Physiological responses and performance factors for double-poling and diagonal-stride treadmill roller-skiing time-trial exercise

PURPOSE

To compare physiological responses between a self-paced 4-min double-poling (DP) time-trial (TTDP) versus a 4-min diagonal-stride (DS) time-trial (TTDS). The relative importance of peak oxygen uptake ([Formula: see text]O2peak), anaerobic capacity, and gross efficiency (GE) for projection of 4-min TTDP and TTDS roller-skiing performances were also examined.

METHODS

Sixteen highly trained male cross-country skiers performed, in each sub-technique on separate occasions, an 8 × 4-min incremental submaximal protocol, to assess individual metabolic rate (MR) versus power output (PO) relationships, followed by a 10-min passive break and then the TTDP or TTDS, with a randomized order between sub-techniques.

RESULTS

In comparison to TTDS, the TTDP resulted in 10 ± 7% lower total MR, 5 ± 4% lower aerobic MR, 30 ± 37% lower anaerobic MR, and 4.7 ± 1.2 percentage points lower GE, which resulted in a 32 ± 4% lower PO (all P < 0.01). The [Formula: see text]O2peak and anaerobic capacity were 4 ± 4% and 30 ± 37% lower, respectively, in DP than DS (both P < 0.01). The PO for the two time-trial (TT) performances were not significantly correlated (R2 = 0.044). Similar parabolic pacing strategies were used during both TTs. Multivariate data analysis projected TT performance using [Formula: see text]O2peak, anaerobic capacity, and GE (TTDP, R2 = 0.974; TTDS, R2 = 0.848). The variable influence on projection values for [Formula: see text]O2peak, anaerobic capacity, and GE were for TTDP, 1.12 ± 0.60, 1.01 ± 0.72, and 0.83 ± 0.38, respectively, and TTDS, 1.22 ± 0.35, 0.93 ± 0.44, and 0.75 ± 0.19, respectively.

CONCLUSIONS

The results show that a cross-country skier's "metabolic profile" and performance capability are highly sub-technique specific and that 4-min TT performance is differentiated by physiological factors, such as [Formula: see text]O2peak, anaerobic capacity, and GE.

Using Multivariate Data Analysis to Project Performance in Biathletes and Cross-Country Skiers

PURPOSE

To determine whether competitive performance, as defined by International Biathlon Union (IBU) and International Ski Federation (FIS) points in biathlon and cross-country (XC) skiing, respectively, can be projected using a combination of anthropometric and physiological metrics. Shooting accuracy was also included in the biathlon models.

METHODS

Data were analyzed using multivariate methods from 45 (23 female and 22 male) biathletes and 202 (86 female and 116 male) XC skiers who were all members of senior national teams, national development teams, or ski-university or high school invite-only programs (age range: 16-36 y). Anthropometric and physiological characteristics were assessed via dual-energy X-ray absorptiometry and incremental roller-ski treadmill tests, respectively. Shooting accuracy was assessed via an outdoor standardized testing protocol.

RESULTS

Valid projective models were identified for female biathletes' IBU points (R2 = .80/Q2 = .65) and female XC skiers' FIS distance (R2 = .81/Q2 = .74) and sprint (R2 = .81/Q2 = .70) points. No valid models were identified for the men. The most important variables for the projection of IBU points were shooting accuracy, speeds at blood lactate concentrations of 4 and 2 mmol·L-1, peak aerobic power, and lean mass. The most important variables for the projection of FIS distance and sprint points were speeds at blood lactate concentrations of 4 and 2 mmol·L-1 and peak aerobic power.

CONCLUSIONS

This study highlights the relative importance of specific anthropometric, physiological, and shooting-accuracy metrics in female biathletes and XC skiers. The data can help to identify the specific metrics that should be targeted when monitoring athletes' progression and designing training plans.

Comparison of the effects of velocity-based vs. traditional resistance training methods on adaptations in strength, power, and sprint speed: A systematic review, meta-analysis, and quality of evidence appraisal

We estimated the effectiveness of using velocity feedback to regulate resistance training load on changes in muscle strength, power, and linear sprint speed in apparently healthy participants. Academic and grey literature databases were systematically searched to identify randomised trials that compared a velocity-based training intervention to a 'traditional' resistance training intervention that did not use velocity feedback. Standardised mean differences (SMDs) were pooled using a random effects model. Risk of bias was assessed with the Risk of Bias 2 tool and the quality of evidence was evaluated using the GRADE approach. Four trials met the eligibility criteria, comprising 27 effect estimates and 88 participants. The main analyses showed trivial differences and imprecise interval estimates for effects on muscle strength (SMD 0.06, 95% CI -0.51-0.63; I² = 42.9%; 10 effects from 4 studies; low-quality evidence), power (SMD 0.11, 95% CI -0.28-0.49; I² = 13.5%; 10 effects from 3 studies; low-quality evidence), and sprint speed (SMD -0.10, 95% CI -0.72-0.53; I² = 30.0%; 7 effects from 2 studies; very low-quality evidence). The results were robust to various sensitivity analyses. In conclusion, there is currently no evidence that VBT and traditional resistance training methods lead to different alterations in muscle strength, power, or linear sprint speed.

Anthropometric, Physiological, and Performance Developments in Cross-country Skiers

PURPOSE

This study aimed to describe changes in laboratory-assessed anthropometric and physiological characteristics, training volumes, and competitive performance in national development-team cross-country skiers over a 25-month period, and to analyze whether changes in competitive performance could be predicted by changes in laboratory-assessed qualities and training volumes.

METHODS

Data collected over 25 months from 30 national development-team cross-country skiers (14 women, 16 men; age, 18-23 yr) were analyzed retrospectively using multivariate statistics. Anthropometric and physiological characteristics were assessed via dual-energy x-ray absorptiometry and incremental roller-ski treadmill tests, respectively. Total training volumes and distributions of low- and high-intensity training were analyzed from online training diaries, and competitive performance was determined by International Ski Federation (FIS) distance and sprint points.

RESULTS

Whole- and upper-body lean mass increased in the full cohort of skiers (n = 30; both P < 0.05), whereas lower-body lean mass, whole-body fat mass, speed and oxygen uptake (V˙O2) at a blood lactate concentration (BLa) of 2 and 4 mmol·L-1, as well as time-trial completion time, power output, and peak V˙O2, improved in the women only (all P < 0.05). Valid predictive models were identified for female skiers' best FIS distance points (R2 = 0.81/Q2 = 0.51) and changes in FIS distance points (R2 = 0.83/Q2 = 0.54), with body mass, fat mass, lean mass, V˙O2peak, and speed at a BLa of 4 mmol·L-1 identified as consistently important variables for projection.

CONCLUSIONS

The valid prediction of competitive performance was achieved for women only in distance events. This study suggests that improvements in body composition and aerobic capacity may be more beneficial for elite female development-level skiers than for their male counterparts. These results have implications for athlete selection and performance development.

