Analysis of muscle fatigue recovery in skiers: a nutritional intervention / Análise na recuperação da fadiga muscular em esquiadores: intervenção nutricional / Análisis en la recuperación de la fatiga muscular en esquiadores: intervención nutricional

ABSTRACT Introduction: Skiing is a sport that demands the high performance of motor coordination with high energy consumption, factors that strongly influence muscle fatigue. Athletes who experience this phenomenon tend to present a decline in performance, generating psychological irritability and impairment in concentration. Diet is closely related to athletic performance, but the proper prescription for skiing athletes still lacks studies. Objective: To explore the methods of recovery from sports fatigue in skiers by providing up-to-date perspectives for effective nutritional intervention during the recovery stage. Methods: Seven young male skiers were selected as research subjects, and caloric intake, among other conditions, was recorded in detail. After three weeks, indices of body weight, body fat rate, serum metabolism, cardiopulmonary capacity, and energy metabolism, among other relevant information, were duly recorded and compared. Results: The intervention did not significantly impact lean body mass indices (p>0.05). The athletes' body weight decreased significantly, and the body fat rate decreased significantly after the nutritional intervention; The analyzed biomarkers were positively impacted, except the urea nitrogen concentration that showed a tendency to increase after the nutritional intervention, an effect that may be linked to the proportional increase of protein intake. Conclusion: The proposed nutritional intervention positively impacted the skiers' energy metabolism, directly impacting the athletes' recovery from sports fatigue. Level of evidence II; Therapeutic studies - investigation of treatment outcomes.

RESUMO Introdução: O esqui é um esporte que exige alto desempenho de coordenação motora com um elevado consumo de energia, fatores que influenciam fortemente a fadiga muscular. Atletas que experienciam esse fenômeno, tendem a apresentar um declínio no nível do desempenho, gerando irritabilidade psicológica e prejuízos na concentração. A dieta está intimamente relacionada ao desempenho atlético, porém a receita adequada para os atletas em esqui ainda carece de estudos. Objetivo: Explorar os métodos de recuperação da fadiga esportiva nos esquiadores fornecendo perspectivas atualizadas para uma intervenção nutricional eficaz durante a etapa de recuperação. Métodos: Sete jovens esquiadores do sexo masculino foram selecionados como sujeitos da pesquisa, e a ingestão calórica, entre outras condições foram detalhadamente registradas. Após três semanas, índices de peso corporal, taxa de gordura corporal, metabolismo sérico, capacidade cardiopulmonar, metabolismo energético, entre outras informações relevantes foram devidamente registradas e comparadas. Resultados: A intervenção não impactou significativamente nos índices de massa magra corporal (p>0,05). O peso corporal dos atletas diminuiu significativamente e a taxa de gordura corporal diminuiu significativamente após a intervenção nutricional; os biomarcadores analisados foram positivamente impactados, a exceção da concentração de nitrogênio ureico que apresentou tendência de alta após a intervenção nutricional, efeito que pode estar atrelado ao aumento proporcional da ingesta proteica. Conclusão: A proposta de intervenção nutricional apresentou impactos positivos no metabolismo energético dos esquiadores, impactando diretamente na recuperação da fadiga esportiva dos atletas. Nível de evidência II; Estudos terapêuticos - investigação dos resultados do tratamento.

