Eating vegetables at school lunchtimes: Pilot and feasibility studies testing strategies to improve intake.

Vegetable provision at schools in the UK has increased over recent years; however children still eat few of the vegetables that are served to them. Two experimental pilot and feasibility studies implemented a vegetables-served-first (study 1) plus experiential learning (study 2) approach to increase children's (3-5 years and 4-7 years respectively) vegetable consumption at school lunchtimes. Both studies involved vegetables-served-first 10-min before the rest of the meal, with experiential learning techniques (repeated exposure, "veg-first" dinner plates, vegetable songs, videos, and nutrition education) complementing the vegetable service in study 2. Study 1 (n = 38) found that vegetables-served-first, compared with serving all foods together, increased vegetable intake by ∼12 g. Study 2 (n = 69) found that vegetable consumption depended on individual schools. Schools where vegetable intake was low showed increases in consumption during intervention weeks, whereas schools with high vegetable intake showed little change. Acceptability of interventions was found to be good for children and schools that participated, although concerns about time to serve vegetables first and COVID-related environmental restrictions reduced feasibility for some schools. Child engagement could also be improved by offering a wider variety of vegetables during repeated exposure to reduce monotony. Future research should design interventions using co-design methods including schools to suit their context best, whilst also addressing the problem with a systems approach. Interventions which focus on child learning through experience need to take account of specific school environments including curricular needs, resources available for school lunch (including both time and space), provision of food, support from teachers and parents, and the culture around eating (e.g. encouragement, pressure to eat, lunchtime competing with playtime). Joined-up systems approaches could enhance both provision and uptake of vegetables at school meals.

Parental intentions to implement vegetable feeding strategies at home: A cross sectional study.

In order to increase vegetable intake by children, parents are encouraged to implement strategies that promote trying and eating vegetables at mealtimes. Qualitative studies have previously highlighted barriers parents face in implementing healthy eating practices, such as time, monetary costs and child factors (e.g. fussy eaters). This study aimed to specify the relationships between child and parent factors and their effects on parental intentions to implement vegetable feeding strategies at mealtimes. Parental intentions to implement meal service (serving larger portions, offering variety, serving vegetables first) and experiential learning (repeated exposure, games, sensory play) strategies were examined. Parents (N = 302, 73 male, Mage = 33.5) also explained reasons why certain strategies may or may not work for their child (4-7y). For both types of strategy, higher food fussiness of the child predicted higher parental intentions to implement strategies at home. However, this was competitively mediated by low beliefs that the strategy would work for their child, resulting in weaker overall positive effects on intentions. In the meal service model, parental beliefs that healthy eating is important for their child had a positive, indirect effect on higher intentions, through involved parental feeding practices. However, this was not significant in the experiential learning strategies model. Written parental responses suggest that this may be due to meal service approaches being viewed as easier to implement, with little additional effort required. Increasing parental confidence to implement strategies successfully and managing expectations around successful outcomes of strategies (e.g. tasting, eating) may be important focuses of future interventions to support parents implementing vegetable feeding strategies at mealtimes.

An online study examining children's selection of vegetables at mealtimes: The role of meal contexts, variety and liking.

Associative learning predicts that children expect to eat vegetables together with foods high in carbohydrate and protein at mealtimes. However, choosing to eat and consume vegetables may be less likely if they are presented alongside more palatable, competing foods. This study examined food choices of children (N = 180, 8-11 years, 84 female) in a mealtime context. During an online task, children chose one food for a meal, from a choice of vegetables and either a food high in carbohydrate or protein. Preference was assessed with and without a partial meal stimulus, to test the effect of other foods on the plate. Vegetables were selected more often with a meal stimulus, especially when it consisted of carbohydrate and protein foods, meaning that the vegetable option added nutritional variety to the meal. This effect was moderated by the difference in liking between the food options available. Vegetables were selected more if they were better liked than the competing food option, although it was not necessary that vegetables were better liked if they added nutritional variety to the meal. Food fussy children were less likely to select vegetables, but no other effects of child appetitive traits or parental practices were found on children's food choices. Children may be more likely to select vegetables if they add nutritional variety to a meal and are similarly or better liked than competing food options. Future research could test specific meal configurations which promote children's selection and intake of vegetables at mealtimes.

