Aerobic Endurance Training in Sport Climbing: Capacity (II). Training Load Elements: Objectives, Intensity and Volume

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Versión en español

1. Objectives for Developing Capacity (also known as ARC)

a) Basic objective: Accumulate during the training session many minutes staying on the wall, of actual climbing.

Recommended for the beginning of a cycle, lower and medium level climbers, or those who don't have much experience with training in general.

b) Advanced objective: Total depletion at the end of the sets or the session.

Best for: experienced or high level climbers, or those who have worked the previous objective long enough.

Dani Fuertes resting on La Rubia, 8c+, Villanueva del Rosario, Málaga. Picture: Javipec

 

2.Intensity

We will use a Low intensity. More exactly, up to 25% of maximum grip force (To learn why we choose a % of maximum strength over maximal oxygen consumption or maximum heart rate like they do in other sports, have a look at this entry).

2.1 Why topping at 25% of maximum grip strength?

We will lean on a number of related conclusions:

a) Some authors suggest that 25% of MVC is the highest intesity where the aerobic metabolism is still the main energy source (Fallentin et col., 1993; Byström, 1994; Kimura et col., 2006), and that is the one we want to optimize here (Usaj et col., 2007; Fryer et col., 2014).

b) One of the stimuli that lead to changes in the blood vessels surrounding certain muscle fibers (angiogenesis and arteriogenesis, see previous entry) is the repeated and sustained increase of blood flow in the area (Hudclicka et col., 1992; Prior et col., 1997, Egginton et col., 2001, Hounker et col., 2003) characteristic of aerobic exercise at the aforementioned intensities.

The growth of new blood vessels and the widening of existing ones aid in the development of aerobic endurance. Climber: Tommy Caldwell on Dawn Wall Project, El Capitan, Yosemite National Park, CA (USA). Photo by: Josh Lowell. Source: Climax magazine #20.

One could think that a higher demand on the muscles would increase even more their need for energy and hence blood flow. By the contrary, in isometric contractions maximal blood flow is registered at very low intensities: around 10-25% of MVC. Past this, at 25-40%, the flow does not actually go up, and it even decreases if we go further (Barnes, 1980; Byström and Kilbom, 1990). Let's explain why:

• On the one hand there has been found a direct association between the intensity of a contraction and blood flow (Sjøgaard, Fagard & Fuel, 1988; Byström & Kilbom, 1990); also between the duration of a contraction and blood flow during the interval between contractions, as well as during recovery after exertion (Byström & Kilbom, 1990; Laughlin et col., 1999).

• On the other hand, though, the harder the contraction, the more intramuscular pressure (Barnes et col., 1980; Sejersted et col., 1984; Thompson et col., 2007). When it comes to isometric contractions a problem arises: the blood vessels get occluded for several seconds, compromising nutrient exchange. This leads to a buildup of liquid as well. According to some authors, this explains isometric fatigue (Sjøgaard, Fagard & Fuel, 1988; Kalliokoski et col., 2003).

More specifically, tests performed with a dynamometer on the muscles of the forearm have found that the blood occlusion starts at 30% of MVC, and is complete at 50-70% (Barcroft & Miller, 1939; Barnes, 1980; Sjøgaard et col., 1998).

Mich Kemeter at Verdon (Francia). Photo by: Alex Buisse.

Source: Gripped Canada´s Climbing Magazine facebook page

2.2 The usual problem... How do we control the intensity during a training session?

From a practical point of view, what kind of holds and what climbing styles do I have to favor?

Looking at what we have already seen we should go for holds that, being on a particular wall, wouldn't represent more than 25% of our maximum grip strength.

a) One possible solution would be to perform a test of maximum climbing time on a certain kind of hold, and looking at the relationship found by Rohmert (1960) and confirmed by successive authors (Allison et col., 2004; Frey & Avin 2010; Looft, 2012) between percentage of MVC during an isometric contraction and maximum duration of such contraction. In short, the higher the intensity the quicker the exhaustion and vice versa. This can also be applied to the number of repetitions/sets in dynamic exercises:

• An isometric contraction at 10% of MVC can be held for about an hour,
• A 12% one about 40 minutes,
• Repeated intermittent contractions at 25% of MVC (10-second contraction / 2-second relaxation) can be sustained for 6-8 minutes.
• Around 30% the time drops to 2-4 minutes.

(Rohmert 1960, Byström, 1994; Allison et col., 2004; Frey & Avin 2010).

