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At least 1,441 records · Page 80Linked to original sources
PubMed2004

The effect of shaft flexibility on junior golfers' performance.

The aims of this study were to examine the effect of shaft flexibility on the performance of junior golfers and to determine whether there is a relationship between golfers' physical characteristics (16 anthropometric measures, age, experience, strength), performance and shaft flexibility. We assessed the performance of 30 male golfers, aged 7-10 years, with three 7-iron golf clubs of different shaft flexibility at a driving range. The performance parameters measured for equipment evaluation were ball distance achieved, shot dispersion and impact position of the ball on the clubface. The results suggest that there is no particular shaft flex suitable for the age group considered and that experience, strength and arm span are the significant factors when selecting optimal shaft flexibility for children.

Arm↗
PubMed2006

Movement and stretching imagery during flexibility training.

The aim of this study was to examine the effect of movement and stretching imagery on increases in flexibility. Thirty volunteers took part in a 4 week flexibility training programme. They were randomly assigned to one of three groups: (1) movement imagery, where participants imagined moving the limb they were stretching; (2) stretching imagery, where participants imagined the physiological processes involved in stretching the muscle; and (3) control, where participants did not engage in mental imagery. Active and passive range of motion around the hip was assessed before and after the programme. Participants provided specific ratings of vividness and comfort throughout the programme. Results showed significant increases in flexibility over time, but no differences between the three groups. A significant relationship was found, however, between improved flexibility and vividness ratings in the movement imagery group. Furthermore, both imagery groups scored significantly higher than the control group on levels of comfort, with the movement imagery group also scoring significantly higher than the stretching imagery group. We conclude that the imagery had stronger psychological than physiological effects, but that there is potential for enhancing physiological effects by maximizing imagery vividness, particularly for movement imagery.

Adult↗
PubMed1996

Anthropometric, strength, endurance and flexibility characteristics of elite and recreational climbers.

There has been remarkable development in the scope and quality of rock climbing in recent years. However, there are scant data on the anthropometry, strength, endurance and flexibility of rock climbers. The aim of this study was to compare these characteristics in three groups of subjects-elite rock climbers, recreational climbers and non-climbers. The 30 male subjects were aged 28.8 +/- 8.1 (mean +/- S.D.) years. Group 1 (n = 10) comprised elite rock climbers who had led a climb of a minimum standard of 'E1' (E1-E9 are the highest climbing grades) within the previous 12 months; Group 2 (n = 10) comprised rock climbers who had achieved a standard no better than leading a climb considered 'severe' (a low climbing grade category); and Group 3 (n = 10) comprised physically active individuals who had not previously done any rock climbing. The test battery included tests of finger strength [grip strength, pincer (i.e. thumb and forefinger) strength, finger strength measured on climbing-specific apparatus], body dimensions, body composition, flexibility, arm strength and endurance, and abdominal endurance. The tests which resulted in significant differences (P < 0.05) between the three groups included the bent arm hang (elite 53.1 +/- 1.32 s; recreational 31.4 +/- 9.0 s; non-climbers 32.6 +/- 15.0 s) and pull-ups (elite 16.2 +/- 7.2 repetitions; recreational 3.0 +/- 4.0 reps; non-climbers 3.0 +/- 3.9 reps); for both tests, the elite climbers performed significantly better than the recreational climbers and non-climbers. Regression procedures (i.e. analysis of covariance) were used to examine the influence of body mass and length. Using adjusted means (i.e. for body mass and leg length), significant differences were obtained for the following: (1) finger strength, grip 1, four fingers (right hand) (elite 447 +/- 30 N; recreational 359 +/- 29 N; non-climbers 309 +/- 30 N), (2) grip strength (left hand) (elite 526 +/- 21 N; recreational 445 +/- 21 N; non-climbers 440 +/- 21 N), (3) pincer strength (right hand) (elite 95 +/- 5 N; recreational 69 +/- 5 N; non-climbers 70 +/- 5 N) and (4) leg span (elite 139 +/- 4 cm; recreational 122 +/- 4 cm; non-climbers 124 +/- 4 cm). For tests 3 and 4, the elite climbers performed significantly better than the recreational climbers and non-climbers for any variable. These results demonstrate that elite climbers have greater shoulder girdle endurance, finger strength and hip flexibility than recreational climbers and non-climbers. Those who aspire to lead 'E1' standard climbs or above should consider training programmes to enhance their finger strength, shoulder girdle strength and endurance, and hip flexibility.