The effect of food type on the portion size effect in children aged 2-12 years: A systematic review and meta-analysis.

Visual cues such as plate size, amount of food served and packaging are known to influence the effects of portion size on food intake. Unit bias is a well characterised heuristic and helps to determine consumption norms. In an obesogenic environment where large portions are common place, the unit or segmentation bias may be overridden promoting overconsumption of both amorphous or unit foods. The aim of this review was to investigate the impact of offering unit or amorphous food on the portion size effect (PSE) in children aged 2-12 years. A systematic search for literature was conducted in Medline, PsycInfo and Web of Science in February 2018. A total of 1197 papers were retrieved following the searches. Twenty-one papers were included in the systematic review, of which 15 provided requisite statistical information for inclusion in a random effects meta-analysis. Increasing children's food portion size by 51-100% led to a significant increase in intake (SMD = 0.47, 95% CI: 0.39-0.55). There was no evidence to suggest that increases in consumption were related to food type (p = 0.33), child age (p = 0.47) or initial portion size served (p=0.14). Residual heterogeneity was not significant (p=0.24). The PSE was demonstrated in children aged 2-12 years when offered both unit and amorphous food items. The effect was not restricted by food type, child age or influenced by initial portion size served. Of the studies included in the meta-analysis between study heterogeneity was low suggesting minimal variation in treatment effects between studies, however, more research is required to understand the mechanisms of the PSE in preschool children. Future research should determine feasible methods to downsize portion sizes served to children.

Israeli and British women's wellbeing and eating behaviours in pregnancy and postpartum.

OBJECTIVES: The study had two main objectives: (a) track changes in self-esteem, eating behaviours and body satisfaction from early pregnancy to 24 months postpartum and (b) to compare changes by context (Israel vs. UK) and maternal body mass index (BMI). BACKGROUND: High maternal BMI is associated with negative body image and restrained eating, which are experienced differently across cultures. METHODS: 156 pregnant women were recruited from Israel and the UK. Seventy-three women were followed up every six months from early postpartum and until 24 months following birth. Women completed questionnaires assessing self-esteem (RSEQ), body image (BIS/BIDQ) and eating behaviours (DEBQ) and self-reported weights and heights so that BMI could be calculated. RESULTS: Women with higher BMI had higher levels of self-esteem and were less satisfied with their body. Healthy-weight women were more likely to lose all of their retained pregnancy weight compared to overweight and obese women. Self-esteem, body image and eating behaviours remained stable from pregnancy until 24 months postpartum. No significant differences were found for any measure by context. CONCLUSION: BMI was the strongest predictor of self-esteem and body dissatisfaction and a higher BMI predicted less weight loss postpartum.

Infant hunger and satiety cues during the first two years of life: Developmental changes of within meal signalling.

Overfeeding in infancy may lead to overweight and obesity in later childhood. Mothers are advised to "tune in" to their infant's hunger, appetite and satiation cues to prevent overfeeding. The present study aimed to 1) assess stability and change in infant hunger and satiety cues (first two years of life) taken at six monthly intervals; 2) track the expression of appetite cues during the course of a meal (beginning, middle and end). Thirty-eight women (mean age 35.3 + 3.7 years) participated in the study. Mothers were within a normal weight range (BMI = 22 + 3.3 kg/m2), most were married (N = 35; 95%) and for most this was not their first child. After an initial investigation (T1) follow-up visits took place every six months with filmed meals involving solid foods. A typical meal contained foods high in protein and carbohydrate plus cooked vegetables. Films were viewed and communication cues (engagement indicating appetite and disengagement indicating satiation) identified and recorded by appearance using the NCAST (Nursing Child Assessment Satellite Training). Coding included the frequency and time at which each cue appeared. Results showed that infants were more likely to communicate potent engagement cues such as babbling, mutual gaze and looking at mother with age. None of the disengagement cues showed any significant main effects of time of follow up. Most, not all, feeding cues were stable across the segment of the feed and did not show a simple linear change across the meal, rather this appeared to develop with age. Raising awareness of these cues with mothers may encourage more responsive and positive mealtime interactions.

Looking for cues - infant communication of hunger and satiation during milk feeding.

