Influence of mass on the speed of wheelchair racing

Reducing the mass of a racing wheelchair improves the winning time even for relatively small mass reductions over short distances (100 m). In this study, the improvement of speed and winning time on mass reduction was modelled mathematically, the speed profiles of 100 m wheelchair races as well as the rolling resistance and drag area of the athlete–wheelchair system was determined experimentally, and the improvement of the winning time through mass reduction was calculated from the mathematical model and experimental data. For winning times of 30 s, the relative improvement of the winning time is at least equal to the relative reduction of mass. For winning times of 15 s, the relative improvement of the winning time is at least half the relative reduction of mass. A reduction by 1 kg results in an overall improvement of the winning time of about 1–2.3% for winning times of 15–30 s (100-m race). In absolute terms, a mass saving of 1 and 5 kg on a 60-kg system would reduce a 15-s winning time for the 100 m by 0.132 and 0.66 s, respectively, and a 30-s winning time by 0.63 and 2.86 s, respectively. The mass of a wheelchair is the most important parameter for improving the winning time. The influence of the mass on the winning time is 4 or 1.5 times greater than the influence of the rolling friction coefficient, and 4 or 5.5 times greater than the influence of the drag area in a 15 or 30-s race, respectively. These principles should be considered when designing a racing wheelchair.     

Energy balance and dietary habits of America's Cup sailors

This research, which was conducted with crew members of an America's Cup team, had the following objectives: (a) to assess energy expenditure and intake during training; (b) to evaluate the sailors' diet, and (c) to identify any dietary flaws to determine the appropriate intake of nutrients, correct possible dietary mistakes, and improve their food habits. Energy expenditure was estimated on 15 sailors using direct measurements (oxygen consumption) and a 3-day activity questionnaire. Oxygen consumption was measured on sailors during both on-water America's Cup sailing training and dry-land fitness training. Composition of the diet was estimated using a 3-day food record. Average daily energy expenditure of the sailors ranged from 14.95 to 24.4 MJ, depending on body mass and boat role, with the highest values found in grinders and mastmen. Daily energy intake ranged from 15.7 to 23.3 MJ (from +6% to -18% of energy expenditure). The contributions of carbohydrate, protein, and fat to total energy intake were 43%, 18%, and 39% respectively, values that are not in accord with the recommended guidelines for athletes. Our results show the importance of assessing energy balance and food habits for America's Cup sailors performing different roles. The practical outcome of this study was that the sailors were given dietary advice and prescribed a Mediterranean diet, explained in specific nutrition lectures.     

我国优秀男子帆板运动员卧拉训练测试与评价的研究

探索我国优秀男子帆板运动员在专项力量训练中的评价指标和相关因素,对帆板项目的上肢向心力量训练及其监控与评 价问题进行了分析研究,为我国帆板运动员的专项力量训练提供科学依据.帆板力量训练应该以提高功率为核心,而提高功率的 关键是提高动作速度.最大上拉速度可以作为评价卧拉峰值功率的敏感指标.较大卧拉重量对于提高帆板运动成绩没有显著贡 献,建议减少在卧拉训练时大重量杠铃的训练,加强中小重量的力量速度和力量耐力训练.     

Acute changes in kinematic and muscle activity patterns in habitually shod rearfoot strikers while running barefoot

The aim of this study was to observe changes in the kinematics and muscle activities when barefoot running was initially adopted by six habitually shod, recreational rearfoot striking runners. Participants ran on a treadmill shod for 5 min, completed 3 × 10-min intervals of barefoot running and then completed a final minute of shod running at a self-selected pace. Dependent variables (speed, joint angles at foot-contact, joint range of motion (ROM), mean and peak electromyography (EMG) activity) were compared across conditions using repeated measures ANOVAs. Anterior pelvic tilt and hip flexion significantly decreased during barefoot conditions at foot contact. The ROM for the trunk, pelvis, knee and ankle angles decreased during the barefoot conditions. Mean EMG activity was reduced for biceps femoris, gastrocnemius lateralis and tibialis anterior during barefoot running. The peak activity across the running cycle decreased in biceps femoris, vastus medialis, gastrocnemius medialis and tibialis anterior during barefoot running. During barefoot running, tibialis anterior activity significantly decreased during the pre-activation and initial contact phases; gastrocnemius lateralis and medialis activity significantly decreased during the push-off phase. Barefoot running caused immediate biomechanical and neuromuscular adaptations at the hip and pelvis, which persisted when the runners donned their shoes, indicating that some learning had occurred during an initial short bout of barefoot running.     

