A Case Study:
We all know that alcohol in too large quantities is not good on any level for triathletes. But do you know exactly how much it affects your training? Is a couple of beers on an evening out with friends really that big a deal?
It affects training a lot and it is a BIG deal. As you’ll see later, the impact can be as much as 5 times more than the fatigue from overreaching that in its own right would warrant backing off your training.
In this article, I’ll show you my personal HRV (heart rate variability) data to demonstrate how an evening out resulted in a massive decrease in HRV and training readiness.
What does alcohol do to your training and training readiness?
Let’s back up a little bit:
What do we know about how alcohol affects training for endurance sports?
- It compromises recovery
- It interferes with carbohydrate synthesis
- It reduces sleep quality and duration
- It causes dehydration
- It impairs motor ability, coordination and reaction times
- It reduces the brain’s ability to process information
(So all those swim technique drills were just a waste…)
What is HRV and how does it measure training readiness?
Heart rate variability or HRV has emerged in recent years as perhaps the best method to measure training readiness. Here’s a summary of a few key concepts:
- HRV measures the variation in time intervals between heartbeats.
- It is an indicator of how well the parasympathetic nervous system functions. This branch of the nervous system controls our recovery, digestion, and other essential aspects of training readiness.
- The number you get on your device is rather arbitrary. But trends compared to your personal baseline can be tracked to measure training readiness, overtraining, and more.
- The 7-day rolling average of HRV is more important than day-to-day values.
- The smallest worthwhile change (SWC, 0.5 times the standard deviation of all previous data points) of the 7-day rolling average is particularly useful for determining whether a change in HRV is significant or not.
This is what happened to my HRV the morning after having 3 beers and going to bed at midnight instead of 10 pm
Let’s move on to my case study:
I had been measuring HRV almost every morning since 28 June 2016. I measure my HRV immediately when I wake up, in the exact same way every time.
On 21 July, I went out for beers with a friend. I had three beers (pints) over the course of three hours from 7 pm to 10 pm. I went to bed at midnight instead of my usual 10:30 pm, so I got 1.5 hours less sleep than usual.
Below you can see my HRV data from this time period. Notice the dramatic drop in HRV the morning after this night out.
- My HRV dropped to 68 from 94 the morning before.
- My 7-day rolling average dropped to 91.1 from 94 the day before.
- My smallest worthwhile change (SWC) for the 7-day average was 0.75 the day before. Meaning, a change larger than 0.75 is more than what would be expected by measurement variation alone. And my 7-day average dropped by a whopping 3.9.
The last point is worth re-emphasizing:
If my 7-day average had dropped by even 0.75, it would have been a sign that I was overly fatigued and had reached a state of non-functional overreaching.
A few days of just easy training or complete rest is the first response to such a sign.
In this case, my 7-day rolling average HRV was reduced by more than 5 times that!
The only right thing to do was to take a day of complete rest or very easy training. I chose the latter option, and the next day my HRV was back to normal.
It’s worth adding that I didn’t feel any effects of the night before when I woke up. But I did feel very stale and sluggish in my easy workout and realized that I wouldn’t have been able to perform a high-quality workout.
Remember, the dramatic effect in my training readiness was caused by just 3 beers and going to bed at midnight.
So if you have important training sessions coming up the next day, try to stick to a policy of one beer only. Two tops.
If you don’t, there’s a big risk that you won’t be ready for the important session. Or worse, you could do the session in this state of reduced training readiness, missing out on a lot of the benefits but still increasing your training load.
That said, don’t let your hobby completely control your life. Having beers with friends is still worth doing every once in a while!
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- The Shocking Impact Of Alcohol On Triathlon Training - August 4, 2016