Effects of postprandial exercise on blood glucose levels in adults with type 1 diabetes: a review

People with type 1 diabetes experience challenges in managing blood glucose around exercise. Previous studies have examined glycaemic responses to different exercise modalities but paid little attention to participants' prandial state, although this is an important consideration and will enhance our understanding of the effects of exercise in order to improve blood glucose management around activity. This review summarises available data on the glycaemic effects of postprandial exercise (i.e. exercise within 2 h after a meal) in people with type 1 diabetes. Using a search strategy on electronic databases, literature was screened until November 2022 to identify clinical trials evaluating acute (during exercise), subacute (≤2 h after exercise) and late (>2 h to ≤24 h after exercise) effects of postprandial exercise in adults with type 1 diabetes. Studies were systematically organised and assessed by exercise modality: (1) walking exercise (WALK); (2) continuous exercise of moderate intensity (CONT MOD); (3) continuous exercise of high intensity (CONT HIGH); and (4) interval training (intermittent high-intensity exercise [IHE] or high-intensity interval training [HIIT]). Primary outcomes were blood glucose change and hypoglycaemia occurrence during and after exercise. All study details and results per outcome were listed in an evidence table. Twenty eligible articles were included: two included WALK sessions, eight included CONT MOD, seven included CONT HIGH, three included IHE and two included HIIT. All exercise modalities caused consistent acute glycaemic declines, with the largest effect size for CONT HIGH and the smallest for HIIT, depending on the duration and intensity of the exercise bout. Pre-exercise mealtime insulin reductions created higher starting blood glucose levels, thereby protecting against hypoglycaemia, in spite of similar declines in blood glucose during activity between the different insulin reduction strategies. Nocturnal hypoglycaemia occurred after higher intensity postprandial exercise, a risk that could be diminished by a post-exercise snack with concomitant bolus insulin reduction. Research on the optimal timing of postprandial exercise is inconclusive. In summary, individuals with type 1 diabetes exercising postprandially should substantially reduce insulin with the pre-exercise meal to avoid exercise-induced hypoglycaemia, with the magnitude of the reduction depending on the exercise duration and intensity. Importantly, pre-exercise blood glucose and timing of exercise should be considered to avoid hyperglycaemia around exercise. To protect against late-onset hypoglycaemia, a post-exercise meal with insulin adjustments might be advisable, especially for exercise in the evening or with a high-intensity component.

Systematic Review and Meta-analysis of Blood Glucose Response to High-intensity Interval Exercise in Adults With Type 1 Diabetes

OBJECTIVES

Exercise-induced hyperglycemia is recognized in type 1 diabetes (T1D) clinical guidelines, but its association with high-intensity intermittent exercise (HIIE) in acute studies is inconsistent. In this meta-analysis, we examined the available evidence of blood glucose responses to HIIE in adults with T1D. The secondary, aim was to examine predictors of blood glucose responses to HIIE. We hypothesized that there would be no consistent effect on blood glucose from HIIE, unless examined in the context of participant prandial status.

METHODS

We conducted a literature search using key words related to T1D and HIIE. Studies were required to include at least 6 participants with T1D with a mean age >18 years, involve an HIIE intervention, and contain pre- and postexercise measures of blood glucose. Analyses of extracted data were performed using a general inverse variance statistical method with a random effects model and a weighted multiple regression.

RESULTS

Nineteen interventions from 15 reports were included in the analysis. A mean overall blood glucose decrease of -1.3 mmol/L (95% confidence interval [CI], -2.3 to -0.2 mmol/L) was found during exercise, albeit with high heterogeneity (I²=84%). When performed after an overnight fast, exercise increased blood glucose by +1.7 mmol/L (95% CI, 0.4 to 3.0 mmol/L), whereas postprandial exercise decreased blood glucose by -2.1 mmol/L (95% CI, -2.8 to -1.4 mmol/L), with a statistically significant difference between groups (p<0.0001). No associations with fitness (p=0.4), sex (p=0.4), age (p=0.9), exercise duration (p=0.9), or interval duration (p=0.2) were found.

CONCLUSION

The effect of HIIE on blood glucose is inconsistent, but partially explained by prandial status.

Type 1 Diabetes and the Menstrual Cycle: Where/How Does Exercise Fit in?

Regular exercise is associated with substantial health benefits for individuals with type 1 diabetes (T1D). However, the fear of hypoglycemia (low blood glucose) due to activity-induced declines in blood glucose levels acts as a major barrier to partaking in exercise in this population. For females with T1D, hormonal fluctuations during the menstrual cycle and their effects on blood glucose levels can act as an additional barrier. The impact that these cyclic changes may have on blood glucose and insulin needs and the consequent risk of hypoglycemia during or after exercise are still unknown in this population. Therefore, in this narrative review, we gathered existing knowledge about the menstrual cycle in T1D and the effects of different cyclic phases on substrate metabolism and glucose response to exercise in females with T1D to increase knowledge and understanding around exercise in this underrepresented population. This increased knowledge in such an understudied area can help to better inform exercise guidelines for females with T1D. It can also play an important role in eliminating a significant barrier to exercise in this population, which has the potential to increase activity, improve mental health and quality of life, and decrease the risk of diabetes-related complications.

The Effect of Starting Blood Glucose Levels on Serum Electrolyte Concentrations during and after Exercise in Type 1 Diabetes

Fear of hypoglycemia is a major exercise barrier for people with type 1 diabetes (PWT1D). Consequently, although guidelines recommend starting exercise with blood glucose (BG) concentration at 7-10 mmol/L, PWT1D often start higher, potentially affecting hydration and serum electrolyte concentrations. To test this, we examined serum and urine electrolyte concentrations during aerobic exercise (cycling 45 min at 60%VO₂peak) in 12 PWT1D (10F/2M, mean ± SEM: age 29 ± 2.3 years, VO₂peak 37.9 ± 2.2 mL·kg^-1·min^-1) with starting BG levels: 8-10 (MOD), and 12-14 (HI) mmol/L. Age, sex, and fitness-matched controls without diabetes (CON) completed one exercise session with BG in the normal physiological range. Serum glucose was significantly higher during exercise and recovery in HI versus MOD (p = 0.0002 and p < 0.0001, respectively) and in MOD versus CON (p < 0.0001). During exercise and recovery, MOD and HI were not significantly different in serum insulin (p = 0.59 and p = 0.63), sodium (p = 0.058 and p = 0.08), potassium (p = 0.17 and p = 0.16), calcium (p = 0.75 and 0.19), and magnesium p = 0.24 and p = 0.09). Our findings suggest that exercise of moderate intensity and duration with higher BG levels may not pose an immediate risk to hydration or serum electrolyte concentrations for PWT1D.

