Real World Interstitial Glucose Profiles of a Large Cohort of Physically Active Men and Women.

The use of continuous glucose monitors (CGMs) in individuals living without diabetes is increasing. The purpose of this study was to profile various CGM metrics around nutritional intake, sleep and exercise in a large cohort of physically active men and women living without any known metabolic disease diagnosis to better understand the normative glycemic response to these common stimuli. A total of 12,504 physically active adults (age 40 ± 11 years, BMI 23.8 ± 3.6 kg/m2; 23% self-identified as women) wore a real-time CGM (Abbott Libre Sense Sport Glucose Biosensor, Abbott, USA) and used a smartphone application (Supersapiens Inc., Atlanta, GA, USA) to log meals, sleep and exercise activities. A total of >1 M exercise events and 274,344 meal events were analyzed. A majority of participants (85%) presented an overall (24 h) average glucose profile between 90 and 110 mg/dL, with the highest glucose levels associated with meals and exercise and the lowest glucose levels associated with sleep. Men had higher mean 24 h glucose levels than women (24 h-men: 100 ± 11 mg/dL, women: 96 ± 10 mg/dL). During exercise, the % time above >140 mg/dL was 10.3 ± 16.7%, while the % time <70 mg/dL was 11.9 ± 11.6%, with the remaining % within the so-called glycemic tight target range (70-140 mg/dL). Average glycemia was also lower for females during exercise and sleep events (p < 0.001). Overall, we see small differences in glucose trends during activity and sleep in females as compared to males and higher levels of both TAR and TBR when these active individuals are undertaking or competing in endurance exercise training and/or competitive events.

Association between pre-exercise food ingestion timing and reactive hypoglycemia: Insights from a large database of continuous glucose monitoring data.

Using a large database of continuous glucose monitoring (CGM) data, this study aimed to gain insights into the association between pre-exercise food ingestion timing and reactive hypoglycemia. A group of 6,761 users self-reported 48,799 pre-exercise food ingestion events and logged minute-by-minute CGM, which was used to detect reactive hypoglycemia (<70 mg/dL) in the first 30 min of exercise. A linear and a non-linear binomial logistic regression model was used to investigate the association between food ingestion timing and the probability of experiencing reactive hypoglycemia. An analysis of variance was conducted to compare the predictive ability of the models. On average, reactive hypoglycemia was detected in 8.34 ± 3.04% of the total events, with <15% of individuals experiencing hypoglycemia in >20% of their events. The majority of the reactive hypoglycemia events were found with pre-exercise food timing between ∼30 and ∼90 min, with a peak at ∼60 min. The superior accuracy (62.05 vs 45.1%) and F-score (0.75 vs 0.59) of the non-linear vs the linear model were statistically superior (P < 0.0001). These results support the notion of an unfavourable 30-to-90 min pre-exercise food ingestion time window which can significantly impact the likelihood of reactive hypoglycemia in some individuals.

Large datasets of self-reported continuous glucose monitoring and food events are used here for the first time to get insights into reactive hypoglycemia, a condition often regarded as negative for endurance performance eventsUsing a binomial non-linear logistic regression model, the association between pre-exercise food ingestion timing and reactive hypoglycemia revealed the presence of an unfavourable window, when reactive hypoglycemia is more likely to occur.Results confirm an individual predisposition to reactive hypoglycemia and, for 8 in 100 individuals, the pre-exercise food ingestion timing can meaningfully impact the likelihood of experiencing reactive hypoglycemia.

Glycaemic patterns of male professional athletes with type 1 diabetes during exercise, recovery and sleep: Retrospective, observational study over an entire competitive season.

AIMS: To analyse glycaemic patterns of professional athletes with type 1 diabetes during a competitive season. MATERIALS AND METHODS: We analysed continuous glucose monitoring data of 12 professional male cyclists with type 1 diabetes during exercise, recovery and sleep on days with competitive exercise (CE) and non-competitive exercise (NCE). We assessed whether differences exist between CE and NCE days and analysed associations between exercise and dysglycaemia. RESULTS: The mean glycated haemoglobin was 50 ± 5 mmol/mol (6.7 ± 0.5%). The athletes cycled on 280.8 ± 28.1 days (entire season 332.6 ± 18.8 days). Overall, time in range (3.9-10 mmol/L) was 70.0 ± 13.7%, time in hypoglycaemia (<3.9 mmol/L) was 6.4 ± 4.7% and time in hyperglycaemia (>10 mmol/L) was 23.6 ± 12.5%. During the nights of NCE days, athletes spent 10.1 ± 7.4% of time in hypoglycaemia, particularly after exercise in the endurance zones. The CE days were characterized by a higher time in hyperglycaemia compared with NCE days (25.2 ± 12.5% vs. 22.2 ± 12.1%, p = .012). This was driven by the CE phase, where time in range dropped to 60.4 ± 13.0% and time in hyperglycaemia was elevated (38.5 ± 12.9%). Mean glucose was higher during CE compared with NCE sessions (9.6 ± 0.9 mmol/L vs. 7.8 ± 1.1 mmol/L, p < .001). The probability of hyperglycaemia during exercise was particularly increased with longer duration, higher intensity and higher variability of exercise. CONCLUSIONS: The analysis of glycaemic patterns of professional endurance athletes revealed that overall glycaemia was generally within targets. For further improvement, athletes, team staff and caregivers may focus on hyperglycaemia during competitions and nocturnal hypoglycaemia after NCE.

