Kym J. Guelfi

Supervised home-based exercise may attenuate the decline of glucose tolerance in obese pregnant women

AIM The significant deterioration of insulin sensitivity and glucose tolerance during pregnancy can have serious health implications for both the pregnant woman and her baby. Although it is well established that regular exercise benefits insulin sensitivity in the nonpregnant population, the effect on glucose tolerance in obese pregnant women is not known. The purpose of this study was to investigate the effect of a supervised 10-week, home-based, exercise programme, beginning at week 18 of gestation, on glucose tolerance and aerobic fitness in previously sedentary obese women. METHODS Twelve sedentary obese women were randomized into an exercise (EX; n=6) or control (CON; n=6) group at 18 weeks of gestation. Those randomized to EX engaged in 10 weeks of supervised home-based exercise (three sessions a week of stationary cycling), while those in the CON group maintained their usual daily activity. Their glucose and insulin responses to an oral glucose tolerance test (OGTT), as well as their aerobic fitness, were assessed both pre- and postintervention. RESULTS Reduced glucose tolerance in the CON, but not EX, group was indicated by a tendency postintervention towards higher blood glucose levels at 1h of the OGTT (P=0.072). Furthermore, at 2h of the postintervention OGTT, blood glucose tended to remain elevated from baseline in the CON (P=0.077). There was also a trend towards increased fitness in the EX (P=0.064), but not the CON group. CONCLUSION Regular aerobic exercise begun during pregnancy may have favourable effects on glucose tolerance and fitness in obese women, and warrants further investigation in a larger sample population.

High-intensity intermittent exercise attenuates ad-libitum energy intake

Objective:To examine the acute effects of high-intensity intermittent exercise (HIIE) on energy intake, perceptions of appetite and appetite-related hormones in sedentary, overweight men.Design:Seventeen overweight men (body mass index: 27.7±1.6 kg m−2; body mass: 89.8±10.1 kg; body fat: 30.0±4.3%; VO2peak: 39.2±4.8 ml kg−1 min−1) completed four 30-min experimental conditions using a randomised counterbalanced design. CON: resting control, MC: continuous moderate-intensity exercise (60% VO2peak), HI: high-intensity intermittent exercise (alternating 60 s at 100% VO2peak and 240 s at 50% VO2peak), VHI: very-high-intensity intermittent exercise (alternating 15 s at 170% VO2peak and 60 s at 32% VO2peak). Participants consumed a standard caloric meal following exercise/CON and an ad-libitum meal 70 min later. Capillary blood was sampled and perceived appetite assessed at regular time intervals throughout the session. Free-living energy intake and physical activity levels for the experimental day and the day after were also assessed.Results:Ad-libitum energy intake was lower after HI and VHI compared with CON (P=0.038 and P=0.004, respectively), and VHI was also lower than MC (P=0.028). Free-living energy intake in the subsequent 38 h remained less after VHI compared with CON and MC (P⩽0.050). These observations were associated with lower active ghrelin (P⩽0.050), higher blood lactate (P⩽0.014) and higher blood glucose (P⩽0.020) after VHI compared with all other trials. Despite higher heart rate and ratings of perceived exertion (RPE) during HI and VHI compared with MC (P⩽0.004), ratings of physical activity enjoyment were similar between all the exercise trials (P=0.593). No differences were found in perceived appetite between trials.Conclusions:High-intensity intermittent exercise suppresses subsequent ad-libitum energy intake in overweight inactive men. This format of exercise was found to be well tolerated in an overweight population.

Acute effect of environmental temperature during exercise on subsequent energy intake in active men

