Brief Answer: It's due to adaptation of muscle to new workload Detailed Answer: Hi Welcome to Healthcare-Magic Greetings of the day Dear Mr XXXX Lifting dumbells is a form Isotonic exercise in which the muscle stretch to their maximum capacity and undergo hypertrophy that is increase in size of muscle fiber. As it's a unaccustomed exercise for you, it's common to experience tremors and fatigue while doing fine movements or some other activity like yoga. It's usually self limiting and resolves once your muscle get adapted to the new workload. I would suggest you the following 1. Go slow with increasing the weight of dumbells. 2. Consume electrolyte rich fluids and avoid dehydration. Rest be assured there is no cause for concern. Take care Best Regards Dr T Shobha Deepak MBBS, MD

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