Complex sentence: An example of a lesser force of 40g is heading a soccer ball, and even with blows in this 30 to 40g range, it's not known whether these pose a cumulative risk of injury.
Split into simpler sentences: An example of a lesser force of 40g is heading a soccer ball. Even with blows in this 30 to 40g range, it's not known whether these add up to a cumulative risk of injury.