RESUMEN Introducción: El esquí es un deporte que exige un alto rendimiento de coordinación motora con un elevado consumo de energía, factores que influyen fuertemente en la fatiga muscular. Los deportistas que experimentan este fenómeno, tienden a presentar un descenso en el nivel de rendimiento, generando irritabilidad psicológica y daños en la concentración. La dieta está estrechamente relacionada con el rendimiento deportivo, pero la prescripción adecuada para los atletas de esquí aún carece de estudios. Objetivo: Explorar los métodos de recuperación de la fatiga deportiva en los esquiadores proporcionando perspectivas actualizadas para una intervención nutricional eficaz durante la etapa de recuperación. Métodos: Se seleccionaron siete jóvenes esquiadores varones como sujetos de investigación, y se registró detalladamente la ingesta calórica, entre otras condiciones. Al cabo de tres semanas, se registraron y compararon debidamente los índices de peso corporal, el índice de grasa corporal, el metabolismo sérico, la capacidad cardiopulmonar y el metabolismo energético, entre otros datos relevantes. Resultados: La intervención no tuvo un impacto significativo en los índices de masa corporal magra (p>0,05). El peso corporal de los atletas disminuyó significativamente y el índice de grasa corporal disminuyó significativamente después de la intervención nutricional. Los biomarcadores analizados tuvieron un impacto positivo, con la excepción de la concentración de nitrógeno ureico que mostró una tendencia a aumentar después de la intervención nutricional, efecto que puede estar relacionado con el aumento proporcional de la ingesta de proteínas. Conclusión: La propuesta de intervención nutricional presentó impactos positivos en el metabolismo energético de los esquiadores, impactando directamente en la recuperación de la fatiga deportiva de los atletas. Nivel de evidencia II; Estudios terapéuticos - investigación de los resultados del tratamiento.

Effect of high- and low-resistance inspiratory muscle training on physiological response to exercise in cross-country skiers.

BACKGROUND: The aim of the study was to evaluate the effect of different kinds of respiratory muscle training (RMT) on work capacity and selected spirometric indices in trained male cross-country skiers. METHODS: The study involved 13 competitively trained, elite Polish male cross-country skiers. The subjects were randomly divided into two groups who completed 7 weeks of RMT: one with gradually increasing resistance (power RMT) and the other with constant resistance (endurance RMT). Both groups' training programs consisted of 30 inspiratory maneuvers performed twice a day, 6 days a week. The first week of RMT started with a low resistance (29 cmH2O). In the following weeks, resistance in the power RMT group was gradually increased, while in the endurance RMT group, inspiratory resistance was maintained at a constant level of 53 cm H2O (36±8% PImax). Maximal inspiratory pressure (PImax), peak inspiratory flow rate (PIF), and stress test indices were measured before and after RMT. The stress test was conducted on a ski ergometer, with a gradual increase in intensity in all-out effort. RESULTS: A significant increase in PImax, PIF, and exercise work capacity (test time, work output, and peak power) was noted in both groups. No significant changes were observed in the VO2max or the selected respiratory variables. CONCLUSIONS: During a short training period (up to 7 weeks), the use of gradual and constant inspiratory resistance during RMT improves exercise and spirometric parameters in a similar way. RMT did not have a considerable impact on breathing efficiency in maximal effort.

The Feasibility and Effects of Acupuncture in an Adolescent Nordic Ski Population.