The dose-response relationship between interval-training and VO2max in well-trained endurance runners: A systematic review

Success in endurance running is primarily determined by maximal aerobic power (VO_2max), fractional utilization, and running economy (RE). Within the literature, two training modalities have been identified to improve VO_2max; continuous training (CT) and interval-training (IT). The efficacy of IT to improve VO_2max in well-trained runners remains equivocal, as does whether a dose-response relationship exists between the IT training load performed and changes in VO_2max. A keyword search was performed in five electronic databases. Seven studies met the inclusion criteria for this systematic review. The training impulse (TRIMP) was calculated to analyse relationships between training load and changes in VO_2max, by calculating the time accumulated in certain intensity domains throughout a training intervention. Non-significant (P>0.05) improvements in VO_2max were reported in six studies, with only one study reporting a significant (P<0.05) improvement following the IT interventions. A relationship between the training session impulse of the interval-training performed (IT S_TRIMP) and VO_2max improvements were observed. The efficacy of IT to improve VO_2max in well-trained runners remains equivocal, nevertheless, the novel method of training-load analysis demonstrates a relationship between the IT S_TRIMP and VO_2max improvements. This provides practical application for the periodization of IT within the training regime of well-trained distance runners.

Variability and physical demands of international seam bowlers in one-day and Twenty20 international matches across five years

OBJECTIVES

To quantify and compare the match demands and variability of international One-Day (ODI) with Twenty20 (T20) cricket matches and to compare ODI match demands when competing home and away.

DESIGN

Single cohort, longitudinal observation.

METHODS

Thirteen international male seam bowlers across 204matches (ODI=160; T20=44) were investigated over five-years (2015-2019). Using global positioning sensors and accelerometers, physical demands were quantified using distance covered at different velocities and the number of entries into high and low intensity acceleration and deceleration bands. Variability was quantified using coefficient of variation (CV) and smallest worthwhile change.

RESULTS

Significantly greater (p<0.05) match demands were found for all physical variables relative to minutes played for T20 against ODI matches, except for distance covered 20-25kmh^-1 which was greater for ODI. Distance covered between 0-7km∙h^-1 showed no significance difference (p=0.60). The number of moderate decelerations (2-4m∙s²) were greater (p=0.04) away compared to home in ODI. All other variables showed no significance. Relative to minutes played, decelerations ≤4m∙s² (within-player ODI CV=75.5%. T20=72.0%) accelerations >4m∙s² (within-player ODI CV=79.2%. T20 CV=77.2%. Between-player ODI CV=84.7%. T20=38.8%) and distance covered >25kmh^-1 (within-player ODI CV=65.5%. T20=64.1%) showed the greatest variability.

CONCLUSIONS

Players are exposed to different physical demands in ODI Vs T20 matches, but not for home Vs away ODI matches. Practitioners should be aware of the large variability in high-speed/intensity accelerations and decelerations across matches.

Skin Temperature, Training Load, and Subjective Muscle Soreness in Junior Endurance Athletes: A Case Study

CONTEXT

The application of infrared thermography to assess the effects of athletic training is increasing. It is not known if changes in skin temperature (Tsk) as assessed by infrared thermography are affected by the training load or the muscle soreness experienced by the athlete.

PURPOSE

To describe the variations in Tsk in body areas affected by running training and examine any relationships with subjective ratings of muscle soreness. The secondary aim was to assess the feasibility of using infrared thermography for assessing training load in 2 junior male middle-distance athletes.

METHODS

Data were collected over a 42-d observational period with Tsk of the quadriceps, knees, shins, lateral hamstrings, biceps femoris, and Achilles tendons, and the subjective ratings of muscle soreness were taken each morning prior to any training. All training load was quantified through heart rate, running speed, and distance covered. Changes in Tsk outside the typical error were identified. Relationships between Tsk and subjective ratings of muscle soreness were also examined.

RESULTS

Over the 42-d observational period, mean Tsk of the regions of interest was reported outside the typical error on day 31 and day 22 for athletes 1 and 2, respectively. These changes in Tsk did not follow trends similar to those of to training loadings. No significant relationships were observed between Tsk of any regions of interest and muscle soreness.

CONCLUSIONS

Although Tsk changed outside the typical error throughout the 42-d observational period, these changes were not reflective of training load quantified through cardiovascular strain or subjective ratings of muscle soreness.

Development in Adolescent Middle-Distance Athletes: A Study of Training Loadings, Physical Qualities, and Competition Performance

Jones, TW, Shillabeer, BC, Ryu, JH, and Cardinale, M. Development in adolescent middle-distance athletes: a study of training loadings, physical qualities, and competition performance. J Strength Cond Res XX(X): 000-000, 2019-The purpose of this study was to examine changes in running performance and physical qualities related to middle-distance performance over a training season. The study also examined relationships between training loading and changes in physical qualities as assessed by laboratory and field measures. Relationships between laboratory and field measures were also analyzed. This was a 9-month observational study of 10 highly trained adolescent middle-distance athletes. Training intensity distribution was similar over the observational period, whereas accumulated and mean distance and training time and accumulated load varied monthly. Statistically significant (p < 0.05) and large effect sizes (Cohen's d) (>0.80) were observed for improvements in: body mass (5.6%), 600-m (4.6%), 1,200-m (8.7%), and 1,800-m (6.1%) time trial performance, critical speed (7.1%), V[Combining Dot Above]O2max (5.5%), running economy (10.1%), vertical stiffness (2.6%), reactive index (3.8%), and countermovement jump power output relative to body mass (7.9%). Improvements in 1,800 m TT performance were correlated with increases in V[Combining Dot Above]O2max (r = 0.810, p = 0.015) and critical speed (r = 0.918, p = 0.001). Increases in V[Combining Dot Above]O2max and critical speed were also correlated (r = 0.895, p = 0.003). Data presented here indicate that improvements in critical speed may be reflective of changes in aerobic capacity in adolescent middle-distance athletes.

Use of remote monitoring with continuous glucose monitoring in young children with Type 1 diabetes: the parents' perspective

AIM

Remote monitoring with continuous glucose monitoring (CGM) in children with Type 1 diabetes mellitus has recently become available, but little is known about caregivers' experiences of its use, particularly in younger children. The aim of this study was to explore parents' everyday experiences of using this technology.

METHODS

The parents of children with Type 1 diabetes diagnosed for > 1 year, aged 2-12 years were invited to participate in a semi-structured interview. Interviews were the second phase of a randomized cross-over study using standard insulin therapy with or without CGM and remote monitoring for two 3-month periods. Open-ended questions were used to explore parents' real-life experiences of the remote monitoring and CGM system. Interviews were analysed using thematic analysis.

RESULTS

Five themes related to remote monitoring emerged: (i) impact on sleep quality for the parents, (ii) peace of mind, (iii) impact on anxiety, (iv) freedom and confidence for the parents and children, and (v) impact on relationships. Furthermore, parents reported on themes related to CGM in general, such as better understanding of how to manage and control their child's diabetes and experiences related to physical or technical aspects.

CONCLUSION

Overall, parents of primary school children reported that using remote monitoring and CGM was a mostly beneficial experience. However, negative aspects within the themes were also reported. These findings will help to provide a structure to discuss parent and child expectations and provide targeted education at the start of using remote monitoring and CGM.