It is known that duration of breastfeeding and responsive feeding are associated with decreased risk of obesity. It is however, not clear whether breastfed infants signal more to mothers to facilitate responsive feeding, compared to formula fed, nor what communication cues are important during the feeding interaction. The present study aimed to explore feeding cues in milk-fed infants and to examine if such cues vary by mode of feeding. Twenty-seven mothers and infants were filmed while breastfeeding or formula feeding. Infants' age ranged from 3 to 22 weeks. Feeding cues were identified using a validated list of communication cues (NCAST). The frequency of each cue during the beginning, middle, and end of the meal was recorded. There were 22 feeding cues identified during the feeds, with significantly more frequent disengagement cues expressed than engagement cues. Significantly more frequent feeding cues were observed at the beginning than at the end of the meal showing that cue frequency changes with satiation. Breastfeeding infants exhibited more engagement and disengagement cues than formula fed infants. Supporting mothers to identify engagement and disengagement cues during a milk feed may promote more responsive feeding-strategies that can be acquired by mothers using different modes of feeding.

Forefronts in portion size. An overview and synthesis of a roundtable discussion.

Establishing eating habits in early life that include appropriate portion sizes of foods which are nutrient dense and low in energy density is considered important in the prevention of obesity in children. This special supplement presents the proceedings of a symposium focusing on advances in scientific understanding of the development of healthy food portion sizes in children and their families. Recent basic research highlights individual differences in children's responsiveness to portion size as well as potential mechanisms of portion size effects. Quantitative approaches highlight the influence of maternal serving in determining intake, while qualitative approaches seek to elaborate caregiver decisions around child portion sizes at meals and snacks. Family-based environmental interventions for child weight control involving food portion size are outlined. An overview of the overarching issues and roundtable discussion on the forefronts of portion size research are presented as well as policy considerations to promote healthy portion control.

"It's like giving him a piece of me.": Exploring UK and Israeli women's accounts of motherhood and feeding.

OBJECTIVE: The present study explored how Israeli and UK mothers integrate feeding into their conceptualisations of mothering 2-6 months post-partum. BACKGROUND: The nature and importance of motherhood is subject to differential contextual, cultural, political and historical influences. We set out to compare experiences of motherhood and feeding between these two countries using a qualitative approach. METHODS: Forty one women (mean age 36.4 ± 2.7 years) from Israel and the UK, mostly married or in a committed relationship were interviewed about their experience of pregnancy, motherhood and feeding. Data were analysed thematically. RESULTS: The experience of motherhood in the early postnatal period was dominated, for all mothers, by the experience of breastfeeding and clustered around three representations of mothering, namely; 1) a devoted mother who ignores her own needs; 2) a mother who is available for her infant but acknowledges her needs as well; and 3) a struggling mother for whom motherhood is a burden. Such representations existed within both cultural groups and sometimes coexisted within the same mothers. UK women described more struggles within motherhood whereas a tendency towards idealising motherhood was observed for Israeli women. CONCLUSION: There are similarities in the ways that UK and Israeli women experienced motherhood and feeding. Where family life is strongly emphasized, mothers reported extremes of idealism and burden and associated an "ideal" mother with a breastfeeding mother. Where motherhood is represented as just one of many roles women take up, they are more likely to represent a "good enough" approach to mothering. Understanding the experience of motherhood and feeding in different cultural settings is important to provide the context for postnatal care specifically where mothers are reluctant to share problems or difficulties encountered.

Potential benefits of satiety to the consumer: scientific considerations.

Foods and dietary patterns that enhance satiety may provide benefit to consumers. The aim of the present review was to describe, consider and evaluate research on potential benefits of enhanced satiety. The proposal that enhanced satiety could only benefit consumers by a direct effect on food intake should be rejected. Instead, it is proposed that there is a variety of routes through which enhanced satiety could (indirectly) benefit dietary control or weight-management goals. The review highlights specific potential benefits of satiety, including: providing appetite control strategies for consumers generally and for those who are highly responsive to food cues; offering pleasure and satisfaction associated with low-energy/healthier versions of foods without feeling 'deprived'; reducing dysphoric mood associated with hunger especially during energy restriction; and improved compliance with healthy eating or weight-management efforts. There is convincing evidence of short-term satiety benefits, but only probable evidence for longer-term benefits to hunger management, possible evidence of benefits to mood and cognition, inadequate evidence that satiety enhancement can promote weight loss, and no evidence on which consumers would benefit most from satiety enhancement. The appetite-reducing effects of specific foods or diets will be much more subtle than those of pharmaceutical compounds in managing hunger; nevertheless, the experience of pharmacology in producing weight loss via effects on appetite suggests that there is potential benefit of satiety enhancement from foods incorporated into the diet to the consumer.