BACKGROUND: Studies investigating the use and effectiveness of acupuncture in adults after exercise have been well documented. Fewer studies involving acupuncture have been completed in the adolescent athlete population. To our knowledge, there are no published studies that investigate the use of acupuncture in adolescent athletes within their field of play. OBJECTIVE: To primarily assess the feasibility of performing acupuncture in adolescent Nordic skiers within their athletic environment, and secondarily to measure the effect of acupuncture on muscle soreness and sense of well-being. DESIGN: Prospective feasibility study. SETTING: Local outdoor cross country ski trails and indoor lodge. PARTICIPANTS: Fifteen healthy participants (80% female, 20% male; age 14-17 years) were involved on at least 1 of 5 treatment days. INTERVENTION: Fifteen-minute treatments were administered using traditional needle acupuncture following the first 5 consecutive Nordic Ski Team practices of the season in an attempt to capture the effect of acupuncture on delayed-onset muscle soreness (DOMS). Acupuncture points specific to muscle groups in the lower limbs that are commonly reported as painful during Nordic skiing were chosen. Pre- and posttreatment surveys included visual analogue scales (VAS) to track participant responses. OUTCOME MEASURES: Time, cost, side effects, and participant to provider ratio was observed to determine feasibility. Effect on muscle soreness and sense of well-being was measured via pre- and posttreatment VAS (0-10) rating analyses. RESULTS: Total time required by research staff on treatment days was 90 minutes; total cost, $1500; temperature range, -13.9°C to -2.8°C, and largest participant to acupuncturist ratio, 7:1. No major side effects occurred. The majority (73%) of participants reported minimal side effects; most common was treatment site pain. The overall pre- to posttreatment effect on muscle soreness (average over 5 days) demonstrated significantly improved posttreatment scores (P = .04). The effect of the day (average over pre- and posttreatment values) demonstrated significantly higher muscle soreness scores on day 3 versus day 1 (P = .03). At study completion, all participants indicated that they would consider acupuncture in the future and would recommend treatments to friends or teammates. CONCLUSION: Providing acupuncture to adolescent Nordic ski athletes in the practice field under extreme temperatures is feasible with the appropriate resources. Despite mild side effects, acupuncture was well received by the athletes. Lessons learned from this trial can provide a framework for delivering acupuncture to other athletes in their training environment. LEVEL OF EVIDENCE: IV.

Differences in food intake and nutritional habits between Spanish adolescents who engage in ski activity and those who do not / Ingesta de alimentos y hábitos nutricionales entre adolescentes españoles que practican y no practican esquí

Background: Increasing obesity among adolescents in the industrialized world may result from poor nutritional habits and inadequate exercise. Aim: To determine differences in food intake, nutritional habits, and body mass index between Spanish adolescents who engage in ski activity and those who do not. Methods: A socio-demographic survey, food frequency questionnaire, 24-hr dietary recall, and physical activity questionnaire were completed by 300 Spanish schoolchildren aged 10 to 18 yrs. Results were compared (Student’st, chi-square and Fisher’s exact test) between adolescents engaged (SP) and not engaged (N-SP) in skiing according to their sex. Results: SP adolescents devoted > 4 h/day to physical activity versus < 1 h for N-SP adolescents. No significant differences were found in nutrient intake or nutritional habits between SP and N-SP adolescents. Protein and fat intakes of both groups were above recommended levels. A higher proportion of N-SP than SP males were overweight. Logistic regression analysis showed that the maintenance of a normal weight was favored by the practice of skiing, the consumption of sugar-free drinks, and supplementation with vitamins/mineral salts and was negatively associated with body weight dissatisfaction, intake of nutritional supplements other than vitamins or minerals, and the consumption of snacks. Conclusions: The diet of this adolescent population was poorly balanced. Engagement in physical activity appears to be a key factor in maintaining a healthy body mass index (AU)

Antecedentes: El aumento de la obesidad entre los adolescentes en países desarrollados puede ser consecuencia de malos hábitos alimentarios y falta de actividad. Objetivo: Determinar las diferencias en la ingesta dealimentos, hábitos nutricionales e índice de masa corporal entre adolescentes españoles que practican esquí y los que no lo hacen. Métodos: Una muestra de 300 adolescentes españoles de 10 a 18 años completó una encuesta que incluyó variables sociodemográficas, un cuestionario de frecuencia de consumo de alimentos, recordatorio de 24h y un cuestionario de actividad física. Se utilizaron test de comparación paramétricos y no paramétricos para comparar los resultados entre adolescentes que practican (SP) y no practican (N-SP) esquí, en función al sexo. Resultados: Los adolescentes SP dedicaron más de 4h diarias a la realización de actividad física mientras que los adolescentes N-SP dedicaron menos de 1 hora diaria a la actividad física. No se encontraron diferencias significativas en la ingesta de nutrientes o los hábitos nutricionales entre adolescentes SP y N-SP. La ingesta de proteínas y lípidos de ambos grupos estuvo por encima de los niveles recomendados. El sobrepeso fue más frecuente entre adolescentes N-SP. El análisis de regresión logística mostró que el mantenimiento de un peso normal se ve favorecido por la práctica del esquí, el consumo de bebidas sin azúcar y la suplementación con vitaminas/minerales y se asoció negativamente con la insatisfacción con el peso corporal, el consumo de suplementos nutricionales distintosa vitaminas o minerales y el consumo de aperitivos. Conclusiones: La dieta de esta población adolescente fue desequilibrada. La participación en la actividad física parece ser un factor clave en el mantenimiento de un índice de masa corporal saludable (AU)

