Jessica E. Bourne

Where does HIT fit? An examination of the affective response to high-intensity intervals in comparison to continuous moderate- and continuous vigorous-intensity exercise in the exercise intensity-affect continuum.

Affect experienced during an exercise session is purported to predict future exercise behaviour. Compared to continuous moderate-intensity exercise (CMI), the affective response to continuous vigorous-intensity exercise (CVI) has consistently been shown to be more aversive. The affective response, and overall tolerability to high-intensity interval training (HIT), is less studied. To date, there has yet to be a comparison between HIT, CVI, and CMI. The purpose of this study was to compare the tolerability and affective responses during HIT to CVI and CMI. This study utilized a repeated measures, randomized, counter-balanced design. Forty-four participants visited the laboratory on four occasions. Baseline fitness testing was conducted to establish peak power output in Watts (Wpeak). Three subsequent visits involved a single bout of a) HIT, corresponding to 1-minute at ∼100% Wpeak and 1-minute at ∼20% Wpeak for 20 minutes, b) CMI, corresponding to ∼40% Wpeak for 40 minutes, and c) CVI, corresponding to ∼80% Wpeak for 20 minutes. The order of the sessions was randomized. Affective responses were measured before, during and after each session. Task self-efficacy, intentions, enjoyment and preference were measured after sessions. Participants reported greater enjoyment of HIT as compared to CMI and CVI, with over 50% of participants reporting a preference to engage in HIT as opposed to either CMI or CVI. HIT was considered more pleasurable than CVI after exercise, but less pleasurable than CMI at these times. Despite this participants reported being just as confident to engage in HIT as they were CMI, but less confident to engage in CVI. This study highlights the utility of HIT in inactive individuals, and suggests that it may be a viable alternative to traditionally prescribed continuous modalities of exercise for promoting self-efficacy and enjoyment of exercise.

High-Intensity Interval Training as an Efficacious Alternative to Moderate-Intensity Continuous Training for Adults with Prediabetes

Aims. High-intensity interval training (HIIT) leads to improvements in various markers of cardiometabolic health but adherence to HIIT following a supervised laboratory intervention has yet to be tested. We compared self-report and objective measures of physical activity after one month of independent exercise in individuals with prediabetes who were randomized to HIIT (n = 15) or traditional moderate-intensity continuous training (MICT, n = 17). Method. After completing 10 sessions of supervised training participants were asked to perform HIIT or MICT three times per week for four weeks. Results. Individuals in HIIT (89 ± 11%) adhered to their prescribed protocol to a greater extent than individuals in MICT (71 ± 31%) as determined by training logs completed over one-month follow-up (P = 0.05, Cohens d = 0.75). Minutes spent in vigorous physical activity per week measured by accelerometer were higher in HIIT (24 ± 18) as compared to MICT (11 ± 10) at one-month follow-up (P = 0.049, Cohens d = 0.92). Cardiorespiratory fitness and systolic blood pressure assessed at one-month follow-up were equally improved (Ps < 0.05). Conclusions. This study provides preliminary evidence that individuals with prediabetes can adhere to HIIT over the short-term and do so at a level that is greater than MICT.

Short-term high-intensity interval and moderate-intensity continuous training reduce leukocyte TLR4 in inactive adults at elevated risk of type 2 diabetes

Exercise can have anti-inflammatory effects in obesity, but the optimal type and intensity of exercise are not clear. This study compared short-term high-intensity interval training (HIIT) with moderate-intensity continuous training (MICT) in terms of improvement in cardiorespiratory fitness, markers of inflammation, and glucose control in previously inactive adults at elevated risk of developing type 2 diabetes. Thirty-nine inactive, overweight/obese adults (32 women) were randomly assigned to 10 sessions over 2 wk of progressive HIIT (n = 20, four to ten 1-min sessions at ∼90% peak heart rate, 1-min rest periods) or MICT (n = 19, 20-50 min at ∼65% peak heart rate). Before and 3 days after training, participants performed a peak O2 uptake test, and fasting blood samples were obtained. Both HIIT (1.8 ± 0.4 vs. 1.9 ± 0.4 l/min, pre vs. post) and MICT (1.8 ± 0.5 vs. 1.9 ± 0.5 l/min, pre vs. post) improved peak O2 uptake (P < 0.001) and lowered plasma fructosamine (P < 0.05). Toll-like receptor (TLR) 4 (TLR4) expression was reduced on lymphocytes and monocytes after both HIIT and MICT (P < 0.05) and on neutrophils after MICT (P < 0.01). TLR2 on lymphocytes was reduced after HIIT and MICT (P < 0.05). Plasma inflammatory cytokines were unchanged after training in both groups, but MICT led to a reduction in fasting plasma glucose (P < 0.05, 5.9 ± 1.0 vs. 5.6 ± 1.0 mmol/l, pre vs. post). Ten days of either HIIT or MICT can improve cardiorespiratory fitness and glucose control and lead to reductions in TLR2 and TLR4 expression. MICT, which involved a longer duration of exercise, may be superior for reducing fasting glucose.