BACKGROUND The performance of exercise while immersed in cold water has been shown to influence energy intake in the subsequent meal. However, the effect of ambient temperature during land-based exercise is not known. OBJECTIVES Our aims were to investigate the effect of exercise performed in the heat on energy intake in the subsequent meal and to determine concentrations of circulating appetite-related hormones. DESIGN In a randomized, counterbalanced design, 11 active male participants completed 3 experimental trials in a fasted state: exercise in the heat (36 degrees C), exercise in a neutral temperature (25 degrees C), and a resting control (25 degrees C). The exercise trials consisted of treadmill running for 40 min at 70% VO(2peak). After each trial, participants were presented with a buffet-type breakfast of precisely known quantity and nutrient composition, which they could consume ad libitum. RESULTS Energy intake was greater after exercise in the neutral temperature compared with the control (P = 0.021) but was similar between exercise in the heat and the control and between the 2 exercise trials. When accounting for the excess energy expended during exercise, relative energy intake during exercise in the heat was lower than the control (P = 0.002) but was similar between exercise in the neutral temperature and the control and between exercise in the heat and in the neutral temperature. The lower relative energy intake after exercise in the heat was associated with an elevated tympanic temperature and circulating concentrations of peptide YY (P < 0.05). CONCLUSION Exercise in a neutral environmental temperature is associated with higher energy intake in the subsequent meal compared with a control, whereas exercise in the heat is not.

Beneficial effects of 12 weeks of aerobic compared with resistance exercise training on perceived appetite in previously sedentary overweight and obese men

OBJECTIVE To investigate the effect of 12 weeks of aerobic (AER) compared with resistance training (RES) on perceived hunger and fullness, together with appetite-related hormones in both the fasted state and postprandially. METHODS Thirty-three inactive, overweight and obese men (age 49±7 years; BMI 30.8±4.2 kg/m(2)) were allocated to either AER exercise (n=12), RES exercise (n=13) or a control group (CON; n=8). AER and RES completed 12 weeks of training (3 sessions per week), while CON continued their sedentary routine. Perceived hunger and fullness, together with appetite-related hormones (active ghrelin, leptin, insulin, pancreatic polypeptide (PP), and peptide tyrosine tyrosine (PYY)) were assessed pre and post-intervention in the fasted state and in response to oral glucose consumption (1284 kJ; 75 g carbohydrate). RESULTS Both AER and RES training elicited a decrease in fat mass (p<0.05), while CON did not. There was no difference in perceived hunger either in the fasted state (p>0.05) or in response to caloric consumption (p>0.05) following the intervention in any group. In contrast, both fasting and postprandial perceived fullness was higher following AER exercise (p<0.05), but not RES exercise or CON. These observations were not associated with alterations in fasting or postprandial active ghrelin, PP or PYY, although fasting and postprandial leptin was reduced following both AER and RES training (p<0.05). CONCLUSION Aerobic exercise training is associated with an increase in satiety, while an equivalent period of resistance training is not.

Energy intake and appetite-related hormones following acute aerobic and resistance exercise

Previous research has shown that resistance and aerobic exercise have differing effects on perceived hunger and circulating levels of appetite-related hormones. However, the effect of resistance and aerobic exercise on actual energy intake has never been compared. This study investigated the effect of an acute bout of resistance exercise, compared with aerobic exercise, on subsequent energy intake and appetite-regulating hormones. Ten active men completed 3 trials in a counterbalanced design: 45 min of resistance exercise (RES; free and machine weights), aerobic exercise (AER; running), or a resting control trial (CON). Following exercise or CON, participants had access to a buffet-style array of breakfast foods and drinks to consume ad libitum. Plasma concentrations of a range of appetite-regulating hormones were measured throughout each trial. Despite significantly higher energy expenditure with AER compared with RES (p < 0.05), there was no difference in total energy intake from the postexercise meal between trials (p = 0.779). Pancreatic polypeptide was significantly higher prior to the meal after both RES and AER compared with CON. In contrast, active ghrelin was lower following RES compared with both CON and AER (p ≤ 0.05), while insulin was higher following RES compared with CON (p = 0.013). In summary, the differential response of appetite-regulating hormones to AER and RES does not appear to influence energy intake in the postexercise meal. However, given the greater energy expenditure associated with AER compared with RES, AER modes of exercise may be preferable for achieving short-term negative energy balance.

