One sports-related science experiment for a younger child is to track how well he performs physical activities at various times of day. An older child can test which sport provides the best workout by taking his pulse after different exercises, then write a possible explanation of why the results vary.
The Science Buddies website offers many additional ideas for sports-related science projects. Descriptions of the experiments appear with some explanation of the possible results. A child can choose from easy, intermediate or advanced academic levels, depending on his grade. The website also lists the difficulty of the activity level involved in each experiment.
Education.com also offers a variety of experiment ideas from which a student to can choose. Each experiment idea lists research questions, the materials needed and directions for carrying out the experiment. It also lists resources the student can read for further understanding.
The All Science Fair Projects website offers a list of science experiments that were performed by users. A student can pick from elementary, middle or high school level projects. He can then read what the experiment is intended to prove, what steps are involved and what results were obtained. The student can recreate the experiment and then compare his results to others.