Introduction

Physical activity and exercise are fundamental components of type 1 diabetes (T1D) management and are important for overall health. Physical activity, defined as “any voluntary bodily movement produced by skeletal muscles that results in an increase in energy expenditure,” [1, 2] plays an important role in managing T1D [3, 4]. Large-scale studies have shown that physical activity improves cardiovascular health 5, reduces the risk of diabetes-related complications [5-7], and even lowers the risk of early death [8-10]. 

Exercise is a subset of physical activity that is “planned, structured, and repetitive, aiming to improve or maintain physical fitness and health” [1, 2]. For people with T1D, exercise can help manage blood glucose levels, boost cardiovascular health, and improve insulin sensitivity. Exercise isn't just about movement – it’s about strategic and deliberate action to enhance your health.

In this chapter, we will discuss the many benefits of physical activity and exercise for people with T1D, and in addition, outline why reducing sitting time and extended periods of sedentary behaviour is important.

 

Metabolic Benefits of Physical Activity for People with T1D

Physical activity offers many benefits to people with T1D when managing glucose levels. Active individuals are more likely to hit their target HbA1c levels [5, 11-13] because muscle contractions during physical activity enhance insulin sensitivity and help with insulin-independent glucose disposal [14-16]. Therefore, physical activity is a powerful non-pharmacological tool for managing blood glucose levels. 

The T1DEXI study, which involved nearly 500 individuals with T1D in real-world settings, found that on days with higher step counts, people experienced higher time in range (TIR) but also more time below range (TBR) [17]. Another study by Riddell et al. showed that mean glucose levels reduced and TIR increased on active days compared to sedentary days over four weeks [18]. Interestingly, the type of exercise the participants did during these observations didn’t matter—whether it was aerobic, high-intensity interval training, or resistance exercise, the TIR improvements were similar [18]. However, it was also found that while, on average, exercise boosted daily TIR by 6%, it slightly increased the 24-hour time in hypoglycaemia [19].

Looking at long-term glucose management (measured using HbA1c), a 2012 meta-analysis concluded that regular aerobic endurance training can improve HbA1c levels in individuals with T1D [20]. However, we still need more research to determine whether other types of exercise, such as resistance exercise, can also improve HbA1c levels in people with T1D [21].

Physical activity has consistently been shown to lower daily insulin dose requirements [3]. The T1DEXI study also showed this, with higher step counts linked to small reductions in total daily insulin doses over four weeks in adults with T1D [17].

There is clear evidence that accumulated daily physical activity is associated with greater insulin sensitivity in healthy adults without diabetes [22] and that several types of exercise enhance insulin sensitivity in adults with type 2 diabetes [23]. However, only a few studies have investigated these effects in people with T1D. One study showed promising results after a 12-week exercise program in nine adolescents with T1D, demonstrating a 23% improvement in insulin sensitivity [24]. A 4-week high-intensity interval training (HIIT) program in individuals with T1D and overweight led to reductions in total daily insulin doses [25]. Lee et al. investigated the effects of a 12-week HIIT program in 15 individuals with overweight or obesity and T1D, finding that HbA1c levels decreased in participants who stuck to the program, but there were no changes in insulin doses, body mass index (BMI), waist circumference, or elasticity of the blood vessels from the heart (aortic stiffness) [26]. 

Although resistance exercise is part of the guidelines [13], it hasn’t been extensively researched in T1D [27, 28]. While one study found that a single session of strenuous resistance exercise did not change insulin sensitivity [29], long-term resistance training studies have not used gold-standard methodologies to explore its full potential. We need more research to explore how resistance training programs might influence insulin sensitivity in individuals with T1D. This is important due to the popularity of resistance training and its proven benefits for other areas of health, such as greater muscle mass and quality.

Lastly, let's consider the impact of daily physical activity on body composition. This is crucial in the context of insulin resistance and the development of what has sometimes been termed ‘double diabetes’ — a combination of T1D with insulin resistance and features of type 2 diabetes, which increases cardiovascular risk [30]. Although not extensively investigated in T1D, two small studies [11, 31] have shown positive effects of physical activity on BMI, waist circumference, and fat mass [11, 31]. Our research has shown that higher daily physical activity levels, lower sedentary behaviour, and greater exercise capacity are favourably associated with cardiovascular and metabolic health markers, such as elasticity of the blood vessels (arterial stiffness), body composition, long-term glycaemic control, daily insulin dosage, and estimated insulin sensitivity in adults with T1D [32].

