The adjustment of diet and insulin dose during long-term endurance exercise in type 1 (insulin-dependent) diabetic men

Exercise in adults with type 1 diabetes mellitus

Regular physical activity improves cardiometabolic and musculoskeletal health, helps with weight management, improves cognitive and psychosocial functioning, and is associated with reduced mortality related to cancer and diabetes mellitus. However, turnover rates of glucose in the blood increase dramatically during exercise, which often results in either hypoglycaemia or hyperglycaemia as well as increased glycaemic variability in individuals with type 1 diabetes mellitus (T1DM). A complex neuroendocrine response to an acute exercise session helps to maintain circulating levels of glucose in a fairly tight range in healthy individuals, while several abnormal physiological processes and limitations of insulin therapy limit the capacity of people with T1DM to exercise in a normoglycaemic state. Knowledge of the acute and chronic effects of exercise and regular physical activity is critical for the formulation of clinical strategies for the management of insulin and nutrition for active patients with T1DM. Emerging diabetes-related technologies, such as continuous glucose monitors, automated insulin delivery systems and the administration of solubilized glucagon, are demonstrating efficacy for preserving glucose homeostasis during and after exercise in this population of patients. This Review highlights the beneficial effects of regular exercise and details the complex endocrine and metabolic responses to different types of exercise for adults with T1DM. An overview of basic clinical strategies for the preservation of glucose homeostasis using emerging technologies is also provided.

Nutritional intake when cycling under racing and training conditions in professional male cyclists with type 1 diabetes

This study sought to detail and compare the in-ride nutritional practices of a group of professional cyclists with type 1 diabetes (T1D) under training and racing conditions. We observed seven male professional road cyclists with T1D (Age: 28 ± 4 years, HbA_1c: 6.4 ± 0.4% [46 ± 4 mmol.mol^-1], VO_2max: 73.9 ± 4.3 ml.kg ^-1.min^-1) during pre-season training and during a Union Cycliste Internationale multi-stage road cycling race (Tour of Slovenia). In-ride nutritional, interstitial glucose, and performance variables were quantified and compared between the two events.    The in-ride energy intake was similar between training and racing conditions     (p = 0.909), with carbohydrates being the major source of fuel in both events during exercise at a rate of 41.9 ± 6.8 g.h^-1 and 45.4 ± 15.5 g.h^-1 (p = 0.548), respectively. Protein consumption was higher during training (2.6 ± 0.6 g.h^-1) than race rides (1.9 ± 0.9 g.h^-1; p = 0.051).   A similar amount of time was spent within the euglycaemic range (≥70-≤180 mg.dL^-1): training 77.1 ± 32.8% vs racing 73.4 ± 3.9%; p = 0.818. These data provide new information on the in-ride nutritional intake in professional cyclists with T1D during different stages of the competitive season.

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.

Glycemic responses to strenuous training in male professional cyclists with type 1 diabetes: a prospective observational study

INTRODUCTION

This prospective observational study sought to establish the glycemic, physiological and dietary demands of strenuous exercise training as part of a 9-day performance camp in a professional cycling team with type 1 diabetes (T1D).

RESEARCH DESIGN AND METHODS

Sixteen male professional cyclists with T1D on multiple daily injections (age: 27±4 years; duration of T1D: 11±5 years; body mass index: 22±2 kg/m²; glycated hemoglobin: 7%±1% (50±6 mmol/mol); maximum rate of oxygen consumption: 73±4 mL/kg/min) performed road cycle sessions (50%-90% of the anaerobic threshold, duration 1-6 hours) over 9 consecutive days. Glycemic (Dexcom G6), nutrition and physiological data were collected throughout. Glycemic data were stratified into predefined glycemic ranges and mapped alongside exercise physiology and nutritional parameters, as well as split into daytime and night-time phases for comparative analysis. Data were assessed by means of analysis of variance and paired t-tests. A p value of ≤0.05 (two-tailed) was statistically significant.

RESULTS

Higher levels of antecedent hypoglycemia in the nocturnal hours were associated with greater time spent in next-day hypoglycemia overall (p=0.003) and during exercise (p=0.019). Occurrence of nocturnal hypoglycemia was associated with over three times the risk of next-day hypoglycemia (p<0.001) and a twofold risk of low glucose during cycling (p<0.001). Moreover, there was trend for a greater amount of time spent in mild hypoglycemia during the night compared with daytime hours (p=0.080).

CONCLUSION

The higher prevalence of nocturnal hypoglycemia was associated with an increased risk of next-day hypoglycemia, which extended to cycle training sessions. These data highlight the potential need for additional prebed carbohydrates and/or insulin dose reduction strategies around exercise training in professional cyclists with T1D.

TRIAL REGISTRATION NUMBER

DRKS00019923.

