American College of Sports Medicine position stand: prevention of cold injuries during exercise

Pontos de transição da frequência cardíaca em teste progressivo máximo

Foi realizada análise do comportamento da frequência cardíaca (FC) e identificação dos pontos de inflexão (PIFC) e de deflexão da FC (PDFC) em teste progressivo máximo, em sujeitos do sexo feminino e masculino. Vinte universitários foram submetidos ao teste em cicloergômetro. A FC foi monitorada para posterior análise e identificação dos pontos de transição (PT). A FC apresentou comportamento sigmóide, com identificação de PT em todos os sujeitos, sendo: a) em 65% PIFC (64 ± 27W; 29 ± 9%Pmáx e 126 ± 12bpm; 66 ± 5%FCmáx) e PDFC (177 ± 45W; 81 ± 10%Pmáx e 178 ± 8bpm; 93 ± 4%FCmáx); b) em 30% apenas PIFC (80 ± 32W; 36 ± 14%Pmáx e 125 ± 13bpm; 66 ± 5%FCmáx) e c) em 5% o PDFC isolado (103W; 57%Pmáx e 150bpm; 82%FCmáx). O PIFC foi encontrado em carga significativamente inferior ao PDFC, sem diferenças na carga e FC relativas entre os sexos.

Interactions between cold ambient temperature and older age on haptic acuity and manual performance

The impact of exposure to cold on individuals' motor skills demands a deeper understanding of the ways in which cold weather influences psychomotor and haptic performance. In this study, various facets of psychomotor performance were evaluated in order to determine the impacts of ambient cold exposure on older persons. Healthy younger and older persons performed a battery of haptic psychomotor tests at room (23° C) and cold (1° C) ambient temperatures. The results indicate that older individuals do not perform as well as younger persons across the battery of tests, with cold temperature further degrading their performance in dexterity tasks (in, for example, Minnesota Manual Dexterity test placing: F [1, 16] = 10.23, p < .01) and peak precision grip force generation (F [1, 16] = 18.97, p < .01). The results suggest that cold weather may have an impact on the occupations older persons are able to perform during the winter months.

Evidence of cardiac functional reserve upon exhaustion during incremental exercise to determine VO2max

BACKGROUND

There remains considerable debate regarding the limiting factor(s) for maximal oxygen uptake (VO2max). Previous studies have shown that the central circulation may be the primary limiting factor for VO2max and that cardiac work increases beyond VO2max.

AIM

We sought to evaluate whether the work of the heart limits VO2max during upright incremental cycle exercise to exhaustion.

METHODS

Eight trained men completed two incremental exercise trials, each terminating with exercise at two different rates of work eliciting VO2max (MAX and SUPRAMAX). During each exercise trial we continuously recorded cardiac output using pulse-contour analysis calibrated with a lithium dilution method. Intra-arterial pressure was recorded from the radial artery while pulmonary gas exchange was measured continuously for an assessment of oxygen uptake.

RESULTS

The workload during SUPRAMAX (mean±SD: 346.5±43.2 W) was 10% greater than that achieved during MAX (315±39.3 W). There was no significant difference between MAX and SUPRAMAX for Q (28.7 vs 29.4 L/min) or VO2 (4.3 vs 4.3 L/min). Mean arterial pressure was significantly higher during SUPRAMAX, corresponding to a higher cardiac power output (8.1 vs 8.5 W; p<0.06).

CONCLUSIONS

Despite similar VO2 and Q, the greater cardiac work during SUPRAMAX supports the view that the heart is working submaximally at exhaustion during an incremental exercise test (MAX).

Putting the benefits and risks of aerobic exercise in perspective

Although considerable epidemiologic and clinical evidence suggests that structured exercise, increased lifestyle activity, or both are cardioprotective, the absolute and relative risk of cardiovascular and musculoskeletal complications appear to increase transiently during vigorous physical activity. The estimated relative risk of exercise-related cardiac events ranges from 2.1 to 56 and is highest among habitually sedentary individuals with underlying cardiovascular disease who were performing unaccustomed vigorous physical exertion. Moreover, an estimated 7 million Americans receive medical attention for sports and recreation-related injuries each year. These risks, and their modulators, should be considered when endorsing strenuous leisure time or exercise interventions. If the current mantra "exercise is medicine" is embraced, underdosing and overdosing are possible. Thus, exercise may have a typical dose-response curve with a plateau in benefit or even adverse effects, in some individuals, at more extreme levels.

Determination of Best Criteria to Determine Final and Initial Speeds within Ramp Exercise Testing Protocols

