I found this by accident. I thought it would be an interesting read. I'm curious what thoughts You guys pick out of this article. http://strengthnutrition101.blogspot.com/2012/03/isometric-training-has-been-around-for.html
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Health, Fitness, Non-Apparatus Exercise, Unarmed Self-Defense, Firearms Self Defense
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I also agree that the longer hold with modest muscle tension would be more beneficial than short maximal one for older people. Continuous multipoint holding might be a good variant to keep long tension without the loss of attention to the isometric exercise.