Wednesday 7 June 2017

Why you need to slow down to speed up!

Apologies for using one of the trending cliche's in the world of sport science and exercise prescription as the title for this blog post, but I do think it describes the post below quite well!

This June, I was asked to write a short intro to my club's monthly newsletter and it seemed to go down quite well so I thought I'd add it to my blog (with a bit of editing to reflect the new audience).



Dear Athletes,
With the beginning of Summer 2017 we are now officially in ‘race-season’, I'm sure many of you have raced at high-profile and grass-roots events both abroad, and domestically already.
On race day, we push ourselves hard, often to the limit, and it's likely that your peak performances this year will follow a consistent block of training with an appropriate tapering period before the main event. I thought that as we will likely all be doing at least one race effort this year, now would be a good time to talk about the importance of balancing recovery and training load.
To maximise the physiological adaptations that lead to improved performance you will need to balance training Duration, Intensity and Recovery. Recovery is arguably the most important factor in a training programme. However, recovery does not always involve simply not training, or putting your feet up for the afternoon. Intense training sessions disrupt our body’s systems and processes, and the effects can last from a few hours up to several months if the athlete has severely over-trained. It is important that we are resting after these sessions but also before we go into them. The concept that underlies this training principle is the process of Sympathetic (fight or flight) Activation and Parasympathetic (rest and digest) Withdrawal of the autonomic nervous system during exercise. At rest, parasympathetic tone is high and regulatory body functions such as digestion, heart rate, and skeletal muscle activation are running in the background, unperturbed. When we exercise, the brain withdraws the output of parasympathetic neurons and increases sympathetic outflow – this enables our heart rate to increase to near maximum, dilatation of blood vessels, recruitment of large numbers of muscle fibres, and redistribution of blood to the working muscles while reducing it to lower-priority areas (e.g. the gastric system). This process is regulated by both volitional mechanisms e.g. pedalling harder, and feedback loops that are proliferated by chemical signals from neurotransmitters. The thing is – when you stop exercising, you simply stop. However, while your heart rate can go back down to near-resting levels fairly quickly, it takes time for the other processes described to recover and for our bodies to return to their resting set-point (homeostasis). High levels of neural output mean that the neurons of the sympathetic nervous system can remain excited for prolonged periods following very intense exercise.



On top of prolonged elevated sympathetic activation there can also be a delay in parasympathetic re-activation following exercise-stimulated withdrawal due to high levels of circulating hormones. This double whammy is the reason your heart is still pounding and you can’t get to sleep after a heavy track, swim or turbo session in the evening! What is the impact of this on performance? If the sympathetic system remains activated it will become fatigued: several studies have shown that multiple hard-days result in diminished sympathetic neural output, causing reductions in muscular strength, cardiac output, and motor-pattern coordination – hence, reduced speed/increased perception of effort.
Based on what I’ve written so far it may seem like I’ve strongly advocated against the inclusion of such strenuous training. The point I want to get across is that you can’t go hard all the time and expect to see consistent improvement. The practical information of this article is that both light-intensity (<75% Max heart rate) and heavy-intensity exercise (>85% Max HR) stimulate physiological adaptations that facilitate improved endurance. Lower intensity exercise (LIT) does not cause the disruptions to autonomic balance that persist after exercise, but high-intensity exercise (HIT) does. HIT increases maximal exercise capacity while LIT increases the capability to absorb large training volumes.

Both domains, or zones, have benefits. Yet amateur triathletes frequently train in the middle of these zones. Training at this intensity still yields benefits, especially if the athlete is new to the sport as any training stimulus would produce improvement. For the more experienced athlete who wants to maximise their training hours it is necessary to reduce the time spent in the middle zone. This middle-intensity training (MIT) is often performed between the lactate threshold, which is where your blood lactate increases above resting levels, and typically occurs at >75% HRMax, and the anaerobic threshold, which typically occurs at ~85-90% MHR, and demarks the high-intensity domain. Mid-intensity exercise may feel like you’re working hard but it produces greater levels of neural and muscular fatigue than LIT, additionally it is not intense enough to elicit the adaptations seen after HIT.

Ironically, it is the time-conscious athlete who must feel like they are maximising every minute of training, who pushes themselves too hard on their easy days. Thus, based on what I see on Strava every day there is very little difference between ‘race-pace’ and their ‘easy-pace’. This delta needs to be increased to truly maximise your training sessions. As with all things in life, it helps to follow the 80:20 rule – have 80% of your training be at <75% of your HRMax, with at least 10 of the remaining 20% being >85% HRmax. The result will be that you are fresher for the harder sessions by not going into them fatigued, able to maximise your sympathetic output during harder sessions, and gaining positive adaptations from the lower-intensity exercise without delaying recovery.

Domain
HR Range
Effort Duration
Recovery
Adaptation
Low Intensity (LIT)
<75% Max
10 mins to >12 hours in some cases!
Usually low (<24hrs) but depends on duration
Increased capillaries and mitochondrial enzymes, joint angle specific efficiency improvements related to motorneuron learning
Mid Intensity (MIT) (Often race-intensity for sportive/half-ironman athletes)
75-85% Max
10 mins to 5 hours
Depends on duration but always longer and more pronounced than an equivalent time at low intensity
Blend of L and H intensity adaptations but increased blood lactate diminishes LIT gains and reduced intensity diminishes HIT gains.
High Intensity (HIT)
>85-90% Max
30 seconds to 120 minutes – large range of intensity within this zone
>24 hours but usually 48 hours before maximal outputs can be reached again
Increased cardiac output, improved oxygen economy, increased lactate elimination.

I hope this information helps everyone more carefully plan their training and racing this year. Comment or tweet me @james_jogs to discuss!
                Yours in triathlon,

                James D

No comments:

Post a Comment