating water stored inside the body to the surrounding air. That's why humid air always feels warmer than dry air, because the rate of sweat evaporation is slower when the humidity is high. The second mechanism of protecting the body from overheating during exercise is fatigue. As the body warms, fatigue makes further exercise more difficult, slowing the rate at which the body generates heat that must be removed from the body.
Without fatigue, the waste heat generated in your muscles would overheat your mitochondria, causing irrevocable damage.
The mechanical efficiency of muscles is only 20–30%. When exercise is continued over a long period of time, the internal body temperature increases because the energy created by the skeletal muscle metabolism is largely converted into thermal energy. Maintaining a balance between heat production and heat removal during exercise ensures that you can continue exercising, preventing the development of thermal shock. - Jastrzebska et al. 2022
The importance of this heat/exercise relationship was underscored in a recent study of 23 men of various fitness levels. Researchers measured the skin temperature of the subjects immediately after strenuous exercise, and again a few minutes later. Those subjects who cooled the fastest were also exhibited the greatest cardiovascular fitness levels (Jastrzebska et al. 2022).
If that's the case, then we should all experience a greater capacity for strenuous exercise when we have access to extra cooling -- just like when a cool breeze or a dip in a cold stream refreshes and energizes us. Removing that excess heat from the body signals to our mitochondria that they are not at risk of hyperthermic damage, and consequently are free to process more glucose and fats into new energy and perform at a higher level of cardiovascular fitness.
Precooling vs percooling
Grahn & Heller were extracting heat from the palms in the middle of the workout -- e.g., during rest periods between sets -- which is called percooling.
But Mike's customers were precooling in whole body ice bath before their workouts, so how did they get similar results?
In Dangers of Deliberate Cold Exposure I wrote about the phenomenon of afterdrop, in which core body temperature continues to decline, even after emerging from the ice bath. Unlike the palm-cooling device that operates under a vacuum, cold water immersion will cause vasoconstriction -- particularly in the hands and feet. However, when blood returns from the core to the extremities, as during a post-ice bath workout, it contacts the regions of the skin and muscle that were cooled during the ice bath prior to returning to the heart. Thus, heat is transferred away from the blood into the cold skin.
Precooling stores cold in the extremities to prevent overheating during exercise -- i.e., starting at a lower skin temperature slows warming of the body and postpones fatigue.
This observation is more evidence that suggests you should not be using your ice bath to recover from your exercise. You should be using exercise to recover from your ice bath.
Precooling protocol
Several scientific studies have confirmed the precooling effect for enhanced exercise performance. For example, a study of 14 male runners discovered that whole-body precooling in 5C air improved endurance and reduced cardiovascular stress (Lee & Haymes 1995). Similar results were found for whole body cold water immersion in cyclists (White et al. 2003). A recent review found that precooling prior to exercise in the heat was more effective for thermal management than ingesting fluids (Alhadad et al. 2019).
The precooling protocol that works best for you might be different from the methods employed in those studies. Nevertheless, here's a protocol from which you can begin, and then adapt to suit your body and your workout.
20 minutes prior to weight training, precool with whole body deliberate cold exposure in your ice bath. Submerge all the way up to your armpits -- not just up to your waist. Studies show that partial cold water immersion produces different effects than whole body.
Carry out your normal workout within 20 minutes of your ice bath.
During the rest/recovery periods of the workout, if you have access to a palm cooling device that operates under a vacuum, use the device to extract heat and reduce fatigue. However, do not cool your palms by submerging them in the Forge during your workout. The ice bath water is so cold that it will reinitiate vasoconstriction in your palms, and prevent heat extraction.
After training, wait 3-4 hours before any further cold therapy for maximum anabolic gains.
However, during multi-day competitions, ice bath immediately after competition to restore muscles to maximum performance faster.
UPDATE 20 Sep 2022
A new study out of Japan found that percooling during a workout improves peak performance. Scientists tested 12 male university rugby players on an exercise bicycle in hot conditions. Athletes improved peak performance when they drank who drank a −2°C ice slurry beverage, compared with those who drank the same beverage at 30°C, or 30°C water.
Meanwhile, a similar study of New Zealand rugby players found that percooling with ice slurry and ice towels resulted in an similar improvement in peak power performance during 4 min cycling trials (Fenemor et al. 2022). These findings corroborate our experience, which is that ice cooling improves exercise performance.
UPDATE 26 Oct 2022
An Australian study tested the effects of pre-heating workouts by subject athletes to hot water immersion (HWI, or hot tub) prior to bicycle sprints. They discovered that pre-heating diminishes performance by about 15%, which reinforces the theory that fatigue is the body's way of protecting mitochondria from damage from overheating (Dennis et al. 2022).
UPDATE 26 Nov 2022
A new study tested the effects of continuous cooling on long-distance runners. Research fitted an experimental group of runners with a cooling cap, and a control group with caps that had no cooling.
Guess who ran faster?
Runners wearing the continuous cooling cap ran faster. They also experienced lower forehead temperatures and reported greater thermal comfort (Spannagl et al. 2022).
UPDATE 6 June 2023
Yet another new study showed benefits of pre- and percooling on exercise performance. In this one, eight men were evaluated for exercise performance on a stationary bicycle in hot environments. Researchers measured exercise performance when ingesting an ice slurry prior to and during exercise in both humid and dry environments, compared to ingesting only warm water.
By now, it probably doesn't surprise you to learn that the cooled cyclists performed 75% better under humid conditions than the control group that was hydrated, but not cooled. (Under dry conditions, the effect was only a 25% improvement, Choo et al. 2023).
What might surprise you about this study is that skin temperature in the precooled group started out higher than in the control group -- despite the fact that core temperature was lower.
Compared to ice baths, drinking an ice slurry puts the cold inside the body. By dropping core body temperature without activating the thermoreceptors on the skin, it's not clear how the autonomic nervous system that controls brown fat activation might respond to drinking the ice slurry. However, what really interested the authors is the impact on sweating.
They acknowledged that prior studies have noticed that ice drinks reduce sweat, and that previous authors have speculated that the lower sweat rate during exercise in the heat might be detrimental.
An important limitation surrounding the use of ice drinks relates to its negative influence on sweat production. Indeed, intermittent ingestion of ice drinks has been shown to transiently decrease local sweat rate, leading to a lower net heat loss during exercise in hot and dry environments. Given that sweat evaporation is the only unidirectional pathway from the skin to the environment, and the only means of heat loss when air temperature exceeds skin temperature, it has been purported that ICE may negatively influence heat balance during exertional heat challenges in hot and dry environments. - Choo et al. (2023)
These new findings suggest that per- and precooling with ice drinks is beneficial for exercise performance in hot environments, despite the reduced sweat rate. Perhaps the body doesn't sweat as much only because it doesn't have to.
About the Author
Thomas P Seager, PhD is an Associate Professor in the School of Sustainable Engineering at Arizona State University. Seager co-founded the Morozko Forge ice bath company and is an expert in the use of ice baths for building metabolic and psychological resilience. Subscribe to https://seagertp.substack.com/ for more information from Seager on taking charge of your own physical & mental health.