Performing one or more verification VO2 workload(s) immediately after an incremental to maximal graded exercise test significantly increases the proportion of participants who meet the job-related aerobic fitness standard for structural firefighters.

PURPOSE: Graded exercise tests (GXTs) are commonly used to determine the maximal oxygen consumption (VO2max) of firefighter applicants. However, the criteria used to confirm VO2max are inconsistent and have a high inter-subject variability, which can compromise the reliability of the results. To address this, a verification phase (VP) after the GXT has been proposed as a "gold standard" protocol for measuring VO2max. METHODS: 4179 male and 283 female firefighter applicants completed a GXT and a VP to measure their VO2max. VO2peak values measured during the GXT were compared to the VO2 values measured during the VP. The proportion of participants who met the job-related aerobic fitness standard during the GXT was compared to that of those who met the required standard during the VP. RESULTS: For male and female participants that required the VP to attain their VO2max, the VO2peak values measured during the GXT (47.3 ± 6.0 and 41.6 ± 5.3 mL kg-1 min-1) were, respectively, 10.1% and 10.3% lower than the VO2 values measured during the VP (52.1 ± 6.7 and 45.9 ± 6.4 mL kg-1 min-1), p < 0.001. Furthermore, the proportion of male and female participants who met the job-related aerobic fitness standard significantly increased from the GXT to the VP by 11.6% and 29.9%, respectively, p < 0.001. CONCLUSION: These results strongly support the use of a VP to confirm VO2max, especially for females, older and overweight individuals. These findings are applicable to other physically demanding public safety occupations and when examining the efficacy of training interventions on VO2max.

No Disadvantage to Insulin Pump Off vs Pump On During Intermittent High-Intensity Exercise in Adults With Type 1 Diabetes.

OBJECTIVE: Evidence suggests that patients with type 1 diabetes (T1D) performing aerobic exercise with their insulin pump connected (pump on) vs pump disconnected (pump off) have an increased risk of hypoglycemia. It has not been examined whether this risk remains during high-intensity exercise. This study compared the effects of pump on (50% basal insulin at exercise onset) vs pump off (0% basal insulin at exercise onset) on glucose concentrations during intermittent high-intensity exercise in adults with T1D and on patients' own perspective of their glycemia. METHODS: Twelve adults with T1D using insulin pump therapy completed two 40-min intermittent high-intensity exercise bouts. Insulin adjustments included: 1) pump set to 50% of usual basal rate (pump on) or 2) pump suspended (pump off) during exercise, in random order. Blood glucose was recorded every 10 min during exercise and, after providing subjects with an initial reference glucose value before exercise, participants were asked to estimate their glucose during exercise. RESULTS: Glucose levels were higher in pump off (8.1±1.3 mmol/L) vs pump on (7.4±2.1 mmol/L) at exercise start (p<0.05), but were similar by the end of exercise (p=0.9). During exercise, hypoglycemia incidence did not differ between conditions (1 of 12 for both). However, the percentage of time in hypoglycemia at 12 h after exercise was 5±8% vs 1±2% for pump on vs pump off, respectively (p=0.3). Participants were better able to estimate their own glucose during pump on vs pump off (r2=0.46 vs r2=0.11). CONCLUSIONS: Pump on vs pump off at exercise onset showed no significant differences in blood glucose concentrations during 40 min of intermittent high-intensity exercise.

Reproducibility in the cardiometabolic responses to high-intensity interval exercise in adults with type 1 diabetes.

AIMS: Patients with type 1 diabetes (T1D) often report a rise in their blood glucose level following brief intense exercise. We sought to determine the reproducibility of the cardiometabolic responses to high-intensity interval training (HIIT). METHODS: Sixteen adults with T1D, using an optimized multiple daily injection with basal insulin glargine 300 U/mL (Gla-300), performed four fasted HIIT sessions over a 4-6-week period. Exercise consisted of high-intensity interval cycling and multimodal training over 25 min. RESULTS: Heart rate and rating of perceived exertion rose similarly in all sessions, as did lactate, catecholamine and growth hormone levels. Plasma glucose increased in response to HIIT in 62 of 64 visits (97%), with an overall increase of 3.7 ±â€¯1.6 mmol/L (Mean ±â€¯SD) (P < 0.001). In within-patient comparisons, the change in plasma glucose among the four HIIT sessions was significantly correlated with a composite correlation of 0.58 ([r2 = 0.34]; 95% CI 0.35-0.80; P < 0.01). CONCLUSIONS: Intersession observations of four separate HIIT sessions showed high intrasubject reproducibility in the cardiometabolic responses to exercise, including the rise in plasma glucose, when adults with T1D perform the activity in a fasted state.

A Pilot Study Validating Select Research-Grade and Consumer-Based Wearables Throughout a Range of Dynamic Exercise Intensities in Persons With and Without Type 1 Diabetes: A Novel Approach.