Optimization of Exercise Countermeasures for Human Space Flight: Operational Considerations for Concurrent Strength and Aerobic Training

The physiological challenges presented by space flight and in microgravity (μG) environments are well documented. μG environments can result in declines muscle mass, contractile strength, and functional capabilities. Previous work has focused on exercise countermeasures designed to attenuate the negative effects of μG on skeletal muscle structure, function, and contractile strength and aerobic fitness parameters. Exposure to μG environments influences both strength and aerobic type physical qualities. As such, the current exercise recommendations for those experiencing μG involve a combination of strength and aerobic training or “concurrent training.” Concurrent training strategies can result in development and maintenance of both strength and aerobic capabilities. However, terrestrial research has indicated that if concurrent training strategies are implemented inappropriately, strength development can be inhibited. Previous work has also demonstrated that the aforementioned inhibition of strength development is dependent on the frequency of aerobic training, modality of aerobic training, the relief period between strength and aerobic training, and the intra-session sequencing of strength and aerobic training. While time constraints and feasibility are important considerations for exercise strategies in μG, certain considerations could be made when prescribing concurrent strength and aerobic training to those experiencing human space flight. If strength and aerobic exercise must be performed in close proximity, strength should precede aerobic stimulus. Eccentric strength training methods should be considered to increase mechanical load and reduce metabolic cost. For aerobic capacity, maintenance cycle and/or rowing-based high-intensity intermittent training (HIIT) should be considered and cycle ergometry and/or rowing may be preferable to treadmill running.

Effect of combining pre-exercise carbohydrate intake and repeated short sprints on the blood glucose response to moderate-intensity exercise in young individuals with Type 1 diabetes

AIMS

To determine whether pre-exercise ingestion of carbohydrates to maintain stable glycaemia during moderate-intensity exercise results in excessive hyperglycaemia if combined with repeated sprints in individuals with Type 1 diabetes.

METHODS

Eight overnight-fasted people with Type 1 diabetes completed the following four 40-min exercise sessions on separate days in a randomized counterbalanced order under basal insulinaemic conditions: continuous moderate-intensity exercise at 50% V ˙ O 2 peak; intermittent high-intensity exercise (moderate-intensity exercise interspersed with 4-s sprints every 2 min and a final 10-s sprint); continuous moderate-intensity exercise with prior carbohydrate intake (~10 g per person); and intermittent high-intensity exercise with prior carbohydrate intake. Venous blood was sampled during and 2 h after exercise to measure glucose and lactate levels.

RESULTS

The difference in marginal mean time-averaged area under the blood glucose curve between continuous moderate-intensity exercise + prior carbohydrate and intermittent high-intensity exercise + prior carbohydrate during exercise and recovery was not significant [0.2 mmol/l (95% CI -0.7, 1.1); P = 0.635], nor was the difference in peak blood glucose level after adjusting for baseline level [0.2 mmol/l (95% CI -0.7, 1.1); P = 0.695]. The difference in marginal mean time-averaged area under the blood glucose curve between continuous moderate-intensity and intermittent high-intensity exercise during exercise and recovery was also not significant [-0.2 mmol/l (95% CI -1.2, 0.8); P = 0.651].

CONCLUSIONS

When carbohydrates are ingested prior to moderate-intensity exercise, adding repeated sprints is not significantly detrimental to glycaemic management in overnight fasted people with Type 1 diabetes under basal insulin conditions.

Dietary protein affects both the dose and pattern of insulin delivery required to achieve postprandial euglycaemia in Type 1 diabetes: a randomized trial

AIM

To quantify the insulin requirement for a high-protein meal compared with a low-protein meal, controlling for carbohydrate and fat content.

METHODS

In this crossover study, young people with Type 1 diabetes were randomized to consume a high- (60 g) or low-protein meal (5 g), each containing 30 g carbohydrate and 8 g fat. A variation of the insulin clamp technique was used to determine the insulin requirements to maintain euglycaemia for the following 5 h.

RESULTS

A total of 11 participants (mean ± sd age 16.5 ± 2.7 years, HbA_1c 52 ± 8.7 mmol/mol [6.9 ± 0.8%], diabetes duration 6.9±5.1 years) completed the study. The mean insulin requirements for the high-protein meal were higher than for the low-protein meal [10.3 (CI 8.2, 12.57) vs 6.7 units (CI 4.7, 8.8); P=0.001], with inter-individual requirements ranging from 0.9 to six times the low-protein meal requirement. Approximately half the additional insulin [1.1 units/h (CI 0.5, 1.8; P=0.001)] was given in the first 2 h, compared with an additional 0.5 units/h (CI -0.2, 1.2; P=0.148) in the second 2 h and 0.1 units (CI -0.6, 0.8; P=0.769) in the final hour.

CONCLUSIONS

A high-protein meal requires ~50% more insulin to maintain euglycaemia than a low-protein meal that contains the same quantity of carbohydrate. The majority is required within the first 2 h. Inter-individual differences exist in insulin requirements for dietary protein.

A randomized comparison of three prandial insulin dosing algorithms for children and adolescents with Type 1 diabetes

AIM

To compare systematically the impact of two novel insulin-dosing algorithms (the Pankowska Equation and the Food Insulin Index) with carbohydrate counting on postprandial glucose excursions following a high fat and a high protein meal.

METHODS

A randomized, crossover trial at two Paediatric Diabetes centres was conducted. On each day, participants consumed a high protein or high fat meal with similar carbohydrate amounts. Insulin was delivered according to carbohydrate counting, the Pankowska Equation or the Food Insulin Index. Subjects fasted for 5 h following the test meal and physical activity was standardized. Postprandial glycaemia was measured for 300 min using continuous glucose monitoring.

RESULTS

33 children participated in the study. When compared to carbohydrate counting, the Pankowska Equation resulted in lower glycaemic excursion for 90-240 min after the high protein meal (p < 0.05) and lower peak glycaemic excursion (p < 0.05). The risk of hypoglycaemia was significantly lower for carbohydrate counting and the Food Insulin Index compared to the Pankowska Equation (OR 0.76 carbohydrate counting vs. the Pankowska Equation and 0.81 the Food Insulin Index vs. the Pankowska Equation). There was no significant difference in glycaemic excursions when carbohydrate counting was compared to the Food Insulin Index.

CONCLUSION

The Pankowska Equation resulted in reduced postprandial hyperglycaemia at the expense of an increase in hypoglycaemia. There were no significant differences when carbohydrate counting was compared to the Food Insulin Index. Further research is required to optimize prandial insulin dosing.

The time lag prior to the rise in glucose requirements to maintain stable glycaemia during moderate exercise in a fasted insulinaemic state is of short duration and unaffected by the level at which glycaemia is maintained in Type 1 diabetes

AIMS

To determine the duration of the low hypoglycaemia risk period after the start of moderate-intensity exercise performed under basal insulinaemic conditions and whether this period is affected by the level at which glycaemia is maintained under these conditions.

