Carbohydrate Ingestion Increases Interstitial Glucose and Mitigates Neuromuscular Fatigue During Single-Leg Knee Extensions.

INTRODUCTION: We aimed to investigate the neuromuscular contributions to enhanced fatigue resistance with carbohydrate ingestion, and to identify whether fatigue is associated with changes in interstitial glucose levels assessed using a continuous glucose monitor (CGM). METHODS: Twelve healthy participants (6 males, 6 females) performed isokinetic single-leg knee extensions (90°/s) at 20% of the maximal voluntary contraction (MVC) torque until MVC torque reached 60% of its initial value (i.e, task failure). Central and peripheral fatigue were evaluated every 15 min during the fatigue task using the interpolated twitch technique (ITT), and electrically evoked torque. Using a single-blinded cross-over design, participants ingested carbohydrates (CHO) (85 g sucrose/h), or a placebo (PLA), at regular intervals during the fatigue task. Minute-by-minute interstitial glucose levels measured via CGM, and whole blood glucose readings were obtained intermittently during the fatiguing task. RESULTS: CHO ingestion increased time to task failure over PLA (113 ± 69 vs. 81 ± 49 min; mean ± SD; p < 0.001) and was associated with higher glycemia as measured by CGM (106 ± 18 vs 88 ± 10 mg/dL, p < 0.001) and whole blood glucose sampling (104 ± 17 vs 89 ± 10 mg/dL, p < 0.001). When assessing the values in the CHO condition at a similar timepoint to those at task failure in the PLA condition (i.e., ~81 min), MVC torque, % voluntary activation, and 10 Hz torque were all better preserved in the CHO vs. PLA condition (p < 0.05). CONCLUSIONS: Exogenous CHO intake mitigates neuromuscular fatigue at both the central and peripheral levels by raising glucose concentrations rather than by preventing hypoglycemia.

Associations between daily step count classifications and continuous glucose monitoring metrics in adults with type 1 diabetes: analysis of the Type 1 Diabetes Exercise Initiative (T1DEXI) cohort.

AIMS/HYPOTHESIS: Adults with type 1 diabetes should perform daily physical activity to help maintain health and fitness, but the influence of daily step counts on continuous glucose monitoring (CGM) metrics are unclear. This analysis used the Type 1 Diabetes Exercise Initiative (T1DEXI) dataset to investigate the effect of daily step count on CGM-based metrics. METHODS: In a 4 week free-living observational study of adults with type 1 diabetes, with available CGM and step count data, we categorised participants into three groups-below (<7000), meeting (7000-10,000) or exceeding (>10,000) the daily step count goal-to determine if step count category influenced CGM metrics, including per cent time in range (TIR: 3.9-10.0 mmol/l), time below range (TBR: <3.9 mmol/l) and time above range (TAR: >10.0 mmol/l). RESULTS: A total of 464 adults with type 1 diabetes (mean±SD age 37±14 years; HbA1c 48.8±8.1 mmol/mol [6.6±0.7%]; 73% female; 45% hybrid closed-loop system, 38% standard insulin pump, 17% multiple daily insulin injections) were included in the study. Between-participant analyses showed that individuals who exceeded the mean daily step count goal over the 4 week period had a similar TIR (75±14%) to those meeting (74±14%) or below (75±16%) the step count goal (p>0.05). In the within-participant comparisons, TIR was higher on days when the step count goal was exceeded or met (both 75±15%) than on days below the step count goal (73±16%; both p<0.001). The TBR was also higher when individuals exceeded the step count goals (3.1%±3.2%) than on days when they met or were below step count goals (difference in means -0.3% [p=0.006] and -0.4% [p=0.001], respectively). The total daily insulin dose was lower on days when step count goals were exceeded (0.52±0.18 U/kg; p<0.001) or were met (0.53±0.18 U/kg; p<0.001) than on days when step counts were below the current recommendation (0.55±0.18 U/kg). Step count had a larger effect on CGM-based metrics in participants with a baseline HbA1c ≥53 mmol/mol (≥7.0%). CONCLUSIONS/INTERPRETATION: Our results suggest that, compared with days with low step counts, days with higher step counts are associated with slight increases in both TIR and TBR, along with small reductions in total daily insulin requirements, in adults living with type 1 diabetes. DATA AVAILABILITY: The data that support the findings reported here are available on the Vivli Platform (ID: T1-DEXI; https://doi.org/10.25934/PR00008428 ).

Is There an Optimal Time of Day for Exercise? A Commentary on When to Exercise for People Living With Type 1 or Type 2 Diabetes.

Exercise is a cornerstone of diabetes self-care because of its association with many health benefits. Several studies that have explored the best time of day to exercise to inform clinical recommendations have yielded mixed results. For example, for people with prediabetes or type 2 diabetes, there may be benefits to timing exercise to occur after meals, whereas people with type 1 diabetes may benefit from performing exercise earlier in the day. One common thread is the health benefits of consistent exercise, suggesting that the issue of exercise timing may be secondary to the goal of helping people with diabetes establish an exercise routine that best fits their life.

