Breastfeeding media coverage and beliefs during the COVID-19 pandemic in Mexico: implications for breastfeeding equity.

BACKGROUND: Because breastfeeding offers short- and long- term health benefits to mothers and children, breastfeeding promotion and support is a public health priority. Evidence shows that SARS-CoV-2 is not likely to be transmitted via breastmilk. Moreover, antibodies against SARS-CoV-2 are thought to be contained in breastmilk of mothers with history of COVID-19 infection or vaccination. WHO recommends direct breastfeeding as the preferred infant feeding option during the COVID-19 pandemic, even among women with COVID-19; but conflicting practices have been adopted, which could widen existing inequities in breastfeeding. This study aims to describe how information about breastfeeding was communicated in Mexican media during the pandemic and assess Mexican adults' beliefs regarding breastfeeding among mothers infected with COVID-19. METHODS: We conducted a retrospective content analysis of media coverage on breastfeeding in Mexico between March 1 and September 24, 2020, excluding advertisements. For the content analysis, we performed both a sentiment analysis and an analysis based on strengths, weaknesses, opportunities, and threats (SWOT) for breastfeeding promotion. Additionally, we conducted a descriptive analysis of nationally representative data on adults' beliefs about breastfeeding from the July 2020 round of the ENCOVID-19 survey in Mexico and stratified the results by gender, age, and socioeconomic status. RESULTS: A total of 1014 publications on breastfeeding were identified on the internet and television and in newspapers and magazines. Most information was published during World Breastfeeding Week, celebrated in August. The sentiment analysis showed that 57.2% of all information was classified as positive. The SWOT analysis indicated that most information focused on current actions, messages, policies, or programs that enable breastfeeding (i.e., strengths) or those not currently in place but that may enable breastfeeding (i.e., opportunities) for breastfeeding promotion. However, ENCOVID-19 survey results showed that 67.3% of adults living in households with children under 3 years of age believe that mothers with COVID-19 should not breastfeed, and 19.8% do not know whether these mothers should breastfeed. These beliefs showed differences both by gender and by socioeconomic status. CONCLUSIONS: While the Mexican government endorsed the recommendation on breastfeeding during the COVID-19 pandemic, communication was sporadic, inconstant and unequal across types of media. There was a widespread notion that mothers with COVID-19 should not breastfeed and due to differences on beliefs by socioeconomic status, health inequities could be exacerbated by increasing the risk of poorer breastfeeding practices and preventing vulnerable groups from reaping the short and long-term benefits of breastfeeding.

The cutest little baby face: a hormonal link to sensitivity to cuteness in infant faces.

We used computer image manipulation to develop a test of perception of subtle gradations in cuteness between infant faces. We found that young women (19-26 years old) were more sensitive to differences in infant cuteness than were men (19-26 and 53-60 years old). Women aged 45 to 51 years performed at the level of the young women, whereas cuteness sensitivity in women aged 53 to 60 years was not different from that of men (19-26 and 53-60 years old). Because average age at menopause is 51 years in Britain, these findings suggest the possible involvement of reproductive hormones in cuteness sensitivity. Therefore, we compared cuteness discrimination in pre- and postmenopausal women matched for age and in women taking and not taking oral contraceptives (progestogen and estrogen). Premenopausal women and young women taking oral contraceptives (which raise hormone levels artificially) were more sensitive to variations of cuteness than their respective comparison groups. We suggest that cuteness sensitivity is modulated by female reproductive hormones.

Addressing noncommunicable diseases in primary care: the case of type 2 diabetes.