"How we do it": A qualitative study of strategies for adopting an exercise routine while living with type 1 diabetes

Introduction

For people living with type 1 diabetes (T1D) the challenge of increasing daily physical activity (PA) is compounded by the increased risks of hypoglycemia and glucose variability. Little information exists on the lived experience of overcoming these barriers and adopting and maintaining an active lifestyle while living with T1D.

Research Design and Methods

We conducted a patient-led qualitative study consisting of semi-structured interviews or focus groups with 22 individuals at least 16 years old living with T1D. We used existing patient co-researcher networks and snowball sampling to obtain a sample of individuals who reported being regularly physically active and had been diagnosed with T1D for at least one year. We used an interpretive description analysis to generate themes and strategies associated with maintaining an active lifestyle while living with T1D. We involved patient co-researchers in study design, data collection, and interpretation.

Results

14 self-identified women and 8 self-identified men (ages 19-62, median age 32 years) completed the study, led by either a researcher, or a patient co-researcher and research assistant regarding their strategies for maintaining an active lifestyle. We identified five themes that facilitate regular sustained PA: (1) Structure and organization are important to adopt safe PA in daily life "I can't do spontaneous exercise. I actually need a couple hours of warning minimum"; (2) Trial and error to learn how their body responds to PA and food "Once you put the time and effort into learning, you will have greater success"; (3) Psychosocial aspects of PA "…because it's not just your body, it's your soul, it's your mind that exercise is for"; (4) Diabetes technology and (5) Education and peer support. Strategies to overcome barriers included (1) Technology; (2) Integrating psychosocial facilitators; (3) Insulin and carbohydrate adjustments; and (4) Planning for exercise.

Conclusions

Living an active lifestyle with T1D is facilitated by dedicated structure and organization of routines, accepting the need for trial and error to understand the personalized glycemic responses to PA and careful use of food to prevent hypoglycemia. These themes could inform clinical practice guidelines or future trials that include PA interventions.

The Resistance Exercise in Already Active Diabetic Individuals (READI) Randomised Clinical Trial

OBJECTIVE

To evaluate the incremental impact of resistance training on HbA1c, fitness, body composition and cardiometabolic risk factors in aerobically-active people with type 1 diabetes.

RESEARCH DESIGN AND METHODS

The Resistance Exercise in Already-active Diabetic Individuals (READI) trial (NCT00410436) was a four-centre randomized parallel-group trial. After a 5-week run-in period with diabetes management optimization, 131 aerobically-active individuals with type 1 diabetes were randomized to resistance exercise (n = 71, intervention - INT) or control (n = 60, CON) for 22 additional weeks. Both groups maintained their aerobic activities and were provided dietary counselling throughout. Exercise training was three times per week at community-based facilities. The primary outcome was HbA1c, and secondary outcomes included fitness (peak oxygen consumption, muscle strength), body composition (anthropometrics, dual-energy X-ray absorptiometry, computed tomography) and cardiometabolic risk markers (lipids, apolipoproteins). Assessors were blinded to group allocation.

RESULTS

There were no significant differences in HbA1c change between INT and CON. Declines in HbA1c [INT: 7.75 ± 0.10% (61.2 ± 1.1 mmol/mol) to 7.55 ± 0.10% (59 ± 1.1 mmol/mol); CON: 7.70 ± 0.11% (60.7 ± 1.2 mmol/mol) to 7.57 ± 0.11% (59.6 ± 1.3 mmol/mol); intergroup difference in change -0.07 [95% CI -0.31, 0.18]. Waist circumference decreased more in INT than CON after six months (p = 0.02). Muscular strength increased more in INT than in CON (p < 0.001). There were no intergroup differences in hypoglycemia or any other variables.

CONCLUSIONS

Adding resistance training did not impact glycemia, but it increased strength and reduced waist circumference, in aerobically active individuals with type 1 diabetes.

Reassessing the evidence: prandial state dictates glycaemic responses to exercise in individuals with type 1 diabetes to a greater extent than intensity

Recent guidelines suggest that adding anaerobic (high intensity or resistance) activity to an exercise session can prevent blood glucose declines that occur during aerobic exercise in individuals with type 1 diabetes. This theory evolved from earlier study data showing that sustained, anaerobic activity (high intensity cycling) increases blood glucose levels in these participants. However, studies involving protocols where anaerobic (high intensity interval) and aerobic exercise are combined have extremely variable glycaemic outcomes, as do resistance exercise studies. Scrutinising earlier studies will reveal that, in addition to high intensity activity (intervals or weight lifting), these protocols had another common feature: participants were performing exercise after an overnight fast. Based on these findings, and data from recent exercise studies, it can be argued that participant prandial state may be a more dominant factor than exercise intensity where glycaemic changes in individuals with type 1 diabetes are concerned. As such, a reassessment of study outcomes and an update to exercise recommendations for those with type 1 diabetes may be warranted.

Comparison of Nocturnal Glucose After Exercise Among Dual-Hormone, Single-Hormone Algorithm-Assisted Insulin Delivery System and Usual Care in Adults and Adolescents Living with Type 1 Diabetes: A Pooled Analysis

Background: Available studies comparing the efficacy of dual-hormone (DH)-algorithm-assisted insulin delivery (AID), single-hormone (SH)-AID and usual care on postexercise overnight glucose in people with type 1 diabetes (T1D) have had different outcomes. By pooling data from all available studies, we aim to draw stronger conclusions. Methods: Data were pooled from two three-arm, open-label, randomized, controlled, crossover studies. Forty-one adults [median (Q1, Q3) age: 34.0 years (29.5, 51.0), mean HbA1c: 7.5% ± 1.0%] and 17 adolescents with T1D [age: 14.0 (13.0, 16.0), HbA1c: 7.8% ± 0.8%] underwent DH-AID, SH-AID, and usual care. Each intervention involved evening aerobic exercise (60-min). The primary outcome, time in range% (TIR%) overnight (00:00-06:00) postexercise based on continuous glucose monitoring, was compared among treatments using linear mixed effect model or generalized linear mixed model. Results: Among adults, mean TIR% was 94.0% ± 11.9%, 83.1% ± 20.5%, and 65.1% ± 37.0% during DH-AID, SH-AID, and usual care intervention, respectively (P < 0.05 for all between-group comparisons). DH-AID was superior to SH-AID and usual care, and SH-AID was superior to usual care regarding hypoglycemia and hyperglycemia prevention, but not glycemic variability. Among adolescents, DH-AID and SH-AID reduced dysglycemia, but not glycemic variability, better than usual care. Glycemic outcomes were similar between DH-AID and SH-AID. Conclusion: AID systems allow improved postexercise nocturnal glycemic management than usual care for both adults and adolescents. DH-AID was better than SH-AID among adults, but not adolescents.

