Dirk Aerenhouts

From block clearance to sprint running: Characteristics underlying an effective transition

Abstract The aim of this study was to characterize the specifics of the sprint technique during the transition from start block into sprint running in well-trained sprinters. Twenty-one sprinters (11 men and 10 women), equipped with 74 spherical reflective markers, executed an explosive start action. An opto-electronic motion analysis system consisting of 12 MX3 cameras (250 Hz; 325,000 pixels) and two Kistler force plates (1000 Hz) was used to collect the three-dimensional (3D) marker trajectories and ground reaction forces (Nexus, Vicon). The 3D kinematics, joint kinetics, and power were calculated (Opensim) and were time normalized to 100% from the first action after gunshot until the end of second stance after block clearance (Matlab). The results showed that during the first stance, power generation at the knee plays a significant role in obtaining an effective transition, representing 31% of power generation in the lower limb, in the absence of preceding power absorption. Furthermore, the sprinter actively searches a more forward leaning position to maximize horizontal velocity. Since success during sprinting from the second stance onwards involves high hip and ankle activation, the above-mentioned three characteristics are specific skills required to successfully conclude the transition from start block into sprint running.

Health aspects, nutrition and physical characteristics in matched samples of institutionalized vegetarian and non-vegetarian elderly (> 65yrs)

BackgroundEpidemiological studies indicate that a well balanced vegetarian diet offers several health benefits including a lower prevalence of prosperity diseases in vegetarians compared to omnivores. It was the purpose of the present study to compare nutritional and physical characteristics in matched samples of institutionalized vegetarian (V) and non-vegetarian (NV) elderly.MethodsTwenty-two female and 7 male V (females: 84.1 ± 5.1yrs, males: 80.5 ± 7.5yrs) and 23 female and 7 male NV (females: 84.3 ± 5.0yrs, males: 80.6 ± 7.3yrs) participated. All subjects were over 65 years of age, and free of major disease or physical handicap. Dietary intake, blood profile, anthropometrics, and handgrip strength were determined.ResultsMean daily energy intake was 6.8 ± 2.0MJ in V females, and 8.0 ± 1.4MJ in the NV females, only the V did not reach the recommended value of 7.8 MJ. Male V and NV had a mean daily energy intake of 8.7 ± 1.6MJ and 8.7 ± 1.2MJ respectively (RDI: 8.8 MJ). Mean carbohydrate intake was significantly below the RDI in NV only (female V: 47.8 ± 7.5E%, female NV: 43.3 ± 4.6E%, male V: 48.1 ± 6.4E%, male NV: 42.3 ± 3.6E%), while protein (female V: 17.3 ± 3.4E%, female NV: 19.5 ± 3.5E%, male V: 17.8 ± 3.4E%, male NV: 21.0 ± 2.0E%), and saturated fat intake (female V: 25.4 ± 8.2 g/day, female NV: 32.2 ± 6.9 g/day, male V: 31.4 ± 12.9 g/day, male NV: 33.4 ± 4.7 g/day) were too high in both V and NV. Mean micronutrient intakes met the RDIs in all 4 groups. Mean blood concentrations for vitamin B12, folic acid, iron, and calcium were normal in all 4 groups. Mean zinc blood serum was below the reference value in all groups, whereas estimated zinc intake was in agreement with the RDI. The mean blood cholesterol concentration was above the 200 mg/dl upper limit in the V group (213 ± 40 mg/dl) and below that limit in the NV (188 ± 33 mg/dl) group. Mean BMI was 26.1 ± 4.7 kg/m2 in the female V, 26.8 ± 3.7 kg/m2 in the female NV, 23.5 ± 3.7 kg/m2 in the male V, and 25.2 ± 4.2 kg/m2 in the male NV. V and NV scored below the reference values for the handgrip strength test.ConclusionsGenerally, our results show a similar profile for V and NV concerning dietary intake, blood values, and physical characteristics. Attention should be paid to the intake of mono- and disaccharides and saturated fats in the diet of both V and NV. This study indicates that a vegetarian lifestyle has no negative impact on the health status at older age.

Association between cognitive performance, physical fitness, and physical activity level in women with chronic fatigue syndrome.

