The objectives of this study were to investigate the effect of handle shape on the grip force distribution in the hand and on the muscle forces during maximal power grip tasks. Eleven subjects maximally grasped 3 handles with different external shapes (circular, elliptic, and double-frustum). A handle dynamometer, equipped with both a force sensor and a pressure map, was used to record the forces exerted at the hand/handle interface. The finger and wrist joint postures were also computed from synchronized kinematic measurement. These processed data were then used as input of a biomechanical hand model to estimate muscle forces. The results showed that handle shape influences the maximal grip force, the grip force distribution, and the finger joint postures. Particularly, we observed that the elliptical shape resulted in a 6.6% lower maximal grip force compared with the circular and double-frustum handle. Concomitantly, the estimated muscle forces also varied significantly according to the handle shape, with up to 48% differences for the flexor digitorum superficialis muscle for example. Interestingly, different muscle coordination strategies were observed depending on the handle shape, therefore suggesting a potential influence of these geometrical characteristics on pathological risks such as tendonitis.
Jérémy Rossi, Benjamin Goislard De Monsabert, Eric Berton and Laurent Vigouroux
Hichem Souissi, Anis Chaouachi, Karim Chamari, Mohamed Dogui, Mohamed Amri and Nizar Souissi
The purpose of this study was to examine the time-of-day effects on short-term performances in boys. In a balanced and randomized study design, 20 boys performed four anaerobic tests of strength and power (grip strength, Squat-Jump, Five-jump and cycle Wingate tests) at 08:00, 14:00 and 18:00 hr on separate days. The results showed a time-of-day effect on oral temperature. Analysis of variance revealed a significant time-of-day effect for short-term performances for strength, cycle, and jump tests. The post hoc analysis revealed that performances improved significantly from morning to afternoon but no significant differences were noticed between 14:00 and 18:00 hr. The differences between the morning and the afternoon (the highest value measured either at 14:00 or at 18:00 hr) reached 5.9% for grip strength, 3.5% for the squat jump test, 5% for the five jump test, and 5.5% for Ppeak and 6% for Pmean during the Wingate test. A significant positive correlation was found between temperature and short-term performances. In conclusion, a time-of-day effect in the child’s maximal short-term exercise performances exists in relation with core temperature. Such variations would have pronounced effects when expressed in training programs and competitions.
Barry Thombs and David Sugden
Forty Down syndrome children in five groups between the ages of 6 and 16 years were examined on a number of manual tasks. These involved a variety of hand actions during peg displacement, transportation, manipulation, and relocation. A number of age related changes were noted. With increasing age there was an almost linear increase in the use of precision as opposed to power grips, offering the older children a greater range of responses. In general the older children were more consistent in their approach than younger children, although this was not a linear increase and was also dependent on the type of task. On a number of speed measures, the older children were faster at performing the task, although small subject numbers and within-group variability prevented some differences from being significant.
Jane E. Clark, Farid Bardid, Nancy Getchell, Leah E. Robinson, Nadja Schott and Jill Whitall
in age groups 24–32 weeks. Older infants (age 36–52 weeks) grasped the cube between the thumb and one or more fingers, which indicated that the fingers were starting to move independently from the palm. This developmental change in grasping is referred to as the transition from ‘power grip’ to
Richard B. Kreider
( Anzell, Potteiger, Kraemer, & Otieno, 2013 ; Evans, 2019 ; Kerksick et al., 2009 ; Kraemer et al., 2003 ; Vantarakis et al., 2017 ). For example, Kraemer et al. (2003) reported that 9 months of resistance training resulted in significant increases in fat-free mass; anaerobic power; grip strength