Why you're not getting jacked with functional training - the interference effect and concurrent trai



As a nutrition coach, one of my duties is to reign in or manage client expectations.

So what’s your goals?

“I want to look like Matt Fraser/Sara Sigmundsdottir”

Can you be any more specific?

“I want a 6 pack, a 2 x bodyweight squat and a sub 6:30 2000m row time”

“In 6 weeks”

“But I train 3-5 times per week”

“And I’ve been training for 1 year”. ....

It’s not going to happen. Any time soon at least anyway.

It’s like starting bodybuilding and expecting to reach Mr Olympia within your first year. Keep dreaming.

I’m not trying to squash dreams but it’s important to understand the training and nutrition that goes into building the physiques of your top athletes. Not to mention being able to perform like them.

Firstly, they don’t train ‘CrossFit™’ per se. They follow carefully periodised training plans focusing on different elements spread across up to 30 sessions per week, not the CrossFit.com 6 x 60-90mins sessions. Although there’s nothing wrong with this and makes for a great programme for the general population, to be jacked, strong, and fit requires SERIOUS dedication, time and effort. Which the majority of recreational athletes simply don’t have.


Are there exceptions. Of course, the genetic predisposition of the athlete will have a big influence on what you can achieve from a similar type of training (Mitchell et al. 2013), training experience (ex rugby players, weightlifters do well) and not to mention your assisted (steroids) athletes.

One of the beauties of CrossFit™ is its variety, although this paradigm of becoming a true Jack of all trades can be its own limiting factor. A combination of both endurance and strength training will have a dampening effect on one another. It makes sense. Solely concentrating on getting stronger will make things far easier than if you throw in training for an Olympic distance triathlon!

But why is it?

1. You’ll be tired. It sounds obviously but by doing a shed load of strength work will make it harder to do any additional cardio on top of it, and vice versa. Try rowing your best 2000m time after a 5 x 5 lot of back squats, it will be tough, resulting in less work, thus less adaption.

2. Concurrent training and the interference effect


When you lift weights or eat protein, a signal is sent to your body saying that you need to make your muscles stronger. This signalling pathway is called mammalian target of rapamycin (mTOR). On the other end of the spectrum, the AMPK pathway is activated in response to metabolic stress during endurance exercise (low fuel, high energy demand). The concurrent training effect can be explained by these two pathways being antagonistic to some degree, where the AMPK pathway may inhibit the activation of mTOR and resulting hypertrophy (Mitchell et al., 2013). Although they may not completely counteract one another, they can still lead to a dampening effect. (Eddens et al., 2017)

So essentially, as Wilson (2012) stated, if you do lots of cardio it will effects your ability to get jacked!

So what can you do?

You just have to a little smart about your training. Literature suggests (McCarthy, 2002) that strength and hypertrophy may not be effected from concurrent only up to a point, it’s only when the frequency increases past 4 days per week, or the intensity of endurance exercise increases above 80% VO2max­, endurance exercise slows or limits an increase in strength. So if you add a few conditioning sessions alongside your strength workouts it’s not going to have much of an effect, whereas if you do a lot more there’s going to be bigger consequences.

The type of endurance training also plays a role. Combining your strength training with HIT rather than continuous training, may provide a greater anabolic stimulus (muscle building capacity) by promoting mTOR signalling aforementioned. The incorporation of a little bit HIT into concurrent training programs may therefore be more favourable, rather than inhibitory, for the accretion of muscle mass and strength (Fyfe, 2016).

OK so what happens if you need to do both like in competitive fitness.

1. Split your sessions up - In an ideal situation, you would completely separate your sessions to reduce this interference effect. For athletes like in competitive fitness whereby you need to do it all, try and split your sessions up as much as you can. Murach (2016) highlighted how the interference effect does not have as much of an impact as once thought if you can do this.

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2. Prioritise your sessions - If you’re like most people and can only train once per day, simply prioritise what you need to work on most. What is your main goal? Is it strength, is it your engine, or is it gymnastics. Perform these sessions first when you’re not tired. For greater hypertrophy gains, starting with weight also seems more beneficial.

Or if you’re just looking to get a little fitter and lose a few pounds don’t worry about it and follow what’s on the board!

In a nutshell


  • If you do strength work you’ll get jacked

  • If you do strength work and a little bit of cardio, and mainly HIT then you can still get jacked but it’s harder

  • If you do lots of cardio and strength work in the same session you probably won’t get very jacked or that fit.

  • Splitting up your sessions into conditioning and strength sessions will have the biggest positive effect

  • If you only have time for one session per day, prioritise the order by what you want to improve most

Need more help with building a better diet for your sport? See how we can help here: www.boxnutrition.co.uk/services



Further reading:

  • Eddens, L., van Someren, K. and Howatson, G. (2017) 'The Role of Intra-Session Exercise Sequence in the Interference Effect: A Systematic Review with Meta-Analysis', Sports medicine (Auckland, N.Z.), . doi: 10.1007/s40279-017-0784-1 [doi].

  • Fyfe, J.J., Bartlett, J.D., Hanson, E.D., Stepto, N.K. and Bishop, D.J. (2016) 'Endurance Training Intensity Does Not Mediate Interference to Maximal Lower-Body Strength Gain during Short-Term Concurrent Training', Frontiers in Physiology, 7, pp. 487. doi: 10.3389/fphys.2016.00487.

  • Han, G., Gong, H., Wang, Y., Guo, S. and Liu, K. (2015) 'AMPK/mTOR-mediated inhibition of survivin partly contributes to metformin-induced apoptosis in human gastric cancer cell', Cancer biology & therapy, 16(1), pp. 77-87. doi: 10.4161/15384047.2014.987021 [doi].

  • Hickson, R.C. (1980) 'Interference of strength development by simultaneously training for strength and endurance', European journal of applied physiology and occupational physiology, 45(2-3), pp. 255-263.

  • McCarthy, J.P., Pozniak, M.A. and Agre, J.C. (2002) 'Neuromuscular adaptations to concurrent strength and endurance training', Medicine and science in sports and exercise, 34(3), pp. 511-519.

  • Mitchell, C. J., Churchward-Venne, T. A., Bellamy, L., Parise, G., Baker, S. K., & Phillips, S. M. (2013). Muscular and Systemic Correlates of Resistance Training-Induced Muscle Hypertrophy. PLoS ONE, 8(10), e78636. http://doi.org/10.1371/journal.pone.0078636

  • Murach, K.A. and Bagley, J.R. (2016a) 'Skeletal Muscle Hypertrophy with Concurrent Exercise Training: Contrary Evidence for an Interference Effect', Sports medicine (Auckland, N.Z.), 46(8), pp. 1029-1039. doi: 10.1007/s40279-016-0496-y [doi].

  • Perez-Schindler, J., Hamilton, D.L., Moore, D.R., Baar, K. and Philp, A. (2015) 'Nutritional strategies to support concurrent training', European journal of sport science, 15(1), pp. 41-52. doi: 10.1080/17461391.2014.950345 [doi].

  • Wilson, J.M., Marin, P.J., Rhea, M.R., Wilson, S.M., Loenneke, J.P. and Anderson, J.C. (2012) 'Concurrent training: a meta-analysis examining interference of aerobic and resistance exercises', Journal of strength and conditioning research, 26(8), pp. 2293-2307. doi: 10.1519/JSC.0b013e31823a3e2d [doi].

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