Refining the forward and backward roll – Floor Gymnastics Exercises (Senior 4 Physical Education) | Ganzaa

Floor Gymnastics Exercises

Lessons

Senior 4 · Physical Education

Floor Gymnastics Exercises

3 lessons

Lesson 1 of 3

Refining the forward and backward roll

25 min

Why a ball rolls and a plank does not

Lie a football and a broom handle on a slope: the ball rolls smoothly, the handle tumbles awkwardly. Your body is the same. Curled into a tight ball it turns quickly and smoothly; stretched out it turns slowly. Every roll in gymnastics, and every somersault, is controlled by changing shape. In Senior 1 and Senior 2 you learned the basic forward and backward roll and linked them with other shapes. At Senior 4 the aim is quality and control: rolls that finish standing without hands, rolls in the straddle and pike shapes, and the mechanics that explain why each fault happens.

Definition

Tuck, pike and straddle: the basic body shapes. Tuck: knees and hips bent, knees to the chest. Pike: legs straight and together, bent only at the hips. Straddle: legs straight and wide apart.

Moment of inertia $(I)$ : a body's resistance to changes in its rotation. It grows with mass and, much more, with how far that mass lies from the axis: $I = m k^{2}$ , where $k$ is the radius of gyration.

Angular velocity $(\omega)$ : rate of rotation, in radians per second.

Angular momentum $(L)$ : the "amount of rotation", $L = I\omega$ . If no outside turning effect acts, $L$ stays constant.

Spotting: hands-on help from a trained person at the right moment and place, so that a gymnast can learn a skill safely.

The mechanics of shape

When a gymnast is in the air (a dive roll or a somersault), angular momentum is conserved, so $I_{1}\omega_{1} = I_{2}\omega_{2}$ : making $I$ smaller makes $\omega$ larger. On the mat the floor also pushes on the body, so $L$ is not exactly constant, but the same principle holds: a tight, round tuck keeps the roll turning, and opening the body at the right moment slows it so the gymnast can stand.

Worked example

Worked example 1: tuck versus straight. A 50 kg gymnast leaves the floor in a dive roll with angular momentum $L = 15\,\mathrm{kg\,m^{2}\,s^{-1}}$ . Using the radii of gyration in the diagram, find her angular velocity and the time for one full turn in the tuck and in the straight shape.

Moments of inertia: $I_{\text{tuck}} = 50 \times 0.25^{2} = 3.1\,\mathrm{kg\,m^{2}} \qquad I_{\text{straight}} = 50 \times 0.50^{2} = 12.5\,\mathrm{kg\,m^{2}}$
Angular velocities, $\omega = \frac{L}{I}$ : $\omega_{\text{tuck}} = \frac{15}{3.125} = 4.8\,\mathrm{rad\,s^{-1}} \qquad \omega_{\text{straight}} = \frac{15}{12.5} = 1.2\,\mathrm{rad\,s^{-1}}$
Time for one turn, $T = \frac{2\pi}{\omega}$ : $T_{\text{tuck}} = \frac{2\pi}{4.8} = 1.3\,\mathrm{s} \qquad T_{\text{straight}} = \frac{2\pi}{1.2} = 5.2\,\mathrm{s}$

Halving the radius of gyration divides $I$ by $2^{2} = 4$ , so the tuck turns four times faster. This is why a gymnast who opens too early in a roll stalls halfway, and why "chin on chest, knees to chest" is the first coaching point of every roll.

Refining the forward roll

Phase	Key points
Preparation	Stand tall, arms up; crouch and place the hands flat, shoulder-width apart, a short distance in front of the feet
Rotation	Chin to chest; push with the legs and lift the hips; the back of the head and then the upper back (never the top of the head) touch the mat; stay round
Finish	Keep the tuck, heels close to the seat; reach forward with the arms and stand up without pushing on the mat

Variation	What changes	Mechanical challenge
Forward roll to stand without hands	Arms reach forward at the end, feet close to the seat	Enough angular momentum to bring the centre of mass over the feet
Straddle forward roll	Legs open wide just before the feet land; hands push down between the legs	Larger $I$ at the end, so a faster start is needed
Pike forward roll	Legs straight and together throughout; finish in a pike stand	Larger $I$ all the way: needs strong hip flexors and good flexibility
Forward roll to straight jump	Roll to stand, then jump with arms up, landing with bent knees	Converting rotation into a vertical take-off

Refining the backward roll

Sit back close to the heels, keep the tuck, and roll onto the rounded back. Place the hands on the mat beside the ears, fingers pointing towards the shoulders, as the hips pass over the head. Push hard through straight arms so the head and neck are freed of weight, and land on the feet.