Limited scientific evidence suggests that physical activity is directly related to cognitive performance in patients with chronic fatigue syndrome (CFS). To date, no other study has examined the direct relationship between cognitive performance and physical fitness in these patients. This study examined whether cognitive performance and physical fitness are associated in female patients with CFS and investigated the association between cognitive performance and physical activity level (PAL) in the same study sample. We hypothesized that patients who performed better on cognitive tasks would show increased PALs and better performance on physical tests. The study included 31 women with CFS and 13 healthy inactive women. Participants first completed three cognitive tests. Afterward, they undertook a test to determine their maximal handgrip strength, performed a bicycle ergometer test, and were provided with an activity monitor. In patients with CFS, lower peak oxygen uptake and peak heart rate were associated with slower psychomotor speed (p < 0.05). Maximal handgrip strength was correlated with working memory performance (p < 0.05). Both choice and simple reaction time were lower in patients with CFS relative to healthy controls (p < 0.05 and p < 0.001, respectively). In conclusion, physical fitness, but not PAL, is associated with cognitive performance in female patients with CFS.

Energy and macronutrient intake in adolescent sprint athletes: A follow-up study

Abstract Macronutrient intake, height, weight, and body composition of 60 adolescent sprint athletes were estimated every 6 months over 3 years. Seven-day food records were analysed based on the Belgian and Dutch food databanks. The age of participants at the start of the 3-year study was 14.8 ± 1.6 years for female athletes and 14.7 ± 1.9 years for male athletes. Girls and boys gained height (3.4 ± 4.6 cm and 5.9 ± 6.6 cm respectively) and weight (5.6 ± 3.5 kg and 8.7 ± 5.5 kg respectively), whereas percent body fat remained unchanged in both girls and boys (around 17.0% and 8.5% respectively). Mean protein intake of around 1.5 g · kg−1 body weight was within recommendations on each occasion for both sexes. Carbohydrate intakes between 5 and 7 g · kg−1 body weight support a training programme of moderate intensity. Total and saturated fat intakes were high at the start of the study (girls: 31.8 ± 3.5% and 12.2 ± 2.0% of energy intake; boys: 30.3 ± 4.6% and 12.0 ± 1.9% of energy intake) and it appeared to be difficult to achieve and maintain lower intakes. Consistent low fluid intakes around 40 ml · kg−1 body weight were observed. General non-stringent advice for improvement of the diet resulted in significant favourable changes only for the consumption of wholegrain bread, vegetables, and soft drinks. Dietary habits of adolescent sprint athletes are not always according to guidelines and are relatively stable but repeated advice can induce moderate improvements.

Comparison of anthropometric characteristics and sprint start performance between elite adolescent and adult sprint athletes

Abstract The aim of this study was to examine the physical characteristics and somatotype of junior and senior athletes in relation to sprint start and acceleration performance. Nineteen female junior, 23 male junior, 9 female senior, and 16 male senior sprint athletes performed three maximal 20-m sprints. The starting blocks were instrumented to measure forward propulsion forces. Running velocity was measured by a laser positioned behind the athlete at 1 m height. Anthropometric measures were used to calculate somatotype and skeletal muscle mass. Body composition was estimated by underwater weighing densitometry. Junior and senior athletes were of similar height in both sexes. Male seniors were heavier, had larger limb circumferences, and a higher skeletal muscle mass than male juniors. Only the limb circumferences of the female seniors were larger than those of the female juniors. Female juniors were balanced ectomorphs, while female seniors were situated centrally on the somatochart (2.7–2.2–3.9 vs. 2.6–3.1–3.1; P=0.772, 0.047, and 0.066 respectively). Male juniors were mesomorphic ectomorphs, while male seniors were ectomorphic mesomorphs (1.8–3.3–3.6 vs. 1.6–4.2–2.8; P=0.148, 0.002, and 0.002 respectively). All sprint starts were similar for the junior and senior athletes of both sexes. Senior athletes accelerated more than the junior athletes, which resulted in higher running velocities after 5 m (senior vs. junior: females, 5.51±0.32 vs. 6.01±0.27 m · s–1, P=0.001; males, 5.85±0.38 vs. 6.13±0.44 m · s–1, P=0.043). The greater muscularity of senior compared with junior athletes did not result in better sprint start dynamics, but they did accelerate more and ran faster. These results show that late-adolescent boys in particular are still developing their muscularity. The technical complexity of the sprint start and the negative influence of a higher body mass may partly explain the comparable sprint start dynamics of the junior and senior athletes. We suggest that strength training should be combined with sufficient attention to technical skills to allow a positive transfer.