The relationship between transformational teaching and adolescent physical activity: The mediating roles of personal and relational efficacy beliefs

The purpose of this study was to examine the extent to which transformational teaching, exhibited by secondary school physical education teachers, predicts within-class physical activity and leisure-time physical activity among adolescents. The study used a prospective observational design and involved data collected from 874 Grade 10 adolescents (Mage = 15.41, (SD) = .61). Through use of structural equation modeling, the results revealed that adolescents’ perceptions of transformational teaching were positively related to within-class physical activity and leisure-time physical activity, and these effects were mediated by adolescents’ estimation of their teacher’s confidence in their abilities (i.e. relation-inferred self-efficacy) and self-efficacy beliefs.

A qualitative investigation of adults’ perceived benefits, barriers and strategies for consuming milk and milk products

Objective: Milk and milk products provide important nutrients and have been associated with numerous health benefits in addition to bone health, including a healthy weight and a reduction of risk for certain conditions such as type 2 diabetes, hypertension, cardiovascular disease and colorectal cancer. Nonetheless, consumption of milk and milk products has declined over the past two decades. A qualitative investigation of men’s and women’s outcome expectancies for, and facilitators and barriers to, consuming milk and milk products is an essential first step for the creation of theory-based messages for the consumption of milk and milk products. Design: Qualitative group interview study. Setting: Research was conducted at community centres in Kelowna, British Columbia, Canada. Method: We undertook eight in-depth qualitative group interviews. Separate groups were conducted for men (n = 20, Mage = 42 ± 6) and women (n = 20, Mage = 38 ± 7) and adequate (≥2 servings/day) and under-consumers (<2 servings/day). The interview schedule, grounded in social cognitive theory, included questions probing participant’s perceptions of milk and milk products and strategies for meeting dietary recommendations for milk product consumption. Data were analysed using hierarchical content analysis. Results: Perception of contamination of milk and milk products was one of the most common barriers. Consuming milk and milk products as part of a routine and making plans to consume milk and combining milk and milk products with other foods emerged as common strategies from ensuring adequate consumption. Within these themes, gender differences were apparent. Conclusion: Messages promoting milk and milk product consumption should target consumers’ beliefs about the benefits of milk products and provide strategies for increasing their consumption.

A systematic review of behavioural interventions to increase maternal calcium intake

Pregnancy and lactation are a time when adequate calcium consumption is essential for the development of the fetus and to ensure the health of the mother. Over 50% of Canadian women of childbearing and rearing age fail to meet the recommended daily intake of calcium. Identification of effective behavioural intervention strategies for increasing calcium intake is needed within this specific population. This paper brings together all published behavioural interventions designed to increase calcium consumption in pregnant, lactating or post-partum mothers in a systematic review. Relevant studies were obtained through searches of MEDLINE, EMBASE, PsycINFO, CINAHL and the Cochrane Library with no date restrictions. Studies were evaluated using previously published criteria for evaluating calcium behaviour change interventions. This systematic literature review identified five behavioural calcium interventions conducted within this population. Three interventions aimed to improve overall dietary behaviours, the fourth aimed to promote breastfeeding (including increasing calcium consumption) and the fifth aimed to increase daily servings of yoghurt. Only one of the five interventions yielded large effect sizes, with a mean change of 954 mg of calcium per day post-intervention. The number of behavioural change techniques did not appear to be related to intervention efficacy. Only one study used a theoretical framework to guide the intervention. This review highlights the lack of research examining behaviour change interventions aimed at increasing calcium consumption in pregnant, lactating and post-partum women and provides practical suggestions for researchers wishing to intervene with this population in the future.

A systematic review of interventions aimed at increasing calcium intake in adults: where do we go from here?

Identification of effective intervention characteristics for increasing calcium intake is important given the widespread failure of adults to meet dietary guidelines for calcium in many developed countries. This paper synthesises, in a systematic review, all interventions published between 1980-2012, that were designed to increase calcium consumption in adults. Eighteen interventions were identified and subsequently analysed using Hendries intervention intensity scaling system (2012), permitting comparison of interventions of varying designs. Michie et al. (2011) refined CALO-RE taxonomy was used to classify behaviour change techniques used within the interventions. Five interventions yielded large effect sizes, with a mean change of 333.18 mg of calcium per day post-intervention. Although the number of behaviour change techniques was unrelated to intervention effectiveness, the interventions yielding the largest effects employed techniques that involved education regarding: a) the consequences of increasing calcium intake; b) how to increase calcium intake. This review highlights promising calcium consumption behaviour change characteristics, grounded in behaviour change theories, and emphasises the need for future research that incorporates more male samples.

The influence of high-intensity interval training and moderate-intensity continuous training on sedentary time in overweight and obese adults

High-intensity interval training (HIIT) elicits health benefits but it is unclear how HIIT impacts sedentary behaviour. In this preliminary study, we compared the effects of supervised HIIT or moderate-intensity continuous training (MICT) on sedentary time in overweight/obese adults. In both groups, percentage of time spent in sedentary activities was significantly reduced during the supervised exercise intervention (time main effect, P = 0.03), suggesting that both HIIT and MICT replaced time spent previously being sedentary.