This study compared strategies to define final and initial speeds for designing ramp protocols. V_O2max was directly assessed in 117 subjects (29 ± 8 yrs) and estimated by three nonexercise models: (1) Veterans Specific Activity Questionnaire (VSAQ); (2) Rating of Perceived Capacity (RPC); (3) Questionnaire of Cardiorespiratory Fitness (CRF). Thirty seven subjects (30 ± 9 yrs) performed three additional tests with initial speeds corresponding to 50% of estimated V_O2max and 50% and 60% of measured V_O2max. Significant differences (P < 0.001) were found between V_O2max measured (41.5 ± 6.6 mL·kg⁻¹·min⁻¹) and estimated by VSAQ (36.6 ± 6.6 mL·kg⁻¹·min⁻¹) and CRF (45.0 ± 5.3 mL·kg⁻¹·min⁻¹), but not RPC (41.3 ± 6.2 mL·kg⁻¹·min⁻¹). The CRF had the highest ICC, the lowest SEE, and better limits of agreement with V_O2max compared to the other instruments. Initial speeds from 50%–60% V_O2max estimated by CRF or measured produced similar V_O2max (40.7 ± 5.9; 40.0 ± 5.6; 40.3 ± 5.5 mL·kg⁻¹·min⁻¹ resp., P = 0.14). The closest relationship to identity line was found in tests beginning at 50% V_O2max estimated by CRF. In conclusion, CRF was the best option to estimate V_O2max and therefore to define the final speed for ramp protocols. The measured V_O2max was independent of initial speeds, but speeds higher than 50% V_O2max produced poorer submaximal relationships between workload and V_O2.

Cold weather issues in sideline and event management

Exercise in cold environments exerts a unique physiologic stress on the human body, which, under certain conditions, may result in a cold-related injury. Environmental factors are the most important risk factors for the development of hypothermia in athletes. Frostbite occurs as a result of direct cold injury to peripheral tissues. The biggest risk for frostbite is temperature. Trench foot is a result of repeated and constant immersion in cold water. Chilblains are local erythematous or cyanotic skin lesions that develop at ambient air temperatures of 32°F to 60°F after an exposure time of about 1 to 5 h. Cold urticaria is, essentially, an allergic reaction to a cold exposure and can be controlled with avoidance of the cold. There are a number of risk factors and conditions that predispose athletes to cold injury, but exercise in the cold can be done safely with proper education and planning.

Critical care for frostbite

Frostbite, a preventable cold-weather injury, occurs when the skin temperature cools to below 0°C with the formation of extracellular ice crystals. On rewarming, an inflammatory response develops, contributing to ischemia and tissue loss. The severity of injury depends on the temperature, duration of exposure, and amount and depth of frozen tissue. Environmental, individual, behavioral, and physiologic factors increase susceptibility to cold. Rapid rewarming and watchful waiting remains the mainstay of treatment. Prevention can be accomplished through increasing public awareness of the adverse effects of cold exposure, and recognizing and mitigating the risks associated with the development of frostbite.

Cardiopulmonary assessment in primary ciliary dyskinesia

BACKGROUND

Primary ciliary dyskinesia (PCD) is a rare, usually autosomal recessive disorder of ciliary dysfunction associated with lung involvement, which has a great impact on health. There is limited information concerning the aerobic fitness of children and adolescents with PCD. The aim of this study was to assess cardiopulmonary functional capacity and its relationship with pulmonary function and physical activity (PA) levels in patients with PCD.

DESIGN

Ten patients with PCD (age 13·2 ± 2·8 years) underwent spirometry and cardiopulmonary exercise testing. PA was investigated through a questionnaire. Eight age- and body mass index-matched healthy children were enrolled as controls. Main variables were forced expiratory volume at 1 s, peak oxygen uptake (VO(2peak) ) and time spent in PA.

RESULTS

Forty per cent of patients with PCD had impaired lung function as expressed by FEV(1) < 85% predicted. Only patients with impaired lung function exhibited reduced VO(2peak) (18·1 ± 7·9 mL/kg/min). Time spent in total daily PA was slightly lower in patients than controls, with no difference between patients with normal or reduced lung function. In multiple regression models, male gender (β = 0·518, P = 0·018), age (β = 0·752, P = 0·035) and time spent in vigorous PA (β = 0·353, P = 0·049) were independent predictors of aerobic fitness.

CONCLUSIONS

Assessment of resting pulmonary function and cardiopulmonary functional capacity could contribute to the evaluation of pulmonary impairment in PCD. Given the benefit of physical exercise on airway clearance and on general health and quality of life, patients with PCD should be encouraged to adopt an active lifestyle.

Repeatability of aerobic capacity measurements in Parkinson disease

PURPOSE

Maximal or peak aerobic capacity (VO(2peak)) during a maximal-effort graded exercise test is considered by many to be the "gold standard" outcome for assessing the effect of exercise training on cardiorespiratory fitness. The reliability of this measure in Parkinson disease (PD) has not been established, where the degree of motor impairment can vary greatly and is influenced by medications. This study examined the reliability of VO(2peak) during a maximal-effort graded exercise test in subjects with PD.

METHODS

Seventy healthy middle-aged and older subjects with PD Hoehn and Yahr stage 1.5-3 underwent a screening/acclimatization maximal-effort treadmill test followed by two additional maximal-effort treadmill tests with repeated measurements of VO(2peak). A third VO(2peak) test was performed in a subset of 21 subjects.

RESULTS

The mean VO(2peak) measurement was 2.4% higher in the second test compared with the first test (21.42 ± 4.3 vs 21.93 ± 4.50 mL·kg(-1)·min(-1), mean ± SD, P = 0.03). The intraclass correlation coefficients (ICC) for VO(2peak) expressed either as milliliters per kilogram per minute or as liters per minute were highly reliable, with ICC of 0.90 and 0.94, respectively. The maximum HR (ICC of 0.91) and final speed achieved during the tests (ICC of 0.94) were also highly reliable, with the respiratory quotient being the least reliable of the parameters measured (ICC of 0.65).