METHODS

This was a prospective, randomized counterbalanced study. Eight participants with Type 1 diabetes (mean ± sd age 21.5 ± 4.0 years) underwent either a euglycaemic (5-6 mmol/l) or hyperglycaemic clamp (9-10 mmol/l) on separate days and were infused with insulin at basal rates and [6,6-² H]glucose while cycling for 40 min at 50% maximum oxygen consumption rate. The main outcome measures were the glucose infusion rates required to maintain stable glycaemia and glucoregulatory hormone levels, and rates of glucose appearance and disappearance.

RESULTS

During the first 20 min of exercise, the glucose infusion rate did not increase significantly, irrespective of the level at which glycaemia was maintained, but increased acutely between 20 and 25 min under both conditions. Maintaining higher glycaemia resulted in higher glucose infusion rate during, but not early post-exercise. With the exception of epinephrine, the glucoregulatory hormone levels and rates of glucose appearance and disappearance were similar between conditions.

CONCLUSION

Irrespective of the levels at which glycaemia is maintained, there is a 20-min low exogenous glucose demand period during which the exogenous glucose requirements to maintain stable glycaemia do not increase during moderate exercise performed at basal insulin level.

The glycaemic benefits of a very-low-carbohydrate ketogenic diet in adults with Type 1 diabetes mellitus may be opposed by increased hypoglycaemia risk and dyslipidaemia

AIMS

To investigate whether very-low-carbohydrate high-fat diets, typical of ketogenic diets, can improve glycaemic control without causing any ill health effects in adults with Type 1 diabetes.

METHODS

In this observational study, 11 adults with Type 1 diabetes (seven men, four women, mean ± sd age 36.1± 6.8 years, mean ± sd duration of diabetes 12.8 ± 10.3 years), who followed a ketogenic diet (< 55 g carbohydrate per day) for a mean ± sd of 2.6 ± 3.3 years (β-hydroxybutyrate 1.6 ± 1.3 mmol/l), underwent sampling and analysis of fasting blood, and were fitted with a blinded continuous glucose monitor for 7 days to measure glycaemic variability.

RESULTS

The mean ± sd HbA1c levels were 35±4 mmol/mol (5.3±0.4%), and participants spent 74±20 and 3±8% of their time in the euglycaemic (4-8 mmol/l) and hyperglycaemic (>10 mmol/l) ranges, respectively, with little daily glycaemic variability (sd 1.5±0.7 mmol/l; coefficient of variation 26±8%). Blood glucose levels were <3.0 mmol/l for 3.6% of the time, and participants experienced a median (range) of 0.9 (0.0-2.0) daily episodes of hypoglycaemia. Total cholesterol, LDL cholesterol, total cholesterol/HDL cholesterol ratio, and triglycerides were above the recommended range in 82%, 82%, 64% and 27% of participants, respectively; however, HDL cholesterol levels were within the recommended range for all participants. Participants displayed no or little evidence of hepatic or renal dysfunction.

CONCLUSION

This study provides the first evidence that, ketogenic diets in adults with Type 1 diabetes are associated with excellent HbA1c levels and little glycaemic variability, but may also be associated with dyslipidaemia and a high number of hypoglycaemic episodes.

Psychiatric disorders during early adulthood in those with childhood onset type 1 diabetes: Rates and clinical risk factors from population-based follow-up

AIM

To determine the incidence of and risk factors for psychiatric disorders in early adulthood in patients with childhood onset type 1 diabetes (T1D).

METHODS

In this retrospective-cohort study, we identified a population-based childhood onset T1D cohort and an age and sex matched (5:1) non-diabetic comparison cohort. Data linkage was used to access inpatient hospitalization data, mental health support service data, and mortality data to follow-up both cohorts into early adulthood.

RESULTS

The mean age of T1D diagnosis was 9.5 years (SD 4.1), with a mean age at end of follow-up of 26.4 years (SD 5.2, max 37.7). The diagnosis of any psychiatric disorder was observed for 187 of 1302 (14.3%) in the T1D cohort and 400 of 6422 (6.2%) in the comparison cohort [adjusted hazard ratio (HR) 2.3; 95% CI 1.9, 2.7]. Anxiety, eating, mood, and personality and behaviour disorders were observed at higher rates within the T1D cohort. Comorbid psychiatric disorders were more frequent, at the cohort level, within the T1D cohort (2-3 disorders 3.76% vs 1.56%) and service utilization was higher (15+ contacts 6.8% vs 2.8%); though these differences did not remain when restricted to only those individuals diagnosed during follow-up. A history of poor glycaemic control was associated with an increased risk of anxiety, mood, and 'any' disorder (HR ranging from 1.35 to 1.42 for each 1% increase in mean paediatric HbA1c).

CONCLUSION

Our findings highlight the need for access to mental health support services as part of routine patient care for young adults with T1D, and for better predictive tools to facilitate targeting at-risk patients with early intervention programs.

Home-based vs inpatient education for children newly diagnosed with type 1 diabetes

BACKGROUND

Initial management of children diagnosed with type 1 diabetes (T1D) varies worldwide with sparse high quality evidence regarding the impact of different models of care.

AIM

To compare the inpatient model of care with a hybrid home-based alternative, examining metabolic and psychosocial outcomes, diabetes knowledge, length of stay, and patient satisfaction.

SUBJECTS AND METHODS

The study design was a randomized-controlled trial. Inclusion criteria were: newly diagnosed T1D, aged 3 to 16 years, living within approximately 1 hour of the hospital, English-speaking, access to transport, absence of significant medical or psychosocial comorbidity. Patients were randomized to standard care with a 5 to 6 day initial inpatient stay or discharge after 2 days for home-based management. All patients received practical skills training in the first 48 hours. The intervention group was visited twice/day by a nurse for 2 days to assist with injections, then a multi-disciplinary team made 3 home visits over 2 weeks to complete education. Patients were followed up for 12 months. Clinical outcomes included HbA1c, hypoglycemia, and diabetes-related readmissions. Surveys measured patient satisfaction, diabetes knowledge, family impact, and quality of life.

RESULTS

Fifty patients were recruited, 25 to each group. There were no differences in medical or psychosocial outcomes or diabetes knowledge. Average length of admission was 1.9 days shorter for the intervention group. Families indicated that with hindsight, most would choose home- over hospital-based management.

CONCLUSIONS

With adequate support, children newly diagnosed with T1D can be safely managed at home following practical skills training.

A 10-second sprint does not blunt hormonal counter-regulation to subsequent hypoglycaemia

AIM

To investigate whether a 10-second (s) sprint impairs the counter-regulatory response to subsequent hypoglycaemia.

METHODS

Nine people (five male, four female) with Type 1 diabetes, aged 21.1 ± 4.5 years, performed a 10-s rest or a 10-s maximum-effort sprint in random order on different days, while subjected to an euinsulinaemic-euglycaemic clamp. This was followed by a hyperinsulinaemic-hypoglycaemic glucose clamp 2.5 h later to induce hypoglycaemia for 40 min. At timed intervals, the counter-regulatory hormonal responses to hypoglycaemia were measured. Blood pressure, heart rate and hypoglycaemic symptoms were also assessed.

RESULTS

During the hypoglycaemic clamp, epinephrine, norepinephrine, growth hormone and cortisol levels increased significantly from baseline, and their responses were similar after both rest and sprint conditions. In particular, plasma epinephrine rose eightfold, from 197 ± 103 pmol/l to 1582 ± 1118 pmol/l after the rest condition, and from 219 ± 119 pmol/l to 1900 ± 898 pmol/l after the sprint condition.