The rapid growth of noncommunicable diseases represents a formidable global health challenge. Here we use type 2 diabetes as a case study to illustrate the rise of noncommunicable diseases and call attention to the important role of primary care systems in addressing these diseases in low- and middle-income countries. Comprehensive screening for diabetes should be implemented through primary care systems to increase early detection of prediabetes and undiagnosed diabetes - a first step to diabetes prevention and management. In addition, primary care systems should strengthen and expand capacity to link patients to appropriate interventions based on their diabetes status and provide care coordination (e.g. leveraging task-shifting and technology), and integrate clinic and community resources for diabetes prevention and control. Additional strategies should include continuous quality improvement, health systems strengthening, workforce development, and affordable and sustainable financing. Together, these actions could elevate the role of primary care in addressing diabetes in low- and middle-income countries and help advance global progress towards reducing diabetes complications, and also preventing or delaying diabetes among those at risk.

Submaximal exercise responses of tetraplegics and paraplegics.

This study describes responses of 21 wheelchair users to a continuous, increasing work rate test to exhaustion on a wheelchair ergometer. Heart rate, ventilation, O2 uptake, respiratory exchange ratio, ventilation equivalent for O2, and O2 pulse were determined for each minute. Subjects were divided into tetraplegic (n = 8), high-lesion paraplegic (n = 6), and low-lesion paraplegic (n = 7) groups. Linear regression analyses, with O2 uptake as the independent variable, were used to determine the strength of relationships within each group and differences between groups in slopes and intercepts of regression equations. All variables were significantly (P less than 0.05) related to O2 uptake (r = 0.42-0.94). The only significant difference between the high- and low-lesion paraplegic groups was for heart rate intercept, as the heart rate for the low-lesion group tended to be lower at any given O2 uptake. Tetraplegics had a higher intercept and/or slope for ventilation equivalent, ventilation, and respiratory exchange ratio and lower intercepts for heart rate and O2 pulse. These differences in responses to a progressive exercise task are logically related to the differences in maximal O2 uptake, functional muscle mass, and vasomotor and cardiac control of the groups.

A critical review of the literature on ratings scales for perceived exertion.

The study of human performance and perceived exertion during physical activity has been an area of considerable interest and research for over 50 years. This review considers the evidence of many investigators who have been researching the physiological basis as well as non-physiological basis for the ratings of perceived exertion. During low levels of activity, physical perception in the working muscles appears to be the primary stimulus for effort perception. When work intensity exceeds the lactate threshold, incremental elevations in blood lactate complement peripheral input from the neuromuscular mechanisms. Once a critical absolute ventilatory threshold is reached, central input also contributes to effort perception. In most instances, peripheral input predominates over central cues, although it has been shown that pronounced central cues may dominate the perception of effort. Central (heart rate, VE, VO2) or local (muscle and blood lactate, adenosine triphosphate, creatine phosphokinase, glycogen) cues highlighted in these studies demonstrate both the complexity of effort perception, and the need for better understanding of the physiological components upon which it is based. Athletes have been shown to have a greater tendency to reduce perceptual ratings than their non-active counterparts. In view of these observations, it is apparent that a theoretical framework based upon physiological and psychological considerations may exist to support the concept of training-induced alterations in perceived exertion. This appears to be particularly true in higher ranges of exercise intensity. Part of the problem in reaching a conclusion on the issue of perceptual ratings trainability centres upon the agreement on what should be recognised as a significant decrement in perceived exertion. It is concluded that there is considerable variation in the findings of the literature and that any reported variations in performance may well be greatly influenced by intersubject variability, the type of exercise, and nutritional status of subject. Further research is required to understand this issue better.

Metabolic responses and mechanisms during water immersion running and exercise.

The low impact nature of exercise in the water has increased interest in this form of exercise and specifically in water running as a cross-training modality. It is used as a possible preventative and therapeutic modality for rehabilitation. The high impact nature of land running predisposes the runner to stress of the lower limbs and overuse injuries. The need to reduce impact, as well as provide a low impact or non-weight-bearing condition for rehabilitation, has led runners and their coaches to the water. This increased interest by coaches and their athletes, attending sports medicine physicians and rehabilitative professionals has stimulated research into water immersion to the neck (WI) running. Exercise in the water has long been used by rehabilitative professionals with patients who have physically debilitating conditions (i.e. arthritis, musculoskeletal disorders) as it provides a medium for even those with limited mobility to exercise and relax their muscles. Numerous comparative studies into WI running from a metabolic as well as a training perspective have been published. WI has also long been used to simulate weightlessness for the comparative study of cardiorespiratory function and thermoregulation. WI and the associated cephalad shift in blood volume has implications on exercise responses during WI running exercise. In addition, the non-weight-bearing nature of WI running also raises issues of the cross-training benefits of WI running. WI running style and prior familiarity with the activity have been found to have a direct relationship with the comparability of WI to land running. This review presents current research into WI running, training specificity and comparative physiology.

