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Background: Racing drivers require multifaceted cognitive and physical abilities in a multitasking situation. A knowledge of their physical capacities may help to improve fitness and performance. Objective: To compare reaction time, stability performance capacity, and strength performance capacity of elite racing drivers with those of age-matched, physically active controls. Methods: Eight elite racing drivers and 10 physically active controls matched for age and weight were tested in a reaction and determination test requiring upper and lower extremity responses to visual and audio cues. Further tests comprised evaluation of one-leg postural stability on a two-dimensional moveable platform, measures of maximum strength performance capacity of the extensors of the leg on a leg press, and a test of force capacity of the arms in a sitting position at a steering wheel. An additional arm endurance test consisted of isometric work at the steering wheel at + 30 degrees and -30 degrees where an eccentric threshold load of 30 N.m was applied. Subjects had to hold the end positions above this threshold until exhaustion. Univariate one way analysis of variance (alpha = 0.05) including a Bonferroni adjustment was used to detect group differences between the drivers and controls. Results: The reaction time of the racing drivers was significantly faster than the controls ( p = 0.004). The following motor reaction time and reaction times in the multiple determination test did not differ between the groups. No significant differences (p> 0.05) were found for postural stability, leg extensor strength, or arm strength and endurance. Conclusions: Racing drivers have faster reaction times than age-matched physically active controls. Further development of motor sport-specific test protocols is suggested. According to the requirements of motor racing, strength and sensorimotor performance capacity can potentially be improved.
How much is too much?
(2010)
Although dietary nutrient intake is often adequate, nutritional supplement use is common among elite athletes. However, high-dose supplements or the use of multiple supplements may exceed the recommended daily allowance (RDA) of particular nutrients or even result in a daily intake above tolerable upper limits (UL). The present case report presents nutritional intake data and supplement use of a highly trained male swimmer competing at international level. Habitual energy and micronutrient intake were analysed by 3 d dietary reports. Supplement use and dosage were assessed, and total amount of nutrient supply was calculated. Micronutrient intake was evaluated based on RDA and UL as presented by the European Scientific Committee on Food, and maximum permitted levels in supplements (MPL) are given. The athlete’s diet provided adequate micronutrient content well above RDA except for vitamin D. Simultaneous use of ten different supplements was reported, resulting in excess intake above tolerable UL for folate, vitamin E and Zn. Additionally, daily supplement dosage was considerably above MPL for nine micronutrients consumed as artificial products. Risks and possible side effects of exceeding UL by the athlete are discussed. Athletes with high energy intake may be at risk of exceeding UL of particular nutrients if multiple supplements are added. Therefore, dietary counselling of athletes should include assessment of habitual diet and nutritional supplement intake. Educating athletes to balance their diets instead of taking supplements might be prudent to prevent health risks
that may occur with long-term excess nutrient intake.
Exercise may increase reactive oxygen species production, which might impair cell integrity and contractile function of muscle cells. However, little is known about the effect of regular exercise on the antioxidant status of adolescents. Purpose: This study aimed to evaluate the impact of exercise on the antioxidant status and protein modifications in adolescent athletes. Methods: In 90 athletes and 18 controls (16 +/- 2 yr), exercise-related energy expenditure was calculated on the basis of a 7-d activity protocol. Antioxidant intake and plasma concentrations of alpha-tocopherol, carotenoids, and uric acid were analyzed. Plasma antioxidant activity was determined by Trolox equivalent (TE) antioxidant capacity and electron spin resonance spectrometry. Protein modifications were assessed with structural changes of transthyretin using a matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Data were analyzed by two-way ANOVA and post hoc by the Tukey-Kramer test (alpha = 0.05). Results: Antioxidant intake correlated with energy intake and was within the recommended daily allowance for vitamins C and E and beta-carotene. Plasma levels of neither nutritional antioxidants nor uric acid differed between the groups. TE antioxidant capacity was higher in athletes (men = 1.47 perpendicular to 0.2 mmol TE per liter, women = 1.45 perpendicular to 0.2 mmol TE per liter) compared with controls (men = 1.17 +/- 0.04 mmol TE per liter, women = 1.14 +/- 0.04 mmol TE per liter) and increased with exercise-related energy expenditure (P = 0.007). Transthyretin cysteinylation rate differed between the groups, with the highest rate of protein modifications in moderately active subjects (P = 0.007). Conclusions: Results suggest that if the nutritional choice of athletes is well balanced, enough antioxidants are provided to meet recommended amounts. Moreover, regular exercise increases blood antioxidant capacity in young athletes, whereas chronic exercise was not shown to promote protein modifications. Thus, in young athletes who are sufficiently supplied with antioxidants, beneficial effects of exercise on antioxidant status rather than on oxidative stress may be anticipated.