CONCLUSIONS

Our results demonstrate that measurement of VO(2peak) is reliable and repeatable in subjects with mild to moderate PD, thereby validating use of this parameter for assessing the effects of exercise interventions on cardiorespiratory fitness.

Specific alterations of physiological parameters in competitive race walkers

Race walking is the technical and athletic expression of fast walking and it can be considered as a type of endurance performance. The purpose of this study was to examine whether 12 weeks of a specially designed training program results in the further training enhancement of endurance performance and the related physiological parameters in already well-trained race walkers competing at the national and international level. The investigation protocol consisted of determining the maximal oxygen uptake (VO2peak) and related gas exchange values using an automated cardiopulmonary exercise system and of determining blood lactate variables (aerobic threshold - LTAer and the maximal lactate steady state - MLSS) during walking with proper technique at 8, 10, 12 and 14 km·h-1 for 4 minutes without rest in between. Thereafter, the speed on the treadmill was increased by 0.5 km·h-1 every two minutes until exhaustion to determine VO2peak. After 12 weeks of a specially designed endurance training, statistically significant increases in VO2peak (61.8±8.5 mL·kg-1·min-1 pre vs. 66.9±9.5 mL·kg-1·min-1 post training; p<0.05) and blood lactate variables (VO2-LTAer and VO2-MLSS; p<0.05) were noted. The obtained results suggest that the applied training program can improve endurance and race performance in previously well trained race walkers.

The relationship among HRpeak, RERpeak, and VO2peak during treadmill testing in girls

Clear criteria for maximal oxygen consumption (VO2max) determination in youth are not available, and no studies have examined this issue in girls. Our purpose was to determine whether different peak heart rate (HRpeak) and peak respiratory exchange ratio (RERpeak) cut points affect girls' (N = 453; M age = 13.3 years, SD = .1) VO2max during a maximal treadmill test. A multivariate analysis of variance revealed VO2max (ml kg(-1) min(-1) differed significantly among HRpeak, 180-189 b min(-1) = 34 (SD = .8), 190-194 bmin(-1) = 35 (SD = .9), 195-199 b min(-1) = 38 (SD = .8), 200-204 b min(-1) = 40 ml kg1 x min(-1) (SD = .8), and > or = 205 bmin(-1) = 42 ml kg1 x min(-1) (SD = .7) but not RERpeak. In studies where evidence of a VO2 plateau was examined, peak oxygen consumption (VO2peak) did not differ between plateau and no-plateau groups. Although our results suggest the association between lower VO2peak and lower peak heart rate is a true cardiovascular limit to aerobic energy production, we cannot rule out participant effort.

Physical capacity of girls with mild and moderate idiopathic scoliosis: influence of the size, length and number of curvatures

Introduction

Idiopathic scoliosis affects the locomotor system; however, it can considerably impair the function of cardiovascular and respiratory systems. The aim of the study was to assess parameters indicating the physical capacity of adolescent girls with mild or moderate idiopathic scoliosis.

Materials and Methods

The study included 97 girls, aged 10–18 years: 70 girls, aged 13.84 ± 2.2 years, with idiopathic thoracic scoliosis (Cobb angle 10°–40°) formed the study group and 27 healthy girls, aged 13.2 ± 1.9 years, formed the control group. The girls underwent the Physical Work Capacity 170 (PWC170) test on a cycle ergometer based on two 5-min submaximal physical effort events. The maximum oxygen intake was calculated and expressed in l/min and ml/kg/min. The impact of the curvature angle value, of the number of vertebrae within the curve and of the number of the curves on the physical capacity parameters was analyzed.

Results

The maximal oxygen intake (l/min) and PWC170 (W; W/kg) values were considerably lower in girls with scoliosis of 25°–40° than in the control group. No significant differences were observed between girls with mild scoliosis (10°–24°) and the control group. Statistical analysis did not show any significant impact of the number of vertebrae affected by scoliosis and the number of curvatures on VO₂max (l/min; ml/kg/min) and the PWC170 (W) indicator. In the group of girls with scoliosis involving more than nine vertebrae, the PWC170 (W/kg) indicator was significantly lower than in the control group. A similar correlation was observed between girls with double-curved scoliosis and the control group (p < 0.05).

Conclusion

The maximum oxygen intake and the output during the PWC170 test is lower in girls with moderate scoliosis than in the control group. The value of maximum oxygen intake and output obtained during the PWC170 test in girls with mild scoliosis does not differ significantly from the values obtained in the control group. The number of vertebrae involved in scoliotic deformation and the number of curvatures cause significant decrease in only the relative value of the output obtained during an exercise test.

Frostbites in circumpolar areas

Circumpolar areas are associated with prolonged cold exposure where wind, precipitation, and darkness further aggravate the environmental conditions and the associated risks. Despite the climate warming, cold climatic conditions will prevail in circumpolar areas and contribute to adverse health effects. Frostbite is a freezing injury where localized damage affects the skin and other tissues. It occurs during occupational or leisure-time activities and is common in the general population among men and women of various ages. Industries of the circumpolar areas where frostbite occurs frequently include transportation, mining, oil, and gas industry, construction, agriculture, and military operations. Cold injuries may also occur during leisure-time activities involving substantial cold exposure, such as mountaineering, skiing, and snowmobiling. Accidental situations (occupational, leisure time) often contribute to adverse cooling and cold injuries. Several environmental (temperature, wind, wetness, cold objects, and altitude) and individual (behavior, health, and physiology) predisposing factors are connected with frostbite injuries. Vulnerable populations include those having a chronic disease (cardiovascular, diabetes, and depression), children and the elderly, or homeless people. Frostbite results in sequelae causing different types of discomfort and functional limitations that may persist for years. A frostbite injury is preventable, and hence, unacceptable from a public health perspective. Appropriate cold risk management includes awareness of the adverse effects of cold, individual adjustment of cold exposure and clothing, or in occupational context different organizational and technical measures. In addition, vulnerable population groups need customized information and care for proper prevention of frostbites.