CONCLUSION

A 10-s sprint is unlikely to blunt the subsequent hormonal counter-regulation to hypoglycaemia in individuals with Type 1 diabetes.

Current nonclinical testing paradigm enables safe entry to First-In-Human clinical trials: The IQ consortium nonclinical to clinical translational database

The contribution of animal testing in drug development has been widely debated and challenged. An industry-wide nonclinical to clinical translational database was created to determine how safety assessments in animal models translate to First-In-Human clinical risk. The blinded database was composed of 182 molecules and contained animal toxicology data coupled with clinical observations from phase I human studies. Animal and clinical data were categorized by organ system and correlations determined. The 2×2 contingency table (true positive, false positive, true negative, false negative) was used for statistical analysis. Sensitivity was 48% with a 43% positive predictive value (PPV). The nonhuman primate had the strongest performance in predicting adverse effects, especially for gastrointestinal and nervous system categories. When the same target organ was identified in both the rodent and nonrodent, the PPV increased. Specificity was 84% with an 86% negative predictive value (NPV). The beagle dog had the strongest performance in predicting an absence of clinical adverse effects. If no target organ toxicity was observed in either test species, the NPV increased. While nonclinical studies can demonstrate great value in the PPV for certain species and organ categories, the NPV was the stronger predictive performance measure across test species and target organs indicating that an absence of toxicity in animal studies strongly predicts a similar outcome in the clinic. These results support the current regulatory paradigm of animal testing in supporting safe entry to clinical trials and provide context for emerging alternate models.

Reproducibility of the plasma glucose response to moderate-intensity exercise in adolescents with Type 1 diabetes

AIMS

The aim of the study was to evaluate the reproducibility of the plasma glucose response to moderate-intensity exercise performed on different days under controlled conditions in adolescents with Type 1 diabetes.

METHODS

Eight adolescents with Type 1 diabetes on continuous subcutaneous insulin infusion completed two exercise sessions, each on two separate days, under basal insulin and fasting conditions. On each day, participants cycled twice for 30 min at 55% of their peak rate of oxygen consumption, with each exercise session separated by a 30-min rest.

RESULTS

Plasma insulin levels were similar between testing days and exercise sessions. The mean absolute drop in plasma glucose from the commencement to the end of exercise was 1.6 ± 0.5 mmol/l on day 1 and 1.9 ± 0.7 mmol/l on day 2 (P = 0.3). In response to the first exercise session, plasma glucose levels relative to baseline did not change significantly (0.2 ± 0.6 and -0.2 ± 0.5 mmol/l on days 1 and 2). By contrast, the change in plasma glucose during the second exercise session was -1.1 ± 0.7 and -1.3 ± 0.7mmol/l on days 1 and 2, respectively. The mean absolute intra-individual difference in the change in plasma glucose between testing days were 0.7 ± 0.5 [95% confidence interval (CI) 0.4-1.0] and 0.7 ± 0.4 (95% CI 0.4-1.0) mmol/l, at the end of the first and second exercise sessions respectively.

CONCLUSIONS

The plasma glucose response to moderate-intensity exercise under similar glycaemic and basal insulin conditions can be reproducible in adolescents with Type 1 diabetes.

Regulatory Forum Opinion Piece*: Use and Utility of Animal Models of Disease for Nonclinical Safety Assessment: A Pharmaceutical Industry Survey

An Innovation and Quality (IQ) Consortium focus group conducted a cross-company survey to evaluate current practices and perceptions around the use of animal models of disease (AMDs) in nonclinical safety assessment of molecules in clinical development. The IQ Consortium group is an organization of pharmaceutical and biotechnology companies with the mission of advancing science and technology. The survey queried the utilization of AMDs during drug discovery in which drug candidates are evaluated in efficacy models and limited short-duration non-Good Laboratory Practices (GLP) toxicology testing and during drug development in which drug candidates are evaluated in GLP toxicology studies. The survey determined that the majority of companies used AMDs during drug discovery primarily as a means for proactively assessing potential nonclinical safety issues prior to the conduct of toxicology studies, followed closely by the use of AMDs to better understand toxicities associated with exaggerated pharmacology in traditional toxicology models or to derisk issues when the target is only expressed in the disease state. In contrast, the survey results indicated that the use of AMDs in development is infrequent, being used primarily to investigate nonclinical safety issues associated with targets expressed only in disease states and/or in response to requests from global regulatory authorities.

Influence of Environmental Conditions on Performance and Heart Rate Responses to the 30-15 Incremental Fitness Test in Rugby Union Athletes

Natera, AOW, Jennings, J, Oakley, AJ, and Jones, TW. Influence of environmental conditions on performance and heart rate responses to the 30-15 incremental fitness test in rugby union athletes. J Strength Cond Res 33(2): 486-491, 2019-The purpose of this study was to examine the differences in performance and heart rate (HR) responses between a high heat outdoor condition (34.0° C, 64.1% humidity) and a temperate indoor condition (22.0° C, 50.0% humidity) during the 30-15 intermittent fitness test (30-15IFT). Eight highly trained Rugby Union players (28.1 ± 1.5 years, 181.4 ± 8.8 cm, 88.4 ± 13.3 kg) completed the 30-15IFT in 2 different temperature conditions. Dependent variables recorded and analyzed included: final running speed of the 30-15IFT, HR at rest (HR rest), maximum HR (Max HR), HR recovery, average HR (HR ave), and submaximal HR corresponding to 25, 50, and 75% of final test speed (HR 25%, HR 50%, and HR 75%) and HR at 13 km·h (HR 13 km·h). Greater running speeds were achieved when the test was conducted indoors (19.4 ± 0.7 km·h vs. 18.6 ± 0.6 km·h, p = 0.002, d = 1.67). Average HR and HR 13 km·h were greater when the test was conducted outdoors (p ≤ 0.05, d > 0.85). Large effect sizes were observed for the greater HR at submaximal intensities (d > 0.90). The results of this study highlight the influence of temperature on 30-15IFT performance and cardiac responses. It is recommended that prescription of training based on 30-15IFT results reflects the temperature that the training will be performed in and that practitioners acknowledge that a meaningful change in assessment results can be the result of seasonal temperature change rather than training-induced change.