Complementary feeding and "donner les bases du goût" (providing the foundation of taste). A qualitative approach to understand weaning practices, attitudes and experiences by French mothers.

Complementary feeding (CF) practices vary within and across cultures but have been investigated only to a very limited extent. It is however important to understand CF practices and how they differ, as CF sets the foundation for children's later food choices. The present study was set out to examine practices, attitudes and experiences of CF including the introduction of vegetables amongst French mothers (n=18, 25-39 years). Thematic analysis of transcribed focus groups and interviews revealed the perceived importance of the weaning period, as a critical milestone for infants' development but with a sense of "now or never" for introducing new tastes including vegetables. Flavour exposure and taste discovery during weaning were identified as the beginning of a "taste journey", in which educating the palate with a variety of different foods was considered important for children's later eating habits. Weaning was described as emotional and complex, a transition period in which the baby makes progress away from milk towards the family diet and which goes beyond mere nutrition. Advice was sought from official sources, but adapted to the needs of infants. In agreement with earlier observations of French adults, pleasure and taste development were considered of primary importance. In particular, French mothers believed complementary feeding lay the foundations of taste early in life.

Feeding infants and young children. From guidelines to practice-conclusions and future directions.

Infant feeding is a challenging and intricate process. Food intake is shaped by prior experience of flavours derived from the maternal diet in utero and via human milk, by ongoing experience of foods eaten during the first years of life including the variety, types and frequency of foods offered. The ways in which parents interact with their children including the way foods are presented, the emotional context they cultivate and the feeding practices they use can influence their children's eating habits, either positively or negatively. There is a mismatch between what government guidelines advise parents in relation to the "when, what and how" to feed children including during the weaning period and what parents actually do. Acquisition of food preferences and the establishment of eating habits in the early years form part of an ongoing, complex developmental process, however there is a gap between experimental evidence on best practice in infant feeding and what parents receive as advice about feeding. It is timely, therefore, to translate these findings into solutions for parents. Practical support for infant feeding should be evidence based, parent-focused and contingent on the needs of the developing child since infant feeding sets the foundation of healthy eating habits for life.

Utilising an integrated approach to developing liking for and consumption of vegetables in children.

Children eat too few vegetables and this is attributed to disliked flavours and texture as well as low energy density. Vegetables confer selective health benefits over other foods and so children are encouraged to eat them. Parents and caregivers face a challenge in incorporating vegetables into their child's habitual diet. However, liking and intake may be increased through different forms of learning. Children learn about vegetables across development from exposure to some vegetable flavours in utero, through breastmilk, complementary feeding and transitioning to family diets. Infants aged between 5 and 7 m are most amenable to accepting vegetables. However, a range of biological, social, environmental and individual factors may act independently and in tandem to reduce the appeal of eating vegetables. By applying aspects of learning theory, including social learning, liking and intake of vegetables can be increased. We propose taking an integrated and individualised approach to child feeding in order to achieve optimal learning in the early years. Simple techniques such as repeated exposure, modelling, social praise and creating social norms for eating vegetables can contribute to positive feeding experiences which in turn, contributes to increased acceptance of vegetables. However, there is a mismatch between experimental studies and the ways that children eat vegetables in real world settings. Therefore, current knowledge of the best strategies to increase vegetable liking and intake gained from experimental studies must be adapted and integrated for application to home and care settings, while responding to individual differences.

Emotions and eating. Self-reported and experimentally induced changes in food intake under stress.