Avaliação da capacidade máxima de exercício: uma revisão sobre os protocolos tradicionais e a evolução para modelos individualizados

Os ajustes fisiológicos ao exercício têm sido extensivamente estudados. Apesar do consenso sobre a importância de testes de exercício para a avaliação do consumo máximo de oxigênio (<img border=0 width=32 height=32 id="_x0000_i1065" src="../../../../img/revistas/rbme/v17n5/img01.jpg">O2máx), diferenças expressivas entre os protocolos utilizados podem comprometer a comparação de dados e sua utilização clínica ou funcional. A presente revisão analisou os principais protocolos correntemente utilizados na avaliação do <img border=0 width=32 height=32 id="_x0000_i1064" src="../../../../img/revistas/rbme/v17n5/img01.jpg">O2máx, destacando suas vantagens e limitações. Além disso, compararam-se as características de protocolos escalonados em estágios com aquelas de modelos individualizados, conhecidos como protocolos em rampa. Foram revisados 102 estudos publicados entre os anos 1955 e 2009. Os resultados indicaram que, apesar de a maior parte dos estudos apontar vantagens dos protocolos em rampa sobre os mais tradicionais, há uma evidente carência de recomendações sobre diversos aspectos de sua elaboração. São raros os estudos que analisaram a influência de variáveis dos protocolos em rampa sobre os desfechos pretendidos, como o consumo máximo de oxigênio e limiares de transição metabólica. Há dúvidas acerca da melhor maneira de se determinar a capacidade máxima de exercício, velocidade inicial do teste, razão de incremento, interação velocidade/inclinação e tempo de teste. Em suma, os testes em rampa vêm sendo aplicados com base na experiência dos avaliadores, sem que haja realmente um 'protocolo' que norteie a sua montagem. Estudos que possam contribuir para o desenvolvimento de critérios mais formais e precisos para a elaboração de protocolos em rampa, portanto, fazem-se necessários.

Is it time to retire the A.V. Hill Model?: A rebuttal to the article by Professor Roy Shephard

Recent publications by Emeritus Professor Roy Shephard propose that a "small group of investigators who have argued repeatedly (over the past 13 years) for a 'Central Governor'," should now either "Put up or shut up." Failing this, their 'hypothesis' should be 'consigned to the bottom draw for future reference'; but Professor Shephard's arguments are contradictory. Thus, in different sections of his article, Professor Shephard explains: why there is no need for a brain to regulate exercise performance; why there is no proof that the brain regulates exercise performance; and why the brain's proven role in the regulation of exercise performance is already so well established that additional comment and research is unnecessary. Hence, "The higher centres of an endurance athlete … call forth an initial effort … at a level where a minimal accumulation of lactate in the peripheral muscles is sensed." Furthermore, "a variety of standard texts have illustrated the many mutually redundant feedback loops (to the nervous system) that limit exercise." Yet, the figure from Professor Shephard's 1982 textbook does not contain any links between the nervous system, "many mutually redundant feedback loops" and skeletal muscle. This disproves his contradictory claims that although there is neither any need for, nor any proof of, any role of the brain in the regulation of exercise performance, the physiological mechanisms for this (non-existent) control were already well established in 1982. In contrast, the Central Governor Model (CGM) developed by our "small group … in a single laboratory" after 1998, provides a simple and unique explanation of how 'redundant feedback loops' can assist in the regulation of exercise behaviour. In this rebuttal to his article, I identify (i) the numerous contradictions included in Professor Shephard's argument; (ii) the real meaning of the facts that he presents; (iii) the importance of the evidence that he ignores; and (iv) the different philosophies of how science should be conducted according to either the Kuhnian or the Popperian philosophies of scientific discovery. My conclusion is that the dominance of an authoritarian Kuhnian philosophy, which refuses to admit genuine error or "the need to alter one's course of belief or action," explains why there is little appetite in the exercise sciences for the acceptance of genuinely novel ideas such as the CGM. Furthermore, to advance the case for the CGM, I now include evidence from more than 30 studies, which, in my opinion, can only be interpreted according to a model of exercise regulation where the CNS, acting in an anticipatory manner, regulates the exercise behaviour by altering skeletal muscle recruitment, specifically to ensure that homeostasis is maintained during exercise. Since few, if any, of those studies can be explained by the 'brainless' A.V. Hill Cardiovascular Model on which Professor Shephard bases his arguments, I argue that it is now the appropriate time to retire that model. Perhaps this will bring to an end the charade that holds either (i) that the brain plays no part in the regulation of exercise performance; or, conversely, (ii) that the role of the brain is already so well defined that further research by other scientists is unnecessary. However, this cannot occur in a discipline that is dominated by an authoritarian Kuhnian philosophy.