Strength and Conditioning and Concurrent Training Practices in Elite Rugby Union

Jones, TW, Smith, A, Macnaughton, LS, and French, DN. Strength and Conditioning and Concurrent Training Practices in Elite Rugby Union. J Strength Cond Res 30(12): 3354-3366, 2016-There is limited published research on strength and conditioning (S&C) practices in elite rugby union (RU). Information regarding testing batteries and programme design would provide valuable information to both applied practitioners and researchers investigating the influence of training interventions or preperformance strategies. The aim of this study was to detail the current practices of S&C coaches and sport scientists working in RU. A questionnaire was developed that comprised 7 sections: personal details, physical testing, strength and power development, concurrent training, flexibility development, unique aspects of the programme, and any further relevant information regarding prescribed training programmes. Forty-three (41 men, 2 women; age: 33.1 ± 5.3 years) of 52 (83%) coaches responded to the questionnaire. The majority of practitioners worked with international level and/or professional RU athletes. All respondents believed strength training benefits RU performance and reported that their athletes regularly performed strength training. The clean and back squat were rated the most important prescribed exercises. Forty-one (95%) respondents reported prescribing plyometric exercises and 38 (88%) indicated that periodization strategies were used. Forty-two (98%) practitioners reported conducting physical testing, with body composition being the most commonly tested phenotype. Thirty-three (77%) practitioners indicated that the potential muted strength development associated with concurrent training was considered when programming and 27 (63%) believed that strength before aerobic training was more favorable for strength development than vice versa. This research represents the only published survey to date of S&C practices in northern and southern hemisphere RU.

Performance and Endocrine Responses to Differing Ratios of Concurrent Strength and Endurance Training

The present study examined functional strength and endocrine responses to varying ratios of strength and endurance training in a concurrent training regimen. Thirty resistance trained men completed 6 weeks of 3 d·wk of (a) strength training (ST), (b) concurrent strength and endurance training ratio 3:1 (CT3), (c) concurrent strength and endurance training ratio 1:1 (CT1), or (d) no training (CON). Strength training was conducted using whole-body multijoint exercises, whereas endurance training consisted of treadmill running. Assessments of maximal strength, lower-body power, and endocrine factors were conducted pretraining and after 3 and 6 weeks. After the intervention, ST and CT3 elicited similar increases in lower-body strength; furthermore, ST resulted in greater increases than CT1 and CON (all p ≤ 0.05). All training conditions resulted in similar increases in upper-body strength after training. The ST group observed greater increases in lower-body power than all other conditions (all p ≤ 0.05). After the final training session, CT1 elicited greater increases in cortisol than ST (p = 0.008). When implemented as part of a concurrent training regimen, higher volumes of endurance training result in the inhibition of lower-body strength, whereas low volumes do not. Lower-body power was attenuated by high and low frequencies of endurance training. Higher frequencies of endurance training resulted in increased cortisol responses to training. These data suggest that if strength development is the primary focus of a training intervention, frequency of endurance training should remain low.

SIXTY SECONDS OF FOAM ROLLING DOES NOT AFFECT FUNCTIONAL FLEXIBILITY OR CHANGE MUSCLE TEMPERATURE IN ADOLESCENT ATHLETES

BACKGROUND

Physiotherapists and other practitioners commonly prescribe foam rolling as an intervention, but the mechanistic effects of this intervention are not known.

PURPOSE

The aim of this investigation was to establish if a single bout of foam rolling affects flexibility, skeletal muscle contractility and reflected temperature.

METHODS

Twelve adolescent male squash players were evaluated on two separate occasions (treatment and control visits) and were tested on both legs for flexibility of the hip flexors and quadriceps, muscle contractility (as measured by tensiomyography) and temperature of the quadriceps (assessed via thermography) at repeated time points pre- and post a 60s rolling intervention (pre-, immediately post, 5, 10, 15, and 30 minutes post). They rolled one leg on the treatment visit and did not perform rolling on the control visit.

RESULTS

The main outcome measure was the flexibility of hip flexor and quadriceps at repeated time points up to 30 minutes post intervention. The average foam rolling force was 68% of subject's body weight. This force affected the combination of hip and quadriceps flexibility (p = 0.03; 2.4 degrees total increase with foam rolling) but not each muscle independently (p = 0.05 - 0.98) following a single 60s bout. Muscle contractility is not affected (p = 0.09 - 0.93) and temperature is not increased by foam rolling across time points (p = 0.19).

CONCLUSIONS

A single sixty-second bout of rolling applied to the quadriceps induces a small significant change in flexibility that is of little practical relevance, while muscle contractility and temperature remain unchanged. Investigation of larger doses of rolling is merited in athletic populations to justify current practice.

LEVEL OF EVIDENCE

2c.

Safety and efficacy of the predictive low glucose management system in the prevention of hypoglycaemia: protocol for randomised controlled home trial to evaluate the Suspend before low function

INTRODUCTION

Innovations with sensor-augmented pump therapy (SAPT) to reduce hypoglycaemia in patients with type 1 diabetes are an ongoing area of research. The predictive low glucose management (PLGM) system incorporates continuous glucose sensor data into an algorithm and suspends basal insulin before the occurrence of hypoglycaemia. The system was evaluated in in-clinic studies, and has informed the parameters of a larger home trial to study its efficacy and safety in real life.

METHODS AND ANALYSIS

The aim of this report is to describe the study design and outcome measures for the trial. This is a 6-month, multicentre, randomised controlled home trial to test the PLGM system in children and adolescents with type 1 diabetes. The system is available in the Medtronic MiniMed 640G pump as the 'Suspend before low' feature. Following a run-in period, participants are randomised to either the control arm with SAPT alone or the intervention arm with SAPT and Suspend before low. The primary aim of this study is to evaluate the time spent hypoglycaemic (sensor glucose <3.5 mmol/L) with and without the system. The secondary aims are to determine the number of hypoglycaemic events, the time spent hyperglycaemic, and to evaluate safety with ketosis and changes in glycated haemoglobin. The study also aims to assess the changes in counter-regulatory hormone responses to hypoglycaemia evaluated by a hyperinsulinaemic hypoglycaemic clamp in a subgroup of patients with impaired awareness. Validated questionnaires are used to measure the fear of hypoglycaemia and the impact on the quality of life to assess burden of the disease.

ETHICS AND DISSEMINATION

Ethics committee permissions were gained from respective Institutional Review boards. The findings of the study will provide high quality evidence of the ability of the system in the prevention of hypoglycaemia in real life.

TRIAL REGISTRATION NUMBER

ACTRN12614000510640, Pre-results.

The effect of age on the relationship between cardiac and vascular function

Age-related changes in cardiac and vascular function are associated with increased risk of cardiovascular mortality and morbidity. The aim of the present study was to define the effect of age on the relationship between cardiac and vascular function. Haemodynamic and gas exchange measurements were performed at rest and peak exercise in healthy individuals. Augmentation index was measured at rest. Cardiac power output, a measure of overall cardiac function, was calculated as the product of cardiac output and mean arterial blood pressure. Augmentation index was significantly higher in older than younger participants (27.7 ± 10.1 vs. 2.5 ± 10.1%, P<0.01). Older people demonstrated significantly higher stroke volume and mean arterial blood pressure (P<0.05), but lower heart rate (145 ± 13 vs. 172 ± 10 beats/min, P<0.01) and peak oxygen consumption (22.5 ± 5.2 vs. 41.2 ± 8.4 ml/kg/min, P<0.01). There was a significant negative relationship between augmentation index and peak exercise cardiac power output (r=-0.73, P=0.02) and cardiac output (r=-0.69, P=0.03) in older participants. Older people maintain maximal cardiac function due to increased stroke volume. Vascular function is a strong predictor of overall cardiac function in older but in not younger people.