Afternoon aerobic and resistance exercise have limited impact on 24-h CGM outcomes in adults with type 1 diabetes: A secondary analysis

AIMS

This study examined post-exercise glycemic variability in individuals with type 1 diabetes after acute bouts of resistance (RE) and aerobic exercise (AE) compared to a no-exercise day (CON). We hypothesized that exercise days would have greater glucose variability (standard deviation - SD, coefficient of variation - CV), and less time in range (TIR), compared to CON.

METHODS

A secondary analysis was conducted on previously collected data. Twelve active participants with type 1 diabetes performed three testing sessions in random order with at least 48 h in between: AE (45-min treadmill run at 60%VO_2max), RE (three sets of eight repetitions, seven weight-lifting exercises), and CON (45-min no-exercise control). Interstitial glucose levels were monitored by blinded continuous glucose monitoring (CGM). Glycemic variability was evaluated for 0-6 h, overnight (00:00-06:00) and 24 h after exercise.

RESULTS

Mean CGM glucose, TIR, and time above/below range were similar among conditions (P > 0.05). Lower SD (0.8 [0.5-1.1], 1.4 [0.9-2.4]mmol/L, p = 0.009) and CV (11.4 [8.6-15.3], 23.4 [13.7-31.6]%, p = 0.007) were found overnight after AE versus CON. Otherwise, AE and RE had limited impact on post-exercise glycemia.

CONCLUSIONS

Acute RE and AE bouts may have limited impact on post-exercise glycemic variability compared to rest in habitually active individuals with type 1 diabetes.

Differences in Physiological Responses to Cardiopulmonary Exercise Testing in Adults With and Without Type 1 Diabetes: A Pooled Analysis

OBJECTIVE

To investigate physiological responses to cardiopulmonary exercise (CPX) testing in adults with type 1 diabetes compared with age-, sex-, and BMI-matched control participants without type 1 diabetes.

RESEARCH DESIGN AND METHODS

We compared results from CPX tests on a cycle ergometer in individuals with type 1 diabetes and control participants without type 1 diabetes. Parameters were peak and threshold variables of VO₂, heart rate, and power output. Differences between groups were investigated through restricted maximum likelihood modeling and post hoc tests. Differences between groups were explained by stepwise linear regressions (P < 0.05).

RESULTS

Among 303 individuals with type 1 diabetes (age 33 [interquartile range 22; 43] years, 93 females, BMI 23.6 [22; 26] kg/m², HbA_1c 6.9% [6.2; 7.7%] [52 (44; 61) mmol/mol]), VO_2peak (32.55 [26.49; 38.72] vs. 42.67 ± 10.44 mL/kg/min), peak heart rate (179 [170; 187] vs. 184 [175; 191] beats/min), and peak power (216 [171; 253] vs. 245 [200; 300] W) were lower compared with 308 control participants without type 1 diabetes (all P < 0.001). Individuals with type 1 diabetes displayed an impaired degree and direction of the heart rate-to-performance curve compared with control participants without type 1 diabetes (0.07 [-0.75; 1.09] vs. 0.66 [-0.28; 1.45]; P < 0.001). None of the exercise physiological responses were associated with HbA_1c in individuals with type 1 diabetes.

CONCLUSIONS

Individuals with type 1 diabetes show altered responses to CPX testing, which cannot be explained by HbA_1c. Intriguingly, the participants in our cohort were people with recent-onset type 1 diabetes; heart rate dynamics were altered during CPX testing.

Fasting May Alter Blood Glucose Responses to High-Intensity Interval Exercise in Adults With Type 1 Diabetes: A Randomized, Acute Crossover Study

OBJECTIVES

In individuals with type 1 diabetes (T1D), changes in blood glucose (BG) during high-intensity interval exercise (HIIE) are smaller than those observed during aerobic exercise. Study outcomes, however, have been variable, with some demonstrating significant BG decreases and others showing BG increases. This study compared BG outcomes between fasting (AME) and postprandial (PME) HIIE in T1D to test the hypothesis that AME would produce a BG increase, yet PME would cause BG to decline.

METHODS

Twelve (6 men and 6 women) physically active individuals with T1D performed two 45-minute exercise sessions (AME at 7:00 AM, PME at 5:00 PM) in random order, separated by at least 48 hours. Sessions consisted of a 10-minute warmup (50%VO_2peak), followed by 10-second sprints every 2 minutes for 24 minutes, and then an 11-minute cooldown. Capillary glucose was measured pre- and postexercise, and then 60 minutes postexercise. Interstitial glucose was recorded for 24 hours postexercise using continuous glucose monitoring.

RESULTS

AME caused capillary glucose to increase (from 7.6±1.4 to 9.2±2.9 mmol/L during exercise, and 9.9±2.8 mmol/L in recovery), whereas PME produced a decline in capillary glucose (from 9.9±3.1 to 9.5±3.4 mmol/L during exercise and 8.9±2.7 mmol/L during recovery; time × treatment interaction, p=0.014). PME was associated with a higher frequency of hyperglycemic events in the 6 hours and overnight (midnight to 6:00 AM) after exercise.

CONCLUSIONS

Fasting HIIE results in a different BG trajectory than postprandial exercise in T1D, and may be beneficial for hypoglycemia avoidance during exercise.

The competitive athlete with type 1 diabetes

Regular exercise is important for health, fitness and longevity in people living with type 1 diabetes, and many individuals seek to train and compete while living with the condition. Muscle, liver and glycogen metabolism can be normal in athletes with diabetes with good overall glucose management, and exercise performance can be facilitated by modifications to insulin dose and nutrition. However, maintaining normal glucose levels during training, travel and competition can be a major challenge for athletes living with type 1 diabetes. Some athletes have low-to-moderate levels of carbohydrate intake during training and rest days but tend to benefit, from both a glucose and performance perspective, from high rates of carbohydrate feeding during long-distance events. This review highlights the unique metabolic responses to various types of exercise in athletes living with type 1 diabetes. Graphical abstract.