Lipid metabolism during exercise.

Fat is an extremely important substrate for muscle contraction, both at rest and during exercise. Triglycerides (TGs), stored in adipose tissue and within muscle fibres, are considered to be the main source of the free fatty acids (FFAs) oxidised during exercise. It is still unclear, however, how the use of these substrates is regulated during exercise. The regulation seems to be multifactorial and includes: (i) dietary and nutritional status; (ii) hormonal milieu; (iii) exercise mode, intensity and duration; and (iv) training status. On the other hand, the mechanism for FFA transport from its storage as triglycerides in adipose tissue and muscle to its place of utilisation in heart, skeletal muscle, kidney and liver is more clearly understood. It has been determined that the plasma FFA turnover rate is sufficiently rapid to account for most of the fat metabolised during low intensity exercise (25 to 40% VO2max). However, an exercise intensity of 65% VO2max results in a slight decrease in the amount of plasma FFA uptake by muscle tissue. Other studies have found that during prolonged exercise, muscle TGs become the predominant source of energy obtained from fat. Furthermore, it is widely documented that endurance activities increase the energy utilisation from fat while sparing carbohydrate sources. For example, during exercise on a cycle ergometer, nonplasma FFAs and plasma FFAs contribute 40%, and carbohydrates 60%, of the total calculated amount of energy expenditure before exercise and vice versa after exercise (60% nonplasma and plasma FFAs and 40% carbohydrates). Although it was many years before it was fully demonstrated, fat is now known to be transported in the blood as FFA bound to the protein carrier albumin. The mobilisation of FFA is primarily a function of sympathetic nervous activity directed towards the adipocytes, or the 'fat pad'. This nervous activity can be direct or may be an effect of circulating catecholamines such as adrenaline (epinephrine). This article summarises the role of fat metabolism during exercise.

Glycaemic index and optimal performance.

It is widely documented that athletes should consume carbohydrates prior to, during and after exercise. Ingestion of carbohydrates at these times will optimise performance and recovery. In spite of this knowledge, there is a paucity of information available to athletes concerning the types of carbohydrate foods to select. Therefore, it is suggested that the glycaemic index may be an important resource when selecting an ideal carbohydrate. The glycaemic index categories foods containing carbohydrates according to the blood glucose response that they elicit. Carbohydrate foods evoking the greatest responses are considered to be high glycaemic index foods, while those producing a relatively smaller response are categorised as low glycaemic index foods. Athletes wishing to consume carbohydrates 30 to 60 minutes before exercise should be encouraged to ingest low glycaemic index foods. Consuming these types of foods will decrease the likelihood of creating hyperglycaemia and hyperinsulinaemia at the onset of exercise, while providing exogenous carbohydrate throughout exercise. It is recommended that high glycaemic index foods be consumed during exercise. These foods will ensure rapid digestion and absorption, which will lead to elevated blood glucose levels during exercise. Post-exercise meals should consist of high glycaemic index carbohydrates. Low glycaemic foods do not induce adequate muscle glycogen resynthesis compared with high glycaemic index foods.

Physiological and cardiovascular changes associated with deep water running in the young. Possible implications for the elderly.