Effect of carbohydrate feeding on the bone metabolic response to running

Bone resorption is increased after running, with no change in bone formation. Feeding during exercise might attenuate this increase, preventing associated problems for bone. This study investigated the immediate and short-term bone metabolic responses to carbohydrate (CHO) feeding during treadmill running. Ten men completed two 7-day trials, once being fed CHO (8% glucose immediately before, every 20 min during, and immediately after exercise at a rate of 0.7 g CHO·kg body mass⁻¹·h⁻¹) and once being fed placebo (PBO). On day 4 of each trial, participants completed a 120-min treadmill run at 70% of maximal oxygen consumption (V̇o_{2 max}). Blood was taken at baseline (BASE), immediately after exercise (EE), after 60 (R1) and 120 (R2) min of recovery, and on three follow-up days (FU1-FU3). Markers of bone resorption [COOH-terminal telopeptide region of collagen type 1 (β-CTX)] and formation [NH₂-terminal propeptides of procollagen type 1 (P1NP)] were measured, along with osteocalcin (OC), parathyroid hormone (PTH), albumin-adjusted calcium (ACa), phosphate, glucagon-like peptide-2 (GLP-2), interleukin-6 (IL-6), insulin, cortisol, leptin, and osteoprotogerin (OPG). Area under the curve was calculated in terms of the immediate (BASE, EE, R1, and R2) and short-term (BASE, FU1, FU2, and FU3) responses to exercise. β-CTX, P1NP, and IL-6 responses to exercise were significantly lower in the immediate postexercise period with CHO feeding compared with PBO (β-CTX: P = 0.028; P1NP: P = 0.021; IL-6: P = 0.036), although there was no difference in the short-term response (β-CTX: P = 0.856; P1NP: P = 0.721; IL-6: P = 0.327). No other variable was significantly affected by CHO feeding during exercise. We conclude that CHO feeding during exercise attenuated the β-CTX and P1NP responses in the hours but not days following exercise, indicating an acute effect of CHO feeding on bone turnover.

Glycaemic control of Type 1 diabetes in clinical practice early in the 21st century: an international comparison

AIMS

Improving glycaemic control in people with Type 1 diabetes is known to reduce complications. Our aim was to compare glycaemic control among people with Type 1 diabetes using data gathered in regional or national registries.

METHODS

Data were obtained for children and/or adults with Type 1 diabetes from the following countries (or regions): Western Australia, Austria, Denmark, England, Champagne-Ardenne (France), Germany, Epirus, Thessaly and Thessaloniki (Greece), Galway (Ireland), several Italian regions, Latvia, Rotterdam (The Netherlands), Otago (New Zealand), Norway, Northern Ireland, Scotland, Sweden, Volyn (Ukraine), USA and Wales) from population or clinic-based registries. The sample size with available data varied from 355 to 173 880. Proportions with HbA1c < 58 mmol/mol (< 7.5%) and ≥ 75 mmol/mol (≥ 9.0%) were compared by age and sex.

RESULTS

Data were available for 324 501 people. The proportions with HbA1c 58 mmol/mol (< 7.5%) varied from 15.7% to 46.4% among 44 058 people aged < 15 years, from 8.9% to 49.5% among 50 766 people aged 15-24 years and from 20.5% to 53.6% among 229 677 people aged ≥ 25 years. Sex differences in glycaemic control were small. Proportions of people using insulin pumps varied between the 12 sources with data available.

CONCLUSION

These results suggest that there are substantial variations in glycaemic control among people with Type 1 diabetes between the data sources and that there is room for improvement in all populations, especially in young adults.

Clinical and demographic risk factors associated with mortality during early adulthood in a population-based cohort of childhood-onset type 1 diabetes

AIMS

To calculate standardized mortality ratios and to assess the association between paediatric clinical factors and higher risk of mortality during early adulthood in a population-based cohort of subjects with Type 1 diabetes.

METHODS

Subjects with Type 1 diabetes were identified through the Western Australian Children's Diabetes Database and clinical data for those who reached 18 years of age (n = 1309) were extracted. An age- and sex-matched (without diabetes) comparison cohort (n = 6451) was obtained from the birth registry. Mortality records were obtained from the death registry. Participants were followed up until 31 January 2012. Associations of clinical factors (from clinic visits before 18 years of age) with mortality were assessed using Cox proportional hazard models.

RESULTS

The standardized mortality ratio for all-cause mortality was 1.7 (95% CI 0.7-3.3) for male and 10.1 (95% CI 5.2-17.7) for female subjects with Type 1 diabetes (median age at end of study 25.6 years). The adjusted hazard ratio was 1.5 (95% CI 1.1-2.1) for a 1% increase in mean paediatric HbA1c level, 3.8 (95% CI 0.9-15.3) for four episodes of severe hypoglycaemia relative to zero episodes, and 6.21 (95% CI 1.4-28.4) for a low-level socio-economic background relative to a high-level background.

CONCLUSIONS

People with childhood-onset Type 1 diabetes have higher mortality rates in early adulthood. At particularly high risk are women, those with a history of poor HbA1c levels, those with recurrent severe hypoglycaemia during paediatric management, and those from a low socio-economic background. These groups may benefit from intensified management during transition from paediatric to adult care facilities.

Performance and neuromuscular adaptations following differing ratios of concurrent strength and endurance training

The interference effect attenuates strength and hypertrophic responses when strength and endurance training are conducted concurrently; however, the influence of training frequency on these responses remain unclear when varying ratios of concurrent strength and endurance training are performed. Therefore, the purpose of the study was to examine the strength, limb girth, and neuromuscular adaptations to varying ratios of concurrent strength and endurance training. Twenty-four men with >2 years resistance training experience completed 6 weeks of 3 days per week of (a) strength training (ST), (b) concurrent strength and endurance training ratio 3:1 (CT3), (c) concurrent strength and endurance training ratio 1:1 (CT1), or (d) no training (CON) in an isolated limb model. Assessments of maximal voluntary contraction by means of isokinetic dynamometry leg extensions (maximum voluntary suppression [MVC]), limb girth, and neuromuscular responses through electromyography (EMG) were conducted at baseline, mid-intervention, and postintervention. After training, ST and CT3 conditions elicited greater MVC increases than CT1 and CON conditions (p ≤ 0.05). Strength training resulted in significantly greater increases in limb girth than both CT1 and CON conditions (p = 0.05 and 0.004, respectively). The CT3 induced significantly greater limb girth adaptations than CON condition (p = 0.04). No effect of time or intervention was observed for EMG (p > 0.05). In conclusion, greater frequencies of endurance training performed increased the magnitude of the interference response on strength and limb girth responses after 6 weeks of 3 days a week of training. Therefore, the frequency of endurance training should remain low if the primary focus of the training intervention is strength and hypertrophy.

Hypoglycaemia, fear of hypoglycaemia and quality of life in children with Type 1 diabetes and their parents

AIM

To evaluate the association between fear of hypoglycaemia, episodes of hypoglycaemia and quality of life in children with Type 1 diabetes and their parents.