Flat versus Simulated Mountain Trail Running: A Multidisciplinary Comparison in Well-Trained Runners.

This paper compares cardiopulmonary and neuromuscular parameters across three running aerobic speeds in two conditions that differed from a treadmill's movement: flat condition (FC) and unpredictable roll variations similar to mountain trail running (URV). Twenty well-trained male runners (age 33 ± 8 years, body mass 70.3 ± 6.4 kg, height 1.77 ± 0.06 m, V˙O2max 63.8 ± 7.2 mL·kg-1·min-1) voluntarily participated in the study. Laboratory sessions consisted of a cardiopulmonary incremental ramp test (IRT) and two experimental protocols. Cardiopulmonary parameters, plasma lactate (BLa-), cadence, ground contact time (GT) and RPE values were assessed. We also recorded surface electromyographic (sEMG) signals from eight lower limb muscles, and we calculated, from the sEMG envelope, the amplitude and width of peak muscle activation for each step. Cardiopulmonary parameters were not significantly different between conditions (V˙O2: p = 0.104; BLa-: p = 0.214; HR: p = 0.788). The amplitude (p = 0.271) and width (p = 0.057) of sEMG activation peaks did not change between conditions. The variability of sEMG was significantly affected by conditions; indeed, the coefficient of variation in peak amplitude (p = 0.003) and peak width (p < 0.001) was higher in URV than in FC. Since the specific physical demands of running can differ between surfaces, coaches should resort to the use of non-traditional surfaces, emphasizing specific surface-related motor tasks that are normally observed in natural running environments. Seeing that the variability of muscle activations was affected, further studies are required to better understand the physiological effects induced by systematic surface-specific training and to define how variable-surface activities help injury prevention.

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, HbA1c: 6.4 ± 0.4% [46 ± 4 mmol.mol-1], VO2max: 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.

Fast or slow start? The role of running strategies in triathlon.

OBJECTIVES: To investigate the impact of fast-start, steady or slow-start strategies of the running fraction in sprint triathlon on oxygen consumption, perception of fatigue and blood lactate. DESIGN: Thirteen male triathletes (age; 36.4 ±â€¯10.8 yy, height 174.8 ±â€¯7.9 cm, body mass 70.6 ±â€¯11.1 kg; V'O2max 62.4 ±â€¯8.9 ml min-1 kg-1; mean ±â€¯SD) attended the laboratory five times in order to complete two incremental tests and three subsequent cycle-run sessions. METHODS: Three experimental randomized sessions with different effort distribution were compared. The intensities of the 1st running kilometer were set at 95%, 100% and 105% of the second ventilatory threshold for slow, continuous and fast start protocol respectively. Measurement of ventilatory variables, blood lactate and ratings of perceived exertion were collected throughout all sessions. RESULTS: A meaningful difference was found between the slow versus fast start protocol in V'O2 (SE = 0.58, P = 0.0005), BLa- (SE = 0.21, P = 0.0097), HR (SE = 1.23, P = 0.0011) and RPE (SE = 2.83, P = 0.0047) values. No differences in-between protocols were found at the end of the running bout whatever the condition. CONCLUSIONS: Differences in physiological parameters were found between protocols during the first kilometer, not at the end of exercise. The fast start appears to be more correct and useful for performance in racing setting and may be used as a strategy without impacting the remaining running bout in ecological setting.

Attentional bias to emotions after prolonged endurance exercise is modulated by age.

Physical exercise has an impact in biasing attention to positive or negative emotional stimuli. While attentional shift to emotions varies with age, evidence is lacking on the effect of prolonged endurance exercise on age-related attentional bias to emotions. This study aims at filling this knowledge gap, by applying a dot-probe task to measure attentional bias to emotions before and after a half-marathon in healthy participants of different ages (age range 21-65 years). State anxiety, positive and negative affect were also assessed. Younger adults showed attentional bias towards anger and away from sadness after the race, supporting the hypothesis of the congruency between the high-arousing task and the associated emotion (anger) in the modulation of attention. Conversely, older adults showed a bias away from anger, likely representing an attempt to maintain an optimal emotional level after the competition. This study sheds new light on how age impacts on emotional mechanisms involved in prolonged endurance exercise and suggests that regulatory processes in response to stress may be involved differently, depending on age.