A PROTEOMIC ANALYSIS OF THE ACUTE EFFECTS OF HIGH‐INTENSITY EXERCISE ON SKELETAL MUSCLE PROTEINS IN FASTED RATS

1 Quantitative proteomics is a technique that allows for large‐scale comparison of the levels of individual proteins present in a biological sample. This technique has not previously been applied to examine the response of skeletal muscle proteins to an acute bout of exercise. 2 In the present study, quantitative proteomics was applied to investigate whether the levels of individual skeletal muscle proteins are acutely affected by a short bout of high‐intensity exercise. 3 Gastrocnemius muscle was sampled from fasted rats either at rest, immediately following 3 min of high‐intensity exercise or after 30 min of recovery. Muscle samples were submitted to two‐dimensional gel electrophoresis and 61 of the resulting protein spots were selected for quantitative analysis. 4 It was found that skeletal muscle protein levels were generally not acutely affected by a short bout of high‐intensity exercise, with only four of the 61 proteins selected for analysis being significantly altered. These altered proteins were identified using liquid chromatography electrospray ionization–tandem mass spectrometry as creatine kinase, troponin T and a combination of heat shock 20 kDa protein and adenylate kinase 1. 5 In conclusion, quantitative proteomics is sensitive enough to detect acute changes in skeletal muscle protein levels in response to exercise. We have found that the levels of most individual skeletal muscle proteins are not immediately altered in response to a short bout of high‐intensity exercise and recovery in fasted rats.

A randomized clinical trial of exercise during pregnancy to prevent gestational diabetes mellitus and improve pregnancy outcome in overweight and obese pregnant women

BACKGROUND: Obesity and being overweight are becoming epidemic, and indeed, the proportion of such women of reproductive age has increased in recent times. Being overweight or obese prior to pregnancy is a risk factor for gestational diabetes mellitus, and increases the risk of adverse pregnancy outcome for both mothers and their offspring. Furthermore, the combination of gestational diabetes mellitus with obesity/overweight status may increase the risk of adverse pregnancy outcome attributable to either factor alone. Regular exercise has the potential to reduce the risk of developing gestational diabetes mellitus and can be used during pregnancy; however, its efficacy remain controversial. At present, most exercise training interventions are implemented on Caucasian women and in the second trimester, and there is a paucity of studies focusing on overweight/obese pregnant women. OBJECTIVE: We sought to test the efficacy of regular exercise in early pregnancy to prevent gestational diabetes mellitus in Chinese overweight/obese pregnant women. STUDY DESIGN: This was a prospective randomized clinical trial in which nonsmoking women age >18 years with a singleton pregnancy who met the criteria for overweight/obese status (body mass index 24≤28 kg/m2) and had an uncomplicated pregnancy at <12+6 weeks of gestation were randomly allocated to either exercise or a control group. Patients did not have contraindications to physical activity. Patients allocated to the exercise group were assigned to exercise 3 times per week (at least 30 min/session with a rating of perceived exertion between 12‐14) via a cycling program begun within 3 days of randomization until 37 weeks of gestation. Those in the control group continued their usual daily activities. Both groups received standard prenatal care, albeit without special dietary recommendations. The primary outcome was incidence of gestational diabetes mellitus. RESULTS: From December 2014 through July 2016, 300 singleton women at 10 weeks’ gestational age and with a mean prepregnancy body mass index of 26.78 ± 2.75 kg/m2 were recruited. They were randomized into an exercise group (n = 150) or a control group (n = 150). In all, 39 (26.0%) and 38 (25.3%) participants were obese in each group, respectively. Women randomized to the exercise group had a significantly lower incidence of gestational diabetes mellitus (22.0% vs 40.6%; P < .001). These women also had significantly less gestational weight gain by 25 gestational weeks (4.08 ± 3.02 vs 5.92 ± 2.58 kg; P < .001) and at the end of pregnancy (8.38 ± 3.65 vs 10.47 ± 3.33 kg; P < .001), and reduced insulin resistance levels (2.92 ± 1.27 vs 3.38 ± 2.00; P = .033) at 25 gestational weeks. Other secondary outcomes, including gestational weight gain between 25‐36 gestational weeks (4.55 ± 2.06 vs 4.59 ± 2.31 kg; P = .9), insulin resistance levels at 36 gestational weeks (3.56 ± 1.89 vs 4.07 ± 2.33; P = .1), hypertensive disorders of pregnancy (17.0% vs 19.3%; odds ratio, 0.854; 95% confidence interval, 0.434–2.683; P = .6), cesarean delivery (except for scar uterus) (29.5% vs 32.5%; odds ratio, 0.869; 95% confidence interval, 0.494–1.529; P = .6), mean gestational age at birth (39.02 ± 1.29 vs 38.89 ± 1.37 weeks’ gestation; P = .5); preterm birth (2.7% vs 4.4%, odds ratio, 0.600; 95% confidence interval, 0.140–2.573; P = .5), macrosomia (defined as birthweight >4000 g) (6.3% vs 9.6%; odds ratio, 0.624; 95% confidence interval, 0.233–1.673; P = .3), and large‐for‐gestational‐age infants (14.3% vs 22.8%; odds ratio, 0.564; 95% confidence interval, 0.284–1.121; P = .1) were also lower in the exercise group compared to the control group, but without significant difference. However, infants born to women following the exercise intervention had a significantly lower birthweight compared with those born to women allocated to the control group (3345.27 ± 397.07 vs 3457.46 ± 446.00 g; P = .049). CONCLUSION: Cycling exercise initiated early in pregnancy and performed at least 30 minutes, 3 times per week, is associated with a significant reduction in the frequency of gestational diabetes mellitus in overweight/obese pregnant women. And this effect is very relevant to that exercise at the beginning of pregnancy decreases the gestational weight gain before the mid‐second trimester. Furthermore, there was no evidence that the exercise prescribed in this study increased the risk of preterm birth or reduced the mean gestational age at birth.