Background: Gender-specific neuromuscular activity for the ankle (e.g., peroneal muscle) is currently not known. This knowledge may contribute to the understanding of overuse injury mechanisms. The purpose was therefore to analyse the neuromuscular activity of the peroneal muscle in healthy runners. Methods: Fifty-three male and 54 female competitive runners were tested on a treadmill at 3.33 m s(-1). Neuromuscular activity of the M. peroneus longus was measured by electromyography and analysed in the time domain (onset of activation, time of maximum of activation, total time of activation) in % of stride time in relation to touchdown (= 1.0). Additionally, mean amplitudes for the gait cycle phases preactivation, weight acceptance and push-off were calculated and normalised to the mean activity of the entire gait cycle. Findings: Onset of activation (mean; female: 0.86/male: 0.90, p<0.0001) and time of maximum of activation (female: 1.13/male: 1.16, p<0.0001) occurred earlier in female compared to male and the total time of activation was longer in women (female: 0.42/male: 0.39, p=0.0036). In preactivation, women showed higher amplitudes (+ 21%) compared to men (female: 1.16/male: 0.92, p<0.0001). Activity during weight acceptance (female: 2.26/male: 2.41, p = 0.0039) and push-off (female: 0.93/male: 1.07, p = 0.0027) were higher in men. Interpretation: Activation strategies of the peroneal muscle appear to be gender-specific. Higher preactivation amplitudes in females indicate a different neuromuscular control in anticipation of touchdown ("pre-programmed activity"). These data may help interpret epidemiologically reported differences between genders in overuse injury frequency and localisation.
On utilise de plus en plus les tests de verification pour confirmer l'atteinte du consommation d'oxygene maximale (VO(2 max)). Toutefois, le moment et les methodes d'evaluation varient d'un groupe de travail a l'autre. Les objectifs de cette etude sont de constater si on peut administrer un test de verification apres un test d'effort progressif ou s'il est preferable de le faire une autre journee et si on peut determiner le VO(2 max) tout de meme lors de la premiere seance chez des sujets ne repondant pas au critere de verification. Quarante sujets (age, 24 +/- 4 ans; VO(2 max), 50 +/- 7 mL center dot min(-1)center dot kg(-1)) participent a un test d'effort progressif sur tapis roulant et, 10 min plus tard, a un test de verification (VerifDay1) a 110 % de la velocite maximale (v(max)). Le critere de verification est un VO(2) de pointe au VerifDay1 < 5,5 % a la valeur retenue au test d'effort progressif. Les sujets ne repondant pas au critere de verification passent un autre test de verification, mais a 115 % du VerifDay1', et ce, 10 min plus tard pour confirmer le VO(2) de pointe du VerifDay1 en tant que VO(2 max). Tous les autres sujets repassent le VerifDay1 a un jour different (VerifDay2). Six sujets sur quarante ne repondent pas au critere de verification. Chez quatre d'entre eux, on confirme l'atteinte du VO(2 max) au VerifDay1'. Le VO(2) de pointe au VerifDay1 est equivalent a celui du VerifDay2 (3722 +/- 991 mL center dot min(-1) comparativement a 3752 +/- 995 mL center dot min(-1), p = 0,56), mais le temps jusqu'a l'epuisement est significativement plus long au VerifDay2 (2:06 +/- 0:22 min:s comparativement a 2:42 +/- 0:38 min:s, p < 0,001, n = 34). Le VO(2) de pointe obtenu au test de verification ne semble pas conditionne par un test d'effort progressif maximal prealable. On peut donc realiser le test d'effort progressif et le test de verification lors de la meme seance d'evaluation. Chez presque tous les individus ne repondant pas au critere de verification, on peut determiner le VO(2 max) au moyen d'un autre test de verification plus intense.