赛艇运动员产生心理压力的成因及对策

论述了赛艇运动员心理压力表现的类型,并对赛艇运动员产生心理压力进行成因分析,最后提出若干解决赛艇运动员心理压力的心理训练方法。     

Body composition of female road and track endurance cyclists: Normative values and typical changes

The aims of this study were to describe normative values and seasonal variation of body composition in female cyclists comparing female road and track endurance cyclists, and to validate the use of anthropometry to monitor lean mass changes. Anthropometric profiles (seven site skinfolds) were measured over 16 years from 126 female cyclists. Lean mass index (LMI) was calculated as body weight?×?skinfolds^?x. The exponent (x) was calculated as the slope of the natural logarithm of body weight and skinfolds. Percentage changes in LMI were compared to lean mass changes measured using dual-energy X-ray absorptiometry (DXA) in a subset of 25 road cyclists. Compared to sub-elite and elite cyclists, world class cyclists were (mean [95% CI]) 1.18?kg [0.46, 1.90] and 0.60?kg [0.05, 1.15] lighter and had skinfolds that were 7.4?mm [3.8, 11.0] and 4.6?mm [1.8, 7.4] lower, respectively. Body weight (0.41?kg [0.04, 0.77]) and skinfolds (4.0?mm [2.1, 6.0]) were higher in the off-season compared to the early-season. World class female road cyclists had lower body weight (6.04?kg [2.73, 9.35]) and skinfolds (11.5?mm [1.1, 21.9]) than track endurance cyclists. LMI (mean exponent 0.15 [0.13, 0.18]) explained 87% of the variance in DXA lean mass. In conclusion, higher performing female cyclists were lighter and leaner than their less successful peers, road cyclists were lighter and leaner than track endurance cyclists, and weight and skinfolds were lowest early in the season. LMI appears to be a reasonably valid tool for monitoring lean mass changes.     

Energy turnover during 24 hours and 6 days of adventure racing

Abstract

Energy turnover was assessed in two conditions of mixed ultra-endurance exercise. In Study 1, energy expenditure and intake were measured in nine males in a laboratory over 24 h. In Study 2, energy expenditure was assessed in six males during an 800-km Adventure race (mean race time 152.5 h). Individual correlations between heart rate and oxygen uptake ([Vdot]O₂) were established during pre-tests when kayaking, cycling, and running. During exercise, energy expenditure was estimated from continuous heart rate recordings. Heart rate and [Vdot]O₂ were measured regularly during fixed cycling work rates to correct energy expenditure for drift in oxygen pulse. Mean energy expenditure was 18,050 ± 2,390 kcal (750 ± 100 kcal · h^?1) and 80,000 ± 18,000 kcal (500 ± 100 kcal · h^?1) in Study 1 and Study 2 respectively, which is higher than previously reported. Energy intake in Study 1 was 8,450 ± 1,160 kcal, resulting in an energy deficit of 9,590 ± 770 kcal. Body mass decreased in Study 1 (?2.3 ± 0.8 kg) but was unchanged in Study 2. Fat mass decreased in Study 2 (?2.3 ± 1.5 kg). In Study 1, muscle glycogen content decreased by only 60%. Adventure racing requires a high energy expenditure, with large inter-individual variation. A large energy deficit is caused by inadequate energy intake, possibly due to suppressed appetite and gastrointestinal problems. The oxygen pulse, comparing start to 12 h of exercise and beyond, increased by 10% and 5% in Study 1 and Study 2 respectively. Hence, estimations of energy expenditure from heart rate recordings should be corrected according to this drift.     

