Stewart Athletic Development


A beginners guide to Hybrid training part 2: Aerobic / Cardiovascular training for hybrid athletes

Welcome back to part 2 (of 4)of the concurrent training article. Last week we covered the underpinning science of concurrent training, as well as some practical nutrition recommendations. If you have stumbled across this article by chance, I would recommend checking out part one ( ) first. Now, on to the fun stuff. Training to become a hybrid athlete.

The training itself will be split into 2 articles. Firstly, we will look at aerobic training, and also look at the lactate threshold and lactate training. The 3rd article (2nd part of the training section) will look at resistance training for hybrid athlete’s, as well as some recommendations on structuring a training week, & training block.

The first training recommendation is exercising the art of patience when trying to become concurrent AF (AF = As f*ck for everyone who isn’t down with the kids.). Yes, we know you can concurrently make progress in both cardiovascular fitness (and performance) as well as strength, power and hypertrophy adaptations. However, progress is going to be slower. Particularly if 1) you are not using exogenous anabolic hormones (PED’s / steroids) 2) you’re female or 3) you’re in your mid – late 20s & upwards. Sorry, I don’t make the biological or physiological rules. It just do be like that sometimes.

Assuming you have the patience and your nutrition is nailed down, then there are training considerations which need to be made. These considerations will largely be down to your sport or activity, as will be discussed. If you are a long distance athlete (e.g marathon / ultramarathon runner), it is going to be an incredibly slow process, as your training will involve a large endurance component. This type of cardiovascular training has a bigger interference effect (i.e slower rate of adaptation) vs higher intensity cardiovascular training (such as 5k runner, sprint cyclist etc). Therefore, this should be considered when designing & implementing training.

If you are recreationally active or a intermittent sport athlete, you have more wiggle room and things become less tricky. As a result, concurrent adaptations will occur more quickly. You might currently be thing “what the fuck you on about?” But by the end of this article, it will make a bit more sense.

So how can you become concurrent AF?

There are certain training modalities which are more successful for developing adaptations concurrently. Regardless what category of athlete or person you fall into, you can successfully utilise the following modalities effectively. But remember, these are not the only way to achieve concurrent adaptations. Merely recommendations. Some more traditional methods, such as low and moderate steady state training (LISS /MISS) can still be effective. If you are a long distance athlete, you will need to have LISS/ MISS as part of your traing (not as much as you may think however – more on this later). Howver, If you are unsure, you can save yourself a lot of hassle with one simple step

Hire. A Professional!

One training modality which is particularly useful for concurrent training is HIIT. HIIT =High intensity interval training (For those unware) is an exercise modality which is made up of specific intervals (W = work) which are set at a specific time, to emphasise specific energy systems for the appropriate adaptations. These intervals are interspersed by periods of rest (can be active or passive, depending on the modality and other factors).

People like to over complicate HIIT to the high end, with about a million different acronyms for different types. It’s something that can be a bit of a grievance for me. However, I will be yielding to the use of a couple of acrobyms (Don’t @ me)

Specifically, there is a HIIT modality known as sprint interval training (SIT) which has been demonstrably one of the most effective methods in minimising the interference effect. Especially those in the general population and intermittent sport athletes. For those whom are unfamiliar with SIT, I will explain below

A SIT session is made up of short, maximal (And I mean maximal) efforts typically between 5-15s in duration. The Work : Rest (W : R) is also small, typically 1 : 1-5 W : R.

For an example, we will look at a Watt bike session (Settings – Airbrake @ 5-8, Mag brake @1). You will perform 6, 10s sprints, interspersed with 30s rest (W:R = 1:3_ , for 1-3 sets… grim stuff. However, SIT particularly effective in minimising the interference effect, and it has a lot of “bang for it’s buck” . But why?