Two studies investigated the stress-eating relationship. The first examined self-reported changes in intake of snack foods, whilst the second investigated stress-induced overconsumption in a laboratory setting comparing high (HF) and low-fat (LF) snacks. Eighty-nine females completed the Dutch Eating Behaviour Questionnaire (DEBQ) [Van Strien, T., Fritjers, J. E. R., Bergers, G. P. A., & Defares, P. B. (1986). Dutch Eating Behaviour Questionnaire for assessment of restrained, emotional and external eating behaviour. International Journal of Eating Disorders, 5, 295-315] and a self-report measure designed to evaluate changes in eating in response to stress. Increased intake of HF snacks was associated with high emotional eating but not with restraint. A laboratory-based experiment compared intake of HF and LF snacks after ego-threatening and neutral Stroop colour-naming tasks. Intake was suppressed by 31.8% in restrained compared to unrestrained eaters across tasks. Restrained eaters consumed significantly less after ego-threat than after the neutral manipulation, but this was associated only with intake of the LF snack. Restrained eaters' intake of dried fruit was suppressed by 33.2% after ego-threat relative to the neutral task, despite a significant increase in hunger for this group following ego-threat. These results suggest that the type and variety of foods offered influences the link between stress and eating in laboratory settings. Further research should aim to replicate and extend these findings, with a view to informing potential interventions for stress-related eating.

Interventions for Increasing Acceptance of New Foods Among Children and Adults with Developmental Disorders: A Systematic Review.

People with developmental disorders (DD) often display high levels of selective eating, which can result in micronutrient deficiencies. It is therefore essential to explore ways to increase dietary variety in this population. To identify different types of interventions promoting increased acceptance of new foods or dietary variety for DD populations and to determine their effectiveness. Thirty-six studies met criteria for inclusion in the review. Twenty-two types of intervention were identified with 34 studies being reported as effective and 33 of these incorporating components drawn from learning theory. Multi-component interventions centred on operant conditioning, systematic desensitisation and changes to environment and familial practices were reported as effective for individuals.

Acute effects of an alcoholic drink on food intake: aperitif versus co-ingestion.

To compare the effects on appetite and energy intake (EI) within a meal and across 4 days of drinking wine either before (aperitif) or with (co-ingestion) a meal, 11 men attended the laboratory on three occasions. On each occasion participants were given breakfast in the laboratory then 3 h later returned for a two course (garlic bread, pizza) lunch, then recorded food intake for the remainder of the day and the next 3 days. In the control condition, participants ate lunch ad libitum; in the aperitif condition 375 ml of red wine was consumed 20 min before lunch; and in the co-ingestion condition 125 ml of red wine was consumed with the starter and 250 ml of red wine was consumed with the main course. Subjective ratings of appetite and mood were administered before and after the meal. EI at lunch was greater when wine was consumed (p<0.01) (aperitif: 6436+/-435 kJ; co-ingestion: 6254+/-417 kJ) compared to control (5125+/-262 kJ). In particular, intake of the starter was enhanced by wine consumption. Having wine as an aperitif significantly influenced subjective ratings of light headedness and fatigue. These results suggest that the effects of wine on appetite are immediate, and stimulate food intake early in the meal. Total EI during the test days was significantly higher than during subsequent days revealing a tendency to overeat in the laboratory, exacerbated by drinking wine before or with lunch. However, lean healthy men adjusted total EI on the days following the laboratory in all conditions.

Volume and variety: relative effects on food intake.

Volume has been shown to be an important direct control of food intake, since larger volumes of food consumed prior to a meal can inhibit subsequent intake. Variety of food is known to stimulate food intake. The present study was designed to examine the relative effects of manipulating the volume of a soup preload in the context of providing either a single or a variety of sandwich fillings. Thirty participants (15 females; 15 males) attended the laboratory on 4 occasions to receive a low (f=240 ml, 3.6 kJ/g; m=300 ml, 3.6 kJ/g) or high (f=480 ml, 1.8 kJ/g; m=600 ml, 1.8 kJ/g) volume tomato soup preload 30 min before a sandwich lunch with either single or a variety of fillings. Overall, subjects reported significant differences in hunger and fullness as a function of volume manipulations but the satiety quotient (SQ: change in ratings divided by weight of soup) calculated just before lunch indicated a smaller SQ for high than for the low volume soup. Therefore, although subjective ratings were influenced by volume this was not sufficient to affect intake at lunch. Variety (2344+/-200 kJ) increased food intake at lunch compared to the single filling condition (2062+/-171 kJ), an enhancement by variety of 14%. In conclusion, lowering energy density and increasing volume by adding water failed to reduce intake at lunch. Clearly volume effects on intake rely both on amount consumed and energy density. As predicted, variety stimulated food intake and this occurred across volume conditions.

Pleasure and alcohol: manipulating pleasantness and the acute effects of alcohol on food intake.