Two critical psychological components of ski racing: Fun and feelings

The concepts of having fun and being aware of feeling states are presented as two critical factors in ski racing. First, the positive motivational characteristics of ‘fun’ are outlined. It is suggested that fun is not only a concept for young athletes but elite ones as well. Preliminary data based on a questionnaire, completed by the United States Alpine Ski Team and approximately 150 ski coaches, are presented. Second, the discussion on feelings refers to the mental programming of tactile sensations and determining one's emotional arousal (feeling state) prior to, and during, competition. Practical suggestions are made with regard to the psychological states and their effects on ski racing.     

Effective body water and body mass changes during summer ultra-endurance road cycling

Because body mass change (ΔM_b) does not represent all water losses and gains, the present field investigation determined if (a) ΔM_b equalled the net effective body water change during ultra-endurance exercise and (b) ground speed and exercise duration influenced these variables. Thirty-two male cyclists (age range, 35–52 years) completed a 164-km event in a hot environment, were retrospectively triplet matched and placed into one of three groups based on exercise duration (4.8, 6.3, 9.6 h). Net effective body water loss was computed from measurements (body mass, total fluid intake and urine excreted) and calculations (water evolved and mass loss due to substrate oxidation, solid food mass and sweat loss), including (ΔEBW_gly) and excluding (ΔEBW) water bound to glycogen. With all cyclists combined, the mean ΔM_b (i.e. loss) was greater than that of ΔEBW_gly by 1200 ± 200 g (P = 1.4 × 10^–18), was similar to ΔEBW (difference, 0 ± 200 g; P = .21) and was strongly correlated with both (R² = .98). Analysis of equivalence indicated that ΔM_b was not equivalent to ΔEBW_gly, but was equivalent to ΔEBW. Due to measurement complexity, we concluded that (a) athletes will not calculate the effective body water calculations routinely and (b) body mass change remains a useful field-expedient estimate of net effective body water change.     

Two critical psychological components of ski racing: fun and feelings

The concepts of having fun and being aware of feeling states are presented as two critical factors in ski racing. First, the positive motivational characteristics of 'fun' are outlined. It is suggested that fun is not only a concept for young athletes but elite ones as well. Preliminary data based on a questionnaire, completed by the United States Alpine Ski Team and approximately 150 ski coaches, are represented. Second, the discussion on feelings refers to the mental programming of tactile sensations and determining one's emotional arousal (feeling state) prior to, and during, competition. Practical suggestions are made with regard to the psychological states and their effects on ski racing.     

Estimating changes in hydration status from changes in body mass: Considerations regarding metabolic water and glycogen storage

Abstract

The potential for imprecision in the estimation of hydration status from changes in body mass has been outlined previously but the equations derived from these derivations appear inconsistent. Reconciliation of body mass loss in terms of sweat loss and effective body water loss is possible from specific equation sets provided that gains and losses of both body mass and water used in the derivation of sweat loss and to derive effective body water loss are in inclusive equation sets. This is obligatory so that mass and water changes as quantifiable determinants are consistent with both internal processes and external gains and losses. Thus, body mass loss, substrate oxidation, metabolic water, and all the terms used in simultaneous equation sets have to be reconciled not only as identical variables but mathematically balance exactly. The revised equation for effective body water loss given here is different from that originally proposed. Metabolic water is part of body mass loss corrected for substrate oxidation, fluid ingestion, and respiratory water to derive sweat loss and it may not be justified to also include water associated with glycogen as releasable bound water. Accordingly, our calculated effective body water loss is substantially a greater loss than originally supposed but clearly still less than the simple balance between mass loss and fluid ingested.     

Estimating changes in hydration status from changes in body mass: considerations regarding metabolic water and glycogen storage

The potential for imprecision in the estimation of hydration status from changes in body mass has been outlined previously but the equations derived from these derivations appear inconsistent. Reconciliation of body mass loss in terms of sweat loss and effective body water loss is possible from specific equation sets provided that gains and losses of both body mass and water used in the derivation of sweat loss and to derive effective body water loss are in inclusive equation sets. This is obligatory so that mass and water changes as quantifiable determinants are consistent with both internal processes and external gains and losses. Thus, body mass loss, substrate oxidation, metabolic water, and all the terms used in simultaneous equation sets have to be reconciled not only as identical variables but mathematically balance exactly. The revised equation for effective body water loss given here is different from that originally proposed. Metabolic water is part of body mass loss corrected for substrate oxidation, fluid ingestion, and respiratory water to derive sweat loss and it may not be justified to also include water associated with glycogen as releasable bound water. Accordingly, our calculated effective body water loss is substantially a greater loss than originally supposed but clearly still less than the simple balance between mass loss and fluid ingested.     

