Impact of channel model parameters on the wholebody Specific Absorption Rate (SAR) is studied. Closed form expressions are derived for the mean value and the standard deviation of the SAR, taking into account the random nature of the channel parameters. Total sensitivity indices of the SAR with respect to the channel parameters are derived. They are estimated using a Monte-Carlo approach. Non-influential channel parameters are identified. They are then suppressed from channel models for dosimetry purpose.