Control of propulsion and body lift during the first two stances of sprint running: a simulation study

Abstract The aim of this study was to relate the contribution of lower limb joint moments and individual muscle forces to the body centre of mass (COM) vertical and horizontal acceleration during the initial two steps of sprint running. Start performance of seven well-trained sprinters was recorded using an optoelectronic motion analysis system and two force plates. Participant-specific torque-driven and muscle-driven simulations were conducted in OpenSim to quantify, respectively, the contributions of the individual joints and muscles to body propulsion and lift. The ankle is the major contributor to both actions during the first two stances, with an even larger contribution in the second compared to the first stance. Biarticular gastrocnemius is the main muscle contributor to propulsion in the second stance. The contribution of the hip and knee depends highly on the position of the athlete: During the first stance, where the athlete runs in a forward bending position, the knee contributes primarily to body lift and the hip contributes to propulsion and body lift. In conclusion, a small increase in ankle power generation seems to affect the body COM acceleration, whereas increases in hip and knee power generation tend to affect acceleration less.

Sleep characteristics, exercise capacity and physical activity in patients with chronic fatigue syndrome

Abstract Purpose: Unrefreshing sleep and lowered physical activity are commonly observed in chronic fatigue syndrome (CFS) patients, but how they might influence each other remains unexplored. Therefore, this study simultaneously examined the exercise capacity, sleep characteristics and physical activity in CFS patients. Methods: Handgrip strength and cycle exercise capacity were assessed in 42 female CFS patients and 24 inactive control subjects. During four consecutive days and nights, energy expenditure, activity and sleep–wake pattern were objectively registered using a Sensewear Armband. Results: Exercise capacity was significantly lower in CFS patients. In both groups VO2peak correlated with the time subjects were physically active. In CFS patients only, VO2peak correlated negatively with sleeping during the day whilst physical activity level and energy expenditure correlated negatively with sleep latency and lying awake at night. Conclusions: In the present study, CFS patients with higher VO2peak tend to sleep less over day. Occupation in physical activities was negatively associated with sleep latency and lying awake at night. Increased physical activity potentially has beneficial effects on sleep quality in CFS. However, a close monitoring of the effects of increasing physical activity is essential to avoid negative effects on the health status of patients. Implications for Rehabilitation Female patients with chronic fatigue syndrome (CFS) have normal sleep latency and sleep efficiency, but sleep more and spent more time in bed as compared to healthy inactive women. Female CFS patients have lower exercise capacity, and a lower physical activity level as compared to healthy inactive women. CFS patients appear to be more sensitive for sleep quality (sleep latency and lying awake at night), which is associated with a low physical activity level.

Teaching basic life support: a prospective randomized study on low-cost training strategies in secondary schools.

Background Cardiopulmonary resuscitation (CPR) training at school is recommended. Limited school resources prevent implementation. The learning efficacy of low-cost training strategies is unknown. Objective To evaluate the efficacy of different CPR learning strategies using low-cost didactic tools. Methods Children (n=593, 15–16 years) were randomized to four training conditions: (1) manikin+teacher instruction (control group), (2) manikin+video instruction, (3) foam dice+plastic bag+peer training+teacher instruction, and (4) foam dice+plastic bag+peer training+video instruction. After a 50 min training, a 3 min CPR test on a manikin was performed using SkillReporting Software (Laerdal, Norway), and repeated after 6 months. The data of children without previous CPR training were analysed. Analysis of variance and the &khgr;2-test assessed differences between groups. Results Complete data sets were available for 165 pupils. Initially, group 3 scored lower on the mean ventilation volume (P<0.05). The control group scored better than the alternative groups (P<0.05) on the mean compression rate. After 6 months, the differences disappeared. All groups scored equally on ventilation volume (P=0.12), compression depth (P=0.11), compression rate (P=0.10), correct hand position (P=0.46) and number of correct compressions (P=0.76). Ventilation volume was sufficient in 32% of the pupils, 18% had a correct compression depth and 59% had a correct compression rate. Conclusion Training efficacy with low-cost equipment was not different from training with a manikin. The outcome for all training strategies was suboptimal. The basics of CPR can be taught with alternative equipment if manikins are not available.

