After my first couple of competitions and seeing what the competition was like at the national level I saw that, with some hard work, I had an opportunity to be the national champion of something. There aren't that many opportunities in life to be a national champion, so I decided that I was going to take this seriously and keep working at it until I won nationals.
At that point, and for the next couple of years, I began to honestly probably take it too seriously. I've been into lifting since high school and I wanted to understand what my body was doing during a hold so I could come up with the best training strategy. So I did some research.
The arm can be viewed as a class 3 lever. The weight of the stein is trying to force your arm down to the side of your body, pivoting around the fulcrum that is your shoulder joint and your muscles are trying to hold it back up. This is probably the easiest way to describe it from an engineering sort of perspective, although it is actually more complicated than this given the actual angles and the fact that there are multiple muscles, tendons and ligaments involved.
What can you take away from this in practical terms? The longer your arm is, the harder it is to hold anything in your outstretched arm for long periods of time, which may give shorter competitors a slight advantage. Regardless of your height and arm length, training to develop your muscles and practicing to improve your mental toughness are critical for any serious competitor.
The main muscle that you need to focus on training is the deltoid. The anterior or front deltoid (delt for short) does the majority of the work in this situation, but even if you lift, it is naturally one of the smallest muscles in the body. So I focused on and developed exercises that would not only strengthen but also increase endurance in the anterior delt. Depending on the position of the shoulder girdle, the lateral or side deltoid, the rotator cuff and the scapular stabilizer are also likely to play an important role, so I incorporated these into my training as well.
Check out some of the strength training moves that the pros use in our Steinholding Weight Training Exercises guide.