Beta-alanine supplementation improves jumping power and affects severe-intensity performance in professional alpine skiers.

INTRODUCTION: Supplementation with beta-alanine may have positive effects on severe-intensity, intermittent, and isometric strength-endurance performance. These could be advantageous for competitive alpine skiers, whose races last 45 to 150 s, require metabolic power above the aerobic maximum, and involve isometric muscle work. Further, beta-alanine supplementation affects the muscle force-frequency relationship, which could influence explosiveness. We explored the effects of beta-alanine on explosive jump performance, severe exercise energy metabolism, and severe-intensity ski-like performance. METHODS: Nine male elite alpine skiers consumed 4.8 g/d beta-alanine or placebo for 5 weeks in a double-blind fashion. Before and after, they performed countermovement jumps (CMJ), a 90-s cycling bout at 110% VO2max (CLT), and a maximal 90-s box jump test (BJ90). RESULTS: Beta-alanine improved maximal (+7 ± 3%, d = 0.9) and mean CMJ power (+7 ± 2%, d = 0.7), tended to reduce oxygen deficit (-3 ± 8%, p = .06) and lactate accumulation (-12 ± 31%) and enhance aerobic energy contribution (+1.3 ± 2.9%, p = .07) in the CLT, and improved performance in the last third of BJ90 (+7 ± 4%, p = .02). These effects were not observed with placebo. CONCLUSIONS: Beta-alanine supplementation improved explosive and repeated jump performance in elite alpine skiers. Enhanced muscle contractility could possibly explain improved explosive and repeated jump performance. Increased aerobic energy production could possibly help explain repeated jump performance as well.

Differences in food intake and nutritional habits between Spanish adolescents who engage in ski activity and those who do not.

BACKGROUND: Increasing obesity among adolescents in the industrialized world may result from poor nutritional habits and inadequate exercise. AIM: To determine differences in food intake, nutritional habits, and body mass index between Spanish adolescents who engage in ski activity and those who do not. METHODS: A socio-demographic survey, food frequency questionnaire, 24-hr dietary recall, and physical activity questionnaire were completed by 300 Spanish schoolchildren aged 10 to 18 yrs. RESULTS were compared (Student's t, chi-square and Fisher's exact test) between adolescents engaged (SP) and not engaged (N-SP) in skiing according to their sex. RESULTS: SP adolescents devoted > 4 h/day to physical activity versus < 1 h for N-SP adolescents. No significant differences were found in nutrient intake or nutritional habits between SP and N-SP adolescents. Protein and fat intakes of both groups were above recommended levels. A higher proportion of N-SP than SP males were overweight. Logistic regression analysis showed that the maintenance of a normal weight was favored by the practice of skiing, the consumption of sugar-free drinks, and supplementation with vitamins/mineral salts and was negatively associated with body weight dissatisfaction, intake of nutritional supplements other than vitamins or minerals, and the consumption of snacks. CONCLUSIONS: The diet of this adolescent population was poorly balanced. Engagement in physical activity appears to be a key factor in maintaining a healthy body mass index.