Cold-water immersion and the treatment of hyperthermia: using 38.6°C as a safe rectal temperature cooling limit

CONTEXT

Cold-water immersion is recommended for the immediate field treatment of exertional heat stroke. However, concerns exist over potential overcooling of hyperthermic individuals during cold-water immersion.

OBJECTIVE

To evaluate the recommendation that removing previously hyperthermic individuals from a cold-water bath at a rectal temperature (T(re)) of 38.6°C would attenuate overcooling.

DESIGN

Controlled laboratory study.

SETTING

University research laboratory.

PATIENTS OR OTHER PARTICIPANTS

Participants included 6 men and 4 women (age  =  22 ± 3 years, height  =  172 ± 10 cm, mass  =  67.8 ± 10.7 kg, body fat percentage  =  17.1% ± 4.5%, maximum oxygen consumption  =  59.3 ± 8.7 mL·kg(-1)·min(-1)).

INTERVENTION(S)

After exercising at an ambient temperature of 40.0°C for 38.5 ± 9.4 minutes, until T(re) reached 39.5°C, participants were immersed in a 2.0°C circulated water bath until T(re) decreased to either 37.5°C or 38.6°C. Subsequently, participants were removed from the water bath and recovered for 20 minutes at an ambient temperature of 25°C.

MAIN OUTCOME MEASURE(S)

Rectal and esophageal temperatures were measured continuously during the immersion and recovery periods.

RESULTS

Because of the experimental design, the overall time of immersion was greater during the 37.5°C trial (16.6 ± 5.7 minutes) than the 38.6°C trial (8.8 ± 2.6 minutes) (t(9)  =  -4.740, P  =  .001). During the recovery period after cold-water immersion, both rectal (F(1,9)  =  50.540, P < .001) and esophageal (F(1,6)  =  20.365, P  =  .007) temperatures remained greater in the 38.6°C trial than in the 37.5°C trial. This was evidenced by low points of 36.47°C ± 0.70°C and 37.19°C ± 0.71°C for rectal temperature (t(9)  =  2.975, P  =  .016) and of 35.67°C ± 1.27°C and 36.72°C ± 0.95°C for esophageal temperature (t(6)  =  3.963, P  =  .007) during the recovery period of the 37.5°C and 38.6°C trials, respectively.

CONCLUSIONS

Immersion for approximately 9 minutes to a rectal temperature cooling limit of 38.6°C negated any risk associated with overcooling hyperthermic individuals when they were immersed in 2°C water.

Impact of environmental factors on knee injuries in male and female recreational skiers

In alpine skiing, the knee represents the dominant injury location with marked gender differences. Snow, slope and weather conditions as well as altitude and low temperatures are thought to influence the prevalence of knee injuries. Therefore, ski patrol injury reports were used to compare gender-specific prevalence of knee injuries with regard to several environmental factors including the actual air temperatures. A total of 1039 non-contact knee injuries were reported with a corresponding prevalence of knee injuries of 44.4% (males: 30.1%; females: 57.4%). Temperature quartiles of all recorded injuries were calculated to compare gender-specific prevalence of knee injury with regard to temperatures. Comparing the first quartile (mean temperature -11°C) with the fourth quartile (mean temperature +3°C), the prevalence of knee injury in female skiers was higher at low ambient temperatures (61% vs 50%, odds ratio: 1.60, 95% confidence interval: 1.16-2.22; P=0.005) while no such association was found for male skiers. Additionally, knee-injured females showed a twofold prevalence when skiing during snowfall compared with females with other injuries (15.4% vs 8.6%; P=0.001). No other environmental factor showed a significant association with the gender-specific prevalence of knee injury. In conclusion, low ambient temperature and snowfall are important environmental risk factors for knee injuries in female skiers.

Influência do protocolo ergométrico na ocorrência de diferentes critérios de esforço máximo

INTRODUÇÃO E OBJETIVO: Neste estudo investigamos a influência de diferentes protocolos ergométricos na ocorrência dos critérios de esforço máximo. MÉTODOS: Nove sujeitos fisicamente ativos (23 ± 4 anos, 177 ± 10cm, e 77,1 ± 16kg) realizaram três testes de esforço (PR1 - 15W·min-1, PR2 - 50W·3 min-1, e PR3 - 50W·5 min-1) no cicloergômetro. O consumo de oxigênio foi medido em circuito aberto e integrado a cada 20s. Adotaram-se como critérios de esforço máximo: o platô no consumo de oxigênio < 150 mL·min-1; frequência cardíaca máxima (FCmáx) > 95% prevista pela idade; lactato > 8,0 mM; e RER > 1,1. RESULTADOS: O VO2máx não apresentou diferenças entre os protocolos (2,68 ± 1,0; 2,58 ± 1,0 e 2,99 ± 1,3L·min-1 para PR1, PR2 e PR3, p = 0,72). A maior ocorrência do platô foi observada em PR1 (cinco sujeitos). O critério da frequência cardíaca máxima foi satisfeito em três sujeitos em PR3, e o critério do lactato em seis sujeitos, no mesmo protocolo (PR3). O RER > 1,1 foi observado em seis sujeitos em PR1. CONCLUSÃO: Concluímos que a ocorrência de diferentes critérios de esforço máximo é influenciada pela escolha do protocolo ergométrico, não indicando, contudo, valores distintos de VO2máx

