STRIDE CHARACTERISTICS RELATED TO RUNNING VELOCITY IN MAXIMAL SPRINT RUNNING

In sprinting, athletes and coaches strive to increase running speed by means of general and specific training methods. As running velocity is always the product of stride length and stride frequency, in the end, all methods aim to improve one or both of these factors. The relation between stride length, stride rate and running velocity has been discussed in the literature from different points of view. Alexander and Goldspink (1977) analysed the movement speed and stride characteristics of mammals. As they wanted to compare mammals of different sizes, they transferred stride characteristics and speed into dimensionless parameters, taking into account gravity and the length of the leg. Their conclusions should also be valid for humans. But it is not clear if these formulas can predict stride characteristics in maximal sprint running. It was the purpose of this study to analyse whether stride rate and stride length in maximal sprint running are related to running velocity as proposed by Alexander and Goldspink. A better understanding of this relationship could probably help coaches in developing sprint training strategies. In this study twenty male physical education students performed a maximal sprint over 100 meter and seventeen female students ran a 40 meter sprint. Running speed was continuously recorded by means of a velocimeter. Surface electrodes were used to record the muscle activity of four thigh muscles. These EMGrecordings were used to determine the duration of each stride cycle and to calculate mean stride rate per 5 meter-interval. The length of the lower limbs (h) and the acceleration of free fall (g) are used in the definitions of dimensionless running velocity (dV), stride rate(dSR) and stride length (dSL). The average maximal velocity of the male sprinters was 9.37 ±0.52 m/s while the female sprinters attained 7.38± 0.52 m/s. The relation between stride length and running velocity in male 100 meter performance was determined by means of linear regression analysis: dV=0.178+(1.175*dSL). This means that 87% of variance in running velocity seems to be related to differences in stride length. On the other hand variance in stride rate explains less than 20% of the variance in running speed. These findings are confirmed by the results in the 40 meter sprint of the female group: dV=(1.172*dSL)-0.0830 with 80% of variance in dV being explained by variance in dSL and 20% of dV explained by dSR. In contrast to the findings reported in the literature we found a clear linear relationship between dSL and dV, and no significant correlation between dSR and dV. These findings were confirmed in two separate analyses: one with females and another with males. The discrepancies between the results in the literature and this study can probably be explained by the fact that we analyzed pure sprint performances, in contrast to most studies analyzing differences in running speeds ranging from jogging to sprinting. In all-out sprinting, stride rate in the second 5 meter interval is already close to the maximum stride rate; from this point on differences in running speed are mainly due to changes in stride length

EFFECT OF CURVE AND SLOPE ON INDOOR TRACK SPRINTING

In contrast with the standard 400 m outdoor track, indoor sprinting is performed on the more compact 200 m track. The curves of these indoor tracks are normally constructed by means of lateral slopes to reduce the centripetal forces acting on the contact foot of the sprinter. The centripetal force (Fc) is determined by the body mass (m) and the squared running velocity (v) of the athlete, as well as by the radius (R) of the curve: Fc= (m * v²)/R. The inhanging body position of the athlete reduces partly these centripetal forces. It is clear that runners in the inner lanes have to work harder than those running in the outer lanes. Therefore it was the purpose of this study to analyze the time differences among 200 m sprint performances in lane 2, lane 4 and lane 6 on the Flanders Expo track, that will host the European Indoor Championships in the year 2000. This track consists of a unique construction as the inclination axis of the lateral slope is situated in the middle of lane 2. This implies uphill running in lane 3 to 6 when entering the curve and downhill running in lane 1. When leaving the curve it is just the other way round. The runner in lane 2 has to run a flat course over the total distance. Five national level male sprinters performed a 120 m all-out sprint from starting blocks in lanes 2, 4 and 6. A comparable group of six sprinters performed a 120 m sprint, running full speed through the second curve of the 200 m track in the same lanes. The order of running the different lanes was randomised. Infrared sensors and an electronic timing system of Intersoft Electronics enabled the recording of the mean running speed in 15 different intervals. EMG-recordings were used to determine the duration of each stride. A mean 200 m-time was reconstructed by combining the interval times of both groups of subjects. The results of this study indicate that at the end of a complete 200 m run, lane 6-runners have a mean advantage of 0.23 s and 0.10 s compared to lane 2 and lane 4 respectively. Surprisingly this difference is mainly due to the advantage of the forwarded starting position in lane 6, avoiding the uphill running part of the first curve and benefiting optimally of the downhill part at the end of the acceleration phase. The main problem in lane 4 is the uphill running in the first steps of the acceleration. Because of their flat course lane 2-runners, compared to the uphill running in lane 4 and 6, can maintain their maximal velocity one interval longer on entering the second curve. But in the middle of this curve the outer lanes, compared to lane 2, take significant advantage of the greater radius. In spite of the difference in the radius of the curve there is no significant difference in running speed among lane 4 and lane 6. It can be concluded that lane 6 takes advantage of lane 4 in the first curve and makes the difference with lane 2 in the first as well as in the second curve. Analysis of stride characteristics shows that almost all significant differences in running velocity can be explained by differences in stride length. It can be concluded that the chances of an athlete in 200 meter indoor sprinting depend on the lane he is running in