Antecedentes: El aumento de la obesidad entre los adolescentes en países desarrollados puede ser consecuencia de malos hábitos alimentarios y falta de actividad. Objetivo: Determinar las diferencias en la ingesta de alimentos, hábitos nutricionales e índice de masa corporal entre adolescentes españoles que practican esquí y los que no lo hacen. Métodos: Una muestra de 300 adolescentes españoles de 10 a 18 años completó una encuesta que incluyó variables sociodemográficas, un cuestionario de frecuencia de consumo de alimentos, recordatorio de 24h y un cuestionario de actividad física. Se utilizaron test de comparación paramétricos y no paramétricos para comparar los resultados entre adolescentes que practican (SP) y no practican (N-SP) esquí, en función al sexo. Resultados: Los adolescentes SP dedicaron más de 4h diarias a la realización de actividad física mientras que los adolescentes N-SP dedicaron menos de 1 hora diaria a la actividad física. No se encontraron diferencias significativas en la ingesta de nutrientes o los hábitos nutricionales entre adolescentes SP y N-SP. La ingesta de proteínas y lípidos de ambos grupos estuvo por encima de los niveles recomendados. El sobrepeso fue más frecuente entre adolescentes N-SP. El análisis de regresión logística mostró que el mantenimiento de un peso normal se ve favorecido por la práctica del esquí, el consumo de bebidas sin azúcar y la suplementación con vitaminas/minerales y se asoció negativamente con la insatisfacción con el peso corporal, el consumo de suplementos nutricionales distintos a vitaminas o minerales y el consumo de aperitivos. Conclusiones: La dieta de esta población adolescente fue desequilibrada. La participación en la actividad física parece ser un factor clave en el mantenimiento de un índice de masa corporal saludable.

Relations of biomotor structures and performance of technical elements of alpine skiing in Croatian ski instructors.

With the aim of identifying the factors of alpine skiers' biomotor status in predicting their specific skills, three variable sets were used, comprised of the total of 24 measures (9 variables for assessing anthropometric characteristics, 8 variables for assessing motor abilities and 7 variables for assessing specific ski skills of alpine skiing), on a sample of 79 ski instructor candidates. After preliminary analysis procedures which included descriptive operations and factorization of each separate space, relations between the obtained latent dimensions were established by correlation analysis. The extracted varimax factors were defined as follows - three factors in the morphology space: V1 - Voluminosity and transverse dimensionality of the skeleton, V2 - Longitudinal dimensionality of the skeleton, V3 - Subcutaneous fat tissue; 2 factors in the space of motor abilities: V1 - Agility and explosive power, V2 - Static strength and balance; while a general factor of Specific motor skills of alpine skiing was isolated in the space of motor skills. Statistically significant positive correlation was found between agility and explosive power and general factor of skiing skills, which means that agility and explosive power are the basis for quality performance of advanced and cbmpetitive techniques in alpine skiing. Namely, in realization of advanced and competitive techniques of alpine skiing, which imply a high level of skiing skills acquisition and full automatization of performance, all actions are performed by fast and explosive movement direction changes.

Dietary nitrate does not enhance running performance in elite cross-country skiers.

PURPOSE: The objective of this study is to examine the effects of acute ingestion of dietary nitrate on endurance running performance in highly trained cross-country skiers. Dietary nitrate has been shown to reduce the oxygen cost of submaximal exercise and improve tolerance of high-intensity exercise, but it is not known if this holds true for highly trained endurance athletes. METHODS: Ten male junior cross-country skiers (V˙O(2max)) ≈ 70 mL·kg·min) each completed two trials in a randomized, double-blind design. Participants ingested potassium nitrate (614-mg nitrate) or a nitrate-free placebo 2.5 h before two 5-min submaximal tests on a treadmill at 10 km·h (≈55% of V˙O(2max)) and 14 km·h (≈75% of V˙O(2max)), followed by a 5-km running time trial on an indoor track. RESULTS: Plasma nitrite concentrations were higher after nitrate supplementation (325 ± 95 nmol·L) compared with placebo (143 ± 59 nmol·L, P < 0.001). There was no significant difference in 5-km time-trial performance between nitrate (1005 ± 53 s) and placebo treatments (996 ± 49 s, P = 0.12). The oxygen cost of submaximal running was not significantly different between placebo and nitrate trials at 10 km·h (both 2.84 ± 0.34 L·min) and 14 km·h (3.89 ± 0.39 vs. 3.77 ± 0.62 L·min). CONCLUSIONS: Acute ingestion of dietary nitrate may not represent an effective strategy for reducing the oxygen cost of submaximal exercise or for enhancing endurance exercise performance in highly trained cross-country skiers.