The increased number of people taking part in deep water running (DWR) is attributable to the weight-independent characteristic of this form of exercise. Deep water runners should, however, be aware of the respiratory and cardiovascular repercussions that result from exercising in water. It has been well documented that water immersion (WI) alone results in decrements in respiratory and cardiovascular parameters in young individuals immersed in water to the neck. These decrements become more pronounced with exercise, such that maximal oxygen consumption and heart rate (HR) are lower during DWR compared with running on land. Age also seems to influence these parameters; Derion et al. found little to no change in cardiac output, stroke volume and HR during WI in older individuals compared with the decrease experienced in younger individuals. In contrast, gender appears to have no effect on WI or DWR response. Although differences in acute metabolic responses have been observed in numerous studies, training studies examining the effectiveness of using a DWR training programme found that DWR produced equivocal training responses when compared with fit and highly trained individuals running on land. Less convincing evidence has been provided for untrained individuals seeking benefits from a DWR training programme, as some studies showed significant improvements while others did not. There is a current lack of knowledge regarding the use of this form of exercise by frail elderly individuals and/or those with osteoporosis.

Factors affecting performance in an ultraendurance triathlon.

In the recent past, researchers have found many key physiological variables that correlate highly with endurance performance. These include maximal oxygen uptake (VO2max), anaerobic threshold (AT), economy of motion and the fractional utilisation of oxygen uptake (VO2). However, beyond typical endurance events such as the marathon, termed 'ultraendurance' (i.e. >4 hours), performance becomes harder to predict. The ultraendurance triathlon (UET) is a 3-sport event consisting of a 3.8 km swim and a 180 km cycle, followed by a 42.2 km marathon run. It has been hypothesised that these triathletes ride at approximately their ventilatory threshold (Tvent) during the UET cycling phase. However, laboratory assessments of cycling time to exhaustion at a subject's AT peak at 255 minutes. This suggests that the AT is too great an intensity to be maintained during a UET, and that other factors cause detriments in prolonged performance. Potential defeating factors include the provision of fuels and fluids due to finite gastric emptying rates causing changes in substrate utilisation, as well as fluid and electrolyte imbalances. Thus, an optimum ultraendurance intensity that may be relative to the AT intensity is needed to establish ultraendurance intensity guidelines. This optimal UET intensity could be referred to as the ultraendurance threshold.

The role of hyperbaric oxygen therapy in sports medicine.

During the past decade, we have seen a growing number of individuals participating in sport and recreational activities. All indications show an increase in sport participation at every age level. However, the number of sport and recreational injuries as a result of this increase has also risen. Unfortunately, a primary cost related to injury recovery is the time lost from participating in and resuming normal functional activity. This has compelled health care professionals to seek more efficient and effective therapeutic interventions in treating such injuries. Hyperbaric oxygen (HBO) therapy may serve to provide a means of therapy to facilitate a speedier resumption to pre-injury activity levels as well as improve the short and long term prognosis of the injury. Although a growing interest in sports medicine is becoming evident in the literature, the use of HBO as an intervention in this field has received a great deal of cynicism. To date, numerous professional athletic teams, including hockey (NHL), football (NFL), basketball (NBA) and soccer (MLS), utilise and rely on the use of HBO as adjuvant therapy for numerous sports-related injuries acquired from playing competitive sports. However, to date, very little has been published on the application benefits of hyperbaric therapy and sports injuries. The majority of clinical studies examining the efficacy of HBO in treating soft tissue injuries have been limited in their sample size and study design. Further research needs to be conducted suggesting and validating the significant effects of this treatment modality and further grounding its importance in sports medicine.

Relationship between the lactate and ventilatory thresholds during prolonged exercise.