Dietary Acid-Base Balance in Adolescent Sprint Athletes: A Follow-up Study

Sprinters are advised to include additional protein sources in their diet. Basal metabolism and vigorous physical activities generate hydrogen ions that need to be buffered. The present follow-up study estimates the dietary potential renal acid load (PRAL) and net endogenous acid production (NEAP) in adolescent sprint athletes. Seven-day food diaries and anthropometrics of 60 adolescent sprint athletes (mean age at start 14.7 ± 1.9 years) were collected every six months over a three year period. Comparisons were made between athletes with a negative (PRAL(−)) versus positive PRAL (PRAL(+)). For the entire sample, mean PRAL values of up to 6 mEq/day were slightly positive despite a relatively high protein intake of around 1.5 g/kg. The NEAP ranging between 42 and 46 mEq/day remained stable during the study period. Athletes with a PRAL(−) (−8 to −10 mEq/day) consumed significantly more fruit and fruit juice than athletes with a PRAL(+) (+9 to 14 mEq/day). Athletes with a PRAL(+) did not consume more meat, fish and poultry than athletes with a PRAL(−). Grains and dairy products were only discriminative between the two groups on one measurement occasion. Lowering the PRAL can be obtained by increasing the consumption of potatoes, fruits, vegetables and vegetable soup.

Energy expenditure and intake in judo athletes during training camp

For optimal athletic performance, recovery and body composition, athletes need to synchronize diet and physical activi ties. Especially in judo athletes, where competition is organiz ed in weight categories, the balance between energy intake and energy expenditure is of uttermost importance [1]. Data concerning energy intake during training and competition preparation – often a weight reduction periodare available [2,3,4]. However, the literature lacks data on the energy balance during the training period of judo athletes. When not in weight reduction period, special attention needs to be given to energy intake, providing sufficient energy for basal metabolism, physical activities, and recovery without caloric overshoot [5]. A highly positive energy balance during training periods may result in excessive weight gain with negative consequences for the following weight reduction period. In order to properly harmonize an athlete’s dietary intake and training program, assessing the energy balance and physical activity status of the athlete is required [6,7,8]. Energy expenditure during training in judo athletes is not well described. The training program of a judo athlete is diverse, and consists of judo specific training (technique and randori) and non-specific training (resistance training, endurance training), [9,10]. Randori, which is a type of fight training, can be categorized as a high intensity activity with an intermittent pattern of activity and relative rest more or less comparable with a competition fight [10]. The diversity of the training program, the unstructured activities during the randori training, and the contact with the opponent, make it very difficult to estimate energy expenditure with most of the available methods. Monitoring should be done in the athlete’s normal environment enabling maintenance of habitual activity participation and dietary intake. Therefore, the methods used to determine activity pattern and dietary intake should preferably be as accurate as possible and at the same time easy in use with a minimal burden on the athlete. An activity diary (AD) is considered to be one of the most accurate subjective techniques, despite the high participant burden [8]. Though self-report methods can be a principal source of information, other approaches or the use of combined measu res may be needed to characterize better an athlete‘s activity level. Reporting the results with different instruments provides a more complete description of activity levels and permits triangulation of outcomes [11]. The SenseWear Armband (SWA) combines five different sensors into one device attached as an armband around the upper arm. The SWA has shown to give reliable estimates of TEE in healthy free living adults [12,13,14]. Johannsen et al. [14] found a significant agreement between the SWA and doubly labeled water estimates of TEE. Fruin and Rankin [15] found the SWA to provide valid and reliable estimates of energy expenditure at rest and on an ergometer as compared to indirect calorimetry.