Assessment of the postural control strategies used to play two Wii Fit™ videogames.

The Nintendo Wii Fit™ may provide an affordable alternative to traditional biofeedback or virtual reality systems for retraining or improving motor function in populations with impaired balance. The purpose of this study was to evaluate postural control strategies healthy individuals use to play Wii Fit™ videogames. Sixteen young adults played 10 trials of Ski Slalom and Soccer Heading respectively. Centre of pressure (COP) excursion and three-dimensional movement data were acquired to determine variability in medial-lateral COP sway and shoulder-pelvic movement. While there was no difference in medial-lateral COP variability between games during trial 1, there was a significant difference after 10 trials. COP sway increased (59-75 mm) for Soccer Heading while it decreased (67-33 mm) for Ski Slalom from trial 1 to trial 10. During Ski Slalom participants demonstrated decreased shoulder and pelvic movement combined with increased pelvic-shoulder coupling. Conversely, participants demonstrated greater initial shoulder tilt when playing Soccer Heading, with no reduction in pelvic rotation and tilt. Participants decreased pelvic and trunk movements when skiing, suggesting a greater contribution of lower extremity control while they primarily used a trunk strategy to play Soccer Heading.

Nutrition for winter sports.

Winter sports are played in cold conditions on ice or snow and often at moderate to high altitude. The most important nutritional challenges for winter sport athletes exposed to environmental extremes include increased energy expenditure, accelerated muscle and liver glycogen utilization, exacerbated fluid loss, and increased iron turnover. Winter sports, however, vary greatly regarding their nutritional requirements due to variable physiological and physique characteristics, energy and substrate demands, and environmental training and competition conditions. What most winter sport athletes have in common is a relatively lean physique and high-intensity training periods, thus they require greater energy and nutrient intakes, along with adequate food and fluid before, during, and after training. Event fuelling is most challenging for cross-country skiers competing in long events, ski jumpers aiming to reduce their body weight, and those winter sport athletes incurring repeated qualification rounds and heats. These athletes need to ensure carbohydrate availability throughout competition. Finally, winter sport athletes may benefit from dietary and sport supplements; however, attention should be paid to safety and efficacy if supplementation is considered.

Evidence of improved shooting precision in biathlon after 10 weeks of combined relaxation and specific shooting training.

The aim of this study was to test the hypothesis that a combined relaxation (applied tension release, ATR) and specific shooting training regimen may enhance shooting ability of biathlon athletes. Seven biathletes of high national level were randomized into an experimental group (age 20 ± 5 years; Vo2max 60 ± 8 mL kg(-1) min(-1)) and were asked to add this special training intervention to their regular training for 10 weeks, while five other biathletes served as controls (age 19 ± 2 years; Vo2max 57 ± 10 mL kg(-1) min(-1)). The shooting ability of the subjects was assessed before and after the intervention at rest and after roller skiing on a treadmill in a laboratory-based competition simulating assessment. After the intervention period, the experimental group demonstrated a significantly enhanced shooting performance compared to the control group. No changes in Vo2max or in heart rate and Vo2 responses were observed before and after the intervention in either group and there were no differences between the groups in these parameters. Thus, the preliminary conclusion is that a combination of ATR and specific shooting training seems to be instrumental in enhancing the shooting performance in biathlon.

Opuntia ficus indica's effect on heart-rate variability in high-level athletes.