Filling gaps in type 1 diabetes and exercise research: a scoping review and priority-setting project

Our team examined the characteristics of patient engagement (PE) practices in exercise-based randomized trials in type 1 diabetes (T1D), and facilitated T1D stakeholders in determining the top 10 list of priorities for exercise research. Two methodological approaches were employed: a scoping review and a modified James Lind Alliance priority-setting partnership. Published (Medline, Embase, CINAHL and Central databases) and grey literature (www.clinicaltrials.gov) were searched to identify randomized controlled trials of exercise interventions lasting minimum 4 weeks and available in English. We extracted information on PE and patient-reported outcomes (PROs) to identify if patient perspectives had been implemented. Based on results, we set out to determine exercise research priorities as a first step towards a patient-engaged research agenda. An online survey was distributed across Canada to collect research questions from patients, caregivers and healthcare providers. We qualitatively analyzed submitted questions and compiled a long list that a 12-person stakeholder steering committee used to identify the top 10 priority research questions. Of 9962 identified sources, 19 published trials and 4 trial registrations fulfilled inclusion criteria. No evidence of PE existed in any included study. Most commonly measured PROs were frequency of hypoglycemia (n=7) and quality of life (n=4). The priority-setting survey yielded 194 submitted research questions. Steering committee rankings identified 10 priorities focused on lifestyle factors and exercise modifications to maintain short-term glycemic control. Recent exercise-based randomized trials in T1D have not included PE and PROs. Patient priorities for exercise research have yet to be addressed with adequately designed clinical trials.

Blunted circulating irisin in adults with type 1 diabetes during aerobic exercise in a hot environment: a pilot study

Irisin is a novel myokine associated with increased metabolism, which may be upregulated in type 1 diabetes (T1D) during exercise-heat stress. We therefore assessed serum irisin production in young adults with and without T1D during incremental exercise in dry-heat (35 °C). The change in irisin during exercise was lower in individuals with compared with without T1D (-1.79 (SEM 25.68) vs. 59.74 (SEM 79.63) pg/mL; p = 0.024), indicating that irisin expression during exercise-heat stress is blunted in T1D. Novelty We show that, when assessed in young adults with and without T1D during exercise-heat stress, serum irisin production is blunted in T1D.

The Athlete with Type 1 Diabetes: Transition from Case Reports to General Therapy Recommendations

Fear of hypoglycemia is a common barrier to exercise and physical activity for individuals with type 1 diabetes. While some of the earliest studies in this area involved only one or two participants, the link between exercise, exogenous insulin, and hypoglycemia was already clear, with the only suggested management strategies being to decrease insulin dosage and/or consume carbohydrates before and after exercise. Over the past 50 years, a great deal of knowledge has been developed around the impact of different types and intensities of exercise on blood glucose levels in this population. Recent decades have also seen the development of technologies such as continuous glucose monitors, faster-acting insulins and commercially available insulin pumps to allow for the real-time observation of interstitial glucose levels, and more precise adjustments to insulin dosage before, during and after activity. As such, there are now evidence-based exercise and physical activity guidelines for individuals with type 1 diabetes. While the risk of hypoglycemia has not been completely eliminated, therapy recommendations have evolved considerably. This review discusses the evolution of the knowledge and the technology related to type 1 diabetes and exercise that have allowed this evolution to take place.

Morning (Fasting) vs Afternoon Resistance Exercise in Individuals With Type 1 Diabetes: A Randomized Crossover Study

OBJECTIVE

To determine the effect of morning exercise in the fasting condition vs afternoon exercise on blood glucose responses to resistance exercise (RE).

RESEARCH DESIGN AND METHODS

For this randomized crossover design, 12 participants with type 1 diabetes mellitus [nine females; aged 31 ± 8.9 years; diabetes duration, 19.1 ± 8.3 years; HbA1c, 7.4% ± 0.8% (57.4 ± 8.5 mmol/mol)] performed ∼40 minutes of RE (three sets of eight repetitions, seven exercises, at the individual's predetermined eight repetition maximum) at either 7 am (fasting) or 5 pm. Sessions were performed at least 48 hours apart. Venous blood samples were collected immediately preexercise, immediately postexercise, and 60 minutes postexercise. Interstitial glucose was monitored overnight postexercise by continuous glucose monitoring (CGM).

RESULTS

Data are presented as mean ± SD. Blood glucose rose during fasting morning exercise (9.5 ± 3.0 to 10.4 ± 3.0 mmol/L), whereas it declined with afternoon exercise (8.2 ± 2.5 to 7.4 ± 2.6 mmol/L; P = 0.031 for time-by-treatment interaction). Sixty minutes postexercise, blood glucose concentration was significantly higher after fasting morning exercise than after afternoon exercise (10.9 ± 3.2 vs 7.9 ± 2.9 mmol/L; P = 0.019). CGM data indicated more glucose variability (2.7 ± 1.1 vs 2.0 ± 0.7 mmol/L; P = 0.019) and more frequent hyperglycemia (12 events vs five events; P = 0.025) after morning RE than after afternoon RE.

CONCLUSIONS

Compared with afternoon RE, morning (fasting) RE was associated with distinctly different blood glucose responses and postexercise profiles.

Sex-Related Differences in Blood Glucose Responses to Resistance Exercise in Adults With Type 1 Diabetes: A Secondary Data Analysis

OBJECTIVES

In adults with type 1 diabetes, resistance exercise (RE) is associated with more stable blood glucose (BG) levels than aerobic exercise, both during and after exercise. In individuals without diabetes, growth hormone and epinephrine responses to RE differ between the sexes. These hormones are known to affect BG levels in individuals with type 1 diabetes. In this study, we explored whether sex-related differences may exist in BG responses to RE in individuals with type 1 diabetes.

METHODS

A secondary data analysis was conducted on pooled data from 2 studies with identical RE protocols for individuals with type 1 diabetes (13 males, age range 16 to 63 years; 10 females, age range 19 to 45 years). The RE session consisted of 7 resistance-based exercises performed at 5 pm. Plasma glucose samples were collected before, immediately after and 1 h after exercise. Interstitial glucose levels were recorded through blinded continuous glucose monitoring 24 h before, during and 24 h after exercise.

RESULTS

There was a significant sex-by-time interaction (p<0.001) in plasma glucose responses to RE. Plasma glucose decreased significantly in males from 8.6±2.5 to 6.3±2.1 mmol/L (p<0.001) during exercise, whereas females experienced no significant change (7.2±1.3 to 7.3±1.3 mmol/L, p=0.999). In the 6 h after RE, males developed significantly more hypoglycemia, as measured by continuous glucose monitoring (p=0.048).

CONCLUSIONS

Males may have a greater risk of hypoglycemia with an acute bout of RE than females. Further research is needed to examine this phenomenon more closely, as sex-specific recommendations for preventing hypoglycemia around RE may be necessary in type 1 diabetes.

Minimal effect of walking before dinner on glycemic responses in type 2 diabetes: outcomes from the multi-site E-PAraDiGM study

AIM

To examine the effect of walking before dinner on 24-h glycemic control in individuals with type 2 diabetes using the standardized multi-site Exercise-Physical Activity and Diabetes Glucose Monitoring (E-PAraDiGM) Protocol.