Time to move beyond a brainless exercise physiology: the evidence for complex regulation of human exercise performance

In 1923, Nobel Laureate A.V. Hill proposed that maximal exercise performance is limited by the development of anaerobiosis in the exercising skeletal muscles. Variants of this theory have dominated teaching in the exercise sciences ever since, but 90 years later there is little biological evidence to support Hill’s belief, and much that disproves it. The cardinal weakness of the Hill model is that it allows no role for the brain in the regulation of exercise performance. As a result, it is unable to explain at least 6 common phenomena, including (i) differential pacing strategies for different exercise durations; (ii) the end spurt; (iii) the presence of fatigue even though homeostasis is maintained; (iv) fewer than 100% of the muscle fibers have been recruited in the exercising limbs; (v) the evidence that a range of interventions that act exclusively on the brain can modify exercise performance; and (vi) the finding that the rating of perceived exertion is a function of the relative exercise duration rather than the exercise intensity. Here I argue that the central governor model (CGM) is better able to explain these phenomena. In the CGM, exercise is seen as a behaviour that is regulated by complex systems in the central nervous system specifically to ensure that exercise terminates before there is a catastrophic biological failure. The complexity of this regulation cannot be appreciated if the body is studied as a collection of disconnected components, as is the usual approach in the modern exercise sciences.

International travel and the elite athlete

International travel is a frequent occurrence in the life of the elite athlete; such travel can pose challenges to the sport medicine practitioner. Travel is also the reality of many recreational level or sub-elite athletes as opportunities for international competition and training proliferate. An appreciation of the range of responsibilities associated with the preparation for and the strategies to facilitate such travel is essential for any physician charged with the care of athletes and teams. An appreciation of (1) the medical and public health challenges associated with competition in a particular setting; (2) the requirements for vaccination and immunization; (3) the strategies for the management of jet lag and climatic or environmental extremes; (4) the range of supplies and equipment necessary for travel to certain locales; (5) the need to ensure the availability of ample familiar and nutritious foods; (6) the potential need for specialty care in strange settings; (7) the management of common travel-associated illness; and (8) the challenges associated with the evacuation of an injured athlete are fundamental to the successful management of international travel involving athletes and teams. The adoption of a methodical approach to pre-trip planning can ensure an enhanced travel experience, illness-free training and competition, and facilitate optimal performance.

How to test maximal oxygen uptake: a study on timing and testing procedure of a supramaximal verification test

Verification tests are becoming increasingly common for confirming maximal oxygen uptake (VO2 max) attainment. Yet, timing and testing procedures vary between working groups. The aims of this study were to investigate whether verification tests can be performed after an incremental test or should be performed on a separate day, and whether VO2 max can still be determined within the first testing session in subjects not satisfying the verification criterion. Forty subjects (age, 24 ± 4 years; VO2 max, 50 ± 7 mL·min–1·kg–1) performed a maximal incremental treadmill test and, 10 min afterwards, a verification test (VerifDay1) at 110% of maximal velocity (vmax). The verification criterion was a VerifDay1 peak oxygen uptake (VO2 peak) ≤5.5% higher than the incremental test value. Subjects not achieving the verification criterion performed another verification test at 115% vmax (VerifDay1′) 10 min later, trying to confirm VerifDay1 VO2 peak as VO2 max. All other subjects exclusively repeated VerifDay1 on a separate day (VerifDay2). Of the 40 subjects, 6 did not satisfy the verification criterion. In 4 of them, attainment of VO2 max was confirmed by VerifDay1′. VO2 peak was equivalent between VerifDay1 and VerifDay2 (3722 ± 991 mL·min–1 vs. 3752 ± 995 mL·min–1, p = 0.56), whereas time to exhaustion was significantly longer in VerifDay2 (2:06 ± 0:22 min:s vs. 2:42 ± 0:38 min:s, p < 0.001, n = 34). The verification test VO2 peak does not seem to be affected by a preceding maximal incremental test. Incremental and verification tests can therefore be performed within the same testing session. In individuals not achieving the verification criterion, VO2 max can be determined by means of a subsequent, more intense verification test in most but not all cases.

Is it time to retire the 'central governor'?

Over the past 13 years, Noakes and his colleagues have argued repeatedly for the existence of a 'Central Governor', a specific brain centre that provides a feed-forward regulation of the intensity of vigorous effort in order to conserve homeostasis, protecting vital organs such as the brain, heart and skeletal muscle against damage from hyperthermia, ischaemia and other manifestations of catastrophic failure. This brief article reviews evidence concerning important corollaries of the hypothesis, examining the extent of evolutionary pressures for the development of such a mechanism, the effectiveness of protection against hyperthermia and ischaemia during exhausting exercise, the absence of peripheral factors limiting peak performance (particularly a plateauing of cardiac output and oxygen consumption) and proof that electromyographic activity is limiting exhausting effort. As yet, there is a lack of convincing experimental evidence to support these corollaries of the hypothesis; furthermore, some findings, such as the rather consistent demonstration of an oxygen consumption plateau in young adults, argue strongly against the limiting role of a 'Central Governor'.

National Athletic Trainers' Association position statement: environmental cold injuries

OBJECTIVE

To present recommendations for the prevention, recognition, and treatment of environmental cold injuries.

