Sports Watches – Lactate Threshold

Ever heard a fellow runner or athlete (which ever sport you choose) say that they couldn’t finish the race because they “hit a wall”? Or their bodies just couldn’t keep going? Or that they are doing a lengthy cool-down (longer than 10 mins) because they need to get rid of the lactate? Or maybe your coach has mentioned one or two of these? Well this last post of the Sports Watches Series (for the moment) will hopefully clarify a few things.

wall-sm
Hitting the wall

Lactate threshold is one of the measurements that your watch will bring up, especially after a longer run (generally < 60 min) and when you’ve really pushed yourself (into the anaerobic HR Zone; > 80% HRmax); and it is represented as a HR (bt.min-1).

So what is this lactate threshold that not just appears on your watch, but invariably something you’ve heard in passing?

To understand the concept of a lactate threshold, I am going to have to give you a “short” explanation of how the human body works, specifically looking at the muscle physiology – what happens inside the muscle when you start exercising…

 

I’m sure we have all heard someone saying that they had to stop exercising because of a build-up of lactic acid, or someone did a lengthy post-race run/cycle, to “get rid of the lactic acid”. But what is lactic acid?

Lactic acid is made up of lactate (La-) and hydrogen ions (H+), and this is a by-product of pyruvate. Pyruvate itself is a product of the breakdown of either glycogen or glucose (see Figure 1).

breakdown-of-glucose-and-glycogen
Figure 1: Breakdown of Glucose and Glycogen

But, let’s go back a few steps to understand the above process:

When we start exercising, our body breaks down glycogen and glucose (carbs) into pyruvate. Pyruvate can either enter the mitochondria* for oxidation (aerobic metabolism requiring oxygen) for more adenosine triphosphate (ATP) (Energy) or can be reduced into lactic acid (anaerobic metabolism).

*Mitochondria = your body’s cells power plants – they produce energy in the form of ATP (adenosine triphosphate)

The lactic acid that we try and “remove” after an event or training, is a weak acid and is very quickly broken down into its two components, namely Lactate and H+ ions, and as a result, there is never much lactic acid in the muscle and even less in the blood. Especially following heavy exercise sessions, the lactic acid levels return back to normal within 1 hr post-exercise, and this time frame is even further reduced following a lower intensity exercise such as jogging or walking or doing absolutely nothing.

Originally, it was thought that as the exercise intensity increased greater than the rate of VO2max, then oxygen-debt (O2-debt) occurs and the metabolism switches from being aerobic (requiring oxygen) to anaerobic (without oxygen). The thought process following this switch was that it resulted in an abrupt increase in blood lactate levels, resulting in what is called metabolic acidosis. All of this lead to people believing that lactic acid was a metabolic waste product that resulted from us pushing our bodies beyond its capacity to deliver adequate O2 to the working muscles.

If you keep the above figure in mind, as the intensity of an exercise session/bout increases, the mitochondria (remember that this is your cells’ power plant) are unable to oxidize (break down/remove hydrogen ions) all of the pyruvate. As a result we have this increased concentration of pyruvate, which in turn triggers the conversion of pyruvate into lactate through an enzyme. The lactate is then broken down further into the H+ ions and lactic acid (La-). It is the increased amount of H+ ions that could depress muscle function, rather than the La-.

Blood lactate can be taken up and utilized as a fuel source for skeletal muscle, as well as the heart, brain, liver and kidneys. It has been shown that 75% of lactate is removed during exercise, with the remaining 25% being converted to ATP through gluconeogenesis (generation of glucose from non-carbohydrate carbon substrates) in the liver and kidneys. In some instances, lactate can be a more preferred fuel source compared to glucose. Interestingly, lactate uptake, although dependent on concentration gradients, is not limited in transport, such as with insulin-dependent glucose; lactate can offer a fast and efficient fuel source. Lactate, therefore, is not a not a waste product, but rather an important source of energy and potentially a signalling molecule that is continuously formed and utilized, even under fully aerobic conditions.

 

blood-lactate-and-vo2
Figure 2: Lactate Threshold – relationship between VO2max, blood lactate and workload.