How much is too much? - a case report of nutritional supplement use of a high-performance athlete
(2011)
Although dietary nutrient intake is often adequate, nutritional supplement use is common among elite athletes. However, high-dose supplements or the use of multiple supplements may exceed the recommended daily allowance (RDA) of particular nutrients or even result in a daily intake above tolerable upper limits (UL). The present case report presents nutritional intake data and supplement use of a highly trained male swimmer competing at international level. Habitual energy and micronutrient intake were analysed by 3 d dietary reports. Supplement use and dosage were assessed, and total amount of nutrient supply was calculated. Micronutrient intake was evaluated based on RDA and UL as presented by the European Scientific Committee on Food, and maximum permitted levels in supplements (MPL) are given. The athlete's diet provided adequate micronutrient content well above RDA except for vitamin D. Simultaneous use of ten different supplements was reported, resulting in excess intake above tolerable UL for folate, vitamin E and Zn. Additionally, daily supplement dosage was considerably above MPL for nine micronutrients consumed as artificial products. Risks and possible side effects of exceeding UL by the athlete are discussed. Athletes with high energy intake may be at risk of exceeding UL of particular nutrients if multiple supplements are added. Therefore, dietary counselling of athletes should include assessment of habitual diet and nutritional supplement intake. Educating athletes to balance their diets instead of taking supplements might be prudent to prevent health risks that may occur with long-term excess nutrient intake.
Background: The elderly need strength training more and more as they grow older to stay mobile for their everyday activities. The goal of training is to reduce the loss of muscle mass and the resulting loss of motor function. The dose-response relationship of training intensity to training effect has not yet been fully elucidated.
Methods: PubMed was selectively searched for articles that appeared in the past 5 years about the effects and dose-response relationship of strength training in the elderly.
Results: Strength training in the elderly (> 60 years) increases muscle strength by increasing muscle mass, and by improving the recruitment of motor units, and increasing their firing rate. Muscle mass can be increased through training at an intensity corresponding to 60% to 85% of the individual maximum voluntary strength. Improving the rate of force development requires training at a higher intensity (above 85%), in the elderly just as in younger persons. It is now recommended that healthy old people should train 3 or 4 times weekly for the best results; persons with poor performance at the outset can achieve improvement even with less frequent training. Side effects are rare.
Conclusion: Progressive strength training in the elderly is efficient, even with higher intensities, to reduce sarcopenia, and to retain motor function.
Adequate energy intake in adolescent athletes is considered important. Total energy expenditure (TEE) can be calculated from resting energy expenditure (REE) and physical activity level (PAL). However, validated PAL recommendations are available for adult athletes only. Purpose was to comprise physical activity data in adolescent athletes and to establish PAL recommendations for this population. In 64 competitive athletes (15.3 +/- 1.5yr, 20.5 +/- 2.0kg/m(2)) and 14 controls (15.1 +/- 1.1yr, 21 +/- 2.1kg/m(2)) TEE was calculated using 7-day activity protocols validated against doubly-labeled water. REE was estimated by Schofield-HW equation, and PAL was calculated as TEE:REE. Observed PAL in adolescent athletes (1.90 +/- 0.35) did not differ compared with controls (1.84 +/- 0.32, p = .582) and was lower than recommended for adult athletes by the WHO. In conclusion, applicability of PAL values recommended for adult athletes to estimate energy requirements in adolescent athletes must be questioned. Instead, a PAL range of 1.75-2.05 is suggested.
Background: Athletes may differ in their resting metabolic rate (RMR) from the general population. However, to estimate the RMR in athletes, prediction equations that have not been validated in athletes are often used. The purpose of this study was therefore to verify the applicability of commonly used RMR predictions for use in athletes. Methods: The RMR was measured by indirect calorimetry in 17 highly trained rowers and canoeists of the German national teams (BMI 24 +/- 2 kg/m(2), fat-free mass 69 +/- 15 kg). In addition, the RMR was predicted using Cunningham (CUN) and Harris-Benedict (HB) equations. A two-way repeated measures ANOVA was calculated to test for differences between predicted and measured RMR (alpha = 0.05). The root mean square percentage error (RMSPE) was calculated and the Bland-Altman procedure was used to quantify the bias for each prediction. Results: Prediction equations significantly underestimated the RMR in males (p < 0.001). The RMSPE was calculated to be 18.4% (CUN) and 20.9% (HB) in the entire group. The bias was 133 kcal/24 h for CUN and 202 kcal/24 h for HB. Conclusions: Predictions significantly underestimate the RMR in male heavyweight endurance athletes but not in females. In athletes with a high fat-free mass, prediction equations might therefore not be applicable to estimate energy requirements. Instead, measurement of the resting energy expenditure or specific prediction equations might be needed for the individual heavyweight athlete.
Neuromuscular control in functional situations and possible impairments due to Achilles tendinopathy are not well understood.