BACKGROUND

Individuals engaged in sport-related or work-related physical activity in cold, wet, or windy conditions are at risk for environmental cold injuries. An understanding of the physiology and pathophysiology, risk management, recognition, and immediate care of environmental cold injuries is an essential skill for certified athletic trainers and other health care providers working with individuals at risk.

RECOMMENDATIONS

These recommendations are intended to provide certified athletic trainers and others participating in athletic health care with the specific knowledge and problem-solving skills needed to address environmental cold injuries. Each recommendation has been graded (A, B, or C) according to the Strength of Recommendation Taxonomy criterion scale.

Physiologic responses during indoor cycling

During the last decade, there has been active interest in indoor cycling (e.g., spinning) as a method of choreographed group exercise. Recent studies have suggested that exercise intensity during indoor cycling may be quite high and may transiently exceed Vo2max. This study sought to confirm these findings, as the apparent high intensity of indoor cycling has implications for both the efficacy and the risk of indoor cycling as an exercise method. Twenty healthy female students performed an incremental exercise test to define Vo2max and performed 2 videotaped indoor exercise classes lasting 45 minutes and 35 minutes. Vo2, heart rate (HR), and rating of perceived exertion (RPE) were measured during the indoor cycling classes, with Vo2 data integrated in 30-second intervals. The mean %Vo2max during the indoor cycling classes was modest (74 +/- 14% Vo2max and 66 +/- 14%Vo2max, respectively). However, 52% and 35% of the time during the 45- and 35-minute classes was spent at intensities greater than the ventilatory threshold (VT). The HR response indicated that 35% and 38% of the session time was above the HR associated with VT. In 10 of the 40 exercise sessions, there were segments in which the momentary Vo2 exceeded Vo2max observed during incremental testing, and the cumulative time with exercise intensity greater than Vo2max ranged from 0.5 to 14.0 minutes. It can be concluded that although the intensity of indoor cycling in healthy, physically active women is moderate, there are frequent observations of transient values of Vo2 exceeding Vo2max, and a substantial portion of the exercise bouts at intensities greater than VT. As such, the data suggest that indoor cycling must be considered a high-intensity exercise mode of exercise training, which has implications for both efficacy and risk.

Restrictions in systemic and locomotor skeletal muscle perfusion, oxygen supply and VO2 during high-intensity whole-body exercise in humans

Perfusion to exercising skeletal muscle is regulated to match O(2) delivery to the O(2) demand, but this regulation might be compromised during or approaching maximal whole-body exercise as muscle blood flow for a given work rate is blunted. Whether muscle perfusion is restricted when there is an extreme metabolic stimulus to vasodilate during supramaximal exercise remains unknown. To examine the regulatory limits of systemic and muscle perfusion in exercising humans, we measured systemic and leg haemodynamics, O(2) transport, and , and estimated non-locomotor tissue perfusion during constant load supramaximal cycling (498 +/- 16 W; 110% of peak power; mean +/- S.E.M.) in addition to both incremental cycling and knee-extensor exercise to exhaustion in 13 trained males. During supramaximal cycling, cardiac output (Q), leg blood flow (LBF), and systemic and leg O(2) delivery and reached peak values after 60-90 s and thereafter levelled off at values similar to or approximately 6% (P < 0.05) below maximal cycling, while upper body blood flow remained unchanged (approximately 5.5 l min(-1)). In contrast, Q and LBF increased linearly until exhaustion during one-legged knee-extensor exercise accompanying increases in non-locomotor tissue blood flow to approximately 12 l min(-1). At exhaustion during cycling compared to knee-extensor exercise, Q, LBF, leg vascular conductance, leg O(2) delivery and leg for a given power were reduced by 32-47% (P < 0.05). In conclusion, locomotor skeletal muscle perfusion is restricted during maximal and supramaximal whole-body exercise in association with a plateau in Q and limb vascular conductance. These observations suggest that limits of cardiac function and muscle vasoconstriction underlie the inability of the circulatory system to meet the increasing metabolic demand of skeletal muscles and other tissues during whole-body exercise.

'Dynamic' Starling mechanism: effects of ageing and physical fitness on ventricular-arterial coupling

Cardiovascular diseases increase with advancing age, associated with left ventricular and arterial stiffening in humans. In contrast, daily exercise training prevents and/or improves both ventricular and arterial stiffening with ageing. We propose a new approach to quantify the dynamics of the Starling mechanism, namely the beat-to-beat modulation of stroke volume (SV) caused by beat-to-beat alterations in left ventricular filling, which we propose reflects the complex interaction between ventricular and arterial stiffness. We hypothesized that the dynamic Starling mechanism would be impaired with ageing, and that this impairment would be prevented and restored by daily exercise training. Two different approaches were employed: (1) a cross-sectional study to assess the effects of ageing and life-long exercise training; and (2) a longitudinal study to assess the effects of one-year endurance training in the elderly. Spectral transfer function gain between beat-to-beat changes in left ventricular end-diastolic pressure and SV was used as an index of the dynamic Starling mechanism. Gain was significantly lower in the sedentary elderly (70 +/- 3 years) than in both young individuals (27 +/- 6 years) and Masters athletes (68 +/- 3 years), and it was significantly lower in Masters athletes than in young controls (elderly: 0.37 +/- 0.11; Masters athletes: 0.96 +/- 0.55; young: 1.52 +/- 0.42 ml m(-2) mmHg(-1), mean +/- s.d.). Gain increased by 65% after one-year exercise training in the elderly, although the response was quite variable (P = 0.108). These findings suggest that the dynamic Starling mechanism is impaired with human ageing possibly due to ventricular-arterial stiffening. Life-long daily exercise training may minimize this impairment, although the effect may be limited particularly when started later in life.

