Not so fast: Major issues found with 2023 study showing no effect of palm cooling

Not so fast: Major issues found with 2023 study showing no effect of palm cooling

This post is a research review and commentary on the following two articles published in the Journal of Strength and Conditioning in 2023. These articles have been cited as "proof" that palm cooling does not improve performance.  I decided to do a deep dive into the validity of the design and their claims. 

These are the two articles:

1a. The Effects of Palm Cooling on Physiological and Metabolic Responses, Exercise Performance, and Total Volume During High-Intensity Bench Press Exercise in Resistance-Trained Men

1b. No Effect of Interset Palm Cooling on Acute Bench Press Performance, Electromyography Amplitude, or Spectral Frequencies in Resistance-Trained Men

Description of the Study

In short, this study looked to see if there was a difference when palm cooling vs not when resting between sets of bench pressing to failure.

Subjects: 11, healthy, college aged, males with 3-7 years of upper body resistance training experience were included.

Study design: Randomized, double-blind study, with 4 days recovery between the experimental conditions.

Experimental conditions: comparison of thermoneutral (no cooling) vs palmar cooling at 10 deg C (50 deg F) and palmar cooling at 15 deg C (59 deg F).  

Study protocol: 4 sets of max effort bench press reps at 80% of their one rep maximum at a controlled  pace with 3 minutes of rest between each set. The experimental condition of palmar cooling (at 2 different temperatures) was applied for 1 minute of the 3 minute rest periods between sets (cooling applied from seconds 30-90 of the rest period).

Findings: The combined findings of both papers state palm cooling had no observable effects on physiological, metabolic responses during exercise, nor has it any effect on bench press performance, volume load or neuromuscular responses compared with a thermoneutral condition. 

Now that we've described the study, let's examine it critically. 

Critical review of the study

2 Articles, 1 Study

The first issue is that there are two articles published from the same study. These articles used the same data to publish two different articles. This is not uncommon in the research world. However, if someone were to do a research review on the topic of palm cooling they would see that there are two articles from 2023 showing no benefit from palm cooling. This is misleading as it creates the impression that two different studies found no difference, which is not true. Again, this is common practice in research but to the lay person trying to determine if using palmar cooling is worth the investment this could unfairly tilt the scales.

Intervention stopped short and watered down 

This is a well designed study at first glance and even when you dig into some of the details. Many variables were smartly controlled for: tempo of reps, experience of lifters, blinding of participants and graders to testing situations and number of days between testing situations. All of these decisions created the opportunity for a great study. 

The experimental variables were excellent choices as well as there is no current consensus on what temperatures are best for applying palm cooling. This test investigated both 50 and 59 degrees Fahrenheit (which are within the range that most experts suggest and prior studies have investigated) and compared them to a non-cooling control situation. 

Where and how this study may fall short of contradicting prior research showing the benefit of palm cooling for enhanced performance. The shortcomings can be broken down into two categories; too little volume and the duration of cooling was too short.