Abdominal Muscles↗
PubMed1999

An impact analysis of a flexible bat using an iterative solver.

Although technology has now infiltrated and prompted evolution in most mass participation sports, the advances in bat technology in such sports as baseball and cricket have been relatively minor. In this study, we used a simple finite element modelling approach to try to shed new light upon the underlying mechanics of the bat-ball impact, with a view to the future optimization of bat design. The analysis of a flexible bat showed that the point of impact that produced the maximum post-impact ball velocity was a function of the bat's vibrational properties and was not necessarily at the centre of percussion. The details of the analysis agreed well with traditional Hertzian impact theory, and broadly with empirical data. An inspection of the relative modal contributions to the deformations during impact also showed that the position of the node of the first flexure mode was important. In conclusion, considerable importance should be attached to the bat's vibrational properties in future design and analysis.

Baseball↗
PubMed2002

Comparison of 1 and 2 days per week of strength training in children.

The purpose of this study was to compare the effects of 1 and 2 days per week of strength training on upper body strength, lower body strength, and motor performance ability in children. Twenty-one girls and 34 boys between the ages of 7.1 and 12.3 years volunteered to participate in this study. Participants strength trained either once per week (n = 22) or twice per week (n = 20) for 8 weeks at a community-based youth fitness center. Each training session consisted of a single set of 10-15 repetitions on 12 exercises using child-size weight machines. Thirteen children who did not strength train served as age-matched controls. One repetition maximum (1RM) strength on the chest press and leg press, handgrip strength, long jump, vertical jump, and flexibility were assessed at baseline and posttraining. Only participants who strength trained twice per week made significantly greater gains in 1RM chest press strength, compared to the control group (11.5 and 4.4% respectively, p < .05). Participants who trained once and twice per week made gains in 1RM leg press strength (14.2 and 24.7%, respectively) that were significantly greater than control group gains (2.4%). On average, participants who strength trained once per week achieved 67% of the 1RM strength gains. No significant differences between groups were observed on other outcome measures. These findings support the concept that muscular strength can be improved during the childhood years and favor a training frequency of twice per week for children participating in an introductory strength training program.

Adaptation, Physiological↗
PubMed2001

Effect of trans-tibial prosthesis pylon flexibility on ground reaction forces during gait.

This study explored the effects of trans-tibial prosthesis pylon flexibility on ground reaction forces (GRFs) associated with walking and step-down. Four (4) active subjects with unilateral trans-tibial amputation and pylon lengths ranging from 4.9 cm to 25.9 cm were studied wearing an aluminium (rigid) pylon and a nylon (more flexible) pylon. Ground reaction forces were collected for the amputated limb during walking at pre-measured self-selected velocity and when stepping down from a 20 cm box. Pylon material significantly affected the magnitudes and patterns of GRFs in both tests. During walking, the most notable differences were seen in the anteroposterior (AP) direction. With the flexible pylon, the AP propulsive peak was greater (p=0.031), and the irregularities in the AP force curve were reduced. Additionally, when walking with the flexible pylon, the vertical peak associated with weight acceptance occurred earlier (p=0.010), the vertical terminal stance peak occurred later (p=0.012), and stance time was longer (p=0.010). During step-down, the vertical loading rate (p=0.010) and the peak vertical force (p=0.010) were greater with the more flexible pylon. Subjective feedback indicated that subjects could distinguish between the two pylons and felt that the nylon component was more comfortable, more flexible, and would enable them to walk more quickly. These results suggest that the pylon may be an influential component of the prosthesis with respect to gait and comfort, and that some degree of flexibility is desirable.

