The aim of the study was to assess the amount of orally administered carbohydrates needed to maintain euglycemia during moderate-intensity exercise in individuals with type 1 diabetes. Nine participants with type 1 diabetes (four women, age 32.1 ± 9.0 years, BMI 25.5 ± 3.9 kg/m², HbA_1c 55 ± 7 mmol/mol (7.2 ± 0.6%)) on insulin Degludec were randomized to cycle for 55 min at moderate intensity (63 ± 7% VO_2peak) for five consecutive days on either 75% or 100% of their regular basal insulin dose. The impact of pre-exercise blood glucose concentration on the carbohydrate requirement was analyzed by one-way ANOVA stratified for pre-exercise blood glucose quartiles. The effect of the basal insulin dose on the amount of orally administered carbohydrates was evaluated by Wilcoxon matched-pairs signed-rank test. The amount of orally administered carbohydrates during the continuous exercise sessions was similar for both trial arms (75% or 100% basal insulin) with median [IQR] of 36 g (9–62 g) and 36 g (9–66 g) (p = 0.78). The amount of orally administered carbohydrates was determined by pre-exercise blood glucose concentration for both trial arms (p = 0.03). Our study elucidated the importance of pre-exercise glucose concentration related orally administered carbohydrates to maintain euglycemia during exercise in individuals with type 1 diabetes.

Estimation of the intensity of physical activity (PA) based on absolute accelerometer cut points (Cp) likely over- or underestimates intensity for a specific individual. The purpose of this study was to investigate the relationship between absolute moderate intensity Cp and the first ventilatory threshold (VT₁). A group of 24 pregnant and 15 nonpregnant women who performed a submaximal incremental walking test with measures of ventilatory parameters and accelerations from three different accelerometers on the wrist (ActiGraph wGT3X-BT, GENEActiv, Axivity AX3) and one on the hip (Actigraph wGT3X-BT) were analyzed. Cp were determined corresponding to 3 metabolic equivalents of task (MET), using the conventional MET definition (Cp_3.5) (3.5 mL/kg×min) and individual resting metabolic rate (Cp_ind). The ventilatory equivalent (VE/VO₂) was used to determine VT₁. Accelerations at VT₁ were significantly higher (p < 0.01) compared to Cp_3.5 and Cp_ind in both groups. Cp_3.5 and Cp_ind were significantly different in nonpregnant (p < 0.01) but not in pregnant women. Walking speed at VT₁ (5.7 ± 0.5/6.2 ± 0.8 km/h) was significantly lower (p < 0.01) in pregnant compared to nonpregnant women and correspondent to 3.8 ± 0.7/4.9 ± 1.4 conventional METs. Intensity at absolute Cp was lower compared to the intensity at VT₁ independent of the device or placement in pregnant and nonpregnant women. Therefore, we recommend individually tailored cut points such as the VT₁ to better assess the effect of the intensity of PA.

(1): Heart rate performance curve (HRPC) in incremental exercise was shown to be not uniform, causing false intensity estimation applying percentages of maximal heart rate (HR_max). HRPC variations are mediated by β-adrenergic receptor sensitivity. The aim was to study age and sex dependent differences in HRPC patterns in adults with β-blocker treatment (BB) and healthy controls (C). (2): A total of 535 (102 female) BB individuals were matched 1:1 for age and sex (male 59 ± 11 yrs, female 61 ± 11 yrs) in C. From the maximum incremental cycle ergometer exercise a first and second heart rate (HR) threshold (Th1 and Th2) was determined. Based on the degree of the deflection (kHR), HRPCs were categorized as regular (downward deflection (kHR > 0.1)) and non-regular (upward deflection (kHR < 0.1), linear time course). (3): Logistic regression analysis revealed a higher odds ratio to present a non-regular curve in BB compared to C (females showed three times higher odds). The odds for non-regular HRPC in BB versus C decreased with older age (OR interaction = 0.97, CI = 0.94–0.99). Maximal and submaximal performance and HR variables were significantly lower in BB (p < 0.05). %HR_max was significantly lower in BB versus C at Th2 (male: 77.2 ± 7.3% vs. 80.8 ± 5.0%; female: 79.2 ± 5.1% vs. 84.0 ± 4.3%). %P_max at Th2 was similar in BB and C. (4): The HRPC pattern in incremental cycle ergometer exercise is different in individuals receiving β-blocker treatment compared to healthy individuals. The effects were also dependent on age and sex. Relative HR values at Th2 varied substantially depending on treatment. Thus, the percentage of Pmax seems to be a stable and independent indicator for exercise intensity prescription.