The anaerobic threshold is commonly measured by either blood lactate (lactate threshold) or ventilatory gases (ventilatory threshold); however, the relationship between these 2 methods is not conclusive. The lactate threshold has been characterised at either a fixed or variable blood lactate concentration (BLa). Recent studies have indicated a specific blood lactate concentration for each individual which considers the interindividual variations in lactate kinetics (individual anaerobic threshold), following either a continuous, exponential pattern or a discontinuous, threshold-like response. The ventilatory threshold is assessed using a variety of ventilatory parameters, many of which exhibit a threshold-like response during progressive exercise. Despite the apparent causal relationship between the stimulation of the ventilatory chemoreceptors and ultimately the ventilatory response and the accumulation of protons in the circulating blood, evidence does exist which refutes such a connection. Such evidence supporting a coincidental relationship examines no significant change in ventilation with significant increases in blood lactate concentration. Conversely, evidence from patients with McArdle's disease indicates that although no lactic acid is produced, these individuals do experience a threshold-like ventilatory response during incremental exercise. The ability to perform at the anaerobic threshold is now recognised as an integral component of endurance events. Several studies have concluded that the ventilatory threshold is highly correlated with endurance performance, in distances ranging from 26 miles (41.6 km) [r = -0.94] to 5 and 10 km (r = -0.945). The lactate threshold, in particular the individual anaerobic threshold, has been examined from a performance standpoint. Much of the literature supports the individual anaerobic threshold as the exercise intensity at which performance is maximal and able to be sustained for at least 50 minutes. With the variety of techniques utilised in assessing the anaerobic threshold, caution should be taken in interpretation of the results as the different protocols may elicit a variety of responses during incremental exercise. Furthermore, it is essential to account for the individual's unique response to such exercise.

A review of blood lactate and ventilatory methods of detecting transition thresholds.

As far back as the 1930s exercise physiologists recognised the existence of critical levels of work intensity above which lactate accumulation increased drastically and energy production was affected. Investigation of these transition points (thresholds) both invasively and non-invasively has led to much recent controversy. Respiratory exchange variables such as Ve, Ve/VO2, VCO2, excess CO2 and blood lactate have been monitored for simple, double and exponential breakaway points to elucidate these critical work intensities. A number of studies have produced high correlations between endurance performance and anaerobic threshold calculations, further demonstrating the potential existence of critical work intensities. Much of the controversy surrounding these phenomena has centered on mechanisms and nomenclature. The term 'anaerobic threshold' has been severely criticised because in addition to the tissues being oxygen insufficient, an imbalance in the energy systems may have resulted. The anaerobic condition or lactate accumulation may be due to changes in lactate production and removal. Muscle fibre type and the fibre type recruitment patterns may also be important factors in threshold transitions. Further examination is made in this review of non-invasive measures for determining transition thresholds and protocols for elucidating the critical points.

Jet-lag and human performance.

The desynchronisation of an athlete's physiological and psychological cycles has adverse effects on his/her performance. The primary cause of dysrhythmia in an athlete is jet-lag, which is a rapid displacement across the earth's time zones and is often experienced while competing in international events and in continental leagues. General symptoms which arise from dysynchronization include malaise, appetite loss, tiredness during the day and disturbed sleep. The specific symptoms resulting from jet-lag are characterised as phase shifts in physiological and psychological cycles. These phase shifts occur in body temperature, ability to mobilise energy substrates, excretion of water and metabolites, arousal levels, sleep/wake cycles and reaction time. The severity of these adverse effects and therefore the time required for resynchronization depends on the ability to preset the bodily rhythms prior to flying, the number of time zones crossed, the direction of flight, the type of individual (introvert/extrovert), age, social interaction and activity, diet plan and prescribed use of chronobiotic drugs.

A review of the concept of the heart rate deflection point.

The heart rate deflection point (HRDP) is a downward or upward change from the linear HR-work relationship evinced during progressive incremental exercise testing. The HRDP is reported to be coincident with the anaerobic threshold. In 1982, Conconi and colleagues suggested that this phenomenon could be used as a noninvasive method to assess the anaerobic threshold. These researchers developed a field test to assess the HRDP, which has become popularised as the 'Conconi test'. Concepts used to define and assess the anaerobic threshold as well as methodological procedures used to determine the HRDP are diverse in the literature and have contributed to controversy surrounding the HRDP concept. Although the HRDP may be assessed in either field or laboratory settings, the degree of HR deflection is highly dependent upon the type of protocol used. The validity of HRDP to assess the anaerobic threshold is uncertain, although a high degree of relationship exists between HRDP and the second lactate turnpoint. The HRDP appears to be reliable when a positive identification is made; however, not all studies report 100% reproducibility. Although the physiological mechanisms explaining the HRDP are unresolved, a relationship exists between the degree and direction of HRDP and left ventricular function. The HRDP has potential to be used for training regulation purposes. Clinically, it may be incorporated to set exercise intensity parameters for cardiac rehabilitation.