  1. Palm cooling is a method of improving performance through enhanced training volume. Increased volume can be achieved with more reps per set and/or more sets per workout in a resistance training study. This study investigates volume through reps only, as the number of sets are capped. 
    1. This study has only 4 sets of exercise (bench press) included. The first set establishes a starting point so then there are only 3 sets from which to find a difference in performance/volume (reps per set). From my experience of using palm cooling in over one thousand personal and supervised workouts, three sets is too few to find a difference between groups. In a sense, this study may not have given the intervention (palm cooling) a chance to show it's benefits. Perhaps a study comparing 10 or more sets or another that allows for additional sets to be granted based on sustained performance would identify a difference.Figure from palm cooling study showing number of reps performed with each set in each testing condition
    2. In this study the participants performed bench press reps to failure using 80% of their one rep max. This number does not seem unreasonable and likely replicates a common bench press workout for many gym-goers. However, the data show that the average number of completed reps in the first set were around 9 reps (see Figure 2 from the study above). This is a fairly low number of starting reps if detecting a change in rep volume is the goal. The average number of reported reps in set 4 was four reps across all testing groups. What this means is that the study is hoping to detect a possible change in volume between groups when there is only a 5 rep difference from start to finish. With so few reps available to show a difference it would seem that more than 11 participants would be needed to find a detectable difference. The other option would be to select a lower percentage of 1 rep max which would allow for a higher starting number of reps. In our internal testing we typically look at starting set volumes of 20 or more reps. This allows for more variability in the fatigue response between participants and allows performance differences between groups to be revealed. 
  2. The other main issue with this study is the application duration of the experimental intervention. Many prior palm cooling studies have used a 3 minute rest period between efforts, so it is not surprising that this study did the same. What is interesting in this study is that the palm cooling intervention was only applied for 1 of the 3 resting minutes between sets. The stated reason for only cooling for one minute was that this was the recommendation of the device manufacturer. They stated that cooling for longer than 1 minute may cause vasoconstriction in the palms and negate the effect. This is an a baffling precaution as most experts warn about device temperature being too cold as a potential cause of vasoconstriction and not for how long cooling is applied for. The prevailing idea is that a device that is too cold will cause the nervous system to react with constriction of blood vessels but that a 'cool' device (50-60 degrees) is less intense and does not trigger that same response. Also, these researchers were attempting to replicate another bench press study by Kwon, et al. who also did 4 sets with a 3 minute rest break. In that study cooling was applied for the 2.5 of the 3 minutes between sets. The issue with the current study and only cooling for 1 minute out of the 3 minute rest break is that this may not be enough cooling to detect a change. Consider this, for each participant on each testing day they spent 9 minutes of total rest recovering between sets. However, only 3 of those 9 minutes were spent actually cooling. 66% of the time that they could be applying the intervention, they weren't. Most of the time that all three groups were resting they were doing so in the very same way…by not cooling. Again, it seems like the design of this study is set up in a way that would not allow a difference between cooling and non cooling to be found. The intervention in this study is watered down to a point that it has little chance to show an effect.

Some humility needed

All research is tedious, difficult and cumulative. Prior research should not be negated or ignored and the flaws and limitations of any study should be clearly stated and acknowledged in the paper. It is unwise to make big conclusions from any one study. In essence, humility should always be expressed in research. However, the current study concludes:

 “Therefore, cooling cannot be currently recommended as an ergogenic strategy to enhance acute bench press performance or mitigate fatigue during high-intensity resistance training.”

That's a bold statement when prior research has shown that palm cooling is effective and given the limitations of this study (which I've described in this post). A more accurate and humble conclusion from this study would be:

 “The application palm cooling for a small percentage (33%) of the available rest time between 4 sets of bench press sets to failure showed no additional benefit to not cooling and therefore cannot be recommended under these specific circumstances. Additional research is needed to determine if cooling for a greater portion of the rest period, and/or for more sets, and/or with lighter loads would show benefit as previous research has shown.”

All research investigating a given intervention helps inform us on how best to use or not use that intervention. With an ergogenic aid (performance enhancer), like palm cooling, there is still a ton of investigation that has yet to be done. The optimal temperatures, durations of cooling, rep/set/weight schemes have all yet to be established. We know there are incredible motivational changes that happen when body temperature rises with exercises and palm cooling may act on this level as well. This relationship has barely been discussed in the palm cooling research and needs to be investigated.

In summary, this study adds to the growing body of knowledge on the use of palm cooling as a performance enhancing aid. It sheds light on the idea that palmar cooling for a small portion of your rest period between sets or efforts may not provide benefit when doing a few sets of an upper body pressing exercise. However, the results of this study should not be used as proof that palm cooling does not provide benefit in all workout situations as prior work has shown excellent results.

Let me know your thoughts are on this study. We'd also love to learn if you have tried and found palm cooling to be beneficial in your own training or competitions. 

Links to the articles:

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