Thirty controls (CO) and 30 runners with Achilles tendinopathy (AT) were tested on a treadmill at 3.33 m s(-1) (12 km h(-1)). Neuromuscular activity of the lower leg (tibialis anterior, peroneal, and gastrocnemius muscle) was measured by surface electromyography. Mean amplitude values (MAV) for the gait cycle phases preactivation, weight acceptance and push-off were calculated and normalised to the mean activity of the entire gait cycle.
MAVs of the tibialis anterior did not differ between CO and AT in any gait cycle phase. The activation of the peroneal muscle was lower in AT in weight acceptance (p = 0.006), whereas no difference between CO and AT was found in preactivation (p = 0.71) and push-off (p = 0.83). Also, MAVs of the gastrocnemius muscle did not differ between AT and CO in preactivity (p = 0.71) but were reduced in AT during weight acceptance (p = 0.001) and push-off (p = 0.04).
Achilles tendinopathy does not seem to alter pre-programmed neural control but might induce mechanical deficits of the lower extremity during weight bearing (joint stability). This should be addressed in the therapy process of AT.
BAUR, H., A. HIRSCHMULLER, S. MULLER, and F. MAYER. Neuromuscular Activity of the Peroneal Muscle after Foot Orthoses Therapy in Runners. Med. Sci. Sports Exerc., Vol. 43, No. 8, pp. 1500-1506, 2011. Purpose: Foot orthoses are a standard option to treat overuse injury. Biomechanical data providing mechanisms of foot orthoses' effectiveness are sparse. Stability of the ankle joint complex might be a key factor. The purpose was therefore to analyze neuromuscular activity of the musculus peroneus longus in runners with overuse injury symptoms treated with foot orthoses. Methods: A total of 99 male and female runners with overuse injury symptoms randomized in a control group (CO) and an orthoses group (OR) were analyzed on a treadmill at 3.3 m.s(-1) before and after an 8-wk foot orthoses intervention. Muscular activity of the musculus peroneus longus was measured and quantified in the time domain (initial onset of activation (T-ini), time of maximal activity (T-max), total time of activation (T-tot)) and amplitude domain (amplitude in preactivation (A(pre)), weight acceptance (A(wa)), push-off (A(po))). Results: Peroneal activity in the time domain did not differ initially between CO and OR, and no effect was observed after therapy (T-ini: CO = -0.88 +/- 0.09, OR = -0.88 +/- 0.08 / T-max: CO = 0.14 +/- 0.06, OR = 0.15 +/- 0.06 / T-tot: CO = 0.40 +/- 0.09, OR = 0.41 +/- 0.09; P > 0.05). In preactivation (Apre), muscle activity was higher in OR after intervention (CO = 0.97 +/- 0.32, 95% confidence interval = 0.90-1.05; OR = 1.18 +/- 0.43, 95% confidence interval = 1.08-1.28; P = 0.003). There was no group or intervention effect during stance (A(wa): CO = 2.33 +/- 0.66, OR = 2.33 +/- 0.74 / A(po): CO = 0.80 +/- 0.41, OR = 0.88 +/- 0.40; P > 0.05). Conclusions: Enhanced muscle activation of the musculus peroneus longus in preactivation suggests an altered preprogrammed activity, which might lead to better ankle stability providing a possible mode of action for foot orthoses therapy.
Isokinetic dynamometry is a standard technique for strength testing and training. Nevertheless reliability and validity is limited due to inertia effects, especially for high velocities. Therefore in a first methodological approach the purpose was to evaluate a new isokinetic measurement mode including inertia compensation compared to a classic isokinetic measurement mode for single and multijoint movements at different velocities.
Isokinetic maximum strength measurements were carried out in 26 healthy active subjects. Tests were performed using classic isokinetic and new isokinetic mode in random order. Maximum torque/force, maximum movement velocity and time for acceleration were calculated. For inter-instrument agreement Bland and Altman analysis, systematic and random error was quantified. Differences between both methods were assessed (ANOVA alpha = 0.05).
Bland and Altman analysis showed the highest agreement between the two modes for strength and velocity measurements (bias: < +/- 1.1%; LOA: < 14.2%) in knee flexion/extension at slow isokinetic velocity (60 degrees/s). Least agreement (range: bias: -67.6% +/- 119.0%; LOA: 53.4% 69.3%) was observed for shoulder/arm test at high isokinetic velocity (360 degrees/s). The Isokin(new) mode showed higher maximum movement velocities (p < 0.05).
For low isokinetic velocities the new mode agrees with the classic mode. Especially at high isokinetic velocities the new isokinetic mode shows relevant benefits coupled with a possible trade-off with the force/torque measurement. In conclusion, this study offers for the first time a comparison between the 'classical' and inertia-compensated isokinetic dynamometers indicating the advantages and disadvantages associated with each individual approach, particularly as they relate to medium or high velocities in testing and training.
