Training effectively always requires walking the fine line between enough training to get the stimulus required to improve and not overdoing it, which can quickly undermine your efforts and lead to injury. One of the main issues for climbers trying to find the correct training volume is balancing the need for high-intensity strength and power training with the time that it takes to recover from these sessions. As passionate climbers, we don’t like hearing that the key for us to improve is actually to do less. So, what if there was a way to get the same benefits of high-intensity training with less of the impacts we need to recover from? This is the basic theory behind the application of blood flow restriction training for athletes, and we’re pleased to share this article by Dr. Tyler Nelson about his initial study into the application of blood flow restriction to training finger strength.

Dr. Nelson, a sports scientist and climber who owns a chiropractic sports medicine clinic and strength and conditioning business in Salt Lake City called Camp 4 Human Performance, has written other articles for us and he’s been on the TrainingBeta Podcast educating us all on topics like the use of isometrics in climbing training. He has also been quite vocal in promoting the benefits and application of blood flow restriction (BFR) training. However, rather than rely on anecdotal evidence to show the effectiveness of BFR in finger strength training, he conducted a study in an attempt to demonstrate these benefits scientifically.

This article is Tyler’s first presentation of the results of his study on the effectiveness of using BFR training to train finger strength for rock climbing. While this article does give a basic overview of how BFR works, if you are completely unfamiliar with the modality, we recommend you start by listening to Episode 108 of TrainingBeta Podcast where Tyler covers the topic in greater detail. He also wrote an article all about it for us called More for Less: Blood Flow Restriction Training.

Additionally, it’s important to note that while Tyler’s initial results seem promising, this is the first time BFR has been tested in training finger strength. We are presenting this article not because we think that every climber needs to go purchase a set of BFR bands, but because we believe that studies like this and the sharing of information are how we progress our understanding of how to most effectively train for climbing.

Finally, as with all of Tyler’s articles, the discussion here is highly scientific and the use of BFR in training finger strength is still in its infancy. This article is not a quick or easy read and neither TrainingBeta nor Tyler believes that all climbers need to use BFR to improve, but if you are interested in cutting edge climbing research or potentially using BFR in your climbing training you’ll find this article highly informative. Keep an open mind and be prepared to dig in!

Improving Peak Finger Flexor Force at Reduced Loads

Finger Training with Blood Flow Restriction

Tyler Nelson DC, MS, CSCS
Camp4 Human Performance

You don’t have to look far in the sports literature to hear about blood flow restriction training. As the name implies it’s a way to manipulate the body’s circulatory flow that has been shown to re-create the stimulus of high-intensity training with loads as low as 20-50% of a 1-repetition max. As a student, I was exposed to BFR through the rehabilitation literature performed with the original system, the Kaatsu System. For the last couple of years, I’ve been using blood flow restriction training in my clinic on clients who are injured and could not sustain, for a period of time, a normal high-intensity loading program. With good clinical success, supported by literature reviews, I’ve been able to reduce pain, maintain muscle mass, and keep athletes motivated while being sidelined by injury.

The mounting scientific data backing the efficacy of BFR training combined with the clinical success with my clients has been the basis of this investigation into the application of BFR to finger strength training for rock climbing. This article will serve as a basic overview of the mechanisms behind BFR training and an initial presentation of my research into the application of BFR training to improving peak finger flexor force.

Mechanisms Review: A Basic Overview of How BFR Works

Without going into too much detail, it’s safe to say that, with over 400 published peer-reviewed journal articles since 2010, blood flow restriction training is something worth paying attention to. The physiologic effects can be complex with some theoretical speculation in the literature, but the principle is relatively simple. Essentially, by using a specific pneumatic cuff placed around a proximal limb we can restrict a percentage (20-90%) of the arterial inflow while fully occluding the venous outflow from the working muscle. It’s very important to note that even under these restricted conditions we still get blood flow to and from the working muscle. The skeletal muscle pump returns blood from the deep veins back to the heart and this mechanism does not stop with blood flow restriction training. Instead, BFR cuffs simply slow down the skeletal muscle pump making athletes reach their O2 saturation more quickly.

This 02 saturation is important as the primary goal in this training modality is reducing oxygen availability to specific types of muscle fibers so the remaining fibers, which do not use oxygen, are forced to pick up the work. By limiting the oxygen availability, and accumulating acidic byproducts, the smaller fibers (Type I and IIa) cannot perform work efficiently. The muscular work in subsequent sets then is picked up by the largest fibers (TypeIIx) of working muscle. Once we’ve created this chemical absence of homeostasis, we then get a large influx of sensory information sent back to the brain that is responsible for creating the increased hormonal profile we see with BFR training. All of this can be done at percentages as low, or even lower in some cases, as 20% of an athlete’s 1-repetition maximum. The following graph provided by Loenneke shows this mechanism clearly.

