(1) Any evidence offered in whatever form shall be subject to appropriate and timely objection. When objection is made to the admissibility of evidence, such evidence may be received subject to later ruling by the commission. The commission, in its discretion, either with or without objection, may exclude inadmissible, incompetent, cumulative, or irrelevant evidence, or order the presentation of such evidence discontinued. Parties objecting to the introduction of evidence shall briefly state the grounds of objection at the time such evidence is offered. The evidence to be admitted at hearing shall be material and relevant to the issue.