If we look at the above image, you can see how VO2max increases over time/ with an increase in workload, while lactate remains steady, and then tends to increase exponentially. The turning point is where the lactate threshold is recorded. This is the point at which you almost feel like your body just can’t continue, and it’s completely and utterly trainable.

So why have it measured, and how is it measured?

The best way to measure lactate threshold is while you’re having a VO2max test done, and this is in two ways: 1. By finger-prick/earlobe-prick; or 2. Inferred from the VO2max data analysing the O2 uptake and CO2 expired.  Although your VO2max is limited with train-ability, Lactate Threshold (LT) is something that one can train, and try get it to occur later on in the test. VO2max in this regard is the maximal potential of an athlete, while the LT or pace/power at LT is the athletes current ability. The way one trains the LT to be able to sustain higher workloads for longer before lactate accumulation occurs, can be done by training in high-intensity HR zones or by pace/power which equates to a high-intensity. So in essence, one measures the LT in order to identify two things:

  1. How well-trained you currently are.
  2. How to adapt your training to enable you to sustain high-intensity exercise for longer periods of time.

So if you need to have a VO2max test to help determine this, what does that mean for the LT that my watch gives me? Well, just like how your watch uses an algorithm to determine your VO2max, it uses a similar concept for the LT, by looking at your HR – again, this is just an estimation, and a full test should be done to get accurate measures and training recommendations.

 

Just to wrap up:

  • Lactate is not the cause of fatigue
  • Muscle pain experienced after exercise of high-intensity is caused by ultra-structural damage, inflammation and sensitized nocireceptors – NOT lactate
  • Lactate is a quick, efficient source of energy for skeletal muscle, the heart, liver and kidneys
  • Fatigue is multi-faceted and cannot be narrowed down to just one cause

 

If you would like to book or inquire regarding the VO2max and lactate testing please feel free to contact me:

 

References:

 

Hall, M.M., Rajasekaran, S., Thomsen, T.W., and Peterson, A.R. (2016). Lactate: Friend or Foe. PMR Journal, 8: S8 – S15.

Gladden, L.B. (2004). Lactate metabolism: A new paradigm for the third millennium. Journal of Physiology, 558 (1): 5 – 30.

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Sports Watches – VO2max

With all the “snazzy” gadgets that recreational and professional athletes are exposed to these days, it is difficult to not encounter certain “scientific” terms, such as VO2max. Although not so long ago, VO2max testing was only something that professional athletes were exposed to, with the new sports watches, all athletes (recreational, weekend warriors) now have exposure to this measurement.

So what is it? What does it mean? What am I supposed to do with it?

 

Let’s begin by giving a little more information on what VO2max is:

There is an upper limit to the amount of oxygen (O2) that can be consumed during an exercise bout that requires maximal effort. This upper limit is referred to as VO2max, and this is the maximal rate at which an individual can utilize O2 (1). It is determined by the rate at which O2 is transported to the tissues, the O2-carrying capacity of the blood, and the amount of O2 extracted from the blood (2). All of this is measured through indirect calorimetry, in a lab using a metabolic cart or respiratory gas analysers, measuring the pulmonary ventilation and comparing inspired and expired CO2 and O2 concentrations (3).  This measurement has been said to be the single best measurement of cardiorespiratory endurance and aerobic fitness, provided there is no pulmonary disease (1, 2, 4).

 

So how is it measured?

As mentioned it is measured in a laboratory setting, with a mask strapped to your face, with gas analyser tubes running to a computer system. (see images below).

Depending on your predominant sport (running, cycling, swimming, rowing), the use of treadmill, bike etc would change; thus making it more sport specific (or as specific as one can get for lab-based testing). There are so many different types of protocols that one can use – some are continuous speed (treadmill), some continuous incline (treadmill), continuous wattage (bike) protocols, in that the speed, incline or wattage increases at a set rate until you cannot push anymore (ramp or step protocols are also available within these).

