The study investigates two alternative methods (no reference and reciprocal reference) for estimating muscle force during shoulder exercises when a maximal voluntary contraction is not feasible.
Both methods showed moderate to good correlation in estimating actual versus target force, with no significant differences based on which side was tested or the direction of force (internal rotation or external rotation).
The conclusion is that both methods are equally effective and can be used interchangeably for shoulder isometric contractions in healthy adults.