Effects of creatine supplementation on exercise performance.

While creatine has been known to man since 1835, when a French scientist reported finding this constitutent of meat, its presence in athletics as a performance enhancer is relatively new. Amid claims of increased power and strength, decreased performance time and increased muscle mass, creatine is being hailed as a true ergogenic aid. Creatinine is synthesised from the amino acids glycine, arginine and methionine in the kidneys, liver and pancreas, and is predominantly found in skeletal muscle, where it exists in 2 forms. Approximately 40% is in the free creatine form (Crfree), while the remaining 60% is in the phosphorylated form, creatine phosphate (CP). The daily turnover rate of approximately 2 g per day is equally met via exogenous intake and endogenous synthesis. Although creatine concentration (Cr) is greater in fast twitch muscle fibres, slow twitch fibres have a greater resynthesis capability due to their increased aerobic capacity. There appears to be no significant difference between males and females in Cr, and training does not appear to effect Cr. The 4 roles in which creatine is involved during performance are temporal energy buffering, spatial energy buffering, proton buffering and glycolysis regulation. Creatine supplementation of 20 g per day for at least 3 days has resulted in significant increases in total Cr for some individuals but not others, suggesting that there are 'responders' and 'nonresponders'. These increases in total concentration among responders is greatest in individuals who have the lowest initial total Cr, such as vegetarians. Increased concentrations of both Crfree and CP are believed to aid performance by providing more short term energy, as well as increase the rate of resynthesis during rest intervals. Creatine supplementation does not appear to aid endurance and incremental type exercises, and may even be detrimental. Studies investigating the effects of creatine supplementation on short term, high intensity exercises have reported equivocal results, with approximately equal numbers reporting significant and nonsignificant results. The only side effect associated with creatine supplementation appears to be a small increase in body mass, which is due to either water retention or increased protein synthesis.

Oxygen uptake kinetics during exercise.

The characteristics of oxygen uptake (VO2) kinetics differ with exercise intensity. When exercise is performed at a given work rate which is below lactate threshold (LT), VO2 increases exponentially to a steady-state level. Neither the slope of the increase in VO2 with respect to work rate nor the time constant of VO2 responses has been found to be a function of work rate within this domain, indicating a linear dynamic relationship between the VO2 and the work rate. However, some factors, such as physical training, age and pathological conditions can alter the VO2 kinetic responses at the onset of exercise. Regarding the control mechanism for exercise VO2 kinetics, 2 opposing hypotheses have been proposed. One of them suggests that the rate of the increase in VO2 at the onset of exercise is limited by the capacity of oxygen delivery to active muscle. The other suggests that the ability of the oxygen utilisation in exercising muscle acts as the rate-limiting step. This issue is still being debated. When exercise is performed at a work rate above LT, the VO2 kinetics become more complex. An additional component is developed after a few minutes of exercise. The slow component either delays the attainment of the steady-state VO2 or drives the VO2 to the maximum level, depending on exercise intensity. The magnitude of this slow component also depends on the duration of the exercise. The possible causes for the slow component of VO2 during heavy exercise include: (i) increases in blood lactate levels; (ii) increases in plasma epinephrine (adrenaline) levels; (iii) increased ventilatory work; (iv) elevation of body temperature; and (v) recruitment of type IIb fibres. Since 86% of the VO2 slow component is attributed to the exercising limbs, the major contributor is likely within the exercising muscle itself. During high intensity exercise an increase in the recruitment of low-efficiency type IIb fibres (the fibres involved in the slow component) can cause an increase in the oxygen cost of exercise. A change in the pattern of motor unit recruitment, and thus less activation of type IIb fibres, may also account for a large part of the reduction in the slow component of VO2 observed after physical training.

