Climbing Research - Making more questions than answers?

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Dave MacLeod - 29/01/2003

Since I started out in my physiology & sports science degree in 1998 I wanted to do some research into strength and endurance in climbing for my final year project. I got my wish and in October 2001 I sat down in my supervisor's office and we thrashed out some ideas about the physiology of climbing and what questions came to the surface. 60 hours of lab testing later (and much more in front of the computer), some of those original questions were answered and even more were created. Here is a brief tour through what we did and what we found...


The Questions...

In order to understand what limits our performance in climbing, an important question is 'what makes us fall off?' Often, this isn't such an easy question to answer correctly! Clearly, in climbing, there are loads of factors which affect performance and deciding which one is really the limiting factor at any one time is exceptionally difficult. In our project, we decided to focus on some physiological variables affecting endurance capacity in the muscles which flex the fingers. There is plenty of evidence around to show that finger endurance is important for climbing. The aim of our study was to attempt to identify the characteristics in the muscles that lead to good endurance in a climbing specific situation.

Climbing isn't a big sport with lots of money flowing through it. Consequently, it hasn't exactly been grabbed and dragged along with the flow of sports science! Most of what we know (or think we know) about performance and training in climbing is borrowed from other sports with a longer history and specific research. However, there is some scientific literature around, usually thanks to medics or academics who just happen to be climbers as well.

In climbing movements, the fingers (and the muscles in the forearm which flex them) stay still while the rest of the body moves past. Not very remarkable you might think! But this (isometric or 'static' contraction) is actually quite unusual in sport and has huge consequences. In most other sports the muscles are always moving while contracting. This is important because if the muscle is shortening while producing force it literally pumps blood through itself and maintains the essential oxygen supply. When muscles contract without moving, the blood vessels are squeezed shut and no blood can get in unless the contraction is very light or comes to an end.

A few previous studies into forearm endurance in climbers tried to identify how the forearm muscles adapt to training to make trained climbers better than novices. This research showed that rock climbers have an increased ability to dilate the blood vessels in the forearms and achieve greater blood flow rates.

We designed some experiments to monitor changes in several variables while fatiguing the fingers of some climbers. Specifically, we wanted to find out what factors could be influencing climbers ability to get more blood into the muscles. Would the best climbers always be the ones who could get the most blood through the muscle while climbing? Would having extremely strong fingers be a help or a hindrance to forearm blood flow and endurance?

The tests

We tested 11 male climbers who could onsight F7a-F7c and 9 non-climbers. The subjects came into the lab and were put through a range of finger strength and endurance tests. We used a specifically designed finger plate which measured the force produced when the edge was crimped. First, we tested our subjects maximum crimp strength and then calculated a percentage of this for the endurance tests.

On the next visit, our subjects performed a crimp endurance test, pulling at 40% of their maximum strength until failure. The protocol was made as climbing specific as possible by using a 10sec/3sec pulling/resting protocol to mimic pulling on holds and reaching to the next hold in real climbing. During the test, we measured changes in blood pressure, blood flow and blood oxygenation using an infra-red probe fixed to the subjects forearm.

Davelabpic1.jpg Davelabpic2.jpg

Above: Me doing the endurance test. On my left arm is the blood pressure cuff. On my right arm is the infra-red optodes (measuring blood flow). The computer screen monitors the force from the finger plate and cues the contractions and rests.

The findings

The crimp strength of our climbers was much higher than our non-climbers. The highest value recorded on the crimp was 58.5 kg (four fingers, half crimp). There were some unusual results too. The strongest non-climber managed over 51 kg which was stronger than 75% of our climbers! Often, the strength scores would creep up on each attempt and reach the highest value on the 8th or 9th attempt.

The endurance tests took roughly 4.5 minutes to failure, about the same as a medium length sport route. Our endurance measure took into account the force, time and body mass components to give a climbing specific measure (Nsec kg-1). Again our climbers scored much better. There was a trend for the strongest climbers to have shorter times to failure, but the relative force they were exerting was often much higher.

We compared the strength and endurance characteristics of our climbers to their best onsight grade. Finger strength and onsight grade were strongly related, whereas endurance and onsight grade were much less related. This is potentially a massively important finding. Unfortunately, the statistics suggest that we would have needed many more climbers and a bigger spread of grades to have any confidence in this finding!

We had a hypothesis that climbers with a greater increase in blood pressure would do well in the endurance test. We thought that a higher blood pressure might help to force blood through the muscle, against the squeezing force of the contracting muscle fibres. This didn't happen! Again, this result isn't necessarily transferable to real climbing for several reasons.