Background and objectives Treatment of chronic running-related overuse injuries by orthopaedic shoe orthoses is very common but not evidence-based to date.
Hypothesis Polyurethane foam orthoses adapted to a participant's barefoot plantar pressure distribution are an effective treatment option for chronic overuse injuries in runners.
Design Prospective, randomised, controlled clinical trial.
Intervention 51 patients with running injuries were treated with custom-made, semirigid running shoe orthoses for 8 weeks. 48 served as a randomised control group that continued regular training activity without any treatment.
Main outcome measures Evaluation was made by the validated pain questionnaire Subjective Pain Experience Scale, the pain disability index and a comfort index in the orthoses group (ICI).
Results There were statistically significant differences between the orthoses and control groups at 8 weeks for the pain disability index (mean difference 3.2; 95% CI 0.9 to 5.5) and the Subjective Pain Experience Scale (6.6; 2.6 to 10.6). The patients with orthoses reported a rising wearing comfort (pre-treatment ICI 69/100; post-treatment ICI 83/100) that was most pronounced in the first 4 weeks (ICI 80.4/100).
Conclusion Customised polyurethane running shoe orthoses are an effective conservative therapy strategy for chronic running injuries with high comfort and acceptance of injured runners.
The aim of this study was to acquire static and dynamic foot geometry and loading in childhood, and to establish data for age groups of a population of 1-13 year old infants and children.
A total of 10,382 children were recruited and 7788 children (48% males and 52% females) were finally included into the data analysis. For static foot geometry foot length and foot width were quantified in a standing position. Dynamic foot geometry and loading were assessed during walking on a walkway with self selected speed (Novel Emed X, 100 Hz, 4 sensors/cm(2)). Contact area (CA), peak pressure (PP), force time integral (FTI) and the arch index were calculated for the total, fore-, mid- and hindfoot.
Results show that most static and dynamic foot characteristics change continuously during growth and maturation. Static foot length and width increased with age from 13.1 +/- 0.8 cm (length) and 5.7 +/- 0.4 cm (width) in the youngest to 24.4 +/- 1.5 cm (length) and 8.9 +/- 0.6 cm (width) in the oldest. A mean walking velocity of 0.94 +/- 0.25 m/s was observed. Arch-index ranged from 0.32 +/- 0.04 [a.u.] in the one-year old to 0.21 +/- 0.13 [a.u.] in the 5-year olds and remains constant afterwards.
This study provides data for static and dynamic foot characteristics in children based on a cohort of 7788 subjects. Static and dynamic foot measures change differently during growth and maturation. Dynamic foot measurements provide additional information about the children's foot compared to static measures.
Intrasession reliability of insole in-shoe plantar pressure measurements in different foot areas
(2012)
Background: Isokinetic measurements are widely used to assess strength capacity in a clinical or research context. Nevertheless, the validity of isokinetic measures for identifying strength deficits and the evaluation of therapeutic process regarding different pathologies is yet to be established. Therefore, the purpose of this review is to evaluate the validity of isokinetic measures in a specific case: that of muscular capacity in low back pain (LBP).
Methods: A literature search (PubMed; ISI Web of Knowledge; The Cochrane Library) covering the last 10 years was performed. Relevant papers regarding isokinetic trunk strength measures in healthy and patients with low back pain (PLBP) were searched. Peak torque values [Nm] and peak torque normalized to body weight [Nm/kg BW] were extracted for healthy and PLBP. Ranked mean values across studies were calculated for the concentric peak torque at 60 degrees/s as well as the flexion/extension (F/E) ratio.
Results: 34 publications (31 flexion/extension; 3 rotation) were suitable for reporting detailed isokinetic strength measures in healthy or LBP (untrained adults, adolescents, athletes). Adolescents and athletes were different compared to normal adults in terms of absolute trunk strength values and the F/E ratio. Furthermore, isokinetic measures evaluating therapeutic process and isokinetic rehabilitation training were infrequent in literature (8 studies).
Conclusion: Isokinetic measurements are valid for measuring trunk flexion/extension strength and F/E ratio in athletes, adolescents and (untrained) adults with/without LBP. The validity of trunk rotation is questionable due to a very small number of publications whereas no reliable source regarding lateral flexion could be traced. Therefore, isokinetic dynamometry may be utilized for identifying trunk strength deficits in healthy adults and PLBP.