METHODS

Eighty participants were studied under two conditions (exercise vs. non-exercise control) separated by 72 h in a randomized crossover design. Each condition lasted 2 days during which standardized meals were provided. Exercise consisted of 50 min of treadmill walking at 5.0 km/h before the evening meal, while control involved 50 min of sitting. The primary outcome measure was mean glucose during the 24-h period following exercise (or sitting) measured by continuous glucose monitoring.

RESULTS

Of the 80 participants who were initially randomized, 73 completed both exercise and control. Sixty-three participants [29 males, 34 females; age = 64 ± 8 years, body mass index = 30.5 ± 6.5 kg/m² and HbA1c = 51 ± 8 mmol/mol (6.8 ± 0.7%), mean ± SD] complied with the standardized diets and had complete continuous glucose monitoring data. Exercise did not affect mean 24-h glucose compared to control (0.03 mmol/L; 95% CI - 0.17, 0.22, P = 0.778) but individual differences between conditions ranged from - 2.8 to +1.8 mmol/L. Exercise did not affect fasting glucose, postprandial glucose or glucose variability. Glucose concentrations measured by continuous glucose monitoring were reduced during the 50 min of walking in exercise compared to sitting in control (- 1.56 mmol/L; 95% CI - 2.18, - 0.95, p < 0.001).

CONCLUSION

Contrary to previous acute exercise studies, 50 min of walking before dinner in the E-PAraDiGM protocol did not affect 24-h glucose profiles. However, highly heterogeneous responses to exercise were observed.

TRIAL REGISTRATION

NCT02834689.

Effects of Moderate Cycling Exercise on Blood Glucose Regulation Following Successful Clinical Islet Transplantation

CONTEXT

Islet transplantation is effective in preventing hypoglycemia in patients with type 1 diabetes (T1D). However, it is unknown whether transplanted islets regulate plasma glucose concentrations appropriately during and after exercise in human islet transplant recipient (ITxs).

OBJECTIVE

To determine the effect of exercise on plasma glucose, insulin, and glucagon concentrations in ITxs compared with control subjects (CONs) without diabetes.

INTERVENTION

Participants completed two conditions in random order: 45 minutes of aerobic exercise (60% VO2peak) and 45 minutes of seated rest. Blood samples were drawn at baseline, immediately after exercise or rest, and every 15 minutes throughout a 60-minute recovery period. Postexercise (24 hours) interstitial glucose was monitored with continuous glucose monitoring (CGM).

RESULTS

Twenty-four participants (12 ITxs, 12 CONs) completed the protocol. Plasma glucose decreased more over time with exercise in ITxs compared with CONs [main effects of treatment (P = 0.019), time (P = 0.001), and group (P = 0.012)]. Plasma glucose was lower during exercise vs rest in ITxs but not CONs [treatment by group interaction (P = 0.028)]. Plasma glucose decreased more during exercise than during rest [treatment by time interaction (P = 0.001)]. One ITx and one CON experienced plasma glucose concentrations <3.5 mmol/L at the end of exercise, both of whom returned above that threshold within 15 minutes. Nocturnal CGM glucose <3.5 mmol/L was detected in two CONs but no ITxs.

CONCLUSION

Despite a greater plasma glucose decline during exercise in ITxs, hypoglycemia risk was similar during and after exercise in ITxs compared with CONs.

Vigorous Intervals and Hypoglycemia in Type 1 Diabetes: A Randomized Cross Over Trial

Adding vigorous-intensity intervals (VII) to moderate-intensity exercise prevents immediate declines in blood glucose in type 1 diabetes (T1D) however the intensity required to minimize post-exercise hypoglycemia is unknown. To examine this question, ten sedentary T1D individuals completed four treadmill exercise sessions: a control session of 45 minutes of walking at 45–55% of heart rate reserve (HRR) and three sessions consisting of 60 seconds (VII) at 70%, 80%, or 90% of HRR every 4 minutes during exercise at 45–55% of HRR. We used continuous glucose monitoring (CGM) to measure time ≤3.9 mmol/L, glucose variability, hypoglycemia frequency and area under the curve (AUC) for hypoglycemia and hyperglycemia for 12 hours post-exercise. We also examined growth hormone and cortisol responses during and following exercise. In the 12 hours post-exercise, the percentage of time ≤3.9 mmol/L, glucose variability, and AUC for hypoglycemia and hyperglycemia were similar across conditions. The frequency of hypoglycemic events was highest after the 90% intervals compared to the control arm (12 vs 3 events, p = 0.03). There was a trend towards elevated growth hormone with increasing exercise intensity but cortisol levels were similar across conditions. Adding VII to moderate intensity exercise may increase hypoglycemia risk at higher intensities.

Continuous Glucose Monitoring and Exercise in Type 1 Diabetes: Past, Present and Future

Prior to the widespread use of continuous glucose monitoring (CGM), knowledge of the effects of exercise in type 1 diabetes (T1D) was limited to the exercise period, with few studies having the budget or capacity to monitor participants overnight. Recently, CGM has become a staple of many exercise studies, allowing researchers to observe the otherwise elusive late post-exercise period. We performed a strategic search using PubMed and Academic Search Complete. Studies were included if they involved adults with T1D performing exercise or physical activity, had a sample size greater than 5, and involved the use of CGM. Upon completion of the search protocol, 26 articles were reviewed for inclusion. While outcomes have been variable, CGM use in exercise studies has allowed the assessment of post-exercise (especially nocturnal) trends for different exercise modalities in individuals with T1D. Sensor accuracy is currently considered adequate for exercise, which has been crucial to developing closed-loop and artificial pancreas systems. Until these systems are perfected, CGM continues to provide information about late post-exercise responses, to assist T1D patients in managing their glucose, and to be useful as a tool for teaching individuals with T1D about exercise.

Sex-related differences in fuel utilization and hormonal response to exercise: implications for individuals with type 1 diabetes

Sex-related differences in metabolic and neuroendocrine response to exercise in individuals without diabetes have been well established. Men and women differ in fuel selection during exercise, in which women rely to a greater extent on fat oxidation, whereas males rely mostly on carbohydrate oxidation for energy production. The difference in fuel selection appears to be mediated by sex-related differences in hormonal (including catecholamines, growth hormone, and estrogen) response to different types and intensities of exercise. In general, men exhibit an amplified counter-regulatory response to exercise, with elevated levels of catecholamines compared with women. However, women exhibit greater sensitivity to the lipolytic action of the catecholamines and deplete less of their glycogen stores than men during exercise, which suggests that women may experience a greater defense in blood glucose control after exercise than men. Conversely, little is known about sex-related differences in response to exercise in individuals with type 1 diabetes (T1D). A single study investigating sex-related differences in response to moderate aerobic exercise in individuals with T1D found sex-related differences in catecholamine response and fuel selection, but changes in blood glucose were not measured. To our knowledge, there are no studies investigating sex-related differences in blood glucose responses to different types and intensities of exercise in individuals with T1D. This review summarizes sex-related differences in exercise responses that could potentially impact blood glucose levels during exercise in individuals with T1D and highlights the need for further research.

