Thursday, November 13, 2014

Aerobic Endurance Training in Sport Climbing: Capacity (I). Physiological Adaptations

Versión en español

Up to 35 minutes to climb a previously tried route.
In occasions, up to 1 hour to onsight a route.
Most sport climbing routes take between 8 and 25 minutes.
(Data from a study of my own)

Eva López on Fish Eye, 8c. Oliana. Picture by Vojtech Vrzba
As it was noted in the previous entry, rather than training some particular physical quality, it would be more precise to speak of specific physiological effects from now on. As a reminder, here there are the different aspects or objectives related to local aerobic endurance:
  • Capacity (enduring long, low intensity climbs), also known as ARC
  • Efficiency or Steady State (negotiating moderate intensity-medium duration sections).
  • Quick Recovery.
 In this entry we will go over the goals and aspects related to what can be called the Training Zone #1: Capacity. The others will be the subject of the next two.
A Definition of Capacity
We can begin by stating that it is the quality that allows us to sustain a long climb (more than 15 minutes) with minimum fatigue. It can be described as the ability to keep our energy and strength, be it because we spend some of our substrates (energy sources) more slowly or we replenish them faster, or because our muscle efficiency at low intensity improves as a result of factors that we are going to learn.

Some activities that demand capacity are multi-pitch routes, onsighting long or technical routes, or sorting out the moves of a hard route.

Beware! Acknowledging its importance does not mean it has to be the only training goal for those activities. It would be like saying that a marathon runner just needs to run, not very fast, for a couple of hours...

In the English-speaking world it is also known as ARC (Aerobic Energy Restoration and Capillarity), from Goddard and Neumann (1993) for reasons that will become clear (**see recommended readings below).

If you are still unclear of the impact of this aspect on your climbs, I suggest you time your next try to a route that you want to climb. If you use more than 15 minutes to do it, or to sort out the moves, or to onsight it, it’s possible you will find useful the rest of this blog post.
Jose Luis Palao "Primo" on "La Planta de Shiva", L1, Villanueva del Rosario, Málaga.
Phto by Javipec. Source: Javipec Photo.
Physiological Changes in response to Capacity Training

At the physiological level, according to the duration, intensity and particularities of the effort (local aerobic endurance of the small muscles in the forearm), the development of Capacity in sport climbing can imply modest central (cardiovascular) development, but the bulk of the adaptations are both peripheral:

They allow for a faster and optimal oxygen supply to the muscle, as well as a better removal, recycling and oxidation of the products of muscle metabolism (*see glossary below) that have an influence on fatigue, like Pi, ADP, AMP, H+,NH4+, etc. These are the main ones:

a) Increased capillarization at the oxidative or slow twitch fibers (type I or ST) due to the creation of new blood vessels (angiogenesis) as well as to the growth in diameter or caliber (arteriogenesis) (Anderson and Henriksson, 1977; Mizumo et col., 1990; Ferguson and Brown, 1997; Laughlin et col, 2006, 2008; Thompson et col., 2014).

These adaptations are among the most important for the development of endurance in climbing according to several authors (MacLeod et col.,2007, Phillipe et col., 2011, Thompson et col., 2014 and Fryer et col., 2014). The explanation lies on the particularities of climbing:

-The big contrast between the long, intermittent, high intensity isometric contractions needed for successive small, difficult holds (8-15 seconds) and the short time between holds (less than 0,5 seconds, 3 seconds if we are clipping or up to 5 second shakes in a good rest) (López, E., 2014, Doctoral Thesis).
- The mixing of high intensity sections among medium and low intensity ones.
- The succession of movement and static positions (rest stops, clippings...) where the climber tries to recover from fatigue.
Lauren Lee making the second ascent of Master Blaster 5.13+, Zion. Photo: Sonie Trotter. Source: Gripped Canada's Climbing Magazine facebook page
Some authors think that improved capillarization can positively influence oxygen supply and metabolite removal, resulting in faster recovery and the possibility of more effectively training power endurance (anaerobic endurance) later in the training program; this will be addressed in a future blog post. These statements are supported by the significant positive correlation between # of capillaries per square millimeter and the number of repetitions at 70% of 1RM (Terzis et col., 2008), performance at tests with a duration of 30”-3’ (Iaia et col., 2011), recovery when doing short (40”) pauses between high intensity exercises (Tesch and Wright, 1983), and rate of recovery after 50 repetitions of leg extensions (Wright et col., 1983).
b) Elevated threshold for sympathetic activation that promotes vasodilation after and during isometric contractions, and improves tissue perfusion (Sinoway et col., 1987; Ferguson and Brown, 1997, Fryer et col., 2014). During muscle action, the buildup of some metabolites excites nerve endings that induce an activation of the sympathetic system (Sinoway, 1996; Mostoufi, 1998) that can affect efficiency it this response is too strong (this tends to happen when you are undertrained). It’s likely that this nerve excitation is reduced in climbers due to this increased threshold, but also because of lower hormone secretion at a given intensity, better tissue perfusion (Ferguson and Brown, 1997; Fryer et col., 2014 ) and, as we will learn later, an optimized aerobic metabolism.


