The AE-KS103 Butterfly Chest Clamping and Expanding Trainer is a clinical-grade upper limb rehabilitation machine, simulates the adduction and abduction of the upper limb on a horizontal plane — targeting the pectoral, trapezius, and deltoid muscle chains through a bilateral butterfly motion that simultaneously trains both the active agonist muscles and their antagonist counterparts.

The device simulates the adduction and abduction of the upper limb on a horizontal plane, and strengthens the muscle chains of the active and antagonistic muscles. On the premise of ensuring the safety of patients, carry out efficient training; The two-way hydraulic resistance can start from the lowest limit set, with small inertia, so as to avoid damage to patients during use.

Two-Way Hydraulic Resistance — Safety-First Low Inertia Design

The two-way hydraulic resistance can start from the lowest limit set, with small inertia, so as to avoid damage to patients during use — a critical consideration for a device used with cardiopulmonary, elderly, and post-surgical rehabilitation patients whose tissues and cardiovascular systems require careful load management:

1. Starts from lowest resistance limit — The hydraulic resistance begins at the very lowest mechanically possible setting, enabling patients with minimal upper limb strength — including early post-surgical patients, severely deconditioned cardiac rehabilitation patients, and stroke patients with residual upper limb function — to begin training at a genuinely light load without any unsafe initial resistance spike.
2. Two-way resistance — Hydraulic resistance is applied in both the adduction (clamping inward) and abduction (expanding outward) directions. This bidirectional loading means both the agonist muscles of horizontal adduction and the antagonist muscles of horizontal abduction receive therapeutic resistance throughout the complete exercise arc — producing balanced bilateral strengthening of both muscle chains simultaneously, rather than the typical pattern of training only the concentric (pushing) movement and passively returning.
3. Small inertia — The hydraulic resistance mechanism is designed to minimise inertial loading at the start of movement. High inertia in strength training equipment can produce sudden, uncontrolled loading forces at the initiation of movement — particularly dangerous for patients with compromised cardiovascular status, shoulder instability, or rotator cuff pathology where sudden force spikes must be avoided. The KS103's low-inertia hydraulic system ensures that resistance is applied gradually from the moment movement begins, eliminating sudden load shocks.

• Active & Antagonistic Muscle Chain Training — Balanced Strengthening

The device simulates the adduction and abduction of the upper limb on a horizontal plane, and strengthens the muscle chains of the active and antagonistic muscles. 

By applying bidirectional hydraulic resistance throughout the full butterfly motion, the KS103 trains:

• Adduction phase (active/agonist): Pectoralis major (sternal and clavicular heads), anterior deltoid, coracobrachialis, serratus anterior — the primary horizontal adductors that produce chest compression force and anterior shoulder mobility.
• Abduction phase (antagonist becoming agonist): Posterior deltoid, infraspinatus, teres minor, middle and lower trapezius, rhomboids — the horizontal abductors and posterior shoulder stabilisers that control scapular retraction, maintain postural alignment, and balance the anterior shoulder dominance that is characteristically excessive in sedentary patients, cardiac rehabilitation patients, and desk workers.

Training both muscle chains to equivalent strength levels restores the anterior-posterior shoulder force balance that underlies healthy glenohumeral mechanics, optimal rotator cuff loading, and functional upper limb performance.