Could Age, Sex and Physical Fitness Affect Blood Glucose Responses to Exercise in Type 1 Diabetes?

Closed-loop systems for patients with type 1 diabetes are progressing rapidly. Despite these advances, current systems may struggle in dealing with the acute stress of exercise. Algorithms to predict exercise-induced blood glucose changes in current systems are mostly derived from data involving relatively young, fit males. Little is known about the magnitude of confounding variables such as sex, age, and fitness level-underlying, uncontrollable factors that might influence blood glucose control during exercise. Sex-related differences in hormonal responses to physical exercise exist in studies involving individuals without diabetes, and result in altered fuel metabolism during exercise. Increasing age is associated with attenuated catecholamine responses and lower carbohydrate oxidation during activity. Furthermore, higher fitness levels can alter hormonal and fuel selection responses to exercise. Compounding the limited research on these factors in the metabolic response to exercise in type 1 diabetes is a limited understanding of how these variables affect blood glucose levels during different types, timing and intensities of activity in individuals with type 1 diabetes (T1D). Thus, there is currently insufficient information to model a closed-loop system that can predict them accurately and consistently prevent hypoglycemia. Further, studies involving both sexes, along with a range of ages and fitness levels, are needed to create a closed-loop system that will be more precise in regulating blood glucose during exercise in a wide variety of individuals with T1D.

Update on Management of Type 1 Diabetes and Type 2 Diabetes in Athletes

Optimal blood glucose management still remains the biggest challenge in active individuals with diabetes, particularly in insulin users, but some newer strategies have been introduced to maintain blood glucose control. Recent studies emphasize the importance of exercise intensity on glycemic balance. In individuals with type 1 and type 2 diabetes, both resistance and high-intensity intermittent exercise have been shown to confer beneficial physiological adaptations in training studies, while also showing acute glycemic benefits from single sessions. At the same time, anyone training at higher intensities also should take into consideration potential impairments in thermoregulation in individuals with diabetes, which can increase the risk of heat stress during exercise in hot and/or humid conditions. Recent studies of medication effects on electrolyte balance and hydration give a more complete picture of potential exercise risks for athletes with diabetes. Use of the latest diabetes-related technologies also may benefit the athlete with diabetes.

Does exercise pose a challenge to glucoregulation after clinical islet transplantation?

Islet transplantation (ITx) is effective in preventing severe hypoglycemia by restoring glucose-dependent insulin secretion in type 1 diabetes (T1D), but may not normalize glucose regulation. Studies suggest that physical activity plays a role in maintaining β-cell mass and function in individuals with type 2 diabetes and animal models of diabetes. This could indicate that physical activity plays a role in graft survival in ITx recipients. This review's objective is to assess current knowledge related to physical activity in ITx recipients. Responses to other challenges in blood glucose control (i.e., hypoglycemia) in human ITx recipients were examined to provide in-depth background information. To identify studies involving exercise in ITx recipients, a systematic search was performed using PubMed, Medline, and Embase, which revealed 277 English language publications. Publications were excluded if they did not involve ITx recipients; did not involve physical activity or hypoglycemia; or did not report on glucose, insulin, or counterregulatory hormones. During induced hypoglycemia, studies indicate normal suppression of insulin in ITx individuals compared with healthy non-T1D controls. Studies involving exercise in ITx animals have conflicting results, with time since transplantation and transplantation site (spleen, liver, kidney, peritoneal cavity) as possible confounders. No study examining blood glucose responses to physical activity in human ITx recipients was identified. A small number of induced-hypoglycemia studies in humans, and exercise studies in animals, would suggest that glucoregulation is greatly improved yet is still imperfect in this population and that ITx does not fully restore counterregulatory responses to challenges in blood glucose homeostasis.

Resistance exercise in type 1 diabetes

It is relatively well known that moderate-intensity aerobic exercise increases the risk of hypoglycemia in individuals with type 1 diabetes. Conversely, brief high-intensity (anaerobic) activity can cause post-exercise hyperglycemia. Recent evidence has indicated that including small amounts of anaerobic activity, either in the form of short sprints or as resistance exercise (weight lifting), during aerobic exercise sessions may decrease the drop in blood glucose levels associated with moderate-intensity aerobic exercise. This review discusses the recent developments in the area of exercise and type 1 diabetes, with a particular focus on the effects of resistance exercise. Practical exercise recommendations, as well as suggestions for the future direction of research in this area, are also provided.

Resistance Exercise in Already-Active Diabetic Individuals (READI): study rationale, design and methods for a randomized controlled trial of resistance and aerobic exercise in type 1 diabetes

The Resistance Exercise in Already Active Diabetic Individuals (READI) trial aimed to examine whether adding a 6-month resistance training program would improve glycemic control (as reflected in reduced HbA₁c) in individuals with type 1 diabetes who were already engaged in aerobic exercise compared to aerobic training alone. After a 5-week run-in period including optimization of diabetes care and low-intensity exercise, 131 physically active adults with type 1 diabetes were randomized to two groups for 22weeks: resistance training three times weekly, or waiting-list control. Both groups maintained the same volume, duration and intensity of aerobic exercise throughout the study as they did at baseline. HbA₁c, body composition, frequency of hypoglycemia, lipids, blood pressure, apolipoproteins B and A-1 (ApoB and ApoA1), the ApoB-ApoA1 ratio, urinary albumin excretion, serum C-reactive protein, free fatty acids, total daily insulin dose, health-related quality of life, cardiorespiratory fitness and musculoskeletal fitness were recorded at baseline, 3 (for some variables), and 6 months. To our knowledge, READI is the only trial to date assessing the incremental health-related impact of adding resistance training for individuals with type 1 diabetes who are already aerobically active. Few exercise trials have been completed in this population, and even fewer have assessed resistance exercise. With recent improvements in the quality of diabetes care, the READI study will provide conclusive evidence to support or refute a major clinically relevant effect of exercise type in the recommendations for physical activity in patients with type 1 diabetes.

