Muscular Endurance Training - Is Getting Pumped Enough?

June 20, 2024

One of the most challenging things to accurately measure for endurance adaptations is climbing. The diversity of handholds' move distance, wall angle, time under tension, and a climber's body type make measuring endurance messy. An attempt at remedying this in the research has been using a tread wall or campus board (feet on) with a mandatory fixed hold size and time per hand move to try and better understand the physiology behind performance differences. But in the non-research context, climbing four boulder problems, doing repeaters until pumped, and climbing up and down to failure is random at best. We commonly use the perception of fatigue, grip loss, or falling off the wall as an accurate measure, and unfortunately, it's just not that easy.

In the latter context, sleeping habits, stress levels, and pre-climb fueling could explain the daily variations in climbing performance. To understand the muscular and cardiorespiratory adaptations to training, we need training and testing that is simpler, more reproducible, and not reliant on the technical skills necessary for climbing performance. Conversely, we should see climbing practice improve in response to these new adaptations.

Over the last many years, I've invested a lot of time and effort in understanding the adaptations of finger strength training for climbing. My goal was to understand better how and if the fingerboard was an accurate measure of muscle force.

Video: Hang vs. Overhead Curl

In the examples above, I've demonstrated that a supra-maximal load (130-150% of a muscular 1RM) is necessary to properly load the finger flexor muscles on a fingerboard (the same is true when lifting something off the ground). Those methods use a muscle contraction (yielding isometric) type that makes each muscle fiber tolerant of more external load (30-50% more) and is more reflective of the upper body muscle cross-sectional area than literal finger flexor strength. Because each fiber tolerates more load in this way, we use less of them. That is, until the loads get heavy, which adds some risk to the joints of the fingers.

Also, tolerating more load in this fashion should not necessarily equate to having more useable strength on the climbing wall. The specific adaptations we gain from the strength training programs are load-dependent (muscular recruitment) and skill-dependent (coordination). Because of this, we should not expect that same response once the external load is removed and the feet are on the wall. The load will never be there, and thus, coordination (force direction, center of mass, finger joint angles, etc.) will be different.

Here's a more straightforward example of what I'm referring to. Think about the last time you performed your max-weighted pull-up or pull-ups to failure test. The goal is to pull up (concentric or shortening muscle contraction) with as much weight as possible or for as many reps as possible at a given intensity (40-60%). In this scenario, getting the chin over the bar (upward motion) is typically a slow/steady struggle for the one rep or the last few reps until failure. Now, think about how easy it was to lower back down to the starting position on every rep, even the hardest one. Why is it so hard to lift the chin over the bar and not that hard to lower back down?

That difference in load tolerance is what I'm referring to. On the way down, we use around 30-50% fewer muscle fibers than when going up unless the load is supra-maximal (eccentric overload in which we cannot go back up). When we stretch a muscle under load, we gain efficiency and capacity for each fiber by loading the stiff portion of a connective tissue structure called titin at the end of each muscle fiber. This response is a good thing for climbing, but for muscular endurance training, it's an obstacle to accessing muscular adaptations. We will only add more capacity to the muscles by stressing them more intentionally.

At the muscular level, each contraction type creates and handles metabolites (the leftovers of muscle metabolism) differently. At the same intensity, eccentric contractions have more fatigue resistance because they rely on the passive structures. They still create fatigue (stretching does attach and detach muscle fibers) but are not as negatively influenced by it. Conversely, concentric contractions create fatigue and are heavily influenced by it. The metabolite accumulation will reduce shortening velocity and thus coordination first. This fatigue is why getting pumped on a route quickly reduces power (the ability to grab holds).

The limiting factors with muscular endurance are metabolite accumulation and changes in pH levels. It's a waste clearance problem (capillarization), not a lack of fuel problem. You are not falling off a route because you run out of ATP because you never will. You fall off a route because your muscle fibers can no longer shorten quickly, making difficult climbing sections less possible.