There are a few more important things to note regarding the rationale with this research and the intervention itself. Primarily, there are only a few ways that we can enhance muscular recruitment and hypertrophy. Recruitment is all about training your muscle groups to use a higher percentage of the largest fibers for a specific activity than they did previously. Hypertrophy is all about increasing the actual size of those muscle fibers and their ability to grow (side-to-side, and their individual diameter) within a muscle group.  There are two ways we can optimize these mechanisms with conventional training methods.

First, we can exercise at a very high intensity (85-90% with low velocity) for a set number of repetitions (5-7) or we can exercise at a moderate intensity (70-85% with moderate velocity) to muscular failure. In the high-intensity loading state, we choose a load that is so high we have to rely on more fibers, the TypeIIx fibers, to move the heavy load. Conversely, in the high-volume state, we create a level of fatigue over the working sets where we slowly recruit larger and larger motor units with all the work.

The downside of using either of these approaches is the time it takes to recover from that high-intensity muscular work. The fatigue and protein fiber breakdown that accompanies high intensity and moderate loading to failure is significant and reduces overall training frequency. Therein lies the real appeal of using BFR to train the forearms and finger flexors within an athletes training cycle and season. We can still reach muscular failure. However, we are doing so at an intensity that reduces the protein breakdown that accompanies high-intensity loading while still benefiting from the hormonal profile as if we were. These concepts have been documented in the BFR literature many times over.

Research Protocol

Despite the numerous studies on BFR training, to date, there has been no research performed on the use of blood flow restriction training as a mechanism to enhance finger flexor strength. This article is a summary of my initial research into the application of BFR to finger flexor training. In addition to this article, there will be a paper submitted as a retrospective analysis of this study to a peer-reviewed journal.

It is important to note that in most papers on BFR, or occlusion training, there is usually a comparison between three groups, a normal high-intensity group, a low load with blood flow restriction group (LLBFR), and low load without blood flow restriction group (LL). The majority of these studies have demonstrated that low load with blood flow restriction is as useful at maintaining strength and muscle size as the high-intensity loading group.

For my research, I designed the study based on other blood flow restriction studies that were aimed at measuring improvements in peak muscle strength. In general, most BFR papers study a specific exercise or muscle group at intensities approximately 20-50% of an athletes 1-repetition max. They usually compare a low load BFR group to a low load non-BFR group as well as a regular high-intensity group. In this case, we only used the former two, low load with BFR (LLBFR) and a low load non-BFR group (LL).

My goal was to run approximately 8-10 athletes through a specific hangboard protocol I created to assess the plausibility, safety, methodology, and subjective response of this as a training tool for non-injured healthy climbers. Until this study, I had only performed this same protocol on myself during multiple cycles (3-4 weeks) with no noted downside. So, my hypothesis was that using a low load BFR finger training protocol I would be able to track a statistically significant improvement in peak finger force over 10 sessions.

I used a random selection of climbers from the Salt Lake City area who were free of a current finger injury, who had a finger training history of at least 2 years and were able to perform 10 training sessions at 2 per week for 5 weeks. It was quite helpful that I had a wide range of climbing skill levels and training history from 5.10 sport climbers to V13 boulderers.

I assigned one group to the BFR protocol consisting of bilateral restriction at 200-250mmHg on the Bstrong BFR bands (which is approximately 20-50% arterial occlusion pressure), and one control group with bilateral restriction with 5mmHg added pressure. For the control group, the low pressure created a slight pressure to mimic the idea that there was adequate pressure to create the BFR stimulus. This likely created some abnormality in blood flow but nowhere near the extent of the BFR group.

As already mentioned, most BFR papers use a percentage of (20-50%) of an athlete’s 1-repetition maximum to assign training loads. It has been my experience testing athletes’ fingers that body weight is approximately 40-60% of their maximum intensity when using both arms. So, for this study, I did not individualize the protocol for the hang portion. I only manipulated the load to the fingers before the body weight hang. I did this intentionally so as to make it simple for climbers to use as a training tool on the road or at their house. I made the assumption that the edge size would approximate the appropriate intensity and percentage max for each individual so long as they came into the hang with pumped forearms.

The warm-up was standardized so as to reduce the likelihood that any participant was either more or less prepared for the intervention as compared to their peers. The following was the general warm-up we used.