Exercise strategies for hypoglycemia prevention in individuals with type 1 diabetes

IN BRIEF Fear of hypoglycemia is one of the main barriers to physical activity for individuals with type 1 diabetes. Recent studies indicate that anaerobic forms of exercise (i.e., resistance exercise/weight lifting, sprints, and high-intensity intervals) can attenuate exercise-related declines in blood glucose both during and after exercise in young, healthy adults with type 1 diabetes. These responses might vary based on age, sex, and fitness level and in the general safety of relying on them to prevent hypoglycemia.

The "ups" and "downs" of a bike race in people with type 1 diabetes: dramatic differences in strategies and blood glucose responses in the Paris-to-Ancaster Spring Classic

OBJECTIVE

Recommendations for insulin adjustments and carbohydrate intake exist for individuals with type 1 diabetes who are undertaking moderate exercise. Very few guidelines exist for athletes with type 1 diabetes who are competing in events of higher intensity or longer duration. This observational study reports the strategies adopted by 6 habitually active men with type 1 diabetes (glycated hemoglobin = 8.3%±2.0%) undertaking a relatively intense endurance cycling event.

METHODS

Participants wore continuous glucose monitoring (CGM) sensors for 24 hours before competition, while racing and overnight postrace. They were asked to eat their regular meals and snacks and make their usual insulin adjustments before, during and after competition. All food intake and insulin adjustments were recorded in detail.

RESULTS

Participants used a variety of adjustments for exercise. Of 6 participants, 4 decreased their insulin dosages and all participants consumed carbohydrates during the race (mean = 87±57 g). In spite of these strategies, 3 of the 6 participants experienced mild to moderate hypoglycemia (not requiring assistance) during the event. Hyperglycemia was seen in all participants 3 hours postexercise. There were no incidents of nocturnal hypoglycemia.

CONCLUSIONS

Individuals with type 1 diabetes can compete in intensive long-distance athletic events using a variety of nutrition- and insulin-adjustment strategies. In addition to finely tuned insulin adjustments and increased carbohydrate intake, vigilance will always be required to maintain some semblance of glycemic control during events of extended duration.

A systematic review and meta-analysis of exercise interventions in adults with type 1 diabetes

AIMS

Conflicting evidence exists regarding the benefits of physical activity for long-term blood glucose control in adults with type 1 diabetes (T1D). The object of this systematic review was to determine the effects of physical activity on long-term blood glucose control in T1D adults.

METHODS

PubMed/Medline, Embase, CENTRAL, SPORTdiscus, Global Health and ICTRP were searched up to October 2013 for randomized trials of aerobic or resistance exercise training in T1D adults. Exercises had to be performed at least twice weekly for a minimum of two months. The primary outcome was glycated hemoglobin (HbA1c). Secondary outcomes included cardiorespiratory fitness and insulin dose.

RESULTS

Six randomized trials were identified (323 adults); sample sizes ranged from n=6 to n=148 participants receiving the intervention. Five trials had an unknown risk of bias; one trial was deemed to be at high risk of bias. Exercise frequency varied from twice weekly to daily, with intensities (50-90% VO2peak), and session durations (20-120 min) varying widely. Four trials reported HbA1c, which decreased with exercise training (mean difference [MD] -0.78% (-9 mmol/mol), 95% CI -1.14 (-13 mmol/mol) to -0.41 (-5 mmol/mol); p<0.0001; I(2) 0%) compared with controls. Exercise training improved cardiorespiratory fitness by 3.45 ml/kg/min (95% CI 0.59 to 6.31, p=0.02, I(2) 0%) compared with controls. One trial reported an effect on insulin dose (MD -0.4U/kg, 95% CI -0.53 to -0.27, p<0.00001) compared to controls.

CONCLUSION

There are currently insufficient well-designed studies to ascertain the true effect of exercise training on HbA1c in individuals with T1D, but current results are promising.

Whole-body heat loss during exercise in the heat is not impaired in type 1 diabetes

PURPOSE

The objective of this study is to determine whether individuals with type 1 diabetes exhibit impairments in local and whole-body heat loss responses that could affect core temperature regulation during exercise in the heat compared with matched, nondiabetic individuals.

METHODS

Twelve otherwise healthy individuals with type 1 diabetes (HbA1c = 7.7% ± 0.3%) and 12 controls matched for age, sex, body surface area, and physical fitness cycled continuously for 60 min at a set rate of metabolic heat production (approximately 400 W) in a whole-body direct calorimeter (35°C and 20% relative humidity). Local sweat rate (ventilated capsule) was measured on the back and skin blood flow (laser Doppler velocimetry) on the forearm. Core (rectal and esophageal) and mean skin temperatures and heart rate were measured continuously. Whole-body heat exchange and change in body heat content were measured using simultaneous direct whole-body and indirect calorimetry.

RESULTS

The change (mean ± SE) in body heat content was similar between groups during exercise (diabetes, 409 ± 27 kJ; control, 386 ± 33 kJ; P = 0.584) and recovery (diabetes, -115 ± 16 kJ; control, -93 ± 24 kJ; P = 0.457). Local heat loss responses of sweating (P = 0.783) and skin blood flow (P = 0.078) as well as rectal temperature (diabetes, 37.87°C ± 0.10°C; control, 37.85°C; ± 0.13°C; P = 0.977) and heart rate (diabetes, 130 ± 9 beats·min, vs control, 126 ± 8 beats·min, P = 0.326) were comparable at the end of the exercise period.

CONCLUSION

During light-to-moderate-intensity exercise performed under conditions permitting full sweat evaporation, otherwise healthy type 1 diabetic individuals did not show impaired heat loss responses during heat exposure when compared with matched individuals without diabetes.

Performing resistance exercise before versus after aerobic exercise influences growth hormone secretion in type 1 diabetes

We compared growth hormone (GH) and plasma glucose (PG) levels in type 1 diabetic individuals performing aerobic before resistance exercise (AR) to when resistance exercise was performed first (RA). In AR, GH secretion declined in late exercise while it rose throughout exercise in RA, resulting in higher GH in RA versus AR at exercise completion. Higher GH during RA may support PG by increasing hepatic glucose production and lipid mobilization.

Do heat events pose a greater health risk for individuals with type 2 diabetes?