Maximum durations (minutes) for different intesity (%MVC) intermittent contractions (contraction time + relaxation time) and continuous contractions (Byström y Kilbom, 1990)

All these figures have to be taken with a grain of salt, though, because:

i) The participants were untrained people for whom the forearm muscles were not a key performance factor.

ii) There is great variability in low intensity endurance among individuals.

iii) The dyamometer is not considered a specific tool to measure maximum grip strength in climbing (Watss, 2004) neither to assess actual climbing performance. In this regard, we don't know about any climbing-oriented tests that measure maximum time for a wide variety of intensities during real climbing.

Recently López-Rivera, E. (2014) has put forward in her PhD thesis a formula for estimating maximum hang-off duration as a function of edge depth (6-14 mm) and sport level (6b+ to 8c+, n=36), but it is probably valid for higher intensities only (we will go over it in the entries about high intensity endurance) and it remains to be seen its application to actual climbing on holds of similar size to the test ones.

Eva López. Photo by Javipec

b) The common sense approach, a simpler way:

The goal is to find holds and walls of a certain angle that allow us to endure the programmed climbing time at a low intensity:

• For low-mid level or high volume sessions, we will probably choose the largest holds, those deep enough to fit the entire fingers, with a positive and rounded profile (jugs), on vertical or less than vertical walls. For higher levels the holds could be similar, but the wall more steep or overhanging. Trying holds not so deep is a possibility. Anyway, each climber will have to test it...because as you already know, individualization and control of the training load is key for an effective training.

We will learn to associate low intensity to a set of sensations that can be described as follows.

 

2.2.2 Sensations related to the Physiological Effects of Capacity Training

Several authors have assessed the validity of subjective scales of perception to control the intensity in different sports (Seyler, S. in Mujika, 2012 [editor]). To develop our Capacity we have to look for and maintain the following sensations:

Local signs at the forearms:

• Moderate swelling and activation, never stiffness and strong pumping. As we progress in time or sets we may need to shake off every 2-3 moves for 1-2 seconds.
• Some vasodilation that can translate into "heat", reddening, bulging veins...
• Progressive "depletion" (according to the objectives for the session).
• Mild pain. Using the subjective scale from 1 to 5 developed by Binney & MacClure (2006), we should rate at 1 or 2.

Global signs:

• Light increase in breath and heart rate, etc.
• Moderate perspiration.
• As the session progresses, especially at the end of every set, it is normal to notice our movements are "slower", perhaps due to some related factors: a) we start running out of glycogen and use slow-burning fatty acids, b) we need to save energy and the kind of holds we are using allows us to do that, and c) because this way we can relax the free hand a bit longer. When climbing easy parts our hand can stay free for about 0,5 seconds, but it can go up to 1-2 seconds if we climb slower, giving time to the forearm to recover and keep on functioning.

Note: In the future we will publish an entry discussing a proposal for a load control scale in climbing training.
 

3. Volume

From 10 to 40-60 minutes, attending to the use of continuous or interval methods, our level, our training experience, climbing projects and time of the season, etc.

The next post will expand on the continuous and interval methods, and will offer some guidelines to customize total volume, number of sets, rest pauses, etc.

RELATED LINKS

Why we need to train Local Aerobic Endurance: Let the Numbers Talk

Objectives and Bases for Designing an Endurance Training Program in Sport Climbing

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

 

RECOMMENDED READINGS

• Bechtel, S. Unlearning Endurance Training, website: "Climb Strong"[on-line], Entry from January 21th, 2013. Available at: http://www.climbstrong.com/articles/20130121_12
• Guyton, A., and Hall, J. (2006). Textbook of medical physiology, 11th.
• MacLeod, D (2010). 9 out of 10 climbers make the same mistakes: navigation through the maze of advice for the self-coached climber. Rare Breed Productions. (pp 85-89).
• Randall, T Tricks of the endurance training trade, website: "Tom Randall Climbing"[online], Entry from July 9th, 2012. Available at: https://tomrandallclimbing.wordpress.com/2012/07/09/tricks-of-the-endurance-training-trade/
• Wilmore, JH and Costill, DL (2004). Physiology of Sport and Exercise. Human Kinetics.

