STRENGTH AND CONDITIONING

tions, and therefore velocities, can be achieved. For this reason the ability to produce force (strength) and its related component RFD, is an integral part of power production and therefore may be a key component in determining athletic success (6, 7).

THE IMPORTANCE OF THE STRETCH-SHORTENING CYCLE IN SPORTS SPECIFIC TRAINING The need to incorporate speed-strength exercises (such as the snatch, clean, jerk and derivates of

these exercises), and

to perform these at high velocities has been well documented for power-based sports (8). Similarly, when considering ‘pre-habilitation’ of injuries, we need to ensure that the neuromuscular system is adequately trained to tolerate the imposed strains during functional tasks (9). Many explosive movements in sport (such as

one unit’, maintaining a consistent angle between the floor and the back through- out this phase of the lift. The lifters shoulders are still in front of the bar, with the feet still flat on the floor and the centre of pressure back towards the heel of the foot (11,12). This position is the start of the double knee bend, or transi- tion, phase of the lift.

Figure 1c: The end of the transition phase of the lift

optimal combined centre of gravity, and setting up the second pull. The bar must be eased off the floor as opposed to the common fault of ‘ripping’ the bar from the floor. The bar is moved by extending the knees (‘knees back’) through a pushing action of

the feet through the floor.

Meanwhile, the player must have the hips and back rise as one while maintaining a constant angle between the floor and back throughout the first pull. The knees are extended until they are in a position that is slightly behind, and underneath, the bar. At this stage, the centre of pressure of the bar is towards the heel of the foot as it is planted on the floor.

End of the first pull The bar is at the knees: The bar and the lifter have been raised primarily as a result of the lifters knees being extended. The athletes hips and back have risen ‘as

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The transition phase From this position, and without stopping the upward movement of the bar, the player should now re-bend the knees and push them under and in front of the bar. At the same time, the trunk is brought into an upright position, with the bar moving to a position close to the waist at the upper thigh level. The centre of pressure of the bar moves forward to the middle of the foot, in preparation for the following stage.

End of the transition (DKB) phase Figure 1c demonstrates the end of the transition phase of the pull, and is the strongest point of the lift. The bar has been moved to the top of the thigh, and is very close to the body (in fact, it should actually touch the thigh)*2. The greater the distance between the bar and the lifter, the bigger a moment arm is created between the resistive mass and the lifting effort. Not only does this

create an inefficient position from which force can be exerted, but it also will cause the athlete to need to bring the bar back towards him/her at later stages of the lift in order for the bar to be successfully caught in the correct position. Figure 1c also demonstrates a knee angle of approx- imately 130-140o. This has been consis- tently demonstrated to be the optimum knee angle for the generation of vertical power in the legs/thighs (13). Indeed, this can be observed if you try and perform a maximum vertical jump: The base of the countermovement component of the take-off phase would correlate to a knee angle of approximately 130-140o. From this position, the hips are fully through, the trunk is in a near vertical posture and the athlete is in the optimum position for performing a powerful jump- ing motion, with a powerful triple exten- sion of the ankles, hips and knees that will enable the continuation of the upward momentum of the bar.

*2 The rules of competitive weightlifting were changed in 1964 to allow the bar to come into contact with the athlete’s thighs. This occurred as a result of coaches and athletes realising that heavier weights could be lifted by taking advantage of the double knee bend movement. Since this rule change, 99% of the first 5 places that have been achieved at international com- petition have been won using a DKB technique.

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