Falling victim to the Interference Effect

Training for this weekend’s Tough Mudder has come to an end. I had my last run yesterday and am now into three days of rest in preparation for Saturday’s event. I’m not sure I met all my training goals, but it has certainly been an interesting change of pace!

One of my stated goals was to get stronger, possibly by putting on some muscle mass. Despite my best efforts, I have found it really hard to increase both my muscle mass and strength. My weight has hardly changed since the start of July, despite an increase in both protein and calories (on the plus side, even with the increased food intake my body fat hasn’t changed much, which is nice). And I have gotten stronger – I can now bench press almost 10Kg more now than I could in June, with similar increases in leg strength. But I still can’t so a single unassisted pull up and I was hoping to be squatting at least 10 Kg more than my bodyweight by now.

On the other hand, I have substantially increased my running stamina. I can now run for over an hour without too much pain or strain. Given I was starting with a couple of 10 minute runs a week 12 weeks ago, that is serious progress!

However, the running may be what has prevented me from gaining the strength I was hoping for. This is known as the “Interference Effect”, where doing endurance exercise training prevents gains in muscle strength when both types of training are undertaken at the same time. It appears that my struggle to increase muscle strength and running stamina at the same time are typical. In fact, when I was doing the full daily diet diary, my best month for both weight loss and muscle gain was March – when I stopped the twice weekly runs and did strength training exclusively. Not only did I manage to put on muscle mass while restricting my food intake, but my strength increased substantially. By the time of my Javelin competition in April, I was hitting new PB’s in the gym without too much trouble.

So while I am now confident that I will be able to manage all 10-12 miles of the Tough Mudder course, it looks like I will need more help from my team to make it over all 20 obstacles!

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