Quick summary

Endurance Repeaters – Forearm Aerobic Endurance Hangboard Routine

The Endurance Repeaters Aerobic Endurance Hangboard Routine is a less known modification of the standard 7/3 Hangboard Repeaters strength endurance protocol. Endurance Hangboard Repeaters were discussed by Tom Randall and Ollie Tor in the TBP 114. The idea behind this method is to perform intermittent hangs until failure, with the load reduced to only 30 – 40% of your maximum voluntary contraction (MVC). This makes it a very low-intensity aerobic exercise, which will allow you to build up very slowly towards forearm pump, which is much more similar to what happens on a long endurance route [1]

In endurance sports such as long-distance cycling, running or swimming, endurance is traditionally trained through continuous high-volume (e.g., 60 – 90 minutes) training sessions at relatively low intensity, around 60 – 65% of VO2max [2]. This kind of training is known to introduce adaptations, which include improved capillary density and vascular conductance, increases in size and density of the mitochondria, aerobic enzymes and fat oxidation, as well as sparing of muscle glycogen, reduced rates of lactate (La-) production and enhanced La- removal, ultimately resulting in improved O2 supply and thus maximal endurance capacity [3][4][5][6]. Endurance Repeaters are an attempt to apply the traditional endurance training principles to climbing.

Critical Power and the energy store component in aerobic endurance

To better understand the principles behind modern endurance training theory, we need to explain the concept of Critical Power (CP). CP was introduced to reflect the highest exercise intensity that is solely dependent on a renewable aerobic energy supply. Simply speaking, CP is the maximum power that a muscle can keep up for a very long time without fatigue [7]. You may think of CP as the “maximal aerobic power”, though this particular term (MAP) is used in literature to describe the power output associated with VO2max [8]. Since in hangboard training, we deal with dead hangs, which involve isometric muscle action, we will use an analogous term of Critical Force (CF) instead of CP. The higher your CF is, the harder you can climb while relying on the aerobic energy system. CF can be given in newtons, but it usually makes more sense to express it as a percent of the climber’s maximum voluntary contraction (MVC).

The second important parameter is the so-called energy store component W’, which indicates the maximum amount of work that can be performed above CF. The energy store component is constant, regardless of the used force, as long as the force is higher than CF. Numerous experiments have shown that CF is determined by the muscle oxidative function, while W’ depends on finite anaerobic energy sources and that it can be manipulated independently, e.g., by altering muscle phosphocreatine (PCr) stores [9]. An example of a hyperbolic force-time relationship for high-intensity exercise is shown in Figure 1. MVC-7 is the 7-second maximum voluntary contraction [N], the asymptote is the CF [N], and the colored rectangles represent the energy store component W’ [N·s], which is constant for each measurement point [10].

It is, therefore, clear that both CF and W’ are critical parameters, which are bound to decide between failure and success on long endurance routes. Recent research showed that while CP can be improved by low-intensity training below CP, as well as by interval training above CP, best results and highest time efficiency are reached when training is done precisely at CP [11]. We can, therefore, assume that Endurance Repeaters should yield the best results if done at CF.

Critical force and energy store component plot in climbing aerobic endurance

Figure 1: Illustration of the force-time relationship for high intensity exercise, according to [10].

Determination of the Critical Force and W’ for aerobic Endurance Hangboard Repeaters

The exact procedure to determine CF and W’ by using a hangboard was recently thoroughly described by David Giles, Ollie Torr, Tom Randall, and colleagues [10]. The research team examined eleven 7b – 8b+ climbers. First, they determined each climber’s 7-second MVC on a standardized Lattice Training rung (20 mm deep, 10 mm radius) in half crimp position. Then, they performed intermittent dead hang tests until failure at 80%, 60% and 45% of the climbers’ respective MVC. They found a hyperbolic relationship between the load at which the test was taken and the time to exhaustion (TTE), which is in agreement with general training theory [12].

Critical force does not depend on the maximum strength.

The research team determined the CF of the tested climbers to lie between 31.9 – 60% of their MVC, with an average of 41.0 ± 6.2%. What is interesting is that the CF does not seem to depend on the MVC. The climber with the lowest MVC of 121.7% BM (898.8 N) had the second-highest relative CF of 53.5% MVC (480.8 N),  while the strongest climber, with an MVC of 183.0% BM (1199.3 N) had a CF of 40.6% MVC (486.4 N), which was below average. In absolute terms that’s only 5.6 N, or 0.57 kg difference. The above result explains why you often see relatively weak climbers breeze up through endurance routes, while very strong boulderers, with good strength endurance, struggle after just a couple