COMPARISON OF CONCENTRIC AND IMPACT FORCES ON LAND AND IN WATER

Plyometric jump training has been used in athletic training to improve muscle strength and power and injury prevention in young people and adults. There is evidence to support aquatic plyometric training in young athletes for improving strength and power while providing a safer environment with less impact when landing. The aim of this study was to extend the research to include middle-aged adults (40-60 years) who are at a greater risk of physical decline and would benefit from a greater understanding of the forces generated in land-based and aquatic plyometric jumps for adults aged 40-60 years. Thirteen healthy individuals aged 40- 60 years participated in this study. Participants attended three sessions including a familiarisation session, land-based testing and water-based testing. Participants performed three vertical jumps (VJ) on land, three countermovement jumps (CMJ) and three squat jumps (SJ) on a force plate on land and in water. Force traces were analysed for peak force, impact force, flight time, and jump height. Peak forces normalised for bodyweight, jump height, and flight time were significantly higher in the water than on land for the CMJ and SJ (p<.000). Impact forces showed an insignificant increase in the water compared to on land. There was a strong correlation between the VJ and the two land based jumps for all jump characteristics (p<.01) and a strong positive correlation between the percentage of participant height immersed and peak force at take- off for CMJ (r=.794, p<.01) and SJ (r=.682, p<.05). Jump height, flight time, and peak force all increased in the water compared to on land. As the percentage of height immersed increased, so did peak force on take-off. Immersion depths must be considered when prescribing plyometric exercise for adults aged 40-60 years to ensure appropriately targeted exercise prescription.