Background/Purpose
Muscular reflex responses of the lower extremities to sudden gait disturbances are related to postural stability and injury risk. Chronic ankle instability (CAI) has shown to affect activities related to the distal leg muscles while walking. Its effects on proximal muscle activities of the leg, both for the injured- (IN) and uninjured-side (NON), remain unclear. Therefore, the aim was to compare the difference of the motor control strategy in ipsilateral and contralateral proximal joints while unperturbed walking and perturbed walking between individuals with CAI and matched controls.
Materials and methods
In a cross-sectional study, 13 participants with unilateral CAI and 13 controls (CON) walked on a split-belt treadmill with and without random left- and right-sided perturbations. EMG amplitudes of muscles at lower extremities were analyzed 200 ms after perturbations, 200 ms before, and 100 ms after (Post100) heel contact while walking. Onset latencies were analyzed at heel contacts and after perturbations. Statistical significance was set at alpha≤0.05 and 95% confidence intervals were applied to determine group differences. Cohen’s d effect sizes were calculated to evaluate the extent of differences.
Results
Participants with CAI showed increased EMG amplitudes for NON-rectus abdominus at Post100 and shorter latencies for IN-gluteus maximus after heel contact compared to CON (p<0.05). Overall, leg muscles (rectus femoris, biceps femoris, and gluteus medius) activated earlier and less bilaterally (d = 0.30–0.88) and trunk muscles (bilateral rectus abdominus and NON-erector spinae) activated earlier and more for the CAI group than CON group (d = 0.33–1.09).
Conclusion
Unilateral CAI alters the pattern of the motor control strategy around proximal joints bilaterally. Neuromuscular training for the muscles, which alters motor control strategy because of CAI, could be taken into consideration when planning rehabilitation for CAI.
The study was conducted to investigate the quantity and the main food sources of carbohydrate (CHO) intake of junior elite triathletes during a short-term moderate (MOD; 12 km swimming, 100 km cycling, 30 km running per wk) and intensive training period (INT; 23 km swimming, 200 km cycling, 45 km running per wk). Self-reported dietary-intake data accompanied by training protocols of 7 male triathletes (18.1 +/- 2.4 yr, 20.9 +/- 1.4 kg/m(2)) were collected on 7 consecutive days during both training periods in the same competitive season. Total energy and CHO intake were calculated based on the German Food Database. A paired t test was applied to test for differences between the training phases (alpha = .05). CHO intake was slightly higher in INT than in MOD (9.0 +/- 1.6 g . kg(-1) . d(-1) vs. 7.8 +/- 1.6 g . kg(-1) . d(-1); p = .041). Additional CHO in INT was mainly ingested during breakfast (115 +/- 37 g in MOD vs. 175 +/- 23 g in INT; p = .002) and provided by beverages (280.5 +/- 97.3 g/d vs. 174.0 +/- 58.3 g/d CHO; p = .112). Altogether, main meals provided approximately two thirds of the total CHO intake. Pre- and postexercise snacks additionally supplied remarkable amounts of CHO (198.3 +/- 84.3 g/d in INT vs. 185.9 +/- 112 g/d CHO in MOD; p = .231). In conclusion, male German junior triathletes consume CHO in amounts currently recommended for endurance athletes during moderate to intensive training periods. Main meals provide the majority of CHO and should therefore not be skipped. CHO-containing beverages, as well as pre- and postexercise snacks, may provide a substantial amount of CHO intake in training periods with high CHO requirements.
Test-retest-reliability of metabolic and cardiovascular load during isokinetic strength testing
(2012)
Ultrasound evaluation of the patellar tendon cross-sectional area and its relation to maximum force
(2012)
Background Preparticipation examinations (PPE) are frequently used to evaluate eligibility for competitive sports in adolescent athletes. Nevertheless, the effectiveness of these examinations is under debate since costs are high and its validity is discussed controversial.
Purpose To analyse medical findings and consequences in adolescent athletes prior to admission to a sports school.
Methods In 733 adolescent athletes (318 girls, 415 boys, age 12.3+/-0.4, 16 sports disciplines), history and clinical examination (musculoskeletal, cardiovascular, general medicine) was performed to evaluate eligibility. PPE was completed by determination of blood parameters, ECG at rest and during ergometry, echocardiography and x-rays and ultrasonography if indicated. Eligibility was either approved or rated with restriction. Recommendations for therapy and/or prevention were given to the athletes and their parents.