Warm-up (specific part 1)

  1. 4-finger pocket pull-up (large pocket) 3 x 5 at bodyweight
  2. Open hand small edge hang 7:3 x 5 (2-minute rest)
  3. Half crimp medium edge hang 7:3×5 (2-minute rest)
  4. Concentric pull-up with 30% added weight 2 x 3 with 20s rest between sets
  5. 4-finger pocket hang with same weight added 5×1 with 60s rest between sets
  6. Half crimp small edge at body weight 5×1 with 60s rest between sets

Warm-up (specific part 2)

  1. Hang position seated with 50% effort x 1 each edge (19mm, 12.7mm) with 60s rest between sets
  2. Hang position seated with 80% effort x 1 each edge (19mm, 12.7mm) with 60s rest between sets

I need to make a note regarding the pressure used in this particular investigation. I used a type of BFR product that is elastic and contains multiple chambers instead of a classic blood pressure cuff which only has one chamber. It is a more comfortable product (physically on the limb, not metabolically) for the overhead work of hanging from one’s fingers. I have used pneumatic single chamber systems (classic BP cuff) on myself for this same protocol to check that the stimulus was similar in intensity (7 out of 10 discomfort). It is important to note that the pressure used in this research (200-250 mmHg) on my multi-chambered system would occlude arterial blood flow at 100% on a single-chambered system, which is not advised. I have calculated that 200-250mmHg on the product I use is approximately equal to 75-100mmHg on a blood pressure cuff, which is approximately 30-40% arterial occlusion pressure for the males and 40-60% for the females.

Exercise Intervention

Once bands were in place on the arm (below the deltoid and at the upper margin of the biceps brachii) on both arms each group performed the same exercise intervention. The groups used a Tension Climbing Flash Board (upside down) and performed finger curls with added weight from full extension into a fully flexed position (as if they were moving into a full crimp) on the 19mm edge. They were to perform 15-repetitions to complete muscular failure. This ranged in weight per individual from around 35-90 lbs depending on the group assigned. These were performed with a loading pin with weights connected to the sling below while they were standing and curling upward. Upon completion of fatigue at 15-repetitions they immediately set the board down and walked over to the tension hangboard and performed a half-crimp 7-second hang on the smallest edge possible. Most performed this on the 30, 25, or 20mm edge size. However, there were a few participants who could perform their sets on the 10mm edge. The wide range in external load with the finger curls came from whether an athlete was in the BFR group or the control group. The BFR group participants had a much smaller weight than the non-BFR (LL) group.

Upon completion of the hanging portion of the program, they would take a strict 30-second rest. Once the rest (arms at the side in a standing position) was finished they performed the same finger curl protocol with either the addition or reduction of weight so they could hit muscular failure in 15 repetitions. They performed this for 12 sets total, which took approximately 15 minutes. For the remaining 5-minutes, I had the participants leave the bands on and keep the pump in their arms until 20-minutes was over. The same protocol was used on the BFR control group (LL), except that they were using a much larger weight on the finger curls (60-90lbs) to reach muscular failure with the same inter-set rest period.

Pre and Post Intervention Testing

Each athlete was told to come fresh to the pre and post testing session with at least 2-days of rest before. Each participant was tested in the same room, with the same board, same prototype custom strain gauge by Exsurgo Technologies, same chalk, and the same level of emotional support.

For both groups, we did a maximum effort half crimp peak and average finger force test (lbs) on both the 19 and 13mm edge size. I gave the participants three trials each with 2-3 minutes rest between and kept the highest peak value. These were all performed in a seated position with the hips blocked (via squat rack pin with yoga pad around the bar) with both arms overhead at 110-120 degrees of elbow flexion. The participants were queued to bring on the force slowly for 1 second then really bear down at max effort for another 2-4 seconds. As soon as the peak force was hit and a plateau demonstrated, they were told to stop pulling. The average force was taken over the entire time the athlete started their pull until a plateau was reached and they were told to stop. With a sample rate of 250ms, there were approximately 20 force readouts in that timeframe to calculate the average.

Results and Discussion

As you can see from the graphs (table 1) below, participants 1-4 were the BFR group (LLBFR) and participants 5-8 were the control or apparent BFR group (LL). The graphs below show a side-by-side analysis of the pre and post-test peak force and the pre and post-test average force for both edge sizes. If you recall, each effort was sustained until a peak plateau was reached, likely between 3-5 seconds upon which the athlete released tension. So the averages could be less consistent a measure than the peak measure, however, they do demonstrate an overall increase in force impulse (force sum over time).

Table 1

Table 2 represents each participant’s pre and post-test peak and average force on both edge sizes. It also provides a column for the peak and average force difference (change after the intervention) for each participant. Looking at the far right of the data table (table 2) you can see the two primary measures representing each group (LLBFR and LL) at each respective edge size. The average difference in peak force between each group (pre and post-intervention) as well as the difference in the average force of each group.