Carbohydrate Intake in the Context of Exercise in People with Type 1 Diabetes

Although the benefits of regular exercise on cardiovascular risk factors are well established for people with type 1 diabetes (T1D), glycemic control remains a challenge during exercise. Carbohydrate consumption to fuel the exercise bout and/or for hypoglycemia prevention is an important cornerstone to maintain performance and avoid hypoglycemia. The main strategies pertinent to carbohydrate supplementation in the context of exercise cover three aspects: the amount of carbohydrates ingested (i.e., quantity in relation to demands to fuel exercise and avoid hypoglycemia), the timing of the intake (before, during and after the exercise, as well as circadian factors), and the quality of the carbohydrates (encompassing differing carbohydrate types, as well as the context within a meal and the associated macronutrients). The aim of this review is to comprehensively summarize the literature on carbohydrate intake in the context of exercise in people with T1D.

Carbohydrate Loading Followed by High Carbohydrate Intake During Prolonged Physical Exercise and Its Impact on Glucose Control in Individuals With Diabetes Type 1-An Exploratory Study

Background: Prolonged physical exercise (PE) is a challenge in type 1 diabetes with an increased incidence of both hypoglycemia and hyperglycemia. Purpose: To evaluate the impact of two consecutive days of carbohydrate (CHO) loading, followed by high intermittent CHO-intake during prolonged PE, facilitated by a proactive use of Real-Time Continuous Glucose Monitoring (rtCGM), on glucose control in individuals with type 1 diabetes. Methods: Ten physically active individuals with type 1 diabetes were invited to participate in a 3-day long sports camp with the objective to evaluate CHO-loading and high intermittent CHO-intake during prolonged PE. 1.5 months later the same procedure was evaluated in relation to a 90 km cross-country skiing race (Vasaloppet). Participants were instructed to act proactively using rtCGM with predictive alerts to maintain sensor glucose values within target range, defined as 72-180 mg/dl (4-10 mmol/l). Results: Mean glucose values during CHO-loading were: day 1; 140.4 ± 45.0 mg/dl (7.8 ± 2.5 mmol/l) and day 2; 120.6 ± 41.4 mg/dl (6.7 ± 2.3 mmol/l). Mean sensor glucose at start of PE was 126.0 ± 25.2 mg/dl (7.0 ± 1.4 mmol/l) and throughout PE 127.8 ± 25.2 mg/dl (7.1 ± 1.4 mmol/l). Percentage of time spent in range (TIR) respective time spent in hypoglycemia was: CHO-loading 74.7/10.4% and during PE 94.3/0.6%. Conclusions: High intermittent CHO-intake during prolonged PE combined with proactive use of rtCGM is associated with good glycemic control during prolonged exercise in individuals with diabetes type 1. However, the time spent in hypoglycemia during the 2-days of CHO-loading was 10.4% and therefore a lower insulin dose might be suggested to reduce the time spent in hypoglycemia. Clinical Trial Registration: www.ClinicalTrials.gov, identifier NCT03722225.

Insulin Management Strategies for Exercise in Diabetes

There is no question that regular exercise can be beneficial and lead to improvements in overall cardiovascular health. However, for patients with diabetes, exercise can also lead to challenges in maintaining blood glucose balance, particularly if patients are prescribed insulin or certain oral hypoglycemic agents. Hypoglycemia is the most common adverse event associated with exercise and insulin therapy, and the fear of hypoglycemia is also the greatest barrier to exercise for many patients. With the appropriate insulin dose adjustments and, in some cases, carbohydrate supplementation, blood glucose levels can be better managed during exercise and in recovery. In general, insulin strategies that help facilitate weight loss with regular exercise and recommendations around exercise adjustments to prevent hypoglycemia and hyperglycemia are often not discussed with patients because the recommendations can be complex and may differ from one individual to the next. This is a review of the current published literature on insulin dose adjustments and starting-point strategies for patients with diabetes in preparation for safe exercise.

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Zusammenfassung. Wir berichten über einen 64-jährigen Marathonläufer mit bisher 990 erfolgreich gefinishten Marathons, der fälschlicherweise mit Diabetes mellitus Typ 2 diagnostiziert und therapiert wurde. Unter peroraler Therapie mit Metformin kam es zu keiner Reduktion der Blutzuckerwerte. Nach korrekter Diagnose und Therapie mit Insulin ist der Läufer wieder voll im Training, um bald seinen 1000. Marathon zu laufen. Für Sportler mit Diabetes mellitus Typ 1 ist es wichtig, den Blutzucker vor, während und nach Belastung zu messen und die Insulindosis individuell während eines Wettkampfs, wie etwa einem Marathon, zu reduzieren.

Evaluation of glucose control when a new strategy of increased carbohydrate supply is implemented during prolonged physical exercise in type 1 diabetes

PURPOSE

In healthy individuals, high carbohydrate intake is recommended during prolonged exercise for maximum performance. In type 1 diabetes (T1D), this would alter the insulin requirements. The aim of the study was to evaluate the safety of high glucose supplementation during prolonged exercise and the glucose control when a novel strategy of increased carbohydrate supply was implemented during prolonged exercise in T1D.