BACKGROUND: The increasing popularity of wearable technology necessitates the evaluation of their accuracy to differentiate physical activity (PA) intensities. These devices may play an integral role in customizing PA interventions for primary prevention and secondary management of chronic diseases. For example, in persons with type 1 diabetes (T1D), PA greatly affects glucose concentrations depending on the intensity, mode (ie, aerobic, anaerobic, mixed), and duration. This variability in glucose responses underscores the importance of implementing dependable wearable technology in emerging avenues such as artificial pancreas systems. METHODS: Participants completed three 40-minute, dynamic non-steady-state exercise sessions, while outfitted with multiple research (Fitmate, Metria, Bioharness) and consumer (Garmin, Fitbit) grade wearables. The data were extracted according to the devices' maximum sensitivity (eg, breath by breath, beat to beat, or minute time stamps) and averaged into minute-by-minute data. The variables of interest, heart rate (HR), breathing frequency, and energy expenditure (EE), were compared to validated criterion measures. RESULTS: Compared to deriving EE by laboratory indirect calorimetry standard, the Metria activity patch overestimates EE during light-to-moderate PA intensities (L-MI) and moderate-to-vigorous PA intensities (M-VI) (mean ± SD) (0.28 ± 1.62 kilocalories· minute-1, P < .001, 0.64 ± 1.65 kilocalories· minute-1, P < .001, respectively). The Metria underestimates EE during vigorous-to-maximal PA intensity (V-MI) (-1.78 ± 2.77 kilocalories · minute-1, P < .001). Similarly, compared to Polar HR monitor, the Bioharness underestimates HR at L-MI (-1 ± 8 bpm, P < .001) and M-VI (5 ± 11 bpm, P < .001), respectively. A significant difference in EE was observed for the Garmin device, compared to the Fitmate ( P < .001) during continuous L-MI activity. CONCLUSIONS: Overall, our study demonstrates that current research-grade wearable technologies operate within a ~10% error for both HR and EE during a wide range of dynamic exercise intensities. This level of accuracy for emerging research-grade instruments is considered both clinically and practically acceptable for research-based or consumer use. In conclusion, research-grade wearable technology that uses EE kilocalories · minute-1 and HR reliably differentiates PA intensities.

The Effects of Basal Insulin Suspension at the Start of Exercise on Blood Glucose Levels During Continuous Versus Circuit-Based Exercise in Individuals with Type 1 Diabetes on Continuous Subcutaneous Insulin Infusion.

BACKGROUND: Exercise causes glycemic disturbances in individuals with type 1 diabetes (T1D). Continuous moderate-intensity aerobic exercise (CON) generally lowers blood glucose (BG) levels and often leads to hypoglycemia. In comparison, circuit-based exercise (CIRC) may attenuate the drop in BG. The goal of this study is to contrast the effects of basal insulin suspension at the onset of two different forms of exercise (CON vs. CIRC). METHODS: Twelve individuals (six men and six women) with T1D on insulin pump therapy were recruited for the study. All participants completed a maximal aerobic fitness test and two 40-min exercise sessions, consisting of either continuous treadmill walking or a circuit workout. Basal insulin infusion was stopped at the onset of exercise and resumed in recovery. After providing an initial reference value, volunteers were blinded to their [BG] and were asked to estimate their levels during exercise. RESULTS: Oxygen consumption (47.5 ± 7.5 vs. 54.5 ± 13.5 mL·kg-1·min-1, P = 0.03) and heart rate (122 ± 20 vs. 144 ± 20 bpm, P = 0.003) were lower in CON vs. CIRC. Despite the lower workload, BG levels dropped more with CON vs. CIRC (delta BG = -3.8 ± 1.5 vs. -0.5 ± 3.0 mmol/L for CON vs. CIRC, respectively, P = 0.001). Participants were able to estimate their BG more accurately during CON (r = 0.83) vs. CIRC (r = 0.33) based on a regression analysis. CONCLUSION: Despite a lower intensity of exercise, with full basal insulin suspension at the start of exercise, CON results in a larger drop in BG vs. CIRC. These findings have implications for single hormone-based artificial pancreas development for exercise. While this study does not negate the importance of frequent capillary BG monitoring during exercise, it does suggest that if persons are knowledgeable about their pre-exercise BG levels, they can accurately perceive the changes in BG during CON, but not during CIRC.

Classification of Physical Activity: Information to Artificial Pancreas Control Systems in Real Time.

Physical activity has a wide range of effects on glucose concentrations in type 1 diabetes (T1D) depending on the type (ie, aerobic, anaerobic, mixed) and duration of activity performed. This variability in glucose responses to physical activity makes the development of artificial pancreas (AP) systems challenging. Automatic detection of exercise type and intensity, and its classification as aerobic or anaerobic would provide valuable information to AP control algorithms. This can be achieved by using a multivariable AP approach where biometric variables are measured and reported to the AP at high frequency. We developed a classification system that identifies, in real time, the exercise intensity and its reliance on aerobic or anaerobic metabolism and tested this approach using clinical data collected from 5 persons with T1D and 3 individuals without T1D in a controlled laboratory setting using a variety of common types of physical activity. The classifier had an average sensitivity of 98.7% for physiological data collected over a range of exercise modalities and intensities in these subjects. The classifier will be added as a new module to the integrated multivariable adaptive AP system to enable the detection of aerobic and anaerobic exercise for enhancing the accuracy of insulin infusion strategies during and after exercise.

Exercise and the Development of the Artificial Pancreas: One of the More Difficult Series of Hurdles.

Regular physical activity (PA) promotes numerous health benefits for people living with type 1 diabetes (T1D). However, PA also complicates blood glucose control. Factors affecting blood glucose fluctuations during PA include activity type, intensity and duration as well as the amount of insulin and food in the body at the time of the activity. To maintain equilibrium with blood glucose concentrations during PA, the rate of glucose appearance (Ra) to disappearance (Rd) in the bloodstream must be balanced. In nondiabetics, there is a rise in glucagon and a reduction in insulin release at the onset of mild to moderate aerobic PA. During intense aerobic -anaerobic work, insulin release first decreases and then rises rapidly in early recovery to offset a more dramatic increase in counterregulatory hormones and metabolites. An "exercise smart" artificial pancreas (AP) must be capable of sensing glucose and perhaps other physiological responses to various types and intensities of PA. The emergence of this new technology may benefit active persons with T1D who are prone to hypo and hyperglycemia.