2.1) Morphological adaptations
These consist of structural changes in muscle fibers:

a) Increase in the mitochondrial* content of skeletal muscle, i. e., # of mitochondria per mm2 of fiber (Hoppeler et col., 1985; Befroy et col., 2008).
Muscle fibre structure.
b) Development of Slow twitch (type I or ST) fibers, both relative to fast fibers (Costill et col., 1976) in size (hypertrophy) (Mitchell et col., 2012) or in fiber recruitment pattern (Hawley and Stepto, 2001; Arnold y col., 2014). These fibers are more resistant to fatigue, which confers them a vital role not only for maintaining strength at lower intensity for a long time, but also for recovering between intense efforts by helping “recycle” the lactate produced by their neighboring fast twitch (type II) fibers. This takes place at resting points, but also while clipping (about 3 seconds), and even when we release a hold for more than one second; if we are bouldering, it helps recovering between tries. It’s worth noting, though, that these latter adaptations are better achieved through the other two local aerobic endurance goals (efficiency and recovery ability).

Rannveig Aamodt, Red River Gorge,  Kentucky. Picture by Carter Agency. Source:
c) Increased muscle energy substrates, in particular glycogen* and muscle triglycerides (Greiwe et col., 1999; Burgomaster et col., 2005; Burke 2010). One cause of fatigue during prolonged exertion is the depletion of glycogen deposits. On a related note, it has been observed that a big store of one energy source can make cells more reliant on said source (mass action effect); this adaptation can be important for multi-pitch and big wall climbers.

2.2) Metabolic adaptations
Related to the improvement in glycogen and fat aerobic metabolism (especially in slow twitch fibers) that offsets the activation of the anaerobic pathway (lactate production) (Holloszy and Coyle, 1984); also to an increase in lactate clearance (lactate is continuously formed in some tissues like muscle and released from them, and its buildup is mitigated by lactate oxidation).

a) Increased oxidative enzyme* levels; these are involved in the aerobic metabolism (Krebs cycle and electron transport) (Henrikson and Hickner 1993; Burgomaster et col., 2005), especially in type I (slow) fibers and type IIa or mixed fibers (that play a role in anaerobic endurance or power endurance). This elevation, together with greater vasodilation and capillary density (tissue perfusion) has been shown to be very important for isometric grip endurance (Fryer et col., 2014).

b) Increase in lactate transport proteins (MCT1) that move lactate in and out of muscle fibers in order to oxidize it (lactate shuttle) (McCullagh et col., 1997; Everstsen et col., 2001, Thomson et col., 2005; Gladden 2008). This is part of the already mentioned lactate clearance.

Alex Honnold climbing in Devil's Bay, NewFoundland. Photo: North Face. Source: Gripped Canada's Climbing magazine facebook page
c) Increase in glucose transport proteins (GLUT4) that move glucose into muscle fibers to quickly use it (García Manso et col., 2006). In combination with the promotion of glycogen synthase (an enzyme involved in glycogen creation), it makes for a faster replenishment of glycogen when depleted after a high-volume or intense workout (Ryder et col., 1999).

d) Elevated fat oxidation at intensities that previously would have required glycogen (greater reliance on fat oxidation), resulting in “savings of the latter (Kiens et col., 1993; Hawley et col., 1998; Burke et col., 2001). As we already know we need our glycogen for the hardest sections, because fat metabolism is not fast enough to cover the rate of energy consumption that are demanded (Brooks and Mercier, 1994); fat metabolism is ideal for long, low intensity tasks.

Ok, this is all fine, but by now some of you will be growing impatient, just wondering: How do I have to train to achieve these effects? Well, this will be the topic of the next two entries (Load Variables, Training Methods and Planning), soon to be published.


ATP or adenosine triphosphate: It is the foremost energy transporter in the body. It acts as a kind of “energy currency”, transferring energy to other molecules by losing a phosphate group (adenosine diphosphate or ADP). ADP in turn can accept chemical energy in the form of a phosphate group to transform back into ATP (oxidative phosphorylation). Structurally it’s a nucleotide formed by adenosine (one adenine molecule bonded to a five-carbon sugar: ribose) combined with three inorganic phosphates (Pi) through high-energy bonds; that’s why breaking those bonds releases a big amount of energy.

Enzymes: Proteins that facilitate decomposition of chemicals (carbohydrates, fats and proteins) to obtain energy for bodily functions like muscle contraction.

Glycogen: The way the body stores its glucose. Structurally is a glucose polysaccharide stored in the liver and muscles until it is needed. The process by which it gets degraded (oxidized) to obtain energy is called glycolysis. The inverse, when it is resynthesized from several glucose molecules is called glycogenesis.

H+: Hydrogen protons, product of ATP hydrolysis. Its buildup along with other metabolites’ is related to one type of muscle fatigue. It usually accretes when there is a high power demand (energy per time unit), when the aerobic metabolic pathway is underdeveloped or when the energy substrates are depleted.

Mitochondria: It’s the organelle responsible for energy production inside the cell using the aerobic pathway (aerobic oxidative metabolism).

Metabolism: Set of physical and chemical processes that take place in the body with two functions: a) obtaining energy from food and storing it in ATP form and b) producing compounds and creating or replacing structures. When the generation of ATP (energy acquisition) is done without using oxygen it is called anaerobic metabolism; when oxygen is used it is aerobic or oxidative metabolism.

NH4+: Ammonium. Product from the metabolism of phosphagens (ATP and phosphocreatine).


Why we need to train Local Aerobic Endurance: Let the Numbers Talk
Objectives and Bases for Designing an Endurance Training Program in Sport Climbing

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