Differences in the mechanics of takeoff in reverse and forward springboard somersaulting dives

Figures & data

Figure 1. Takeoff for forward somersaulting springboard dive (upper sequence) and reverse somersaulting springboard dive (lower sequence), showing hurdle takeoff, hurdle flight, hurdle landing, maximum board depression, dive takeoff, and flight.

Figure 2. Simple and complex activation profiles for the joint torque generators. For the extensors the simple profile comprised a ramping up and then a ramping down of the activation level whereas the complex profile allowed a double ramp up. For the flexors the simple profile comprised a ramping down followed by a ramping up of the activation profile whereas the complex profile allowed a final ramping down.

Table 1. Overall and joint angle difference scores for the various matching simulations

Dive	Strength	Activation	Overall score	Joint angle score
Forward 2½	Forward	Simple	3.7%	5.5°
Reverse 1½	Forward	Simple	4.6%	7.9°
Reverse 1½	Forward	Complex	3.4%	6.5°
Reverse 1½	Increased	Complex	2.9%	5.6°

Table 2. Comparison of isometric strength parameters [Nm] determined from the matching of the two dives

Isometric parameter	Forward	Reverse
Knee extension	182	182
Knee flexion	143	143
Hip extension	318	318
Hip flexion	192	192
Shoulder extension	109	109
Shoulder flexion	63	67
Ankle plantar flexion	273	354
Ankle dorsi flexion	51	51
Mtp stiffness [nm/rad]	68	68

Table 3. Complexity of torque generator activation profiles determined from the matchings of the two dives

Torque generator	Forward	Reverse
Knee extension	Simple	Simple
Knee flexion	Simple	Complex
Hip extension	Simple	Simple
Hip flexion	Simple	Simple
Shoulder extension	Simple	Simple
Shoulder flexion	Simple	Simple
Ankle plantar flexion	Simple	Complex
Ankle dorsi flexion	Simple	Simple
Mtp extension	Simple	Simple

Table 4. Touchdown, lowest point and takeoff kinematics for the maximal rotating forward and reverse dives: Mass centre horizontal distance from the toes, horizontal velocity of the mass centre, vertical velocity of the mass centre, angular momentum about the mass centre, trunk angle, joint angles

	Touchdown		Lowest point		Takeoff
Variable	Forward	Reverse	Forward	Reverse	Forward	Reverse
Mass centre dist. [m]	−0.23	−0.29	−0.10	−0.21	0.13	−0.08
Hori. Velocity [ms^−1]	0.47	0.48	1.05	0.42	1.19	1.03
Vert. Velocity [ms^−1]	−3.85	−3.40	0.71	0.52	4.46	4.92
Ang. Mom. [kg.m^2s^−1]	3.1	−4.1	0.8	−9.0	67.3	−57.2
Trunk angle [°]	57	65	64	69	32	107
Ball angle [°]	145	150	147	152	180	181
Ankle angle [°]	103	117	101	116	110	165
Knee angle [°]	115	138	135	138	173	150
Hip angle [°]	107	120	144	134	138	183
Shoulder angle [°]	3	−54	144	112	115	188
Elbow angle [°]	128	167	88	143	179	152

Moment of inertia in a straight position is 10.56 kg.m²

Figure 3. Maximised rotation potential simulations for forward somersaulting dive (upper sequence) and reverse somersaulting dive (lower sequence), showing hurdle flight, board touchdown, maximum depression, dive takeoff and five positions in the flight phase.