The maximal nature of the SIT

Sit is supramaximal in nature and highly anaerobic (initially anyway), thus it predominantly recruits’ type IIx & IIa (Fast twitch) fibre types, and high threshold motor units. These are the same fibre types & motor units associated with strength, power & hypertrophy training. As a result, there is much less of an “interference” effect as both are predominantly relying on the same structures & substrates for performance, they are just being stressed in a very different manner. Essentially the training types can compliment each other, but if structured poorly they can be a hinderance (More on this later)

Due to the fibre type / motor unit recruitment it also primarily relies on anaerobic substrates for energy. The short W : R ratios indicate that there is incomplete resynthesis of anaerobic substrates (Intramuscular PCr & glycogen) therefore it has to switch to aerobic pathways. However, aerobic metabolism cannot supply energy as quickly. This substrate degradation / incomplete resynthesis is reflected in the decrease in both peak and average power produced as the number of sprints

Despite SIT appearing (And actually being) a highly anaerobic activity, there are improvements quantifiable in Aerobic capacity from SIT training interventions. But there are caveats. The research (Thus far) indicates that VO2 max plateaus after 3-4 weeks of training SIT training. But, there is generally improvements in both peak and average power produced in the later sprints (Sprint 3 onwards as represented by the second graph), over the later stages of the interventions. This indicates there are still positive adaptations occurring (Despite VO2 plateau), but what?

The improvements are coming from 1) Improved oxidative enzyme activity and  2) Improved lactate kinetics . Looking at point 1, aerobic improvements in HIIT (and SIT) training are from upregulated aerobic glycolytic enzyme activity (a mouthful I know). The firstrate limiting step in aerobic glycolysis is the efficacy of an enzyme known as Phosphofructokinase (PFK).

By increasing the efficiency of PFK (and other glycolytic enzymes – but I’m not making this too physiology heavy) activity, the body is able to produce energy more efficiently via aerobic pathways, thus we see an increase in the later sprints. The improvements in PFK (and other glycolytic enzymes), thus resulting in improved aerobic capacity, have been demonstrated in multiple studies. Whereas, there has been little to know improvement in fat oxidative enzyme activity / no increases in Beta (Fat) oxidation. So. The next time someone tells you that HIIT is “great for burning fat”, you can politely tell them to foxtrot Oscar 

Onto point 2, SIT training is well above the lactate threshold (refer to previous video) thus there is a large amount of blood lactate (BLa) accumulated. Through exposure to higher BLa concentrations, the body becomes more efficient at using lactate as a substrate. Improvements in lactate kinetics, and is reflected in multiple studies measuring BLa in different ways.

As for VO2 plateau? I think its down to the methodology used within HIIT / SIT research. Essentially, the vast majority of the research kept the training variables the exact same. I.e, the intensity & volume of SIT training did not change throughout the entirety of the interventions (typically 4-8 weeks in duration). We know from the G.A.S theory (If unsure what that is, I have a video here – ) that a stimulus needs to be changed (Positively) to elicit positive adaptation. So if week 1 in the intervention was 6x 10s sprints, with 25s recovery, then week 8 would be the same. Ergo, no change in volume or intensity.

You will need to indulge me here. This was actually what my Masters by Research (MbR / MScRes –whatever the f*ck you wanna call it) project was on before I had to abandon it (Thanks Covid). In my Study, I took some simple linear progression and applied it to a 9 week intervention. In my study, the total workload (volume) was increased every 3 weeks, through the addition of another sprint per session (2 extra reps per week). Within each session, the intensity of the sprints were set against a relative % of the individuals body mass. Intensities themselves undulated (in a controlled manner) between 6-8% for females, and 6.5 – 8.5% for males.

This may not have seemed much, but it was enough to elicit adaptation. VO2 maximum was also tested very 3 weeks (Sorry for the participants who are reading this) to monitor any potential changes. With the preliminary data collected, I seen an improvement in VO2, every 3 weeks, in all participants in the training group (regardless of participant height, weight, training status, sex etc). So I was most probably on to something, but alas, it had to be abandoned. Thanks Covid.

This improvement in VO2 indicated that O2 kinetics and maximal O2 uptake will continue to improve if training variables are manipulated to achieve a progressive overload stimulus. Whilst this may seem fairly intuitive, to the best of my knowledge there has not been a laboratory-based study which looked into this (one of the reasons I went down that route). However, if you are a coach you probably have some data from your own athletes (or maybe even yourself) which does support this. Overall, if you are looking into programming conditioning sessions to develop a lot of “bang for your buck”. SIT is a useful tool in your toolbox. But it is not the only one.