Dietary factors associated with obesity indicators and level of sports participation in Flemish adults : a cross-sectional study

BACKGROUND: Obesity develops when energy intake continuously exceeds energy expenditure, causing a fundamental chronic energy imbalance. Societal and behavioural changes over the last decades are held responsible for the considerable increase in sedentary lifestyles and inappropriate dietary patterns. The role of dietary fat and other dietary factors in the aetiology and maintenance of excess weight is controversial. The purposes of the present study were to investigate the dietary factors associated with body mass index (BMI) and waist circumference (WC), and to analyse whether dietary intake varies between subjects with different levels of sports participation. METHODS: Data for this cross-sectional study, including anthropometric measurements, 3-day diet diary and physical activity questionnaire, were collected by the Flemish Policy Research Centre Sport, Physical Activity and Health (SPAH) between October 2002 and April 2004. Results of 485 adult men and 362 women with plausible dietary records were analysed. Analyses of covariance were performed to determine the differences in dietary intake between normal weight, overweight and obese subjects, and between subjects with different levels of sports participation. RESULTS: Total energy intake, protein and fat intake (kcal/day) were significantly higher in obese subjects compared to their lean counterparts in both genders. Percentage of energy intake from fat was significantly higher in obese men compared to men with normal weight or WC. Energy percentages from carbohydrates and fibres were negatively related to BMI and WC in men, whereas in women a higher carbohydrate and fibre intake was positively associated with obesity. Alcohol intake was positively associated with WC in men. Subjects participating in health related sports reported higher intake of carbohydrates, but lower intake of fat compared to subjects not participating in sports. CONCLUSION: This study supports the evidence that carbohydrate, fat, protein and fibre intake are closely related to BMI and WC. The sex differences for dietary intake between obese men and women might reflect the generally higher health consciousness of women. Alcohol intake was only associated with WC, emphasizing the importance of WC as an additional indicator in epidemiological studies. Besides enhancing sports and physical activity, it is necessary to improve the knowledge about nutrition and to promote the well-balanced consumption of wholesome food

Annual Town Meeting Fayette, Maine Year Ending June 30, 2014

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STUDY OF PERFORMANCE RELATED STRENGTH TESTS FOR COMPETITION LEVEL SPRINTERS

Strength is a performance determining factor in sprinting. This study investigates the significance of a variety of isokinetic tests to control strength requirements for sprinters. Eighteen competition level sprinters &1i0 0 m-time = 10.94 s, = 0.22 s) ran a 40 meter sprint and performed 24 isokinetic strength tests on the PROMETT-system Static, concentric, eccentric and plyometric contractions were executed at velocities between 0 and 300 '1s for knee-extensors, knee flexors and ankle extensors. For each movement the torque at three different joint angles was recorded. As the performance determining factors change in relation to running distance, the correlation between the recorded torques and the running speed is graphically presented in relation to running distance (72 graphs). Per type of contraction the torque with the highest correlation with running speed was selected for further analysis. To interpret these graphs three phases are distinguished in a 40 meter sprint. Phase 1 is the phase of initial acceleration (from 0 to 10 m), phase 2 is the phase of continued acceleration (from 10 to 30 m) and phase 3 is the phase of maximum running speed (30 to 40 m). The common variance in torque and running speed data is quantified by means of the determinationcoefficient. The results indicate that isokinetic strength tests can be used to evaluate sprint related strength requirements at a competition level. 30 to 50 percent of variance in running speed within each of the three phases can be declared by a single isokinetic strength test. It may be concluded that the strength of the knee flexors determines 50 % of the variance within the phase of initial acceleration. Ankle extension torques explain 45 % of the variance in running speed within phase 2, and the strength of the knee extensors determines 33 % of variance in maximum running speed. It is also remarkable that for ankle extension only tests were selected with a high movement velocity (200°/s), while for knee extension tests were selected at lower velocities (65 and 130°/s)

MUSCLE FIBRE RECRUITMENT IN SPRINT START AND DIFFERENT JUMPS IN ADOLESCENT SPRINT ATHLETES

The purpose of this study was to identify muscle fibre recruitment pattern during sprint start and jump tests in adolescent sprint athletes. A possible influence of several anthropometric parameters on this recruitment pattern was investigated. Sixty adolescent sprint athletes performed a sprint start and several jump tests with bilateral EMG recording of four lower limb muscles. EMG-signals were resolved into time and frequency using wavelet analysis. Age and muscularity did not influence fibre recruitment. In sprint start only the front leg M. Rectus Femoris generated higher frequencies compared to the rear leg. Compared to all other muscles, significant higher frequencies were found in the M. Gastrocnemius medialis during all movements. These results may lead to a better understanding of the value of using jump tests for talent detection in sprint athletes