Applied physiology of ice hockey.

Today's elite hockey players are physically bigger and have improved levels of physiological fitness when compared with their predecessors. Correspondingly, previous ice hockey studies that have become widely referenced may have little relevance to current players and the way the game is presently played. A great need exists to apply exercise science to the game of ice hockey. Although much has been written about the physiology of ice hockey, there is little information based on well controlled studies. Particularly, there is a paucity of knowledge concerning optimal training schedules, training specificity, recovery profiles and seasonal detraining. Moreover, the reports that do exist have attempted to make comparisons across all levels of skill and talent. Thus, fundamental questions remain as to actual physiological exercise response and specialised training programmes for ice hockey players, particularly at the elite level. There is a demand for new properly designed experiments to find answers pertaining to the appropriate training methods for today's ice hockey players. Future research directions should consider the relationships between performance and such variables as neuromuscular skills, strength, power, peripheral adaptations, travel, hydration, detraining and sport-specific training programmes. Incidence and severity of injury among ice hockey players in relation to fatigue and fitness must also be investigated. Much of the information currently used in ice hockey will remain speculative and anecdotal until these studies are conducted.

Factors associated with exercise adherence among older adults. An individual perspective.

This paper reviews the literature concerning factors at the individual level associated with regular exercise among older adults. Twenty-seven cross-sectional and 14 prospective/longitudinal studies met the inclusion criteria of a mean participant age of 65 years or older. The findings are summarised by demographics, exercise experience, exercise knowledge, physiological factors, psychological factors, activity preferences and perceived social influences. In general, education and exercise history correlate positively with regular exercise, while perceived physical frailty and poor health may provide the greatest barrier to exercise adoption and adherence in the elderly. Social-cognitive theories identify several constructs that correlate with the regular exercise behaviour of older adults, such as exercise attitude, perceived behavioural control/self-efficacy, perceived social support and perceived benefits/barriers to continued activity. As well, stage modelling may provide additional information about the readiness for regular exercise behaviour among older adults. However, relatively few studies among older adults exist compared with middle-aged and younger adults. Further, the majority of current research consists of cross-sectional designs or short prospective exercise trials among motivated volunteers that may lack external validity. Future research utilising longitudinal and prospective designs with representative samples of older adults will provide a better understanding of significant causal associations between individual factors and regular exercise behaviour.

Maximal and ventilatory threshold responses to treadmill and water immersion running.

This study compared the metabolic responses of 13 endurance runners, familiar with nonweight-bearing water immersion (WI) running, at ventilatory threshold (Tvent) and maximal effort (VO2max) for both treadmill and WI running performance. Oxygen consumption (VO2), ventilation (VE), heart-rate (HR), VE/VO2, respiratory exchange ratio (RER), perceived exertion (RPE), and stride frequency (SF) were measured at Tvent and VO2max. Paired t-tests revealed higher VO2max (59.7 vs 54.6 ml.kg.-1min-1), HRmax (190 vs 175 bpm), RERmax (1.20 vs 1.10), VO2 at Tvent (46.3 vs 42.8 ml.kg.-1min-1), HR at Tvent (165 vs 152 bpm) for treadmill versus WI running, respectively. Treadmill and WI VEmax (109.0 vs 105.8 l.min-1), RPEmax (20), VE at Tvent (66.4 vs 65.7 l.min-1), RER at Tvent (0.99 vs 0.98), RPE at Tvent (13 vs 12) were similar, as were blood lactate [BLa] values obtained at 30 s (10.4 vs 9.8 mmol.l-1) and 5 min (9.7 vs 9.2 mmol.l-1) post-test. SF values over time were higher on the treadmill. The lower WI VO2max with similar peak [BLa] and lower SF values suggests that the active musculature and muscle recruitment patterns differ in WI running due to the high viscosity friction of water, and the nonweight-bearing nature of WI running.