REFERENCES

• Allison, B., Desai, A., Murphy, R., & Sarwary, R. M. (2004). Human potential of applying static force as measured by grip strength: Validation of Rohmert’s formula (Doctoral dissertation, Thesis. San Jose State University).
• Barcroft H, and Millen JLE (1939) The blood flow through muscle during sustained contraction. J Physiol (Lond) 97:17--3
• Barnes WS. (1980). The relationship between maximum isometric strength and intramuscular circulatory occlusion. Ergonomics 23: 351–357.
• Binney, D, and McClure, S (2006). Aerobic and anaerobic power: Power endurance. Climb, 26, 64 66.
• Byström, SEG, and Kilbom, Å (1990). Physiological response in the forearm during and after isometric intermittent handgrip. European journal of applied physiology and occupational physiology, 60(6), 457-466. 
• Byström, S (1994). Estimation of aerobic and anaerobic metabolism in isometric forearm exercise. Upsala journal of medical sciences, 99(1), 51-62.
• Fallentin, N, Jørgensen, K, and Simonsen, EB (1993). Motor unit recruitment during prolonged isometric contractions. European journal of applied physiology and occupational physiology, 67(4), 335-341.
• Frey Law, L. A., & Avin, K. G. (2010). Endurance time is joint-specific: a modelling and meta-analysis investigation. Ergonomics, 53(1), 109-129. 
• Fryer, S., Stoner, L., Scarrott, C., Lucero, A., Witter, T., Love, R., ...and Draper, N. (2014). Forearm oxygenation and blood flow kinetics during a sustained contraction in multiple ability groups of rock climbers. Journal of sports sciences, (ahead-of-print), 1-9.
• Hounker M, Schmid A, Schmidt-Trucksass A, Grathwohl D, and Keul J (2003). Size and blood flow of central and peripheral arteries in highly trained able-bodied and disabled athletes. J Appl Physiol 95: 685–691.
• Kimura, N, Hamaoka, T, Kurosawa, Y, and Katsumura, T (2006). Contribution of intramuscular oxidative metabolism to total ATP production during forearm isometric exercise at varying intensities. TheTohoku journal of experimental medicine, 208(4), 307-320.  
• Looft, JM (2012). Modeling and validating joint based muscle fatigue due to isometric static and intermittent tasks.
• López-Rivera, E (2014): Efectos de Diferentes Métodos de Entrenamiento de Fuerza y Resistencia de Agarre en Escaladores Deportivos de distintos Niveles (Tesis Doctoral). Programa de Doctorado en Rendimiento Deportivo, Universidad de Castilla-La Mancha, Toledo, España.
• Rohmert, W, 1960. Determination of the recovery pause for static work of man. Internationale Zeitschrift Fur Angewandte Physiologie, Einschliesslich Arbeitsphysiologie 18, 123-164.
• Seiler, S  (2012). Training Intensity Distribution, Chapter 4. En Mujika, I. (editor), Endurance Training (pág. 31-39). Bizkaia. I. Mujika.
• Sjøgaard, G, Savard, G, and Juel, C (1988). Muscle blood flow during isometric activity and its relation to muscle fatigue. European journal of applied physiology and occupational physiology, 57(3), 327-335.
• Sejersted OM, Hargens AR, Kardel KR, Blom P, Jensen O, and Hermansen L. (1984). Intramuscular fluid pressure during isometric contraction of human skeletal muscle. J Appl Physiol 56: 287–295
• Thompson, B. C., Fadia, T., Pincivero, D. M., and Scheuermann, B. W. (2007). Forearm blood flow responses to fatiguing isometric contractions in women and men. American Journal of Physiology-Heart and Circulatory Physiology, 293(1), H805-H812.
• Kalliokoski, K. K., Laaksonen, M. S., Takala, T. O., Knuuti, J., and Nuutila, P. (2003). Muscle oxygen extraction and perfusion heterogeneity during continuous and intermittent static exercise. Journal of Applied Physiology, 94(3), 953-958.
• Ušaj, A., Jereb, B., Robi, P., and von Duvillard, S. P. (2007). The influence of strength-endurance training on the oxygenation of isometrically contracted forearm muscles. European journal of applied physiology, 100(6), 685-692.
• Watts, P. B. (2004). Physiology of difficult rock climbing. European journal of applied physiology, 91(4), 361-372.

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

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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:

 1-CIRCULATORY ADAPTATIONS
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-MUSCLE ADAPTATIONS

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: dailymail.co.uk

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.

*GLOSSARY

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).