Effect of acute sympathetic activation on leg vasodilation before and after endurance exercise.

Vascular conductance (VC) regulation involves a continuous balance between metabolic vasodilation and sympathetic vasoconstriction. Endurance exercise challenges the sympathetic control on VC due to attenuated sympathetic receptor responsiveness and persistence of muscle vasodilation, especially in endurance athletes, predisposing them to blood pressure control dysfunctions. This study assessed whether acute handgrip-mediated sympathetic activation (SYMP) restrains sudden leg vasodilation before and after a half-marathon. Prior to, and within the 20 min following the race, 11 well-trained runners underwent two single passive leg movement (SPLM) tests to suddenly induce leg vasodilation, one without and the other during SYMP. Leg blood flow and mean arterial pressure were measured to assess changes in leg VC. Undertaking 60 sec of SYMP reduced the baseline leg VC both before (4.0 ± 1.0 vs. 3.3 ± 0.7 ml/min/mmHg; P=0.01; NO SYMP vs. SYMP, respectively) and after the race (4.6 ± 0.8 vs. 3.9 ± 0.8 ml/min/mmHg; P=0.01). However, SYMP did not reduce leg peak vasodilation immediately after the SPLM either before (11.5 ± 4.0 vs. 12.2 ± 3.8 ml/min/mmHg; P=0.35) or after the race (7.2 ± 2.0 vs. 7.3 ± 2.6 ml/min/mmHg; P=0.96). Furthermore, SYMP did not blunt the mean leg vasodilation over the 60 sec after the SPLM before (5.1 ± 1.7 vs. 5.9 ± 2.5 ml/min/mmHg; P=0.14) or after the race (4.8 ± 1.3 vs. 4.2 ± 1.5 ml/min/mmHg; P=0.26). This data suggest that the release of local vasoactive agents effectively opposes any preceding handgrip-mediated augmented vasoconstriction in endurance athletes before and after a half-marathon. Handgrip-mediated SYMP might improve normal vasoconstriction while athletes are still, but not necessarily while they move, as movements can induce a release of vasoactive molecules.

Kinematic and mechanical changes during a long half-marathon race: males and females at uphill/downhill slopes.

BACKGROUND: The aim of this study was to compare the running kinematics and the spring mass model mechanics over an entire half-marathon race in male and female athletes on different slopes (-7%, 0% and +7%). METHODS: 59 recreational runners (39 males and 20 females) participated in this study. Their running steps at own best self-selected speed were video recorded during a half-marathon (i.e. in ecological conditions): the kinematic variables (i.e. running speed, stride length and frequency, contact and flight time) were calculated, as well as the spring-mass characteristics (i.e. leg and vertical stiffness) of their running steps. RESULTS: Males were able to run with greater speeds and lengths compared to females (P<0.001) but with lower flight times (P<0.05), and they reached higher values of both leg and vertical stiffness (P<0.001). During downhill running, step lengths were larger compared to the level and the uphill (+6%) whereas frequencies slightly decreased (-2%), and aerial times were the greatest ones (+17%). During uphill running, contact times were slightly higher compared to other conditions (+3%), and leg stiffness reached the lowest values (-8%). CONCLUSIONS: This study confirmed that there are important alterations in running steps in function of sex and surface slope. Importantly, the response to fatigue (i.e. alterations with the covered distance) does not alter these sex differences and is therefore independent of the sloped conditions.

Effects of endurance exercise on serum concentration of calcitonin gene-related peptide (CGRP): a potential link between exercise intensity and headache.

Background Calcitonin gene-related peptide (CGRP) is a powerful neuropeptide that is strongly involved in headache pain pathogenesis by triggering vasodilation, mast cell degranulation and neurogenic inflammation. This evidence has prompted us to investigate the acute influence of endurance exercise on CGRP concentration in blood. Methods The study population consisted of 48 male amateur runners, who ran a half-marathon distance at 75%-85% of maximal oxygen uptake. Blood was drawn before the run (pre-run) and immediately after each runner ended his trial (post-run). The serum concentration of CGRP was measured with a commercial enzyme-linked immunosorbent assay (ELISA) technique. Results Overall, 22/48 subjects (45.8%) reported suffering from headache, three of whom (6.2%) had an exertional headache, whilst 26/48 (54.2%) subjects did not report at least one headache episode during the previous 6 months (i.e. headache-free). All 48 athletes successfully covered the 21.1 km distance. Serum concentration of CGRP significantly increased by 1.5-fold in the entire group, as well as in the headache-positive and headache-free cohorts. Univariate Spearman's correlation revealed that post-run variation of serum CGRP was significantly and inversely associated with running time (r = -0.30; p = 0.036). Conclusions The serum concentration of CGRP is significantly enhanced by medium-distance endurance exercise and the post-exercise increase is dependent on running intensity. Accordingly, high-exercise intensity might be directly related to triggering both exertional headache and/or migraine episodes.