 

Cardiovascular Health in T1D and the Power of Physical Activity

T1D is associated with an increased risk of cardiovascular disease, including heart disease and stroke. A comprehensive meta-analysis has shown that diabetes, regardless of type, doubles the risk for vascular disease [33], making diabetes an independent risk factor for atherosclerotic cardiovascular disease [34, 35].

Despite advances in diabetes care, people with T1D still face higher rates of cardiovascular issues and related deaths compared to those without diabetes [36, 37]. Heart disease remains the leading cause of health problems and mortality in people with T1D [38-40] despite the advancements in T1D care over the past two decades [37].

The good news is that physical activity and exercise can improve heart health. Data from the FinnDiane study showed that leisure-time physical activity, particularly high-frequency and high-intensity workouts, is linked to a lower risk of cardiovascular events [7]. More research is needed to investigate how exercise intensity affects heart health. Studies in children with T1D suggest that higher-intensity physical activity may positively impact blood vessel elasticity (arterial stiffness) [41, 42]. Future research should explore whether reduced arterial stiffness is (at least partly) responsible for the beneficial effects of physical activity on clinical cardiovascular endpoints [32]. If so, this would provide even more substantial reasons to encourage physical activity in people with T1D. 

Long-term exercise studies for cardiovascular health in T1D are scarce. However, Scott and colleagues reported a 12% reduction in aortic artery stiffness after six weeks of HIIT [43], suggesting exercise is a promising strategy for reducing arterial stiffness. 

By incorporating regular physical activity and structured exercise programmes into their routines, individuals with T1D can potentially reduce their cardiovascular risk. This may also improve their quality of life and life expectancy.

 

Why Cutting Down on Sedentary Time Matters

Managing T1D isn’t just about increasing physical activity. It’s also important to think about reducing sedentary behaviour to improve metabolic and cardiovascular health. While research in this area is limited [44], some studies suggest that prolonged sitting can negatively affect glucose levels in young people with T1D [12, 45]. 

Recent meta-analyses show that youth with T1D tend to be more sedentary and less likely to meet physical activity recommendations than those without diabetes [45, 46]. This highlights the need to investigate the potential adverse effects of prolonged sedentary behaviour on cardiovascular and metabolic health in people with T1D, regardless of their physical activity levels. 

Breaking up sedentary time with short bouts of physical activity might offer substantial health benefits. The recent ‘SIT-LESS’ randomised controlled trial demonstrated this potential by showing improved blood glucose levels after meals and over 48 hours in 32 adults with T1D when prolonged sitting was interrupted with frequent short bouts of light-intensity activity [47].

In conclusion, reducing sedentary behaviour and increasing physical activity should be a key focus in managing T1D to improve metabolic and cardiovascular health. More research is needed to fully understand the independent effects of sedentary behaviour on health outcomes in individuals with T1D.

 

Physical Activity and T1D: The Balancing Act

For many individuals with T1D, the fear of low glucose levels (hypoglycaemia) is a significant barrier to getting physically active [11, 31, 48]. This fear is often linked to difficulties with glucose management and the impact on overall well-being [31], making it challenging to incorporate physical activity into daily life.

Acute exercise-induced hypoglycaemia, late-onset hypoglycaemia, and increased glycaemic variability in the hours following physical activity or exercise are all potential challenges. These issues can make physical activity and exercise seem daunting, especially for those who have had bad experiences. The risk of low and less stable blood glucose around exercise can discourage many people with T1D from being physically active on a regular basis.

To successfully incorporate physical activity into daily life, people with T1D must strike a delicate balance. They must carefully manage their insulin doses, carbohydrate intake, and the timing of their workouts to minimise the risk of hypoglycaemia and other adverse effects. This complex and often overwhelming task requires ongoing education, support, and personalised strategies to ensure safe and effective participation in physical activity. In the next chapter, we’ll dive deeper into why exercise is challenging from a physiological standpoint and provide strategies that can be implemented to help manage glucose levels during a variety of situations.

 

The Final Word

Physical activity and exercise are important aspects of living a healthy and fulfilling life, thanks to their metabolic and cardiovascular health benefits. However, people living with T1D face unique challenges associated with managing glucose levels around exercise, which can make it hard to stay active. It’s also important to consider the risks of physical inactivity and prolonged sitting, as these can add to cardiometabolic risks.