Body composition and hydration status changes in male and female open-water swimmers during an ultra-endurance event

Body mass changes during ultra-endurance performances have been described for running, cycling and for swimming in a heated pool. The present field study of 20 male and 11 female open-water swimmers investigated the changes in body composition and hydration status during an ultra-endurance event. Body mass, both estimated fat mass and skeletal muscle mass, haematocrit, plasma sodium concentration ([Na+]) and urine specific gravity were determined. Energy intake, energy expenditure and fluid intake were estimated. Males experienced significant reductions in body mass (-0.5 %) and skeletal muscle mass (-1.1 %) (P < 0.05) during the race compared to females who showed no significant changes with regard to these variables (P > 0.05). Changes in percent body fat, fat mass, and fat-free mass were heterogeneous and did not reach statistical significance (P > 0.05) between gender groups. Fluid intake relative to plasma volume was higher in females than in males during the ultra-endurance event. Compared to males, females' average increase in haematocrit was 3.3 percentage points (pp) higher, urine specific gravity decrease 0.1 pp smaller, and plasma [Na+] 1.3 pp higher. The observed patterns of fluid intake, changes in plasma volume, urine specific gravity, and plasma [Na+] suggest that, particularly in females, a combination of fluid shift from blood vessels to interstitial tissue, facilitated by skeletal muscle damage, as well as exercise-associated hyponatremia had occurred. To summarise, changes in body composition and hydration status are different in male compared to female open-water ultra-endurance swimmers.     

Body composition and hydration status changes in male and female open-water swimmers during an ultra-endurance event

Young adult soccer players often encounter difficulty progressing from youth competition to being regularly selected for high-level, open-age competition. In an attempt to increase the playing opportunities of semi-professional and amateur under-21 players in first teams, the Royal Belgian Football Association required national division teams to include at least two players younger than 21 in their match selection (under-21 rule). Over four seasons, the following variables were analysed across 2138 semi-professional and amateur soccer players aged 16?–?39 years: (1) the number of times a player was selected to be in the first team squad; (2) the number of times a player was selected to play in the starting line-up; and (3) the number of minutes played. Chi-square analysis demonstrated that second and third division teams had complied with the new selection regulations. However, two-way analysis of variance of individual player data revealed no increase in the number of playing minutes in the under-21 group. It would appear that many teams had complied with the new regulations by selecting young players as substitutes. The results highlight the difficulties that talented young soccer players experience progressing from youth to senior competition. We conclude that the rule imposed by the Royal Belgian Football Association has failed to improve the playing opportunities of young adult soccer players. Alternative strategies for increasing playing opportunities for young talented players are required.     

Errors in the estimation of hydration status from changes in body mass

Abstract

Hydration status is not easily measured, but acute changes in hydration status are often estimated from body mass change. Changes in body mass are also often used as a proxy measure for sweat losses. There are, however, several sources of error that may give rise to misleading results, and our aim in this paper is to quantify these potential errors. Respiratory water losses can be substantial during hard work in dry environments. Mass loss also results from substrate oxidation, but this generates water of oxidation which is added to the body water pool, thus dissociating changes in body mass and hydration status: fat oxidation actually results in a net gain in body mass as the mass of carbon dioxide generated is less than the mass of oxygen consumed. Water stored with muscle glycogen is presumed to be made available as endogenous carbohydrate stores are oxidized. Fluid ingestion and sweat loss complicate the picture by altering body water distribution. Loss of hypotonic sweat results in increased osmolality of body fluids. Urine and faecal losses can be measured easily, but changes in the water content of the bladder and the gastrointestinal tract cannot. Body mass change is not always a reliable measure of changes in hydration status and substantial loss of mass may occur without an effective net negative fluid balance.     