Results Historical (h) and clinical (c) findings (eg, pain, verified pathologies) were more frequent regarding the musculoskeletal system (h: 120, 16.4%; c: 247, 33.7%) compared to cardiovascular (h: 9, 1.2%; c: 23, 3.1%) or general medicine findings (h: 116, 15.8%; c: 71, 9.7%). ECG at rest was moderately abnormal in 46 (6.3%) and severely abnormal in 25 athletes (3.4%). Exercise ECG was suspicious in 25 athletes (3.4%). Relevant echocardiographic abnormalities were found in 17 athletes (2.3%). In 52 of 358 cases (14.5%), x-rays led to diagnosis (eg, Spondylolisthesis). Eligibility was temporarily restricted in 41 athletes (5.6%). Three athletes (0.4%) had to be excluded from competitive sports. Therapy (eg, physiotherapy, medication) and/or prevention (sensorimotor training, vaccination) recommendations were deduced due to musculoskeletal (t:n = 76,10.3%; p:n = 71,9.8%) and general medicine findings (t:n = 80, 10.9%; p:n = 104, 14.1%).
Conclusion Eligibility for competitive sports is restricted in only 5.5% of adolescent athletes at age 12. Eligibility refusals are rare. However, recommendations for therapy and prevention are frequent, mainly regarding the musculoskeletal system. In spite of time and cost consumption, adolescent preparticipation before entering a career in high-performance sports is supported.
Neuromuscular activity of the lower leg is dependent on the task performed, speed of movement and gender. Whether training volume influences neuromuscular activity is not known. The EMG of physically active persons differing in running mileage was analysed to investigate this. 55 volunteers were allocated to a low (LM: < 30 km), intermediate (IM: > 30 km & < 45 km) or high mileage (HM: > 45 km) group according to their weekly running volume. Neuromuscular activity of the lower leg was measured during running (3.33 m.s(-1)). Mean amplitude values for preactivation, weight acceptance and push-off were calculated and normalised to the mean activity of the entire gait cycle. Higher activity in the gastrocnemius group was observed in weight acceptance in LM compared to IM (+30%) and HM (+25%) but lower activity was present in the push-off for LM compared to IM and HM. For the peroneal muscle, differences were present in the push-off where HM showed increased activity compared to IM (+24%) and LM (+60%). The tibial muscle revealed slightly lower activity during preactivation for the high mileage runners. Neuromuscular activity differs during stance between the high and intermediate group compared to low mileage runners. Slight adaptations in neuromuscular activation indicate a more target-oriented activation strategy possibly due to repetitive training in runners with higher weekly mileage.
Introduction: Gait speed is one of the most commonly and frequently used parameters to evaluate gait development. It is characterized by high variability when comparing different steps in children. The objective of this study was to determine intra-individual gait speed variability in children.
Methods: Gait speed measurements (6-10 trials across a 3 m walkway) were performed and analyzed in 8263 children, aged 1-15 years. The coefficient of variation (CV) served as a measure for intra-individual gait speed variability measured in 6.6 +/- 1.0 trials per child. Multiple linear regression analysis was conducted to evaluate the influence of age and body height on changes in variability. Additionally, a subgroup analysis for height within the group of 6-year-old children was applied.
Results: A successive reduction in gait speed variability (CV) was observed for age groups (age: 1-15 years) and body height groups (height: 0.70-1.90 m). The CV in the oldest subjects was only one third of the CV (CV 6.25 +/- 3.52%) in the youngest subjects (CV 16.58 +/- 10.01%). Up to the age of 8 years (or 1.40 m height) there was a significant reduction in CV over time, compared to a leveling off for the older (taller) children.
Discussion: The straightforward approach measuring gait speed variability in repeated trials might serve as a fundamental indicator for gait development in children. Walking velocity seems to increase to age 8. Enhanced gait speed consistency of repeated trials develops up to age 15.
In dynamic H-reflex measurements, the standardisation of the nerve stimulation to the gait cycle is crucial to avoid misinterpretation due to altered pre-synaptic inhibition. In this pilot study, a plantar pressure sole was used to trigger the stimulation of the tibialis nerve with respect to the gait cycle. Consequently, the intersession reliability of the soleus muscle H-reflex during treadmill walking was investigated.
Seven young participants performed walking trials on a treadmill at 5 km/h. The stimulating electrode was placed on the tibial nerve in the popliteal fossa. An EMG was recorded from the soleus muscle. To synchronize the stimulus to the gait cycle, initial heel strike was detected with a plantar pressure sole. Maximum H-reflex amplitude and M-wave amplitude were obtained and the Hmax/Mmax ratio was calculated.