Decreased Diastolic Blood Pressure and Average Grip Strength in Adults With Type 1 Diabetes Compared With Controls: An Analysis of Data From the Canadian Longitudinal Study on Aging.

OBJECTIVES: Our aim in this study was to determine whether aging individuals with type 1 diabetes (T1D) have differences in cardiovascular health, assessed by blood pressure, and skeletal muscle function, assessed by grip strength, compared with matched nondiabetic controls (CON). METHODS: This investigation was a retrospective cohort analysis using baseline and 3-year follow-up data from the Canadian Longitudinal Study on Aging. Bivariate and multivariate regression analyses were used to examine the association between sociodemographic, health, behavioural and T1D-specific variables on blood pressure and grip strength in T1D and CON groups. Generalized estimating equations were used to model the average population changes in blood pressure and grip strength from baseline to follow up. RESULTS: The sample included 126 individuals (63 T1D and 63 CON). Systolic blood pressure was not significantly different between groups at baseline or follow up (p>0.05). However, compared with CON, diastolic blood pressure was significantly lower at both time-points in the T1D group (p<0.001). Grip strength was consistently lower among persons with T1D (p=0.03). In the multivariate regression model, body mass index, age and sex were significantly associated with diastolic blood pressure and grip strength in both groups. In the T1D group, disease duration accounted for a large proportion of the variance in diastolic blood pressure and grip strength (17% and 9%, respectively). The rate of decline in diastolic blood pressure and grip strength did not differ between groups (p>0.05). CONCLUSIONS: Diastolic blood pressure and grip strength appear to be consistently lower and differentially regulated in individuals with T1D vs CON. Aging individuals with T1D may be at risk of premature morbidity and mortality.

Normal to enhanced intrinsic mitochondrial respiration in skeletal muscle of middle- to older-aged women and men with uncomplicated type 1 diabetes.

AIMS/HYPOTHESIS: This study interrogated mitochondrial respiratory function and content in skeletal muscle biopsies of healthy adults between 30 and 72 years old with and without uncomplicated type 1 diabetes. METHODS: Participants (12 women/nine men) with type 1 diabetes (48 ± 11 years of age), without overt complications, were matched for age, sex, BMI and level of physical activity to participants without diabetes (control participants) (49 ± 12 years of age). Participants underwent a Bergström biopsy of the vastus lateralis to assess mitochondrial respiratory function using high-resolution respirometry and citrate synthase activity. Electron microscopy was used to quantify mitochondrial content and cristae (pixel) density. RESULTS: Mean mitochondrial area density was 27% lower (p = 0.006) in participants with type 1 diabetes compared with control participants. This was largely due to smaller mitochondrial fragments in women with type 1 diabetes (-18%, p = 0.057), as opposed to a decrease in the total number of mitochondrial fragments in men with diabetes (-28%, p = 0.130). Mitochondrial respiratory measures, whether estimated per milligram of tissue (i.e. mass-specific) or normalised to area density (i.e. intrinsic mitochondrial function), differed between cohorts, and demonstrated sexual dimorphism. Mass-specific mitochondrial oxidative phosphorylation (OXPHOS) capacity with the substrates for complex I and complex II (CI + II) was significantly lower (-24%, p = 0.033) in women with type 1 diabetes compared with control participants, whereas mass-specific OXPHOS capacities with substrates for complex I only (pyruvate [CI pyr] or glutamate [CI glu]) or complex II only (succinate [CII succ]) were not different (p > 0.404). No statistical differences (p > 0.397) were found in mass-specific OXPHOS capacity in men with type 1 diabetes compared with control participants despite a 42% non-significant increase in CI glu OXPHOS capacity (p = 0.218). In contrast, intrinsic CI + II OXPHOS capacity was not different in women with type 1 diabetes (+5%, p = 0.378), whereas in men with type 1 diabetes it was 25% higher (p = 0.163) compared with control participants. Men with type 1 diabetes also demonstrated higher intrinsic OXPHOS capacity for CI pyr (+50%, p = 0.159), CI glu (+88%, p = 0.033) and CII succ (+28%, p = 0.123), as well as higher intrinsic respiratory rates with low (more physiological) concentrations of either ADP, pyruvate, glutamate or succinate (p < 0.012). Women with type 1 diabetes had higher (p < 0.003) intrinsic respiratory rates with low concentrations of succinate only. Calculated aerobic fitness (Physical Working Capacity Test [PWC130]) showed a strong relationship with mitochondrial respiratory function and content in the type 1 diabetes cohort. CONCLUSIONS/INTERPRETATION: In middle- to older-aged adults with uncomplicated type 1 diabetes, we conclude that skeletal muscle mitochondria differentially adapt to type 1 diabetes and demonstrate sexual dimorphism. Importantly, these cellular alterations were significantly associated with our metric of aerobic fitness (PWC130) and preceded notable impairments in skeletal mass and strength.