On the 19mm edge size, the average difference in peak force over a 5-week training cycle was 90.7 lbs for the BFR group (LLBFR) and 20.2 lbs for the control group (LL). The BFR fingerboard group had a 4.5 times improvement in peak finger force over the control on the same edge size and a 3.15 times improvement in average force produced. When looking at the data on the 13mm edge size the improvement was less dramatic with an average difference in peak finger force being 30.8 lbs (LLBFR), which is 2.07 times that of the control group (LL) and 1.9 times improvement for average force produced.

Table 2

As mentioned previously, the graphs demonstrate less dramatic improvements in peak finger force on the smaller edge size (13mm). I hypothesize this comes from the inability of many participants to hang off their body weight fully pumped on the smaller edge sizes. Only 25% (2 of 8) of the participants were able to perform over 60% of their hang sets on a 15mm or smaller edge size, where most participants were spending their time hanging on the 30, 25, and 20mm edges. That being said, I would also predict that doing regular max weighted hangs (with added weight to failure) on a larger edge size (20mm is the most commonly used) would not be predictive for improved performance on a smaller edge size. This comes from the specific motor unit recruitment that happens by training at a specific edge size.


Given that most research investigations report an improvement in muscular strength and hypertrophy with low load blood flow restriction training, it is feasible that these same principles can be applied to the finger flexors of climbers. This comes at a much-desired drop in tensile stress to the pulley system of the fingers. In addition to reducing stress to the finger flexors of climbers, we can still train specifically on a fingerboard to improve aerobic capacity, muscular recruitment, local energy storage, and capillary networks in the muscle groups specific to climbing performance. These are some additional improvements noted in the BFR literature not tested in this particular study but have been demonstrated elsewhere. What I have done in this paper is to document that in a 5-week time frame with blood flow restriction training at submaximal loads peak and average finger flexor force can be improved with no noted downside.

As I’ve mentioned previously, I do not believe BFR finger training is a complete replacement for high-intensity finger training. Its largest use to date has been on injured or elderly populations. Both of which would not be able to tolerate higher intensity loads. That being said, BFR is now being investigated in athletic populations as a means to augment regular training loads to reduce overloading and injury. There have been multiple papers in which BFR was used side-by-side regular high resistance training as a mechanism to augment strength, power, and aerobic capacity, which reduced the frequency of high-intensity loading. We’ve known for quite a while that high-intensity loading is necessary for long term soft tissue adaptation and tendon density. However, if we can find the right balance between “enough” soft tissue strain using high loads and learn to manage metabolic stressors (muscle recruitment and energy system utilization) with something like BFR, we might find something we’ve always wanted – the same amount of training with less injury risk. 

For the Future

The next thing that needs to be investigated in regards to rock climbing performance and blood flow restriction is the comparison between a LLBFR group and a regular high-intensity loading group. In addition to peak and average finger flexor force, we would use more pre and post-test metrics (alactic power output for 10-seconds, anaerobic capacity for 30-seconds, and rates of force development) which would provide better insights into the mechanisms and adaptation resulting from each intervention. I have performed some of these metrics on a local group of climbers using BFR, which will be the topic of the next paper.

To date, this is the first investigation that measured peak and average finger flexor force both before and after an intervention of blood flow restriction training for the finger flexors of climbers. If you have any questions regarding the protocol, equipment used, safety, or to learn more about blood flow restriction you can contact me directly at TrainingBeta, as gracious as they are for publishing this article, is not responsible for the contents of this article and are mine solely. I do advise people to get educated about using blood flow restriction prior to trying this on yourself. Your risks and liability are your own after reading this paper.


For any additional programing ideas or questions come see me at the Performance Climbing Coach Seminars or email me at You can also find me on instagram @C4HP.


About The Author

Tyler Nelson owns and operates a chiropractic sports medicine clinic and strength & conditioning business in Salt Lake City. While earning his doctoral degree, he completed a dual program Master’s degree in exercise science at the University Of Missouri. While in graduate school he worked with the University of Missouri athletics department and currently is employed through two colleges in Utah. He teaches anatomy and physiology at a community college and works as a team physician for the Brigham Young University athletics department. He is certified through the National Strength and Conditioning Association as a Certified Strength and Conditioning Specialist and spends any extra time in his life with his wife and three kids or trad climbing in Zion National Park. He has been climbing for 17 years and gravitates toward all-day adventure climbing. His expertise in human physiology and cutting-edge knowledge of strength and conditioning science are what drive him to always challenge the norms in training.




TrainingBeta is a site dedicated to training for rock climbing. We provide resources and information about training for routes, bouldering, finger strength, mental training, nutrition for climbers, and everything in between. We offer climbing training programs, climbing training classes, nutrition classes, regular blog posts, interviews on The TrainingBeta Podcast, personal coaching for climbing, and nutrition for climbers.

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