Variation	What changes
Backward roll to straddle stand	The legs open wide as the feet come over; land in a straddle stand
Backward roll to pike stand	Legs straight and together; strong arm push; finish standing with the body folded
Backward roll to front support	The legs reach back and the body stretches out to finish in a push-up position
Backward extension roll (advanced)	The arms push the body up through a handstand before stepping down: taught only by a coach, after a strong handstand

Fault	Cause	Correction
Roll goes sideways onto one shoulder	Hands not placed evenly; head turned	Hands level, eyes on the knees, push equally
Stuck on the back of the neck	Arm push too weak or too late	Practise the push down a gentle slope made with a wedge or folded mats
Stalls halfway and sits back	Body opens too early (large $I$ )	Stay tucked until the feet are on the mat
Lands on the knees	Not enough rotation; feet too far from the seat	Stronger push and a tighter tuck

Video: "How to coach the basic backwards roll variations on floor", Gym Club Solutions. Watch the hand position beside the ears and how each variation changes the finishing shape.

Tip

"Small to spin, big to stop." Make yourself small (tight tuck) to keep rotating; make yourself big (open out, arms reaching) when you want the rotation to end.

Warning

Safety and common mistakes. Never roll onto the top of the head: the neck is not built to take the body's weight. Use mats laid flat with no gaps, one pupil per mat at a time. Do not roll with a full stomach, with jewellery, or straight after spinning. A pupil with neck or back pain does not roll. Dive rolls are taught only by a qualified coach, low and onto a thick mat.

✦

Practice

Describe the tuck, pike and straddle shapes.
State the three phases of the forward roll and one key point for each.
A 45 kg gymnast tucks to a radius of gyration of 0.24 m. Calculate her moment of inertia.
A gymnast in the air has $I = 8.0\,\mathrm{kg\,m^{2}}$ and $\omega = 2.0\,\mathrm{rad\,s^{-1}}$ . She tucks until $I = 2.0\,\mathrm{kg\,m^{2}}$ . Find her new angular velocity.
Explain why a pike forward roll is harder to finish standing than a tuck forward roll.
A pupil's backward roll keeps getting stuck with his weight on his neck. Identify the cause and suggest a practice.
Plan a short sequence of four elements that includes a forward roll variation and a backward roll variation.
Evaluate the advice "open your body as soon as your hips are over your head in a forward roll".

Show answersHide answers

Tuck: knees and hips bent, knees to chest. Pike: legs straight and together, bent at the hips. Straddle: legs straight and wide apart.
Preparation (hands shoulder-width, a little in front of the feet); rotation (chin to chest, roll on the back of the head and upper back); finish (stay tucked, reach forward and stand without hands).
I = 45 × 0.24² = 45 × 0.0576 = 2.6 kg m².
L = 8.0 × 2.0 = 16 kg m² s⁻¹; ω = 16 ÷ 2.0 = 8.0 rad s⁻¹ (four times faster).
In the pike the legs stay straight, so the mass is further from the axis: I is larger and the rotation slower, so more starting momentum, stronger hip flexors and better flexibility are needed to bring the centre of mass over the feet.
His arm push is too weak or too late. Practise rolling down a gentle slope (wedge or folded mats) with hands beside the ears, pushing hard as the hips pass over the head.
For example: stand, arms up → forward roll to straddle stand → backward roll to pike stand → straight jump, land, arms up. (Any four linked elements with both variations.)
Poor advice: opening increases I and slows rotation, so the gymnast stalls on the back and sits down. Stay tucked until the feet are on the mat, then open by reaching forward to stand.

Quick check

A gymnast's radius of gyration halves when she tucks. What happens to her moment of inertia?

Remember

$I = mk^{2}$ and $L = I\omega$ : a tight tuck (small $k$ ) rotates fast; opening slows rotation.
Forward roll: hands shoulder-width, chin tucked, roll on the upper back, stay tucked, reach forward to stand.
Backward roll: hands beside the ears, push hard through straight arms to free the neck.
Variations: straddle, pike, to front support, to jump; advanced extensions only with a coach.

Sources and credits

Roll (gymnastics), Moment of inertia and Angular momentum, Wikipedia contributors, Wikipedia, licensed under CC BY-SA 4.0. Adapted by Ganzaa.
Video: "HOW TO COACH THE BASIC BACKWARDS ROLL VARIATIONS ON FLOOR", Gym Club Solutions, embedded from YouTube.
Body-shape diagram, tables, worked example, practice and quick check: written by Ganzaa. The radii of gyration are typical estimates.

This lesson adapts CC BY-SA material and is shared under CC BY-SA 4.0.

1Why a ball rolls and a plank does not

2The mechanics of shape

3Refining the forward roll

4Refining the backward roll

Why a ball rolls and a plank does not

The mechanics of shape

Refining the forward roll

Refining the backward roll