RELATED ENTRIES

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


**RECOMMENDED READINGS TO EXPAND AND IMPROVE YOUR KNOWLEDGE

• Goddard, D., and Neumann, U. (1993). Performance rock climbing. Stackpole Books. (pp. 105-106; 121-124)
• MacLeod, D. (2010). 9 out of 10 climbers make the same mistakes: navigation through the maze of advice for the self-coached climber. Rare Breed Productions. (pp. 87-88)
• McArdle, W., Katch, F. I., y Katch, V. L. (1990). Exercise Physiology: Nutrition, Energy and Human Performance. LWW. (chapters 6, 7, 15, 16, 18)
• Randall, T. Tricks of the endurance training trade, website "Tom Randall Climbing" Entry from July 9th, 2012. Available at: https://tomrandallclimbing.wordpress.com/2012/07/09/tricks-of-the-endurance-training-trade/
• Wilmore, J. H., and Costill, D. L. (2004). Physiology of Sport and Exercise. Human Kinetics. (chapters 4, 5, 6 and 9)

REFERENCES

• Allison, B., Desai, A., Murphy, R., and Sarwary, R.M. (2004). Human potential of applying static force as measured by grip strength: Validation of Rohmert´s formula. San Jose University
• Andersen, P., and Henriksson, J. (1977). Capillary supply of the quadriceps femoris muscle of man: adaptive response to exercise. The Journal of physiology, 270(3), 677-690.
• Arnold, A. S., Gill, J., Christe, M., Ruiz, R., McGuirk, S., St-Pierre, J., ... & Handschin, C. (2014). Morphological and functional remodelling of the neuromuscular junction by skeletal muscle PGC-1α. Nature communications, 5.
• Brooks and Mercier, J. (1994). Balance of carbohydrate and lipid utilization during exercise: the" crossover" concept. Journal of Applied Physiology, 76, 2253-2253.
• Burgomaster, K. A., Hughes, S. C., Heigenhauser, G. J., Bradwell, S. N., and Gibala, M. J. (2005). Six sessions of sprint interval training increases muscle oxidative potential and cycle endurance capacity in humans. Journal of applied physiology, 98(6), 1985-1990.
• Costill, D. L., Daniels, J., Evans, W., Fink, W., Krahenbuhl, G., and Saltin, B. (1976). Skeletal muscle enzymes and fiber composition in male and female track athletes. J Appl Physiol, 40(2), 149-154.
• Befroy, D. E., Petersen, K. F., Dufour, S., Mason, G. F., Rothman, D. L., and Shulman, G. I. (2008). Increased substrate oxidation and mitochondrial uncoupling in skeletal muscle of endurance-trained individuals. Proceedings of the National Academy of Sciences, 105(43), 16701-16706.
• Evertsen, F., Medbø, J. I., and Bonen, A. (2001). Effect of training intensity on muscle lactate transporters and lactate threshold of cross‐country skiers. Acta Physiologica Scandinavica, 173(2), 195-205.
• Ferguson, R. A., & Brown, M. D. (1997). Arterial blood pressure and forearm vascular conductance responses to sustained and rhythmic isometric exercise and arterial occlusion in trained rock climbers and untrained sedentary subjects. European journal of applied physiology and occupational physiology, 76(2), 174-180.
• Frey Law, L. A., and Avin, K. G. (2010). Endurance time is joint-specific: a modelling and meta-analysis investigation. Ergonomics, 53(1), 109-129.
• Fryer, S., Stoner, L., Scarrott, C., Lucero, A., Witter, T., Love, R., ...and Draper, N. (2014). Forearm oxygenation and blood flow kinetics during a sustained contraction in multiple ability groups of rock climbers. Journal of sports sciences, (ahead-of-print), 1-9.
• García Manso, JM; Vitoria Ortiz, M; Navarro Valdivielso, F; Legido Arce, JC (2006). La resistencia desde la óptica de las ciencias aplicadas al entrenamiento deportivo. Grada Sport Books.
• Gladden, L. B. (2008). A lactatic perspective on metabolism. Medicine and science in sports and exercise, 40(3), 477-485.
• Goddard, D., and Neumann, U. (1993). Performance rock climbing. Stackpole Books.
• Greiwe, J. S., Hickner, R. C., Hansen, P. A., Racette, S. B., Chen, M. M., and Holloszy, J. O. (1999). Effects of endurance exercise training on muscle glycogen accumulation in humans. Journal of Applied Physiology, 87(1), 222-226.
• Hawley, J. A., Brouns, F., and Jeukendrup, A. (1998). Strategies to enhance fat utilisation during exercise. Sports Medicine, 25(4), 241-257.
• Hawley, J. A., & Stepto, N. K. (2001). Adaptations to training in endurance cyclists. Sports Medicine, 31(7), 511-520.
• Holloszy, J. O., and Coyle, E. F. (1984). Adaptations of skeletal muscle to endurance exercise and their metabolic consequences. Journal of applied physiology, 56(4), 831-838.
• Hoppeler H., Howald H., Conley K., Lindstedt S.L., Claasen H., Vock P. and Weibel E.R. (1985). Endurance training in humans: aerobic capacity and structure of skeletal muscle. J Appl Physiol; 59(2):320-7.
• Iaia, F. M., Perez-Gomez, J., Thomassen, M., Nordsborg, N. B., Hellsten, Y., and Bangsbo, J. (2011). Relationship between performance at different exercise intensities and skeletal muscle characteristics. Journal of applied physiology, 110(6), 1555-1563.
• Karpp, J.R. (2000). Interval Training for the Fitness Professional. National Strength & Conditioning Association, 4(22), 64–69
• Kiens, B., Essen-Gustavsson, B., Christensen, N. J., and Saltin, B. (1993). Skeletal muscle substrate utilization during submaximal exercise in man: effect of endurance training. The Journal of Physiology, 469(1), 459-478.
• Laughlin, M. H., Cook, J. D., Tremble, R., Ingram, D., Colleran, P. N., and Turk, J. R. (2006). Exercise training produces nonuniform increases in arteriolar density of rat soleus and gastrocnemius muscle. Microcirculation, 13(3), 175-186.
• López-Rivera, E. (2014): Efectos de Diferentes Métodos de Entrenamiento de Fuerza y Resistencia de Agarre en Escaladores Deportivos de distintos Niveles (Tesis Doctoral).  Programa de Doctorado en Rendimiento Deportivo, Universidad de Castilla-La Mancha, Toledo, España.
• MacLeod, D., Sutherland, D. L., Buntin, L., Whitaker, A., Aitchison, T., Watt, I., ... and Grant, S. (2007). Physiological determinants of climbing-specific finger endurance and sport rock climbing performance. Journal of sports sciences, 25(12), 1433-1443.
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Heat-induced Fatigue

