Maximal muscle strength
1RM tests were carried out in two different abdominal exercise machines: (1) the torso rotation (VR2 Torso Rotation) and (2) the abdominal crunch (VR2 Ab Crunch; both Cybex International, Medway, MA, USA), specifically chosen to target all major abdominal muscles (i.e., m. rectus abdominis, m. obliquus externus/internus abdominis, and m. transversus abdominis). Subjects were instructed to warm‐up by walking/running on a treadmill for 10 min at low to moderate intensity before proceeding to performing 20 repetitions with light loads in the same abdominal exercise machines as used during the test. For both exercises, subjects were told to start in a seated position before commencing the concentric lifting phase. For the torso rotation, both movements to the left and right side were tested, with 1RM collected from the weakest side. During the 1RM test, the load was increased by 2.25–9 kg until the subjects were unable to lift the weight. 1RM was reached within four to six attempts, with each lift interspersed by 2–3 min of rest. The heaviest load a subject could lift represented 1RM.