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Centre of percussion
Published in Paul Grimshaw, Michael Cole, Adrian Burden, Neil Fowler, Instant Notes in Sport and Exercise Biomechanics, 2019
The centre of percussion is an important point in the design and testing of a tennis racket and also other striking implements, such as cricket and baseball bats. The point has important applications for hitting effective shots and also hitting shots that minimise the vibrations that are transferred to the wrists, hands, elbows and/or shoulders, which can cause injury (especially through overuse). A common tennis injury that can result from excessive vibrations at the elbow is termed lateral epicondylitis (“tennis elbow”) and minimising the vibrations experienced at this joint while playing can be an advantage to the prevention of this injury. Many tennis racket companies are now seen incorporating anti-vibration devices on the strings and on the racket frame that aim to reduce these unwanted vibrations. However, it is clear that further research is needed to determine the exact relationship between the centre of percussion and the so-called “sweet spot”, as it is so often called in sporting terminology.
Productivity and workload analysis between manual and motor-manual pruning of Pinus patula at two different lifts
Published in International Journal of Forest Engineering, 2021
Zimbili Bonisiwe Sibiya, Pierre Ackerman, Simon A Ackerman
According to Kirk and Parker (1996a) manual forestry work, with or without hand tools, can lead to high workloads that rapidly reach the upper physical and mental limits of the body. Kirk and Parker (1996a), found that while evaluating ergonomic risks in manual pruning of Douglas fir in New Zealand, that a first lift 2.0 m manual prune constituted “medium to heavy” workloads, while Nutto et al. (2013) found manual pruning to be generally “very hard work” according to the physiological workload classification by Rodahl (1989). Furthermore, manual pruners are exposed to strenuous, repetitive wrist and elbow motions which can, among others, lead to tennis elbow (epicondylitis) condition. Nutto et al. (2013) found a prevalence of absenteeism from work for at least two days a month which was likely attributable to the strenuous nature of the work.
Immediate effects of counterforce brace with and without vibration on pain, muscle strength and range of motion in participants with lateral epicondylitis. A pilot study
Published in Assistive Technology, 2022
Forough Dehghani, Hassan Saeedi, Alireza Khaghani, Masumeh Bagherzadeh Cham
Lateral epicondylitis (tennis elbow) is a common soft tissue lesion caused by damage to the extensor muscles of the wrist upon overuse (Chumbley et al., 2000). This disorder is characterized by pain and tenderness at the lateral epicondyle of the elbow. The extensor tendons of the wrist, especially the extensor carpi radialis brevis tendon, contract at the site of attachment to the humerus due to a series of specific sports activities such as tennis or repetitive occupations which cause stretching and as a result, pain, and inflammation (Kraushaar & Nirschl, 1999; Shiri & Viikari-Juntura, 2011).