Opuntia ficus indica (OFI) has many physiological effects, but a relationship between OFI and heart-rate variability (HRV) has never been established. The aim of this study was to describe the effects of a diet supplement of OFI on HRV in athletes. The first day, heart rate (HR) was measured at rest in supine (SU) and standing (ST) positions to analyze HRV in 10 athletes, followed by a randomized assignment to an OFI (5) or placebo (5) group. The next day, the athletes repeated the HRV test. One month later the crossover protocol was applied. In OFI, the high-frequency-activity HF(SU) (1,773 +/- 2,927 vs. 5,856 +/- 8,326 ms(2), p < .05), HF(ST) (295 +/- 313 vs. 560 +/- 515 ms(2), p < .05), and low-frequency LF(SU) (1,621 +/- 1,795 vs. 6,029 +/- 9,007 ms(2), p < .01) increased. HR(SU) (66 +/- 13 vs. 57 +/- 11 beats/min, p < .01) and HR(ST) (87 +/- 11 vs. 76 +/- 9 beats/min, p < .01) decreased. A diet supplement of OFI increases HF and LF activities and decreases HR.

Serum ferritin as a marker of potential biochemical iron overload in athletes.

OBJECTIVES: Beyond hematological manipulation, iron supplementation therapy is commonplace in athletes to counterbalance physiological or pathologic anemia and to prevent physiologic dysfunction. However, misuse of iron therapy, occasionally resulting in iron overload, is not free from metabolic risks. DESIGN: We planned to measure baseline serum ferritin concentration in sedentary individual and athletes. SETTING: The Institute of Clinical Biochemistry of the Verona University. PARTICIPANTS Serum ferritin was measured in 60 male healthy sedentary controls, 80 amateur road cyclists, 42 male professional cross-country skiers, and 88 professional male road cyclists. ASSESSMENT OF RISK FACTORS: The biochemical iron overload was ascertained by measuring baseline serum ferritin concentration as a reliable approach that mirrors the total body iron content. MAIN OUTCOME MEASUREMENTS: The concentration of serum ferritin in healthy controls was 112 +/- 78 ng/mL, whereas that of amateur cyclists, professional skiers, and professional cyclists was 127 +/- 76 ng/mL (P = 0.185), 183 +/- 130 ng/mL (P = 0.001), and 332 +/- 218 ng/mL (P < 0.001), respectively. RESULTS: Both categories of professional athletes showed significantly increased concentrations of serum ferritin, whereas the concentration of amateur cyclists was comparable to that of healthy sedentary controls. CONCLUSIONS: Professional endurance athletes have serum ferritin concentrations that are 2-fold to 3-fold higher than those of matched sedentary individuals and amateur athletes, exceeding the threshold for the diagnosis of biochemical iron overload and unveiling potential metabolic risks.

The effects of creatine supplementation on high-intensity exercise performance in elite performers.

The aim of this research was to determine whether creatine supplementation at a dose of 20 g x day(-1), given in 4 x 6-g doses (5 g creatine monohydrate and 1 g glucose) for 5 days, was effective in improving kayak ergometer performances of different durations. Sixteen male subjects with the following characteristics [mean (SEM)]: age 21 (1.2) years, height 170.2 (1.7) cm, weight 75.3 (2.3) kg, sigma8 skinfolds 59.3 (2.6) mm, and maximal oxygen consumption 67.1 +/- (4.3) ml x kg x min(-1), undertook three maximal kayak ergometer tests of 90, 150 and 300 s duration on a wind-braked kayak ergometer (CON). Two groups were then randomly formed, with one group taking the supplement (SUP) while the other took a placebo (PLAC). No pre-test differences existed between the SUP and the PLAC groups in any of the variables measured. After supplementation each group then repeated the same kayak ergometer tests as performed previously and after a 4-week "washout period" the groups took either the PLAC or SUP for another 5 days and then completed the final tests. The SUP group completed significantly more work than either the CON or PLAC groups in all of the tests (90 s, P < 0.01; 150 s, P < 0.001; 300 s, P < 0.05). Body mass remained stable throughout the test period in both the CON and PLAC groups, but both were significantly less than the SUP body mass of 77.3 (1.0) kg (P < 0.01). The results of this work indicate that creatine supplementation can significantly increase the amount of work accomplished during kayak ergometer performance at durations ranging from 90 to 300 s.