To examine the effects of manipulating pleasantness on subsequent energy intake following a moderate dose of alcohol, 12 males attended the laboratory on four occasions. On each occasion participants consumed breakfast then 4 h later were offered lunch. Twenty minutes before lunch participants received an alcohol (24 g ethyl alcohol, 1508 kJ, 405 ml) or a no-alcohol (867 kJ, 405 ml) containing beverage followed by a lunch of either "bland" (rated pleasantness=66+/-13 mm) or "flavoured" (73+/-10 mm) foods. Subjective ratings of appetite, mood and pleasantness of several bland and tasty foods were taken before and after preloads and lunch. Ad libitum energy intake at lunch was greater following alcohol in both taste conditions (p<0.01) (Alcohol/Bland, 2053+/-663 kJ; Alcohol/Flavoured, 1989+/-580 kJ) in comparison to the no-alcohol conditions (No-alcohol/Bland, 1548+/-357 kJ; No-alcohol/Flavoured 1670+/-401 kJ). No additive effect of palatability and alcohol was found; alcohol did not differentially affect intake of lunch items. Nor did alcohol increase the pleasantness of foods. Sensory specific satiety (SSS) was observed both following the preload and following lunch, with no discernible effects of alcohol on SSS. In conclusion, alcohol promoted food intake but this did not occur via the additive effects of alcohol and palatability nor through increasing the pleasantness of the taste of foods. Further research on the mechanism underlying the stimulating effects of alcohol on appetite is warranted.

Response to upright exercise after myocardial infarction.

The left ventricular response to upright bicycle exercise was studied in 39 unselected, non-beta blocked patients (mean(SEM) age 54.2(1.7)yr) (mean(SEM) resting ejection fraction 41.9(2.3)%) 8-10 weeks after myocardial infarction. Nine healthy, age matched, sedentary adult men were studied for comparison (mean(SEM) age 49.8(0.9)yr). The stroke volume and cardiac output were measured by impedance cardiography at rest and after each 3 min workload until symptom limited maximum. The patients were separated into three groups based on stroke volume response to graded exercise. Group 1 (n = 14) had a normal stroke volume response to increasing heart rate. In group 2 (n = 13) stroke volume increased initially then decreased by greater than 15% at a heart rate greater than 100-105 beats.min-1. In group 3 (n = 12) stroke volume failed to increase during exercise. In group 1 cardiac output and mean arterial pressure increased whereas vascular resistance decreased during exercise in a normal fashion. Group 2 had an increased mean arterial pressure and systemic vascular resistance throughout exercise while heart rate increased in a similar fashion to group 1 until work of greater than 70 W was undertaken, at which time heart rate increased in a curvilinear fashion and cardiac output was attenuated. Group 3 had an attenuated cardiac output and a higher heart rate during exercise. In this group of patients systemic vascular resistance failed to decrease normally during exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac output measured by impedance cardiography during maximal exercise tests.

The overall accuracy of cardiac output measurements made by impedance cardiography during maximum exercise was studied in man. Initially, the systematic error of the technique was assessed over the range 3.5 to 18 litre . min-1 by comparing with simultaneous measurements of cardiac output made using the direct Fick method. No systemic error was demonstrated in 40 estimations made in 20 subjects. The random error was assessed in 4 subjects in a steady state at rest and during exercise at 80 and 130 W and found to be less than 5% in each subject. The reproducibility of maximum exercise response was assessed in six healthy male subjects (age 26.2 +/- 4.4 years, +/- SEM) who underwent maximum exercise tests twice, 1 week apart, on a bicycle ergometer. Simultaneous recordings of cardiac output and oxygen uptake (VO2) at rest and during each 3 min stage of exercise were made. Highly significant correlations were obtained in the stroke volume (r = 0.84, p less than 0.001), cardiac output (r = 0.98, p less than 0.001) and VO2 (r = 0.98, p less than 0.001) between the two tests. Average maximum cardiac output was 27.0 +/- 1.2 litre . min-1 (+/- SEM) and maximum VO2 was 4.4 +/- 0.2 litre . min-1 (+/- SEM). These results show that measurements of cardiac output were reproducible over one week. Impedance cardiography is non-invasive technique which is as accurate as invasive methods and can be used for maximal exercise testing.