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In muscle properties section there are two options "activation 1 and 2"(parameter used for time constant in ramping up of muscle force) by default it was around 7 and 1.35.How much maximum value can I give to it, so that it doesn't reaches some unrealistic value?

What is the muscle type and what are the names of the properties?

It looks like you are using the Schutte muscle model. Please see the literature that describes this model---for example:
Schutte et al., "Improving the efficacy of electrical stimulation-induced leg cycle ergometry: an analysis based on a dynamic musculoskeletal model", https://doi.org/10.1109/86.242425.