Errors in the estimation of hydration status from changes in body mass

Hydration status is not easily measured, but acute changes in hydration status are often estimated from body mass change. Changes in body mass are also often used as a proxy measure for sweat losses. There are, however, several sources of error that may give rise to misleading results, and our aim in this paper is to quantify these potential errors. Respiratory water losses can be substantial during hard work in dry environments. Mass loss also results from substrate oxidation, but this generates water of oxidation which is added to the body water pool, thus dissociating changes in body mass and hydration status: fat oxidation actually results in a net gain in body mass as the mass of carbon dioxide generated is less than the mass of oxygen consumed. Water stored with muscle glycogen is presumed to be made available as endogenous carbohydrate stores are oxidized. Fluid ingestion and sweat loss complicate the picture by altering body water distribution. Loss of hypotonic sweat results in increased osmolality of body fluids. Urine and faecal losses can be measured easily, but changes in the water content of the bladder and the gastrointestinal tract cannot. Body mass change is not always a reliable measure of changes in hydration status and substantial loss of mass may occur without an effective net negative fluid balance.     

Nutritional intake and body composition changes in a UCI World Tour cycling team during the Tour of Spain

Abstract

The aim of this study was to quantify the food intake of an International Cyclist Union (UCI) World Tour professional cyclist team and to analyse changes in body composition during the Tour of Spain. Nine male professional road cyclists (31.3?±?3.0 years) volunteered to participate in the study. Nutritional data were collected each day throughout the 3-week Tour by two trained investigators who weighed the food ingested by the cyclists. Mean nutritional intake of the cyclists was as follows: carbohydrate, 12.5?±?1.8?g/kg/day of body weight (BW) (65.0?±?5.9%); fat, 1.5?±?0.5 g/kg/day BW (17.9?±?5.6%); and protein, 3.3?±?0.3?g/kg/day BW (17.1?±?1.6%). Intake of all micronutrients, except for folate, vitamin D and potassium (which were 78.7%, 46% and 84% of Recommended Dietary Allowances (RDA), respectively), exceeded the RDA. Height, weight, skinfolds, circumferences and diameters were taken following the guidelines outlined by the International Society for the Advancement of Kinanthropometry. Body density, body fat percentage, muscle mass, total muscle mass and fat mass of the arms and thighs were calculated. Percentage body fat, fat mass and upper arm fat mass significantly decreased (p < .05) after the Tour independent of the equation method used in the calculations. Total muscle mass remained unchanged. Generally, this sample of cyclists consumed more protein and less fat than the recommended amount and had low weight, BMI and fat mass. It is suggested that sports nutritionists design personalised diets in order to maintain a correct proportion of nutrients as well as controlling possible anthropometrical changes that could affect performance.     

America's Cup yacht racing: Race analysis and physical characteristics of the athletes

Abstract

The America's Cup is the oldest competing trophy in sport, yet little is known of the nature and intensity of racing or the physical characteristics of the athletes. In this study, aspects of the physical demands of America's Cup yacht racing were analysed, including the intensity of exercise and activity pattern of “grinding”. Anthropometric data were collected from 92 professional male America's Cup sailors, and fitness data from a top-4 and a lower-7 ranking team during the 32nd America's Cup. Over the 135 races, mean race duration was 82 min (s = 9), with 20 tacks (s = 10) and 8 gybes (s = 3) per race. Grinding bouts were 5.5 s (s = 5.4; range: 2.2–66.3) long, with 143 exercise bouts per race and an exercise-to-rest ratio of 1:6. Mean and peak heart rate was 64% and 92% of maximum for all positions, with bowmen highest (71% and 96%). Grinders were taller, heavier, and stronger than all other positions. Body fat was similar between positions (13%, s = 4). The higher-standard team was stronger and had greater strength endurance, which probably contributed to their quicker manoeuvres. Intensity of exercise was dependent on the similarity of competing boats and the role of the athlete. The short duration and intermittent nature of grinding is indicative of predominantly anaerobic energy provision.