| Summary: | Jumping exercises, comprising plyometrics and ballistic jumps, are commonly used and important in the development of athletic performance. However, our ability to describe training doses with accurate and meaningful measures lags significantly behind other forms of training. Furthermore, the assessment and understanding of the kinetic and kinematic characteristics which underpin effective performance are still emerging. This thesis begins by comparing methods of quantifying intensity and volume of such exercises. Measures of intensity which may be considered internal (muscle activation) and external (ground reaction forces) were compared across a range of commonly used jump exercises. It was concluded that intensity and volume may be best described through kinetic measures, namely relative peak ground reaction forces (PF) and relative net impulse respectively. The second study then applied this methodology to assess the kinetic performance of an elite group of track and field athletes in order to gain an understanding of the demands of plyometric exercise on elite performers. This highlighted the difference in PF experienced between high level athletes and recreational counterparts with elite athletes achieving relative PF in the order of double that seen in recreational subjects within the literature and the previous study. The methodology also included a more discrete assessment of PF within specific phases of the jump, described as impact, braking, concentric and landing phases, to extend previously described methods within the literature and increase the level of insight into the specific demands on an exercise. The highest forces were observed during the impact and landing phases whilst PF within the eccentric and concentric phases were comparable with each other for each given exercise. The final two studies of this thesis aimed to further the understanding of the biomechanical characteristics which underpin effective jump performance by applying a temporal phase analysis (TPA) to ballistic and plyometric exercise respectively . Comparisons of three distinct populations (elite jumpers, professional rugby players and recreational athletes) during ballistic exercise using this novel methodology provided further evidence to support the emerging picture of two alternative models of superior countermovement jump performance. The first of these is characterised by the superior neuromuscular capability of an athlete to produce concentric impulse within the timeframe of a jump. The second is characterised by an altered kinetic and kinematic signature with a greater negative displacement leading to the development of greater eccentric impulse and an augmented concentric phase. Finally, the novel application of the TPA to a drop jump demonstrated, for the first time, the efficacy of the TPA to provide additional insight into plyometric exercise. These results from an elite athlete population illustrated a model of effective drop jumping which was characterised by a brief ground contact time and stiff landing technique leading to greater force at zero velocity and an augmented concentric phase in comparison with a more compliant technique.
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