METHODS

Eight subjects with T1D participated in a sports camp including sessions of prolonged exercise and individualized feedback during three consecutive days. This was later followed by a 90 km cross-country skiing race. Large amounts of carbohydrates, 75 g/h, were supplied during exercise and the insulin requirements were registered. Glucose was measured before, during and after exercise aiming at euglycaemia, 4-8 mmol/L (72-144 mg/dL). During the race, continuous glucose monitoring (CGM) was used as an aspect of safety and to allow direct and individual adjustments.

RESULTS

Compared to ordinary carbohydrate supply during exercise, the high carbohydrate supplementation resulted in significantly increased insulin doses to maintain euglycaemia. During the cross-country skiing race, the participants succeeded to reach mean target glucose levels; 6.5 ± 1.9 mmol/L (117 ± 34 mg/dL) and 5.7 ± 1.5 mmol/L (103 ± 27 mg/dL) at the start and finish of the race, respectively. Episodes of documented hypoglycemia (<4 mmol/L/72 mg/dL) were rare. CGM was used for adjustments.

CONCLUSION

In this study, large carbohydrate supplementation in T1D individuals during prolonged aerobic exercise is safe and allows the subjects to maintain glycaemic control and indicates the feasibility of CGM under these conditions.

Telemedicine in US Army soldiers with type 1 diabetes

A retrospective study of a telemedicine clinic for active duty US Army soldiers with type 1 diabetes was conducted. Fifty-one consecutive patients (mean age 33.9 years) were enrolled into the clinic. All soldiers with known or newly diagnosed type 1 diabetes received three weekly office visits for intensive diabetes education. After this, all communication occurred via a messaging system consisting of texting, web-based download, and/or email to a diabetes management team. For urgent matters, 24/7 direct paging or telephone access was provided. Routine adjustments in insulin dosing were accomplished via email. Soldiers were followed for a mean of 17.1 months. Baseline, three-month, and end of study glycated hemoglobin (A1C) values were 9.8, 7.3, and 6.9, respectively. There were no significant differences in end of study A1C levels between patients with known vs. newly diagnosed type 1 diabetes, nor were there any differences between those patients who received insulin via pump therapy vs. multiple daily injections. Telemedicine was safe and effective in lowering A1C levels in US Army soldiers with type 1 diabetes.

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.

Diabetes in the competitive athlete

Diabetes mellitus is the most common group of metabolic diseases and is characterized by hyperglycemia resulting from defects in insulin secretion, insulin action, or both. Most patients with diabetes are type 2 (90%); the remaining patients have type 1 disease. Athletes with diabetes range from the athlete participating in various youth sports to the competitive Olympic athlete and present a significant challenge to themselves and the medical staff who care for them on a daily basis. Each sport and the type of exercise have their own effects on diabetes management with numerous factors that significantly affect glucose levels, including stress, level of hydration, the rate of glycogenolysis and gluconeogenesis, and the secretion of counter-regulatory hormones. This article provides a general overview of diabetes mellitus, the effects of exercise on glucose levels, and a detailed review of the potential complications encountered in the management of diabetes in the athlete.

Syncope

In brief Syncopal episodes are usually benign, but some causes can be life-threatening. The differential diagnosis is extensive and includes vasovagal reaction, decreased intravascular volume, metabolic disorders, cardiac disorders, medication use and abuse, Valsalva maneuver, and intracranial conditions. A detailed account of the event and a medical history direct the workup. Combining a thorough physical examination that emphasizes the cardiovascular and neurologic systems with selective laboratory tests and noninvasive diagnostic studies may reveal why the patient lost consciousness during his or her athletic activities.

Exercise in type 1 (insulin-dependent) diabetic patients treated with continuous subcutaneous insulin infusion. Prevention of exercise induced hypoglycaemia

The study was performed to investigate the effects of mild to moderate exercise on blood glucose levels, metabolite concentrations and responses of counterregulatory hormones in tightly controlled Type 1 (insulin-dependent) diabetic patients treated by continuous subcutaneous insulin infusion, and to quantify the measures necessary to prevent acute and late exercise-induced hypoglycaemia. Seven male patients started a 60 min exercise period 90 min after an insulin bolus and a standard breakfast; they were monitored during a post-exercise resting period of 5 h 30 min. Different basal and premeal insulin infusion rates were applied. (Near)normoglycaemia prevailed throughout the study during the control protocol when the subjects did not exercise and received their usual insulin dose. When they exercised without changing the insulin dose, four patients were forced to stop due to hypoglycaemia. This effect of exercise could be attenuated but not completely avoided if the basal infusion rate of insulin was discontinued during the exercise period. The pronounced increase in catecholamine and growth hormone concentrations during exercise were not sufficient to prevent hypoglycaemic reactions. Hypoglycaemia during exercise could only be prevented when the premeal insulin bolus was reduced by 50% in addition to the discontinuation of the basal insulin infusion during exercise. In order to reduce late hypoglycaemic reactions after exercise the best measure proved to be a reduction of the basal insulin infusion rate by 25% during post-exercise hours. Administration of only 50% of the basal insulin infusion rate during this time was associated with blood glucose levels being raised up to 8 mmol/l.(ABSTRACT TRUNCATED AT 250 WORDS)