What about mid – long distance competitors?

You are probably thinking “that’s all well and good for average joe’s and intermittent sport athlete’s. But what effect does SIT have on mid – long distance events?”. And it is a fair question. It can still have a positive effect for sure, but is not necessarily the most effective method for long distance events. However, it is a common misconception that you have to be doing multiple long distance sessions each week. Well I’m here to tell you that you don’t (I can hear the  “wait, what?!” comments now) and that this may actually be hindering you.

These kinds of sessions take a huge physical toll from a biomechanical / structural perspective. This is especially true for runners / running which involves repeated contacts on a (usually) hard surface. Stress fractures and repeated strain injuries (RSI’s) are particularly high in endurance athlete’s due to this misconception that if you aren’t clocking up huge miles, you aren’t improving performance. So how can you improve mid – long distance performance, without turning into Forrest Gump?

Intervals again are the solution here, but in a slightly different format. When we are doing aerobic or anaerobic conditioning, we are trying to stress a specific energy system. However it is important to remember that when exercising, the energy systems don’t work independently of each other, but cohesively. However, the emphasis / contribution of each energy system is dependent on the stressor the body is exposed to (more on the energy systems can be found here ).

SIT raining predominantly stresses the Alactic (also known as the ATP-PCr or Phosphagen system) for energy. Thus, SIT is predominantly used for developing the Alactic system (although there are aerobic benefits). So by the power of deduction you can probably guess what these intervals will be focusing on..

Yup, you guessed it. They will be aerobic or glycolytic intervals (depending on what your needs are). These intervals are also pretty horrible (I’d actually say worse but that’s just me) but, no one said training would be easy. The principle is the same in that there is a specific W : R ratio, it’s just the times change depending on the energy systems. Essentially, the heart and the body will adapt to the stress that you put it under. It doesn’t really give a shit how it is stressed, just as long as it is done in a manner which is conducive to your specific needs & requirements of your sport or activity. There are factors such as orthopaedic, biomehcanical and structural adaptations which also need to be considered, which is where a thorough understanding of training, and exercise anatomy, physiology and biomechanics is important for designing a sensible & appropriate training block.

Many of the improvements for aerobic and anaerobic glycolytic intervals are the same in terms of uprated glycolytic enzyme activity and movement economy. However, BLa concentrations will also be lower (specifically when performing aerobic intervals), perhaps even working in and around the lactate threshold on some intervals (more on this below). But rather than going into too much more detail on HIIT (And basically repeating myself) I will leave you with an interval cheat sheet.

Conditioning cheat sheet

Lactate threshold training – all its cracked up to be?

If you have been around any hybrid or endurance athlete’s for a period of time and discussed training with them, the “lactate threshold” and threshold training will have undoubtedly been mentioned at some point. Many endurance athletes like to talk about the lactate threshold and “threshold training” as the holy grail of endurance training (it is important, don’t get me wrong) but they are often unsure what the lactate threshold actually is. Usually what they referred to as the lactate threshold, is actually something else (I have also made this mistake in the past, don’t worry!). So why do people get it wrong?

This is partly due to discrepancies within literature and in writing. Different papers and authors use various terms around Lactate interchangeably, and it confuses matters. Sometimes, the onset of blood lactate accumulation (OBLA) is referred to as the lactate threshold, but this is incorrect. The actual lactate threshold varies between person, and is defined as “the point where blood lactate (BLa) levels rise 1mmol-1 above baseline. Baseline BLa levels vary between 0.8 1.5mmol-1 and are dependant on a variety of factors. OBLA however, occurs at 4mmol-1, (regardless of training status and is a different thing) and is the point where BLa production exceeds the rate of clearance.

However, the time taken to reach OBLA does vary between individuals, and is dependant on training status. More well-trained individuals (i.e those with a greater aerobic capacity & lactate kinetics) will take a longer time to reach OBLA than less trained individuals. They are also able to sustain higher outputs during their activity. I.e, they are moving faster, for longer before OBLA hits. For mid – long distance events you want to delay the time until OBLA occurs for as long as possible. This is referred to as maximum lactate steady state (MLSS).