New insights into managing the risk of hypoglycaemia associated with intermittent high-intensity exercise in individuals with type 1 diabetes mellitus: implications for existing guidelines.

Exercise is generally recommended for individuals with type 1 diabetes mellitus since it is associated with numerous physiological and psychological benefits. However, participation in exercise can also increase the risk of experiencing severe hypoglycaemia, a potentially life-threatening condition, both during exercise and for up to 31 hours of recovery. Fortunately, this risk of exerciseinduced hypoglycaemia can be managed by adjusting the dosage of self-administered exogenous insulin and nutritional intake to maintain blood glucose levels within the normal physiological range. In order to provide evidence-based guidelines to allow individuals with type 1 diabetes to safely participate in a range of physical activities, much previous research has focused on understanding the metabolic and hormonal responses to exercise. Consequently, it is well established that moderate-and high-intensity exercise have a contrasting effect on blood glucose levels and require different management strategies to maintain euglycaemia. On the other hand, the response of blood glucose levels to a combination of moderate-and high-intensity exercise, a pattern of physical activity referred to as intermittent high-intensity exercise (IHE) has received little research attention. This is despite the fact that this type of exercise characterises the activity patterns of most team and field sports as well as spontaneous play in children.The lack of previous research into the glucoregulatory responses to IHE is reflected in existing guidelines, which either do not address IHE, or suggest similar management strategies for blood glucose levels during and after IHE as for moderate- or high-intensity exercise alone. It is important, however, to appreciate that there are fundamental differences in the metabolic responses to intermittent exercise compared with other types of exercise.Recently, a series of investigations into the glucoregulatory responses to IHE that replicates the work-to-recovery ratios observed in team and field sports have been conducted. The findings of these studies do not support the existing recommendations for managing blood glucose levels during IHE. Hence, the purpose of this article is to discuss the results of these recent studies, which provide new insight into the management of blood glucose levels during and after IHE and have implications for current guidelines aimed at minimising the risk of hypoglycaemia. These findings, along with future investigations, should provide valuable information for health professionals and individuals with type 1 diabetes on the management of blood glucose levels during and after exercise to allow for safe participation in intermittent activities along with their peers.

Effects of static stretching in warm-up on repeated sprint performance.

Sim, AY, Dawson, BT, Guelfi, KJ, Wallman, KE, and Young, WB. Effects of static stretching in warm-up on repeated sprint performance. J Strength Cond Res 23(7): 2155-2162, 2009-The aim of this study was to examine the effects of static stretching during warm-up on repeated sprint performance and also to assess any influence of the order in which dynamic activities (i.e., run-throughs and drills) and static stretching are conducted. Thirteen male team sport players completed a repeated sprint ability test consisting of three sets of maximal 6 × 20-m sprints (going every 25 seconds) after performing one of three different warm-up protocols in a within-subjects counterbalanced design. Each warm-up protocol involved an initial 1000-m jog, followed by either dynamic activities only (D), static stretching followed by dynamic activities (S-D), or dynamic activities followed by static stretching (D-S). First (FST), best (BST) and total (TST) 20-m sprint times were determined for each individual set of the repeated sprint ability test and overall (3 sets combined). Although consistent significant differences were not observed between trials for TST, BST, and FST, the mean values for TST in all individual sets and overall were generally slowest in the D-S condition (D = 60.264 ± 1.127 seconds; S-D = 60.347 ± 1.774 seconds; D-S = 60.830 ± 1.786 seconds). This trend was supported by moderate to large effect sizes and qualitative indications of “possible” or “likely” benefits for TST, BST, and FST for the D and S-D warm-ups compared to D-S. No significant differences or large effect sizes were noted between D and S-D, indicating similar repeated sprint ability performance. Overall, these results suggest that 20-m repeated sprint ability may be compromised when static stretching is conducted after dynamic activities and immediately prior to performance (D-S).