Weight bearing exercise can elicit similar peak muscle activation as medium–high intensity resistance exercise in elderly women

Purpose: To assess whether stepping-based weight bearing exercise (WBE) can elicit peak activation of upper leg muscles similar to resistance exercise (RE) at an intensity required to induce strength gains in elderly women. Methods: Muscular activation of several upper leg muscles was measured during RE and WBE in a cohort of 19 healthy elderly women (69.3 ± 3.4 years). WBE consisted of forward and lateral stepping with step heights of 10, 20 and 30 cm. Muscular activation was compared to 60% of one-repetition maximum (1-RM) of congruent RE. Results: Peak activation during WBE was higher than RE at 60% 1-RM during forward and lateral stepping in vastus lateralis starting at 20 cm (p = 0.049 and p = 0.001), and biceps femoris at 30 cm step height (p = 0.024 and p = 0.030). Gluteus maximus peak activation matched RE at 60% 1-RM at 20 and 30 cm step height regardless of step direction (p ≥ 0.077). Peak activation of the rectus femoris and gluteus medius matched RE activation at 60% 1-RM during lateral stepping at 30 cm (p = 0.355 and p = 0.243, respectively) but not during forward stepping. WBE did not induce similar activation as RE in the semitendinosus. Conclusion: In WBE, most upper leg muscles were recruited at an equal or higher intensity than in RE at 60% 1-RM. Lateral stepping at 30 cm step height showed the highest training potential of all WBE’s applied

Bench stepping with incremental heights improves muscle volume, strength and functional performance in older women

Aim: Task-specific exercises such as bench stepping can improve functional ability and reduce falling incidents in older adults. However, such exercises are often not optimized to improve muscle volume and force-velocity characteristics. This study determined the effects of a 12-week stepping program using incremental step heights (STEEP), on muscle volume, strength, power, functional ability and balance performance in older women. Methods: Forty-five community-dwelling women (69y ± 4) were randomly assigned to the STEEP group or a non-training CONTROL group. Training intensity was primarily determined by step height, while training volume remained equal. Thigh muscle volume (CT-scan), force-velocity characteristics of the knee extensors (Biodex dynamometer) and functional ability (Short Physical Performance Battery, timed stair ascent, 10-m walk test and countermovement jump height) were determined pre- and post-intervention. In addition, 3D trunk accelerations were recorded at the lower back to assess balance during the Short Physical Performance Battery balance tests. Results: Two-way ANOVA showed that the STEEP program increased thigh muscle volume, knee extensor isometric peak torque, dynamic peak power, unloaded rate of velocity development and improved performance on all functional tests to a greater extent than CONTROL (p <.05), except the countermovement jump. No improvements were found for peak velocity and balance performance (p >.05). Conclusion: Our results indicate that bench step training with incremental step heights simultaneously improves functional ability, thigh muscle volume and force-velocity characteristics of the knee extensors in older women

Association of Sit-to-Stand Capacity and Free-Living Performance Using Thigh-Worn Accelerometers among 60- to 90-Yr-Old Adults

Purpose Five times sit-to-stand (STS) test is commonly used as a clinical assessment of lower-extremity functional ability, but its association with free-living performance has not been studied. Therefore, we investigated the association between laboratory-based STS capacity and free-living STS performance using accelerometry. The results were stratified according to age and functional ability groups. Methods This cross-sectional study included 497 participants (63% women) 60-90 yr old from three independent studies. A thigh-worn triaxial accelerometer was used to estimate angular velocity in maximal laboratory-based STS capacity and in free-living STS transitions over 3-7 d of continuous monitoring. Functional ability was assessed with short physical performance battery. Results Laboratory-based STS capacity was moderately associated with the free-living mean and maximal STS performance (r = 0.52-0.65, P &lt; 0.01). Angular velocity was lower in older compared with younger and in low- versus high-functioning groups, in both capacity and free-living STS variables (all P &lt; 0.05). Overall, angular velocity was higher in capacity compared with free-living STS performance. The STS reserve (test capacity - free-living maximal performance) was larger in younger and in high-functioning groups compared with older and low-functioning groups (all P &lt; 0.05). Conclusions Laboratory-based STS capacity and free-living performance were found to be associated. However, capacity and performance are not interchangeable but rather provide complementary information. Older and low-functioning individuals seemed to perform free-living STS movements at a higher percentage of their maximal capacity compared with younger and high-functioning individuals. Therefore, we postulate that low capacity may limit free-living performance.</p