Branched-chain amino acid supplementation during repeated prolonged skiing exercises at altitude.

This study was conducted to test the hypothesis that a branched-chain amino acid (BCAA) supplementation would minimize changes in body composition and alterations in plasma amino acid profile induced by prolonged exercises at altitude. Twenty-four highly trained subjects participated in six successive sessions of ski mountaineering (6-8 hr duration, altitude 2,500-4,100 m). Twelve subjects took a dietary supplement of BCAA (BCAA group) and 12 took a dietary supplement that was 98% carbohydrate (C group). Body weight decreased in C subjects (-2.1%, p < .01), while the body weight loss recorded in the BCAA group was not statistically significant (-1.2%, NS). Changes in body composition that resulted from repeated skiing exercise at altitude were not significantly minimized by BCAA administration. Peak power output recorded during an incremental bicycle exercise decreased in C subjects but did not change significantly in BCAA subjects. Results of this study demonstrate that neither changes in body composition related to the ski mountaineering program nor muscular performance during isometric contraction was significantly affected by BCAA administration.

Discrimination between cross-country and downhill skiers by pulmonary and local 31PNMR evaluations.

The purpose of the present study was to correlate data on calf muscle metabolism using 31P nuclear magnetic resonance spectroscopy with measurements of whole body maximal oxygen consumption and maximal power output, and to determine whether the combination of these data could be used to predict athletic ability. Experiments were performed in a 2.35 Tesla, 35 cm diameter electromagnet on the leg muscle of sedentary human subjects (N = 6) and groups of athletes trained for endurance (cross-country skiers, N = 7) or strength performance (downhill skiers, N = 5). The exercise protocol consisted of successive plantar flexions performed at graded fractions of the maximal voluntary contraction (MVC). The results obtained from NMR investigation (changes in content of inorganic phosphate: Pi, phosphocreatine: PC and muscle ATP, and intracellular pH) were then compared with those of maximal O2 consumption (VO2max) and maximal power (MP). When the data on athletes were compared with those obtained on sedentary subjects, the curves illustrating the relationship between the imposed load and the Pi/PC ratio were significantly shifted toward high output power for a given Pi/PC value. It also appeared from this study that specific training in force development (downhill skiing) induced a slighter decrease in PC level than for endurance (cross-country skiers) despite improvement in physical performance. A slight but significant intracellular acidification was observed in the muscles of sedentary subjects and downhill skiers for contraction at, respectively, 50% and 80% of MVC, but not in the skeletal muscles of cross-country skiers.(ABSTRACT TRUNCATED AT 250 WORDS)

Muscle bioenergetics in skiers: studies using NMR spectroscopy.

Sedentary human subjects (n = 6) and two homogeneous groups of athletes, trained for down-hill skiing (n = 5) and cross-country skiing (n = 7), were subjected to cardiorespiratory testing and to evaluation of the bioenergetics of calf muscles by means of Phosphorus Nuclear Magnetic Resonance Spectroscopy. The exercise consisted of successive plantar flexions performed at graded fractions of the maximal voluntary contraction force. It appears from this study that the decrease in phosphocreatine level induced by exercise at 80% of maximal voluntary contraction, was smaller in the muscles of athletes who trained for cross-country skiing, than in the muscles of down-hill skiers and control subjects. Intracellular acidosis was virtually absent in cross-country athletes. The rate of restitution of phosphocreatine, after the exercise, was higher in both groups of skiers, compared to sedentary subjects. The maximal oxygen consumption and the maximal alactic power were higher in athletes than in sedentary subjects. NMR data and mechanical measurements are used in consideration with functional systemic indexes to characterize the capabilities of skiers.