Effects of antenatal diet and physical activity on maternal and fetal outcomes: Individual patient data meta-analysis and health economic evaluation

BACKGROUND Diet- and physical activity-based interventions in pregnancy have the potential to alter maternal and child outcomes. OBJECTIVES To assess whether or not the effects of diet and lifestyle interventions vary in subgroups of women, based on maternal body mass index (BMI), age, parity, Caucasian ethnicity and underlying medical condition(s), by undertaking an individual patient data (IPD) meta-analysis. We also evaluated the association of gestational weight gain (GWG) with adverse pregnancy outcomes and assessed the cost-effectiveness of the interventions. DATA SOURCES MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials, Database of Abstracts of Reviews of Effects and Health Technology Assessment database were searched from October 2013 to March 2015 (to update a previous search). REVIEW METHODS Researchers from the International Weight Management in Pregnancy Collaborative Network shared the primary data. For each intervention type and outcome, we performed a two-step IPD random-effects meta-analysis, for all women (except underweight) combined and for each subgroup of interest, to obtain summary estimates of effects and 95% confidence intervals (CIs), and synthesised the differences in effects between subgroups. In the first stage, we fitted a linear regression adjusted for baseline (for continuous outcomes) or a logistic regression model (for binary outcomes) in each study separately; estimates were combined across studies using random-effects meta-analysis models. We quantified the relationship between weight gain and complications, and undertook a decision-analytic model-based economic evaluation to assess the cost-effectiveness of the interventions. RESULTS Diet and lifestyle interventions reduced GWG by an average of 0.70 kg (95% CI -0.92 to -0.48 kg; 33 studies, 9320 women). The effects on composite maternal outcome [summary odds ratio (OR) 0.90, 95% CI 0.79 to 1.03; 24 studies, 8852 women] and composite fetal/neonatal outcome (summary OR 0.94, 95% CI 0.83 to 1.08; 18 studies, 7981 women) were not significant. The effect did not vary with baseline BMI, age, ethnicity, parity or underlying medical conditions for GWG, and composite maternal and fetal outcomes. Lifestyle interventions reduce Caesarean sections (OR 0.91, 95% CI 0.83 to 0.99), but not other individual maternal outcomes such as gestational diabetes mellitus (OR 0.89, 95% CI 0.72 to 1.10), pre-eclampsia or pregnancy-induced hypertension (OR 0.95, 95% CI 0.78 to 1.16) and preterm birth (OR 0.94, 95% CI 0.78 to 1.13). There was no significant effect on fetal outcomes. The interventions were not cost-effective. GWG, including adherence to the Institute of Medicine-recommended targets, was not associated with a reduction in complications. Predictors of GWG were maternal age (summary estimate -0.10 kg, 95% CI -0.14 to -0.06 kg) and multiparity (summary estimate -0.73 kg, 95% CI -1.24 to -0.23 kg). LIMITATIONS The findings were limited by the lack of standardisation in the components of intervention, residual heterogeneity in effects across studies for most analyses and the unavailability of IPD in some studies. CONCLUSION Diet and lifestyle interventions in pregnancy are clinically effective in reducing GWG irrespective of risk factors, with no effects on composite maternal and fetal outcomes. FUTURE WORK The differential effects of lifestyle interventions on individual pregnancy outcomes need evaluation. STUDY REGISTRATION This study is registered as PROSPERO CRD42013003804. FUNDING The National Institute for Health Research Health Technology Assessment programme.