METHODS

This was a cross-sectional, population-based study of 325 children with Type 1 diabetes and their parents. The children were aged 2-18 years. A total of 325 parents of the patients aged 2-18 years and 196 of the patients themselves (aged 8-18 years) completed questionnaires including the PedsQL Diabetes Module, the Hypoglycaemia Fear Survey and Clarke's hypoglycaemia awareness questionnaire. Data were compared with HbA1c results and the history of severe hypoglycaemia episodes.

RESULTS

Parents with the highest levels of fear of hypoglycaemia reported that their children had a reduced quality of life (P < 0.001). Similarly children with the greatest fear also reported a reduced quality of life (P < 0.001); however a history of severe hypoglycaemia was not associated with the child's quality of life as perceived by the child or parent. Episodes of severe hypoglycaemia were associated with an increased fear of hypoglycaemia for the parents (P = 0.004) but not the children. Children in the highest fear quartile also had a higher HbA(1c) concentration compared with those in the lowest fear quartile [increase in HbA(1c) 7 mmol/mol (0.6%), P < 0.01].

CONCLUSIONS

Fear of hypoglycaemia and not episodes of hypoglycaemia per se is associated with increased psychological burden for children with Type 1 diabetes. Interventions to reduce fear of hypoglycaemia in these families may improve their quality of life.

The effect of a short sprint on postexercise whole-body glucose production and utilization rates in individuals with type 1 diabetes mellitus

CONTEXT

Recently we showed that a 10-sec maximal sprint effort performed before or after moderate intensity exercise can prevent early hypoglycemia during recovery in individuals with type 1 diabetes mellitus (T1DM). However, the mechanisms underlying this protective effect of sprinting are still unknown.

OBJECTIVE

The objective of the study was to test the hypothesis that short duration sprinting increases blood glucose levels via a disproportionate increase in glucose rate of appearance (Ra) relative to glucose rate of disappearance (Rd). SUBJECTS AND EXPERIMENTAL DESIGN: Eight T1DM participants were subjected to a euglycemic-euinsulinemic clamp and, together with nondiabetic participants, were infused with [6,6-(2)H]glucose before sprinting for 10 sec and allowed to recover for 2 h.

RESULTS

In response to sprinting, blood glucose levels increased by 1.2 ± 0.2 mmol/liter (P < 0.05) within 30 min of recovery in T1DM participants and remained stable afterward, whereas glycemia rose by only 0.40 ± 0.05 mmol/liter in the nondiabetic group. During recovery, glucose Ra did not change in both groups (P > 0.05), but glucose Rd in the nondiabetic and diabetic participants fell rapidly after exercise before returning within 30 min to preexercise levels. After sprinting, the levels of plasma epinephrine, norepinephrine, and GH rose transiently in both experimental groups (P < 0.05).

CONCLUSION

A sprint as short as 10 sec can increase plasma glucose levels in nondiabetic and T1DM individuals, with this rise resulting from a transient decline in glucose Rd rather than from a disproportionate rise in glucose Ra relative to glucose Rd as reported with intense aerobic exercise.

Measurement of the ZZ production cross section and limits on anomalous neutral triple gauge couplings in proton-proton collisions at sqrt[s] = 7 TeV with the ATLAS detector

A measurement of the ZZ production cross section in proton-proton collisions at sqrt[s] = 7 TeV using data corresponding to an integrated luminosity of 1.02 fb(-1) recorded by the ATLAS experiment at the LHC is presented. Twelve events containing two Z boson candidates decaying to electrons and/or muons are observed, with an expected background of 0.3 ± 0.3(stat)(-0.3)(+0.4)(syst) events. The cross section measured in a phase-space region with good detector acceptance and for dilepton masses within the range 66 to 116 GeV is σ(ZZ → ℓ+ ℓ- ℓ+ ℓ-)(fid) = 19.4(-5.2)(+6.3)(stat)(-0.7)(+0.9)(syst) ± 0.7(lumi) fb. The resulting total cross section for on-shell ZZ production, σ(ZZ)(tot) = 8.5(-2.3)(+2.7)(stat)(-0.3)(+0.4)(syst) ± 0.3(lumi) pb, is consistent with the standard model expectation of 6.5(-0.2)(+0.3) pb calculated at the next-to-leading order in QCD. Limits on anomalous neutral triple gauge boson couplings are derived.

Lower cardiorespiratory fitness in children with Type 1 diabetes

AIMS

The present study aimed to compare cardiorespiratory fitness levels in children with and without Type 1 diabetes. In addition, the relationship between cardiorespiratory fitness and a range of physical and clinical factors was investigated.

METHODS

Eighty-eight children with Type 1 diabetes aged 5-14 years completed a submaximal step test of cardiorespiratory fitness. Sixty-two of these children were successfully matched to control subjects without diabetes based on age, sex and anthropometrics for comparison. In addition, the relationship between cardiorespiratory fitness and a range of physical and clinical variables was assessed in the children with diabetes.

RESULTS

The heart rate response to exercise was higher in children with Type 1 diabetes, indicating reduced cardiorespiratory fitness levels compared with control subjects. Both gender and glycaemic control (HbA(1c) ) were significantly associated with cardiorespiratory fitness, with female sex and poorer glycaemic control associated with reduced fitness.

CONCLUSIONS

Future research should investigate whether the reduced fitness in children with Type 1 diabetes is attributable to lower physical activity levels, or physiological changes resulting from the diabetes pathology itself.

Absence of evidence of translocation of GLUT2 to the apical membrane of enterocytes in everted intestinal sleeves

INTRODUCTION

Traditional models of intestinal glucose absorption confine GLUT2 to the basolateral membrane. Evidence suggests that GLUT2 is translocated to the apical membrane when the enterocyte is exposed to high luminal glucose concentrations.

HYPOTHESIS

GLUT2 translocates to the apical membrane by a PKC signaling mechanism dependent on activity of SGLT1 and the cellular cytostructure.

METHODS

Transporter-mediated glucose uptake was studied in rat jejunum using everted sleeves under seven conditions: Control, SGLT1 inhibition (phlorizin), GLUT2 inhibition (phloretin), both SGLT1 and GLUT2 inhibition, PKC inhibition (calphostin C or chelerythrine), and disruption of cellular cytostructure (nocodazole). Each condition was tested in iso-osmotic solutions of 1, 20, or 50 mM glucose for 1 or 5 min incubations (n = 6 rats each).

RESULTS

Control rats exhibited a saturable pattern of uptake at both durations of incubation. Phlorizin (P ≤ 0.006 each) inhibited markedly and phloretin (P ≤ 0.01 each) inhibited partially glucose uptake in all concentrations and time. Phloretin and phlorizin together completely inhibited uptake (P = 0.004 each). Calphostin C, chelerythrine, and nocodazole had little effect on glucose uptake at either 1 or 5 min. Inhibition of SGLT1 led to near complete cessation of transporter-mediated glucose uptake, while GLUT2 inhibition led to partial inhibition, suggesting some constitutive expression of GLUT2 in the apical membrane. Disruption of PKC signaling or cytoskeletal integrity partially inhibited transporter-mediated glucose uptake only in 1 mM glucose, suggesting a non-specific effect.

CONCLUSIONS

Under these conditions, it does not appear that GLUT2 is translocated to the apical membrane on the cellular cytostructure in response to PKC signaling.