MLSS is the key part for endurance type events, as it is the point where an athlete can sustain their highest outputs, over an extended period of time, without a sharp increase in BLa. Essentially the highest point in outputs where the rate of BLa production is matched by the rate of BLa clearance. I have covered the lactic acid cycle (including the lactate threshold) in much more detail on a video ( ) so rather than reiterating what I have done, I will give you the link to watch it. If you are unfamiliar with the lactic acid cycle, check this out. So how do you train around your MLSS threshold?

For training around MLSS, there are a couple of pieces of equipment and data you will need. If you don’t have this, any approximations are wild guesswork. But if you are at least semi serious about mid – long distance events, you’ll probably have them. Firstly you’ll need some heart rate (HR) data, specifically, your maximum heart rate (MHR). There is a method where you subtract your age from 220 (bpm) to give an estimated MHR, but this method is incredibly crude and usually highly inaccurate. A more accurate way to determine MHR is to do a ramp test (such as a VO2, Ramp or step test – not a sprint test such as a wingate) where MHR is achieved. When doing this test, you need to wear a HR monitor (discussed below) and simply record your MHR during the test.

As you probably guessed, the equipment you will require is a HR monitor. Without your MHR data, you won’t be able to accurately determine the intensity you need to be moving at for MLSS training. For your HR monitor, it will ideally be a fairly decent one (not necessarily lab spec but not from a Mcdonalds happy meal either) that fits around your chest / sternum area. This would be preferable to HR monitors on a smart watch (for obvious reasons) but in this instance, something is definitely better than nothing. HR data is what your MLSS training will be based off (as you presumably don’t have access to VO2 kit in a lab environment but if you do, great!).

OBLA itself occurs at approximately 85% of your HR, and 75% of your VO2 max. Reading this, you are probably thinking “fuck, that’s intense”. And you would be correct, it is. So for MLSS training you need to be just under this – Now you see why you need the HR monitor?.

How you approach this will vary depending on proximity to competition, the type of competition you’re prepping for and also the session itself. As the name suggests, MLSS training leans in favour of continuous training and not intervals as the purpose of this training is to maintain high output efforts continuously. However, you could look at long duration aerobic intervals at the same HR intensities outlined. Personally, I would recommend your intervals be focused on higher intensities, and keep your MLSS training for continuous work. Keep the main thing the main thing, and don’t overcomplicate it. Which brings us on to the conclusions nicely.

Cardiovascular training conclusions

And of course, you are going to have to actually do some distance training, that are at least somewhat close to your competition distances (especially for true endurance work). Or at least, clocking up distances (overall volume) similar to that of competition. You don’t need to do this weekly, but you will need to keep yourself ticking over with longer bouts (such as once every 12-20 days). This is also applicable to short – mid distance athletes, but you do have a lot more wiggle room here, and will get a lot out of good interval work (key part here is good…). However, the reasons for the exposure to the longer sessions (distance and duration) are 3-fold. You need to ensure that you are positively adapting in 1) a physiological manner 2) a tissue capacity / biomechanical manner and 3) a psychological manner.

The physiology is simply to ensure that you are ready to compete, and whilst HIIT and threshold training is important (and absolutely should utilised) you still need practise at “doing the thing”. Similarly, tissue capacity and biomechanical capacity needs to be developed, and that will be done by gradual and sensible exposure to increased distances / difficulty of terrain over time. And finally, you need to psychologically prepare for the event. Physical preparation is all well and good, but how can you know how to keep yourself going and pushing through the hard parts with dead legs, the wind battering in your face in an uphill slog if you have never experienced it or put yourself through it?

Now don’t take this as a “you must make your life more difficult to become mentally tough”. That’s largely macho bullshit. But you do need some exposure so that you have some idea what’s ahead of you.

And that concludes part 2 of 4 in the hybrid athlete training articles .In part 3 we will look at resistance training considerations, and also how to structure a training week. Be sure to check back for it!. If you have any questions about concurrent training, then shoot me a message! Or if you want to become a hybrid athlete, get in touch and we can discuss some hybrid athlete coaching!

Until next time

Stay strong