Chronic medical conditions such as type 2 diabetes may alter the body's normal response to heat. Evidence suggests that the local heat loss response of skin blood flow (SkBF) is affected by diabetes-related impairments in both endothelium-dependent and non-endothelium-dependent mechanisms, resulting in lower elevations in SkBF in response to a heat or pharmacological stimulus. Thermoregulatory sweating may also be diminished by type 2 diabetes, impairing the body's ability to transfer heat from its core to the environment. Diabetes-associated co-morbidities and the medications (particularly those affecting fluid balance) required to treat these conditions may exacerbate the risk of heat-related illness by decreasing SkBF and sweating further. Unfortunately, the majority of studies measure local heat loss responses in the hands and feet and lack measures of core temperature. Therefore, the impact of these impairments on whole-body heat loss remains unknown. This review addresses heat-related vulnerability in individuals with type 2 diabetes by examining the literature related to heat loss responses in this population. Type 2 diabetes, its associated co-morbidities, and the medications required in their treatment may cause dehydration, lower SkBF, and reduced sweating, which could consequently impair thermoregulation. This effect is most evident in individuals with poor blood glucose control. Although type 2 diabetes can be associated with impairments in SkBF and sweating, more physically active individuals requiring fewer medications and having good blood glucose control may be able to tolerate heat as well as those of similar age and body composition.

Is whole-body thermoregulatory function impaired in type 1 diabetes mellitus?

During periods of extreme heat individuals with diabetes have greater rates of heat-related morbidity and mortality compared to their non-diabetic counterparts. The reason for this discrepancy is currently unknown. Furthermore, there is a lack of information about whether or not individuals with type 1 diabetes are at a thermoregulatory disadvantage during strenuous physical activity especially when performed in the heat.

PURPOSE

This review discusses the current literature pertaining to thermoregulatory responses in individuals with type 1 diabetes.

METHODS

We included 14 reviews and 95 original research articles identified by searches of PubMed and Google Scholar and deemed relevant to our subject by three independent readers.

RESULTS

Individuals with poorly controlled type 1 diabetes may have impaired heat sensation, and a reduced capacity to dissipate heat due to lower skin blood flow and sweating responses and a greater tendency towards dehydration compared to individuals without diabetes. Impairments may be attenuated or absent in those with good blood glucose control. We found no published studies examining thermoregulatory responses to physical activity in the heat in individuals with type 1 diabetes.

CONCLUSIONS

Type 1 diabetes may cause impairments in heat loss resulting in a greater level of thermal strain. Advancement in our understanding about the effects of type 1 diabetes on the heat stress response, especially during different challenges to human heat balance associated with changes in both environmental heat load and metabolic heat production (physical activity), will help us to determine where the risk of heat-illness/injury actually exists.

Resistance versus aerobic exercise: acute effects on glycemia in type 1 diabetes

OBJECTIVE

In type 1 diabetes, small studies have found that resistance exercise (weight lifting) reduces HbA(1c). In the current study, we examined the acute impacts of resistance exercise on glycemia during exercise and in the subsequent 24 h compared with aerobic exercise and no exercise.

RESEARCH DESIGN AND METHODS

Twelve physically active individuals with type 1 diabetes (HbA(1c) 7.1 ± 1.0%) performed 45 min of resistance exercise (three sets of seven exercises at eight repetitions maximum), 45 min of aerobic exercise (running at 60% of Vo(2max)), or no exercise on separate days. Plasma glucose was measured during and for 60 min after exercise. Interstitial glucose was measured by continuous glucose monitoring 24 h before, during, and 24 h after exercise.

RESULTS

Treatment-by-time interactions (P < 0.001) were found for changes in plasma glucose during and after exercise. Plasma glucose decreased from 8.4 ± 2.7 to 6.8 ± 2.3 mmol/L (P = 0.008) during resistance exercise and from 9.2 ± 3.4 to 5.8 ± 2.0 mmol/L (P = 0.001) during aerobic exercise. No significant changes were seen during the no-exercise control session. During recovery, glucose levels did not change significantly after resistance exercise but increased by 2.2 ± 0.6 mmol/L (P = 0.023) after aerobic exercise. Mean interstitial glucose from 4.5 to 6.0 h postexercise was significantly lower after resistance exercise versus aerobic exercise.

CONCLUSIONS

Resistance exercise causes less initial decline in blood glucose during the activity but is associated with more prolonged reductions in postexercise glycemia than aerobic exercise. This might account for HbA(1c) reductions found in studies of resistance exercise but not aerobic exercise in type 1 diabetes.

Point accuracy of interstitial continuous glucose monitoring during exercise in type 1 diabetes

BACKGROUND

Previous studies of aerobic exercise have found lower sensor accuracy during exercise. Whether or not resistance exercise would also be associated with lower sensor accuracy has not yet been examined. This study sought to investigate the accuracy of continuous glucose monitoring sensor values at rest, during aerobic exercise, and during resistance exercise.

SUBJECTS AND METHODS

Twelve individuals with type 1 diabetes performed 45 min of aerobic exercise, resistance exercise, or no exercise/rest followed by 60 min of recovery while monitored by continuous glucose monitoring systems.

RESULTS

Sensors underestimated plasma glucose to the greatest extent during rest (-1.29 ± 1.39 mmol/L, P<0.001) and resistance exercise (-0.71 ± 1.35 mmol/L, P<0.001) and least during aerobic exercise (-0.11 ± 1.71 mmol/L, P=0.416).

CONCLUSIONS

Optimal accuracy observed with aerobic exercise might arise from augmented blood flow better equilibrating plasma and interstitial fluid or from the combination of systematic sensor underestimation and sensor lag time.

Insulin pump therapy is associated with less post-exercise hyperglycemia than multiple daily injections: an observational study of physically active type 1 diabetes patients

BACKGROUND

Aerobic exercise typically decreases blood glucose levels in individuals with type 1 diabetes. It is currently unknown if glucose responses to exercise and recovery differ between patients on multiple daily insulin injections (MDI) and continuous subcutaneous insulin infusion (CSII).

SUBJECTS AND METHODS

Nineteen (16 male, three female) physically active individuals with type 1 diabetes took part in this observational study. Interstitial glucose levels (blinded) were compared during 45 min of standardized aerobic exercise (cycling or running at 60% peak aerobic capacity) and during 6 h of postexercise recovery between individuals using MDI (n=9) and CSII (n=10) therapy.

RESULTS

Both MDI and CSII groups had similar reductions in glucose levels during exercise, but responses in early and late recovery differed (group × time interaction, P<0.01). Participants using MDI had greater increases in glucose throughout recovery compared with individuals with CSII. Two-thirds of the MDI patients experienced late-onset post-exercise hyperglycemia (blood glucose >12 mmol/L) compared with only 1/10(th) of the CSII patients (P<0.01).

CONCLUSIONS

Among individuals performing regular moderate-to-heavy intensity aerobic exercise, use of CSII helped to limit post-exercise hyperglycemia compared with MDI therapy and is not associated with increased risk for post-exercise late-onset hypoglycemia.