Data reveals excellent reliability, ICC = 0.89. Test-retest variability was 13.0% (+/- 11.8). The Bland-Altman analysis showed a systematic error of 2.4%.
The plantar pressure sole was capable of triggering the stimulation of the tibialis nerve in a reliable way and offers a simple technique for the evaluation of reflex activity during walking.
Reliability of ultrasound measurements for subcutaneous adipose tissue in elite canoe athletes
(2014)
Objectives-Sonography of muscle architecture provides physicians and researchers with information about muscle function and muscle-related disorders. Inter-rater reliability is a crucial parameter in daily clinical routines. The aim of this study was to assess the inter-rater reliability of sonographic muscle architecture assessments and quantification of errors that arise from inconsistent probe positioning and image interpretation.
Results-Inter-rater reliability was good overall (ICC, 0.77-0.90; IRV, 9.0%-13.4%; bias LoA, 0.2 +/- 0.2-1.7 +/- 3.0). Superior and inferior pennation angles showed high systematic bias and LoA in all setups, ranging from 2.0 degrees +/- 2.2 degrees to 3.4 degrees +/- 4.1 degrees. The highest IRV was found for muscle thickness (13.4%). "When the probe position was standardized, the SEM for muscle thickness decreased from 0.1 to 0.05 cm.
Conclusions-Sonographic examination of muscle architecture of the medial gastrocnemius has good to high reliability. In contrast to pennation angle measurements, length measurements can be improved by standardization of the probe position.
Changes in performance parameters over four consecutive maximal incremental cycling tests were investigated to determine how many tests can be performed within one single day without negatively affecting performance. Sixteen male and female subjects (eight trained (T): 25 +/- 3 yr, BMI 22.6 +/- 2.5 kg center dot m(-2), maximal power output (P-max) 4.6 +/- 0.5 W center dot kg(-1); eight untrained (UT): 27 +/- 3 yr, BMI 22.3 +/- 1.2 kg center dot m(-2), P-max 2.9 +/- 0.3 W center dot kg(-1)) performed four successive maximal incremental cycling tests separated by 1.5 h of passive rest. Individual energy requirements were covered by standardised meals between trials. Maximal oxygen uptake (VO2max) remained unchanged over the four tests in both groups (P = 0.20 and P = 0.33, respectively). P-max did not change in the T group (P = 0.32), but decreased from the third test in the UT group (P < 0.01). Heart rate responses to submaximal exercise were elevated from the third test in the T group and from the second test in the UT group (P < 0.05). The increase in blood lactate shifted rightward over the four tests in both groups (P < 0.001 and P < 0.01, respectively). Exercise-induced net increases in epinephrine and norepinephrine were not different between the tests in either group (P 0.15). If VO2max is the main parameter of interest, trained and untrained individuals can perform at least four maximal incremental cycling tests per day. However, because other parameters changed after the first and second test, respectively, no more than one test per day should be performed if parameters other than VO2max are the prime focus.
We sought to investigate the effects of wearing a mobile respiratory gas analysis system during a treadmill test on blood lactate (bLa) concentrations and commonly applied bLa thresholds. A total of 16 recreational athletes (31 +/- 3 years, V0205: 58 6 ml min(-1)-kg(-1)) performed one multistage treadmill test with and one without gas exchange measurements (GEM and noGEM). The whole bLa curve, the lactate threshold (LT), the individual anaerobic thresholds according to Stegmann(IAT(sr)) and Dickhuth (IAT(Di)), and a fixed bLa concentration of 4 mmob.l(-1) (OBLA) were evaluated. The bLa curve was shifted slightly leftward in GEM compared to noGEM (P<0.05), whereas the heart rate response was not different between conditions (P= 0.89). There was no difference between GEM and noGEM for LT (2.61 +/- 0.34 vs. 2.64 +/- 0.39 m(-1) s(-1) P=0.49) and IAT(st) (3.47 +/- 0.42 vs. 3.55 +/- 0.47m-s(-1), P=0.12). However, IATD(Di) (3.57 +/- 0.39 vs. 3.66 +/- 0.44m-s(-1), P<0.01) and OBLA (3.85 +/- 0.46 vs. 3.96 +/- 0.47m-s-1, P<0.01) occurred at slower running velocities in GEM. The bLa response to treadmill tests is mildly affected by wearing a mobile gas analysis system. This also applies to bLa thresholds located at higher exercise intensities. While the magnitude of the effects is of little importance for recreational athletes, it might be relevant for elite athletes and scientific studies.