Long-term heavy physical work often leads to early retirement and disability pension due to chronic overload, with a need to define upper limits. The aim of this study was to evaluate the value of the first lactate threshold (LTP₁) as a physiological marker for heavy occupational work. A total of 188 male and 52 female workers performed an incremental cycle ergometer test to determine maximal exercise performance and the first and second lactate (LTP₁; LTP₂) and ventilatory thresholds (VT₁; VT₂). Heart rate (HR) recordings were obtained during one eight-hour shift (HR_8h) and oxygen uptake was measured during 20 minutes of a representative work phase. Energy expenditure (EE) was calculated from gas-exchange measures. Maximal power output (P_max), maximal oxygen consumption (VO_{2 max}) and power output at LTP₁ and LTP₂ were significantly different between male and female workers. HR_8h was not significantly different between male and female workers. A significant relationship was found between P_max and power output at LTP₁. HR_8h as a percentage of maximum HR significantly declined with increasing performance (P_max:r = −0.56; p < 0.01; P_LTP1:r = −0.49; p < 0.01). Despite different cardio-respiratory fitness-levels; 95.4% of all workers performed their usual work below LTP₁. It is therefore suggested that LTP₁ represents the upper limit for sustained heavy occupational work; which supports its use to determine work capability and assessing the limits of heavy occupational work.

Duration is a rarely investigated marker of exercise prescription. The aim of this study was to test the feasibility of the methodological approach, assessing effects of different duration constant-load exercise (CLE) on physiological responses (internal load) and recovery kinetics. Seven subjects performed an incremental exercise (IE) test, one maximal duration CLE at 77.6 ± 4.8% $\dot{\mathrm{V}}{\mathrm{O}}_{\mathrm{2}\mathrm{m}\mathrm{a}\mathrm{x}}$, and CLE’s at 20%, 40%, and 70% of maximum duration. Heart rate (HR), blood lactate (La), and glucose (Glu) concentrations were measured. Before, 4, 24, and 48 h after CLE’s, submaximal IE tests were performed. HR variability (HRV) was assessed in orthostatic tests (OT). Rating of perceived exertion (RPE) was obtained during all tests. CLE’s were performed at 182 ± 27 W. HR_peak, La_peak, $\dot{\mathrm{V}}{\mathrm{E}}_{\mathrm{peak}}$, and RPE_peak were significantly higher in CLE’s with longer duration. No significant differences were found between CLE’s for recovery kinetics for HR, La, and Glu in the submaximal IE and for HRV or OT. Despite no significant differences, recovery kinetics were found as expected, indicating the feasibility of the applied methods. Maximum tests and recovery tests closer to CLE’s termination are suggested to better display recovery kinetics. These findings are a first step to prescription of exercise by both intensity and duration on an individual basis.

Background/Objectives: The impact of exercise on affective disorders has been demonstrated in various studies. However, almost no data are available on performance effects. Therefore, this study investigated exercise performance related to the severity of depression symptoms in a pre–post within-subjects design in a 6-week standard inpatient psychiatric rehabilitation program. Methods: A total of 53 individuals (20 female; mean age, 40.98 ± 11.33) with a primary diagnosis of depression performed a cardiopulmonary exercise test (CPX) to obtain maximal oxygen uptake (VO_2max), maximal power output (P_max), and the first and second ventilatory threshold (VT₁, VT₂) at the start and the end of the rehabilitation. Degree of depression was assessed by Becks Depression Inventory (BDI) and the Brief Symptom Inventory test (BSI). Overall activity was measured by accelerometer step-counts. Results: Mean total step-count per day during rehabilitation was high (12,586 ± 2819 steps/day). Patients’ BDI and BSI at entry were 21.6 ± 8.83 and 65.1 ± 6.8, respectively, and decreased significantly (p < 0.001) following rehabilitation, to 10.1 ± 9.5 and 54.5 ± 11.3, respectively. P_max and VO_2max increased significantly (p < 0.001) from entry values (182.6 ± 58.7 W, 29.74 ± 5.92 mL·kg⁻¹·min⁻¹) following rehabilitation: by 11.91 ± 12.09 W and 1.35 ± 2.78 mL·kg⁻¹·min⁻¹, respectively. VT₁ and VT₂ showed a similar behavior. An increase in physical performance could predict improvement in BDI (R² = 0.104, F(1,48) = 5.582, p = 0.022) but not in BSI. Conclusions: The program was associated with improved mental health status in all patients and increased performance in the majority of patients, although increases were small. Since improvements in exercise performance may be positively related to depression symptoms and comorbidities, it is recommended to individualize and tailor exercise programs, which could yield larger effects.