The volume of blood in the muscle during the endurance tests tended to be lower in the climbers compared to non-climbers. In other words, the climber's forearm muscles were producing a greater squeezing or occlusive force on the muscle blood vessels. This finding suggests that the increased muscular strength in our climbers comes from better recruitment of muscle fibres as well as more muscle mass (we roughly measured forearm muscle mass too and the climbers scored better). The most striking finding from the study concerned the patterns of forearm blood flow. When the subjects pulled on the crimp edge, forearm blood flow dropped sharply and continued to fall until the contraction ended (10 secs). During the 3 second rest, the blood flow shot back up again as the blood vessels were completely dilated in response to the oxygen debt and nasty acidic metabolites. This response was much larger in the climbers. In fact, the better the subject was at reperfusing the muscle in these short rest periods, the better the endurance score.


Above: Forearm blood flow during the endurance test. The black trace comes from a climber and the white trace is rom a non-climber. The falling phases are during 10 sec contractions and the rising phases are during 3 sec rests. Zero on the vertical axis is the resting value. Note that the climber has much less blood flow generally but recovers much more during the rests.

So how are the findings interesting for climbers?

Firstly, the framework for dealing with these results needs to be clear. My project was a small study and one of the first of its kind. We worked hard to control for factors which weaken the data by paying close attention to experimental design. However, without established practices in this type of research on which to base the design and without a large number of willing volunteers, the strength of the data is unavoidably weakened. No scientific theories and ideas are ever completely set in stone; more evidence just strengthens the case for having confidence in them. So our results are just a pointer to how things might be in reality, nothing more.

Our results and everyone's anecdotal experience shows that being strong is important, even for doing stamina routes. The question of how much of each we should spend time training is not answered by our data. Some people have said in the past that being very strong means that moves are so easy, you can do them aerobically (i.e. with blood flowing through the muscle all the time). Others have argued that being strong is actually an endurance disadvantage as more blood vessels will be squeezed shut by the increased force of contraction. Our data adds weight to this argument since our stronger climbers had less blood flow during contractions. In reality the physiology and other factors which play a part are much more complex and our data is not extensive enough even to speculate about what is really happening. In real climbing, there remains plenty of interesting anecdotes to fuel the argument. Take Chris Sharma, who didn't tie onto a rope for years and became one of the strongest in the world, yet arrived at Ceuse and after a relatively short adaptation, bagged the hardest stamina route in the world! However, as I said above, there are many factors which could account for this (e.g. genetics) and anecdotes will always be poor substitutes for more thorough investigation.

The most interesting result was the large effect of blood flow return (reperfusion) during our short rest periods on endurance capacity. The statistical evidence for this effect was quite strong. Ever experienced the difference flicking your wrist makes while reaching between holds? Watch Chris Sharma doing it just before he finally sticks the crux of Realization. Wrist flicking or shaking your forearms is just a mechanical way to help blood pump through the muscle.

Fortunately, this effect is trainable. The goal is to increase the density of capillaries (micro blood vessels) in the muscle to maximise the amount of blood coming back in while you reach between holds, clip or shake out. The type of training which produces this adaptation is low intensity, high volume work. Neil Gresham calls it SACC training. It involves doing very easy climbing for extended periods of time (up to 30 mins at a time). The climbing should load your fingers but not make you pumped or gasping for breath. The bonuses of this type of work are that it helps both your stamina on very long routes (like Fated Path) and also short 'power-endurance routes' such as climbing wall routes. It also helps you recover from hard bouldering sessions and learn technique!

Project II

This spring I am doing another project with similar tests to refine the data and look at some new ideas about endurance. Lots of previous muscle fatigue research tells us that when muscles are fatigued isometrically, the rate of relaxation slows after the contraction is ended. We hypothesised that this slowed relaxation could be affecting the rate at which fresh blood can get into the forearm while each hand reaches/rests between holds.


I am looking for volunteers to participate in the new study. I need to find male 12 climbers who have onsighted F7b or above (or equivalent) and fit a few other criteria. I also need to find 12 non-climbers who don't train their hands. I will provide full information to anyone interested. There are no risks, invasive measurements or payment for subjects. Volunteers will need to come to a lab in Glasgow University twice for 45 minutes of testing. The testing is fun (honest!) and you will receive lots of interesting information about your personal strengths and weaknesses in climbing!

Also with thanks to the other researchers: D. L. Sutherland, L. Buntin, A. Whitaker, T. Aitchison, I. Watt, J. Bradley, S. Grant.

Quick recovery on poor stopping places is the key to success on routes like Requiem (E8) Dumbarton. Both finger strength and muscle capillary density affect recovery rates on poor rests.
Recovery starts from the moment you take your hand off the rock. A three second shake out on this hold saved broken bones and the flash on the last move of Shine On (E7) Stanage Edge.
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