When performing a VO2max test, there are several criteria used to identify if the test was indeed a maximal effort:

  1. A plateau of O2 uptake – exercise intensity relationship (an increase in O2 uptake less than 2 mL.kg-1.min-1 or 3% with an increase in exercise-intensity)
  2. A final respiratory exchange ratio (RER) of 1.15 or above
  3. A final HR within 10 bt.min-1 of predicted age-predicted maximum
  4. A post-exercise (4 – 5 min) blood lactate concentration of 8 mmol.L-1 or more
  5. Subjective fatigue or volitional exhaustion
  6. A rating of perceived exertion (RPE) greater than 19 on the Borg Scale
img_20160129_095303
Graph depicting data of a VO2max test, namely the relationship between O2 and CO2. The AT (Anaerobic Threshold) is the point where CO2 continues to increase while O2 starts to increase at a lower rate and/or starts to decrease – in other words, the cross-over point

What does it mean?

VO2max has been considered to be an indicator of both potential for endurance performance and to a lesser extent, training status; however, although a high VO2max may be considered as a prerequisite for elite performance in endurance sports, it does not guarantee that you will achieve at the highest level (1). It’s important to note that there are several factors that determine overall performance, not just aerobic capabilities, and these include: technique, state of training, and psychological factors that can all positively or negatively impact performance. You may physically be capable of achieving, but if your mind isn’t in the game, it makes it difficult to achieve high/top performance – and visa versa. (Don’t underestimate the power of the mind). Additionally, the higher VO2max values recorded in elite middle- and long-distance athletes is also attributed to a combination of genetic endowment and training – so essentially, if your father/mother are/were very athletic and excelled, likelihood of you excelling may also increase (in endurance sports).

 

Ok, so you’ve now partially blamed your folks for the lack of genetic excellence with regards to your endurance capabilities, but you’ve got this VO2max value on your watch, and you want to know how to improve it

 

Your VO2max can improve (increase) with physical activity for 8 – 12 weeks, and then it tends to plateau despite the exercise intensity increasing – just because this happens, doesn’t mean that your endurance performance decreases, it can still increase (remember the other factors I mentioned earlier) (4). So now that we know physical activity can increase VO2max, it’s important to note that this increase is only between 5 and 30% – however, greater increases has been noted in cardiac patients, individuals who started off with minimal initial fitness, and those that have undergone substantial weight-loss (3).

 

Great! You can improve your VO2max!! But sadly, it does decrease with age (just like most things) – So there’s the age factor.

 

Are there differences between males and females? Yes. Males tend to have higher VO2max values when compared to females. – remember the definition earlier, where I mention O2 carrying capacity to the tissues? Well, naturally, males (most of them) tend to have greater muscle mass than females, thus needing greater O2 carrying capacity. But don’t let that think that us women aren’t just as capable 😉

 

Alright, now that we have covered all the essential background information, I suppose I should cover how your watch manages to tell you your VO2max values without you having to run around with a mask on you… There are several calculations that one can use to estimate your VO2max – most of which are based on your age, height, weight, heart rate, and to some degree the speed/power of your training session. When I spoke about training effect, I mentioned the company Firstbeat Technologies Ltd that have developed algorithms and software for some sports watches to enable them to produce all this “science-y” information. This same company has taken one of these calculations, and refined it a little more, instead of just looking at your heart rate, they look at the time between successive HR beats, on/off kinetic information (derived from HR data), and the respiration rate. Important to note that there are limitations to this – it is not a direct estimation, and the watch cannot give you anaerobic energy production. It’s great for those who are just happy to keep going the way they are, but if you are wanting to take your training to the next level, then you should book a VO2max test in a lab. – the benefit of this is that you can find out as to what your exact fat burning zone is, you can find out what fuel source you rely on the most (this coupled with recommendations made by a dietitian can help you out even further), and then there are accurate HR training zones that can be implemented, and the speed at which you should be training to push yourself even more….and there are a few more.

garmin-forerunner-235-vo2max
Garmin VO2max Display

If you’re looking to have a VO2max test done, contact your High performance centre, if you are in  KwaZulu Natal, Prime Human Performance Institute can assist your with taking your training to a whole new level. (Fill in a contact form here, and I can assist you)