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Do you some days get to the gym only to find that you don't feel like training today?
Are you tired even at home, although you have not made any physical effort yet?

Is it not only that you don't feel like doing your chores, but also that you lack the energy to perform them? Perhaps you feel apathy, lack of interest, sleepiness, to the point that even walking can be challenging and those coffees that usually are so helpful don't have the desired effect anymore... Maybe your head hurts, and your resting heart rate is higher than usual. You try to find the cause of such fatigue, but to no avail...

Gathering all the willpower you have left, you put your climbing shoes on and start climbing. But the nightmare is still going on and, even warming up, your arms get pumped in the easiest sections. When a hard move comes, well, you just don't have that kind of power. If you are at the gym and try to do some boulder or strength exercise your heart rate spikes while doing things that you remember being easy before. To top it all, the sweat on your hands makes you slip off the holds all the time...

Do these symptoms ring a bell? Perhaps you have experienced similar circumstances, "incidentally" associated to really hot days?

Well, you are right, those symptoms are due to heat, and heat-induced fatigue.

For life to go on, we need to keep our internal (rectal) body temperature between about 36,1ºC and 37,8ºC. (Córdova 1999).

During exercise, the rate of metabolic heat production goes up, so that if this heat surge is not balanced by the rate at which we dissipate it, our internal temperature can get too high, and this is highly correlated with a decrease in sport performance. Exhaustion and inability to continue an endurance exercise are reached when internal body temperature goes between 39ºC and 40,3ºC, according to González-Alonso et col. (1997).

We also have to realize that for a given intensity, the higher the temperature, the higher the metabolic and cardiovascular stress will be, and that this will contribute to exacerbate our sensation of fatigue:
When it's hot, there is a lot of blood flowing towards the skin instead of the muscles used in the exercise, a higher oxygen consumption, an increase in muscle lactate, heart rate and sweating, and a higher spending of muscle glycogen; all in all, greater energy production (Willmore and Costill, 2007).

It's believed that this fatigue and the changes inside our body can be caused by the direct effects of hyperthermia over the central nervous system, and are a defense mechanism of the body, that works like a "fuse" which prevents the athlete from keeping on producing heat and suffering heat-induced injury, heat stroke or even death (Terrados et col., 2004).
Regulation of body temperature resides in the hypothalamus and it works in a similar fashion to our home's thermostat: when body temperature goes up, our central and peripheral thermoreceptors send signals to the hypothalamus and the cerebral cortex to voluntarily stop exertion, to get further from the heat source, or to boost our heat loss through vasodilation and metabolic activity (Terrados et col., 2004).