"Running with cancer": A qualitative study to evaluate barriers and motivations in running for female oncological patients.

Nowadays, it is widely acknowledged that low physical activity levels are associated with an increase in terms of both disease recurrence and mortality in cancer survivors. In this light, deciphering those factors able to hamper or facilitate an active lifestyle is crucial in order to increase patients' adherence to physical activity. The purpose of this study was to explore barriers and motivations in a sample of female oncological patients, practising running using the ecological model and compare them with healthy controls. Focus group interviews were conducted at Verona University. Participants were 12 female cancer survivors and 7 matched healthy controls who had participated at "Run for Science" project. The interviews were transcribed verbatim and analyzed using content analysis. Transcripts were categorized according to the ecological model, identifying barriers and motivations as themes. About motivations, three sub-themes were included: personal, interpersonal and environmental/organizational factors. Regarding barriers, another sub-theme was recognized: community/policy factors. Compared to healthy controls, survivors expressed motivations and barriers specifically related to their oncological disease. Running was a challenge with their cancer and a hope to give to other patients. Main barriers were represented by treatment-related side effects, inexperienced trainers and external factors, e.g. delivery of incorrect information. Running programs dedicated to oncological patients should consider intrinsic obstacles, related to cancer and its treatment. The interventions should offer a personalized program performed by qualified trainers, together with a motivational approach able to improve participants' adherence to an active lifestyle.

Effects of Flywheel Strength Training on the Running Economy of Recreational Endurance Runners.

Festa, L, Tarperi, C, Skroce, K, Boccia, G, Lippi, G, La Torre, A, and Schena, F. Effects of flywheel strength training on the running economy of recreational endurance runners. J Strength Cond Res 33(3): 684-690, 2019-Running economy (RE) has been defined as the most important determining factor in endurance performance in both elite and recreational runners. The purpose of this study was to evaluate the effect of flywheel strength training (FST) and high-intensity training (HIT) protocols on RE and strength parameters in a group of recreational runners. Twenty-nine recreational runners were recruited to take part in the study and were randomly assigned to FST (n = 9; 44.5 ± 6.0 years; V[Combining Dot Above]O2max 48.8 ± 5.2 ml·min·kg), HIT (n = 9; 42.2 ± 8.6 years; V[Combining Dot Above]O2max 50.3 ± 3.7 ml·min·kg), or low-intensity training (LIT) (n = 11; 45.4 ± 8.0 years; V[Combining Dot Above]O2max 50.2 ± 6.8 ml min kg) groups. Before and after 8 weeks of an experimental period, maximal oxygen uptake (V[Combining Dot Above]O2max), ventilatory thresholds (VTs), maximal dynamic force (1 repetition maximum [1RM]), and anthropometric data were evaluated. The FST group showed significant increases (p < 0.05) in 1RM and RE. No differences were found in the other groups. Significative changes are found for all groups on average speed on 2 and 10 km (p < 0.05). Anthropometric data were unchanged after the training period. The results of this study indicate that in recreational runners, FST seems able to obtain improvements in RE and neuromuscular adaptation.

Effects of Different Training Intensity Distribution in Recreational Runners.

Purpose: To compare the impact of two different training intensity distributions in terms of conditional and performance parameters and spent time to training in recreational athletes. Methods: Two different training intensity distribution model were performed for 8 weeks by 38 recreational runners. Runners recruited were randomly assigned to 2 different training models based on HR intensity detected with maximal test. The percentage distribution splitted in zone 1, 2, and 3 were by 77/3/20 and 40/50/10 in polarized endurance training group (PET) and focused endurance training (FOC) group, respectively. Programs were balanced for total training impulse (TRIMP). To evaluate effects of training, before and after treatment were performed a maximal exercise test to determine Maximal Oxygen Uptake (V'O2max), Ventilatory Threshold (VT), respiratory-compensation point (RCT) Running Economy (RE), and 2 Km performance. To investigate the effects of training on muscular performance were performed one repetition maximum (1 RM), squat jump (SJ), and counter movement jump (CMJ). Results: Both groups significantly improved their velocity at V'O2max (3.2 and 4.0%), at VT (4.0 and 3.2%), RCT (5.7 and 3.4%), the average velocity in 2 Km performance (3.5 and 3.0%) and RE (-5.3 and -8.7%) for PET and FOC, respectively for each variable. No differences were found between the groups on any parameter investigated except about the total training time (PET = 29.9 ± 3.1 h and FOC = 24.8 ± 2.0 h). Conclusion: Focused Endurance Training obtains similar improvements than Polarized Endurance Training saving 17% of training time in recreational runners.