 

 

References:

  1. Eston, R. and Reilly, T. (2009). Kinanthropometry and Exercise Physiology Laboratory Manual: Tests, Procedures and Data. Volume 2: Physiology. Third Edition. Routledge: New York.
  2. Brooks, G.A., Fahey, T.D., and Balwin, K.M. (2005). Exercise Physiology: Bioenergetics and It’s Applications. Fourth Edition. McGraw-Hill Companies, Inc: New York.
  3. Tanner, R.K. and Gore, C.J. (2013). Physiological Tests for Elite Athletes. Second Edition. Human Kinetics: South Australia.
  4. Wilmore, J.H., Costill, D.L., and Kenney, W.L. (2008). Physiology of Sport and Exercise. Human Kinetics: Campaign, IL.

Overtraining & Recovery

Saturday morning, long run, worked hard during the training session, need a little R&R? Ever had that feeling? Ever felt like you’ve hit a plateau? Or ever felt like you’ve come back into training a little too quickly, or too hard?

Overtraining syndrome is a serious set back for many an athlete/weekend warrior. It’s not just about being overtrained, but what it can lead to – injury or worse. Unfortunately we all have that urge/understanding that to get fitter we just have to push ourselves harder and harder, go further and further – “rest is for the wicked”, “sleep when you’re dead” are just some sayings that we should put, ironically, to rest. Yes we need to push ourselves (stress), but we also need to rest (recover).

I’ve had to teach my students about a concept known as the General Adaptation Syndrome (GAS). What this entails is understanding that our bodies need to have some form of stress or overload (exercise) applied to them in order to disturb its homeostasis (balance), with this though, one needs adequate recovery in order for a training effect to occur. The below graph shows us that when we place a stress (exercise) onto our bodies, our performance initially decreases, as we keep training (with adequate rest), our bodies build a resistance to the exercise, and our performance returns to its baseline value, or goes beyond it. When this happens, we tend to find that our performance plateaus,  and this is because we are adapting to the exercise. What we do then is change it up, either increase intensity or duration, but essentially change the stressor, so that we can keep adapting. However, if the stressor is too high (e.g. you haven’t run for a while, you do a high intensity run for a long duration, you don’t rest), your performance decreases substantially, and can lead to overtraining syndrome.

gas

So what happens if you rest adequately and you don’t over-stress your body? Simply put, this:

training-adaptation

The training load needs to be gradually increased over time in order to elicit long-term improvements in fitness levels. As the fitness levels improve, the balance between training and recovery becomes quite important – training must be hard in order to elicit training adaptation, but adequate recovery must be allowed.

How does one know how much rest is adequate?

The lower the intensity of the training session, the less rest required between exercise sessions utilizing the same muscle groups.You should be aiming for 48 – 72 hours recovery. I know, your mind is now racing.. I need to train every day, I need to do a back to back run… Granted this will be the case, especially for those training for big events. Just be clever! Incorporate more stretching, foam rolling, ice bath (if it works for you), and do a little pre-habilitation when you can. And importantly, make sure you are getting good sleep (approx 7 hrs).

How does one know what the training load should be?

The general rule for developing a training load over time for endurance/aerobic training is increasing either distance, or time to complete a set distance by 10% every week. For strength training, there are different percentages of 1 repetition maximum (1-RM) for different training outcomes.

Strength training goal.jpg

How do I know if I am Overtrained?

  • You lose motivation
  • You stop seeing results
  • You become more restless and anxious
  • You feel more lethargic (general fatigue)
  • You experience chronic soreness in your joints, bones and limbs
  • You get sick more often
  • You experience feelings of depression
  • You can’t sleep and experience insomnia
  • You feel more sore after a heavy training session, compared to normal
  • You lose focus and mental concentration

Remember, overtraining isn’t a phenomenon that happens over night after a single bout of exercise. There is a continuum of overtraining development, if one keeps experiencing overload and overreaching, it will inevitably lead to overtraining:

Continuum of overtraining.jpg

I cannot stress the importance of rest and recovery even more.