What can we do to combat the negative effects of heat?

It is vital to drink enough.
For every liter of water lost, heart rate increases about 8 bpm. Less blood gets to the skin, so heat dissipation is compromised, and central body temperature goes up 0,3ºC for each liter of water lost (Coyle, 1994). It has been shown that a loss of just 1% of body weight (0,7kg for a 70kg athlete), causes a 5% reduction in our maximum time doing a continuous endurance exercise.
Also, it's been suggested that hydration with a sugary or isotonic drink (6% sugar), improves the thermoregulatory system (Below, 1995).
The method to follow would be like this:
- drinking about 1 liter of water during the hour previous to competition, about four times 15 minutes apart, 150-250ml of sugary drink each time,
- every 15' during a training session or a climbing day,
- and after training, taking 150% of the body weight lost, in 2-3 times starting with a big one (800-1000ml), and following with smaller ones during recovery (200 ml/15 minutes).

It also seems that adding 5,6g/l of sodium (Shirreffs, 2000) improves body liquid recovery.

A different technique that can be used is precooling. González-Alonso et col.(1999) observed that cyclists who lowered their internal temperature to 36ºC thanks to having been immersed in cold (17ºC) water for 30', were capable of doing 63 minutes of pedaling, in contrast to the 28 minutes that lasted those who were immersed in hot water for 30', and as such had an internal temperature of 38,2ºC. Other studies suggest that the same effect can be obtained by cooling all the body with the exception of those muscles used in the exercise, to avoid vasoconstriction that can compromise performance (Cotter et col., 2001)
Gorostiaga (2004) puts forward the following method for endurance training: doing a 45' precooling before the exercise, that can be performed in two ways: 1) staying inside a room with very cold (3-4ºC) air conditioning or being covered with ice, but using warm clothes over the muscles that are important for the exercise, or 2) staying up to the neck into cold water.
Even though water immersion is recommended, it would seem reasonable to keep out of the water the muscles that will be more needed for the exercise (like keeping your legs out of the water if you are going to run).

Keeping a low body weight will also help dissipating heat. Smaller people can get rid of excess heat easier than bigger and heavier ones, even if they have the same relative amount of body fat. This is because their body surface to body mass ratio is higher. This allows them to dissipate proportionally more heat than bigger individuals (Marino et col., 2000). This said, reduced body fat also helps in conveying heat to our surroundings, because an excess of fat increases the insulating capacity of the skin and slows heat conduction towards the surface (Mc Ardle et col., 1990).

Lastly, prevention and carrying out a good adaptation process to heat will yield good results. The greater benefits will take no more than 3-5 days to become apparent and will be fully developed in about 2 weeks:
We will start to sweat earlier, the sweat will be less thick and higher in volume, our resting heart rate will drop, we will spend less glycogen at a given intensity, and the flow of blood towards the skin will improve. The first changes explain why when we are adapted to heat we need to drink more, not less.
Heat adaptation doesn't mean the athlete getting used to training while dehydrated. To this day there is no evidence that humans can develop adaptations to dehydration.
To obtain a good heat acclimation the following guidelines are in order:

- Avoid intensive anaerobic training during the first week of heat adaptation (González Alonso et col., 1999)

- Exposing oneself to heat for the whole day is more effective than just enduring it while training and spending the rest of the time in air conditioned places. We can take advantage of a/c while sleeping, and during recovery periods. (Noakes: "Exercise in the heat" in "Clinical Sports Medicine", Brukner and Khan, 2007)

- If we want to perform in a hot environment, we should train with heat for at leas 2 weeks while we make sure we are well hydrated and observe the precautions needed to avoid heat stroke. The same goes if the environment is both moist and hot.

-During the first days of adaptation, it's advisable to carry out the more intensive training sessions early in the morning or late in the evening, and reserve the hottest hours of the day for lower intensity sessions (Gorostiaga, 2004). Or we can reduce the intensity in this first phase to 60-70%, and progressively increase it, training at higher loads with high temperature for another 5-10 days until we are fully adapted (Willmore and Costill, 2007).

Unfortunately, it seems that the effects of acclimation are lost if we don't train under hot conditions for 2 to 4 weeks, so...
don't get all depressed if you return home from climbing at that high, cool crag, only to find that you will have to endure once again that feeling of slowly being baked.
Patience.

SOON: Recommendations for Climbing in the Heat

REFERENCES

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