The Effect of Swim Bench Rotation Settings on Simulated Freestyle Swimming Kinematics

Introduction: The swim bench is an isokinetic ergometer designed for competitive swimming training. The KayakPro SwimFast swim bench includes a rotating bench setting; yet specific changes to a swimmer’s kinematics and muscle activity on a rotating bench compared to a fixed bench or in-water swimming are unknown. The purposes of this study were to assess the effect of swim bench setting on freestyle stroke 3D kinematics and muscle activity and evaluate the similarities between the swim bench and pre-existing in-water kinematic data [1].
Methods: Fifteen, male, right-handed, collegiate and national level competitive swimmers [20.4±1.18 yrs., 1.81±5.11 m, 78.5±6.01 kg] participated. Upper limb and torso kinematics were collected bilaterally, and surface electromyography (sEMG) collected on 12, right, upper limb muscles. Participants performed 8 sets (4 rotating & 4 fixed) of 30 seconds freestyle stroke pulling on a KayakPro SwimFast swim bench (KayakPro USA LLC, Florida, USA) at 55 stroke cycles/minute. Kinematic data was filtered with a low-pass Butterworth filter at a 4 Hz cut off, and time normalized to percent stroke cycle (%SC). sEMG data was filtered with a band-pass Butterworth filter between 30 to 500 Hz and normalized to maximum voluntary isometric contraction and %SC. Swim bench setting continuous joint angles and muscle activations were compared using statistical non-parametric mapping, one-tailed, paired t-tests. In-water measures were compared to the swim bench using one-way mixed ANOVAs.
Results: Few kinematic and sEMG differences existed between the rotating and fixed swim bench settings. The fixed swim bench produced significantly greater right shoulder elevation (p = 0.021), posterior deltoid activation (p = 0.015) (Figure. 1), and infraspinatus activation (p = 0.026). Regardless of setting, participants laterally flexed the torso. Compared to in-water data, both settings produced similar elbow flexion ranges; however, the stroke length decreased (p<0.0001), total shoulder roll decreased (p<0.0001), and entry phase duration decreased (p<0.0001) significantly.
Discussion: This study provides novel findings for coaches and researchers to consider regarding the use of the swim bench. The similarities between settings indicate that the rotating swim bench may not substantially augment the simulation of freestyle swimming. However, the reduction in stroke length, total shoulder roll, and entry phase duration with the addition of the lateral torso flexion are notable considerations for long term use.