Muscular endurance training aims to stress the muscle right up to failure, rest until it's recovered (although as minimally as possible), and repeat (although each set will reduce in intensity and duration) for multiple sets until we no longer get the appropriate stimulus. Consequently, stressing the muscles up to failure should build a more robust energy production and waste management system (capillary network). The goal, but also the tricky part, is finding the right intensity and duration to stimulate the muscle fibers because the typical contraction type used with finger training (fingerboard, climbing wall, campus board), as discussed above, is less muscular.

VIDEO: Tyler curling vs pulling smo2

When I compare the same relative intensity (% maximum) lifting something off the ground (yielding isometric) or curling the fingers (overcoming isometric) while measuring muscle oxygen desaturation (SmO2), the overcoming style isometric produces more muscle stress and, thus, fatigue in the finger flexors. In this first example, I demonstrate a 40-50% intensity repeater (5 seconds on: 1-2 seconds off to failure) on different arms, curling (overcoming isometric) and lifting (yielding isometric) upwards while measuring oxygen desaturation (muscles using oxygen) and resaturation (muscles recovering). It has been predictable for the six athletes I've compared this way to have more FDS (flexor digitorum superficialis) muscle stress when performing the overcoming style (curling) isometric.

video: Chris curling vs pulling down smo2

When comparing this standing position to the arm overhead position (more like the climbing position), the results are the same (another six athletes). At the same relative fixed load for each contraction type, doing repeaters at 40-50%, 50-60%, or 60-70%, the overcoming style isometric stressed the muscle more than the yielding style isometric did, even when the arm was overhead.

One important note when comparing the two positions is the increase in muscle desaturation in the overhead position, compared to the lifting position, with the yielding style isometric. It would be easy to confuse this as demonstrating increased muscle activity when the arm is overhead. Instead, it is likely due to the reduced cardiac output and oxygen availability during the exercise because the arms are overheard. In this scenario, the compression in the capillary beds with muscle contraction, connective tissue stretching, and the "uphill" force placed on the blood flow will produce less overall blood flow to the capillary beds, showing a decline in SmO2.

One of the most interesting findings with these two testing protocols is that all participants noted more pump and difficulty completing the endurance task with the yielding style isometric test. I hypothesize that the muscle and connective tissue stretch at a higher relative intensity (30% higher in most participants), creating more ischemia (lack of blood flow) to the working muscles. So, in this context, getting pumped did not equate to more muscle fibers being fatigued. In addition, when exercises increase the perception of effort, the evidence shows that it further reduces muscular recruitment. And neither of these are the goals of muscular endurance training.

climbing research. include citation

Climbing-Specific Exercise Tests:Energy System Contributions and Relationships With Sport Performance January 2022 | Volume 12 | Article 787902. Frontiers in Physiology.

If we look at the climbing endurance research, it suggests four separate tests to measure and target different qualities in the climber. Peak force, or maximum voluntary contraction for a single repetition. Anaerobic power, or a 30-second all-out force test measuring peak, average, and force-time integral. Anaerobic capacity, or a 60% MVC force for duration test measuring the sustainability of the anaerobic system. And the Aerobic capacity test with an intermittent or a 60% repeater test to a force deficit. I've compared all these tests with the positions mentioned above, and all the evidence points toward my suggestion that intentionally applying force to the edge by curling the fingers (overcoming isometric while isolating the finger flexors) provides more muscle stress than hanging from or pulling from it.

So, if the fingerboard or yielding style loading at a given intensity creates more pump with less muscle activity, I'm suggesting that we modify the intention of our muscular endurance training protocols to be less about hanging from or lifting an edge and more about actively applying force (up to the % target) onto that same edge. This new method could be done on the fingerboard (now called a no-hang) and by applying force upward (standing position) in which the working muscle has a greater blood flow. Even though the latter is less like the climbing position, that should not matter. Training is about pushing the physiological needle, not mimicking the technicality of a sport.

In the following article, I'll discuss how to test anaerobic/aerobic power & capacity with the Tindeq Progressor and how to train and track them over a training cycle. Because many climbers now have better training tools, we can eliminate much of the guesswork with our current endurance training practices.

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