Adult↗
PubMed2004

A three centre study of the variability of ankle foot orthoses due to fabrication and grade of polypropylene.

This study investigates if fabrication techniques employed at different orthotic centres affect the characteristics of the manufactured plastic orthoses. Plaster models were formed from the same master mould. The thickness and bending stiffness of the supplied polypropylene sheets were measured prior to fabrication. An orthotic technician at each of the 3 orthotic centres manufactured 4 homopolymer and 4 copolymer polypropylene ankle-foot orthoses (AFOs), following each centre's fabrication practice. Another technician at one of the orthotic centres manufactured an additional 4 homopolymer and 4 copolymer AFOs. The thickness, the dorsiflexion stiffness and plantarflexion stiffness of the 32 fabricated AFOs were monitored and compared. Analysis of the results suggests: Copolymer polypropylene sheets are supplied marginally thicker than homopolymer polypropylene sheets. The difference between the thickness of the 16 copolymer and 16 homopolymer AFOs was not significant. The thickness of the AFOs manufactured in copolymer was less consistent than homopolymer. Dorsiflexion stiffness of the copolymer AFOs was less consistent than homopolymer AFOs. Although the bending stiffness of the copolymer and homopolymer sheets differed significantly, there was no significant difference between the dorsiflexion stiffness of the copolymer and homopolymer AFOs. Plantarflexion stiffness was consistent for both the copolymer and the homopolymer AFOs and there was no significant difference between the plantarflexion stiffness of the copolymer and homopolymer AFOs. The thickness and flexural stiffness of the AFOs manufactured by 2 technicians at the same centre did not differ. These results are useful benchmarks for the flexural stiffness of AFOs.

Ankle↗
PubMedDate not supplied

Changes in physical capacity among middle-aged municipal employees over 16 years.

The purpose of the present study was to identify changes in different components of physical capacity among middle-aged women and men employed in the municipal branch for 16 years. The data were obtained by laboratory measurements and postal questionnaires. The study group consisted of 45 middle-aged subjects, who were on average 51.5 years old at the beginning of the follow-up in 1981 and 67.3 years in 1997. During the 16-year follow-up period, the average physical capacity of these workers decreased by approximately 20%. The study showed that the greatest changes occurred in isometric trunk muscle strength and in the flexibility of the spine, whereas smaller changes were noted in anthropometrics. The decrease of physical capacity was greater among men (range 11.6% to 33.7%) than among women (range 3.3% to 26.7%), although women had more individual variations. On average, people without disease or who were physically active displayed better physical capacity than people with disease or who were physically passive.

Aged↗
PubMed2001

Molecular dynamics studies of sequence-directed curvature in bending locus of trypanosome kinetoplast DNA.

The macroscopic curvature induced in the double helical B-DNA by regularly repeated adenine tracts (A-tracts) plays an exceptional role in structural studies of DNA because this effect presents the most well documented example of sequence specific conformational modulations. Recently, a new hypothesis of its physical origin has been put forward. According to it, the intrinsic bends in B-DNA may represent one of the consequences of the compressed frustrated state of its backbone. The compressed backbone hypothesis agrees with many data and explains some controversial experimental observations. The original arguments of this theory came out from MD simulations of a DNA fragment with a strong bending propensity. Its sequence, however, was not experimental. It was constructed empirically so as to maximize the magnitude of bending in calculations. To make sure that our computations reproduce the experimental effect we carried out similar simulations with an A-tract repeat of a natural base pair sequence found in a bent locus of a minicircle DNA. We demonstrate spontaneous development of static curvature in the course of MD simulations excluding any initial bias except the base pair sequence. Its direction and magnitude agree with experimental estimates. The results confirm earlier qualitative conclusions and agree with the hypothesis of a compressed backbone as the origin of static bending in B-DNA.

Animals↗