VO2max: what do we know, and what do we still need to know?

Maximal oxygen uptake (.VO(2,max)) is a physiological characteristic bounded by the parametric limits of the Fick equation: (left ventricular (LV) end-diastolic volume--LV end-systolic volume) x heart rate x arterio-venous oxygen difference. 'Classical' views of .VO(2,max) emphasize its critical dependence on convective oxygen transport to working skeletal muscle, and recent data are dispositive, proving convincingly that such limits must and do exist. 'Contemporary' investigations into the mechanisms underlying peripheral muscle fatigue due to energetic supply/demand mismatch are clarifying the local mediators of fatigue at the skeletal muscle level, though the afferent signalling pathways that communicate these environmental conditions to the brain and the sites of central integration of cardiovascular and neuromotor control are still being worked out. Elite endurance athletes have a high .VO(2,max) due primarily to a high cardiac output from a large compliant cardiac chamber (including the myocardium and pericardium) which relaxes quickly and fills to a large end-diastolic volume. This large capacity for LV filling and ejection allows preservation of blood pressure during extraordinary rates of muscle blood flow and oxygen transport which support high rates of sustained oxidative metabolism. The magnitude and mechanisms of cardiac phenotype plasticity remain uncertain and probably involve underlying genetic factors, as well as the length, duration, type, intensity and age of initiation of the training stimulus.

Assessing hydration status: the elusive gold standard

Acknowledging that total body water (TBW) turnover is complex, and that no measurement is valid for all situations, this review evaluates 13 hydration assessment techniques. Although validated laboratory methods exist for TBW and extracellular volume, no evidence incontrovertibly demonstrates that any concentration measurement, including plasma osmolality (P(osm)), accurately represents TBW gain and loss during daily activities. Further, one blood or urine sample cannot validly represent fluctuating TBW and fluid compartments. Future research should (a) evaluate novel techniques that assess hydration in real time and are precise, accurate, reliable, non-invasive, portable, inexpensive, safe, and simple; and (b) clarify the relationship between P(osm) and TBW oscillations in various scenarios.

VO2max during successive maximal efforts

The concept of VO(2)max has been a defining paradigm in exercise physiology for >75 years. Within the last decade, this concept has been both challenged and defended. The purpose of this study was to test the concept of VO(2)max by comparing VO(2) during a second exercise bout following a preliminary maximal effort exercise bout. The study had two parts. In Study #1, physically active non-athletes performed incremental cycle exercise. After 1-min recovery, a second bout was performed at a higher power output. In Study #2, competitive runners performed incremental treadmill exercise and, after 3-min recovery, a second bout at a higher speed. In Study #1 the highest VO(2) (bout 1 vs. bout 2) was not significantly different (3.95 +/- 0.75 vs. 4.06 +/- 0.75 l min(-1)). Maximal heart rate was not different (179 +/- 14 vs. 180 +/- 13 bpm) although maximal V(E) was higher in the second bout (141 +/- 36 vs. 151 +/- 34 l min(-1)). In Study #2 the highest VO(2) (bout 1 vs. bout 2) was not significantly different (4.09 +/- 0.97 vs. 4.03 +/- 1.16 l min(-1)), nor was maximal heart rate (184 + 6 vs. 181 +/- 10 bpm) or maximal V(E) (126 +/- 29 vs. 126 +/- 34 l min(-1)). The results support the concept that the highest VO(2) during a maximal incremental exercise bout is unlikely to change during a subsequent exercise bout, despite higher muscular power output. As such, the results support the "classical" view of VO(2)max.

Neuromuscular and circulatory adaptation during combined arm and leg exercise with different maximal work loads

Cardiopulmonary kinetics and electromyographic activity (EMG) during exhausting exercise were measured in 8 males performing three maximal combined arm+leg exercises (cA+L). These exercises were performed at different rates of work (mean+/-SD; 373+/-48, 429+/-55 and 521+/-102 W) leading to different average exercise work times in all tests and subjects. VO2 reached a plateau versus work rate in every maximal cA+L exercise (range 6 min 33 s to 3 min 13 s). The three different exercise protocols gave a maximal oxygen consumption (VO2MAX) of 4.67+/-0.57, 4.58+/-0.52 and 4.66+/-0.53 l min(-1) (P=0.081), and a maximal heart rate (HRmax) of 190+/-6, 189+/-4 and 189+/-6 beats min(-1) (P=0.673), respectively. Root mean square EMG (EMGRMS) of the vastus lateralis and the triceps brachii muscles increased with increasing rate of work and time in all three cA+L protocols. The study demonstrates that despite different maximal rates of work, leading to different times to exhaustion, the circulatory adaptation to maximal exercise was almost identical in all three protocols that led to a VO2 plateau. The EMG(RMS) data showed increased muscle recruitment with increasing work rate, even though the HRmax and VO2MAX was the same in all three cA+L protocols. In conclusion, these findings do not support the theory of the existence of a central governor (CG) that regulates circulation and neuronal output of skeletal muscles during maximal exercise.