Posture Tennis
Improve serve and stroke skills with STEM principles for better performance.
Main Functions of the Skeletal System
It is important to know how the body functions in order to give it a special task to act. The skeletal system is divided into two parts: the axial skeleton and appendicular skeleton. The axial skeleton includes the skull, spinal column, ribs and sternum. The perpendicular skeleton includes all upper and lower extremities, the shoulder girdle and the pelvic girdle. Bones in the human body come in four main shapes, long, short, flat and irregular and are composed of webs of collagen fibers reinforced with calcium and phosphorus. The collagen provides flexibility while the minerals provide tensile strength.
Like the steel framework of a building, the function of the skeleton and the bones is to provide rigidity, which gives the body shape and supports the weight of the muscles and organs. Without this structure, the body would collapse in by itself, compressing the lungs, heart and other organs–impairing their functions. The rigid structure of the skeletal system also allows it to perform another one of the 5 functions of the skeletal system: movement.
The forces from skeletal muscle can control the bone’s movements. When your brain tells some parts of the body to move, some muscles will contract to act — muscles shorten and pull bones to act across joints. Muscles work in pairs — when one shortens, a corresponding muscle lengthens. Physical activity maintains or increases the strength of skeletal muscles. Remember, it is the muscles’ pulling forces that create the body’s movement, not others. Only skeletal muscles work with bones and muscles keep bones in place and also play a role in the movement of bones.
When the muscle contracts, one of the structures usually remains stationary, while the other moves. When muscles contract, the force of muscle contraction is applied to bones, resulting in movement of those bones.
Good Posture – Structural Foundation
Modern life — hours of driving, sitting in front of screens, and constant smartphone use — has drastically reshaped the way people carry their bodies. Shoulders roll forward, scapulae drift apart, and arms float in front of the torso. This collapsed posture not only looks unhealthy — it compromises the functional structure of the upper body and diminishes your ability to move with strength and precision.
In the STM Fitness, posture isn’t about standing still — it’s about creating a strong, efficient structure that supports movement. Good posture is more than good appearance — it’s a core investment in long-term health and dynamic athletic ability. It helps build balance, mobility, and strength, and enhances your awareness of how your body moves, especially during complex movements like the tennis rally.
Here is the basic Posture of Standing from the ground up:
Feel the ground force: Your feet must “give themselves to the ground” — not just stand on it. Most people stand passively, without grounding themselves. STM Fitness teaches you to root your feet so your whole body can align with gravity and move efficiently.
Coordinate your leg joints: The hips, knees, and ankles have different joint structures, but must work in synergy to provide stability, mobility and direction of bending. Learning how to let these joints share the load in dynamic movement is essential.
Spinal alignment: the sacrum acts as a keystone, transferring upper-body weight into the pelvis and legs. By adjusting the sacrum into its natural arch, you activate the powerful lower-body support system that keeps your spine aligned and strong — not tilted forward (anterior pelvic tilt) or backward (posterior tilt).
J-Spine posture: STM Fitness teaches a J-shaped spine model, which emphasizes the natural vertical alignment of the upper spine. This structure supports the ribcage and allows the sternum to lift naturally. When the scapulae are positioned firmly against the back of the ribs, the shoulders can form a stable base from which the arms hang freely and functionally.
Scapular reset: Gently pull your scapulae and shoulders up and back, then let them drop naturally so they rest firmly against your ribcage. This puts your arms in a relaxed position by your sides with slight supination (palms facing slightly forward), and creates a neutral, flat back with wide shoulders.
Neck and head positioning: Think of your eyes as being directly above your spine, aligned to see the horizon. With this intention, your neck finds its natural curve, your ears align with your shoulders, and the head becomes light and balanced — reducing strain on the spine.
In many traditional and indigenous cultures, people naturally use their glute muscles — especially the gluteus medius — every time they take a step. Over time, this builds strong, balanced hips and firm buttocks that provide powerful support for the spine. Most modern people, however, spend too much time sitting. This makes the glutes “lazy” and shifts the workload to smaller muscles that aren’t designed to handle it. The result is weak hips, poor posture, and even back pain.
By learning to engage your glutes while walking and standing, you can restore natural strength and stability. When your glutes are active, your pelvis stays aligned, your spine has better support, and your whole lower body moves more efficiently. This isn’t just about posture — it’s also about performance. Strong, active glutes give you more explosive power for running, jumping, and sports like tennis, where every serve and groundstroke begins with the legs and hips driving the gravity and motion.
Whether swinging a racquet or lifting an object, good posture minimizes strain on your spine and prevents injury. It ensures that force is continuous through your structure efficiently, without overloading weak points like the lower back or shoulders.
In STM Fitness, posture is movement-ready structure — a dynamic platform that lets your muscles fire efficiently and your joints move freely. When your posture is right, your entire body is ready to move.
