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In Amateur Athletes With Type 1 Diabetes, a 9-Day Period of Cycling at Moderate-to-Vigorous Intensity Unexpectedly Increased the Time Spent in Hyperglycemia, Which Was Associated With Impairment in Heart Rate Variability.
Lespagnol, E, Bocock, O, Heyman, J, Gamelin, FX, Berthoin, S, Pereira, B, Boissière, J, Duclos, M, Heyman, E
Diabetes care. 2020;(10):2564-2573
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Abstract
OBJECTIVE In type 1 diabetes, autonomic dysfunction may occur early as a decrease in heart rate variability (HRV). In populations without diabetes, the positive effects of exercise training on HRV are well-documented. However, exercise in individuals with type 1 diabetes, particularly if strenuous and prolonged, can lead to sharp glycemic variations, which can negatively impact HRV. This study explores the impact of a 9-day cycling tour on HRV in this population, with a focus on exercise-induced glycemic excursions. RESEARCH DESIGN AND METHODS Twenty amateur athletes with uncomplicated type 1 diabetes cycled 1,500 km. HRV and glycemic variability were measured by heart rate and continuous glucose monitoring. Linear mixed models were used to test the effects of exercise on HRV, with concomitant glycemic excursions and subject characteristics considered as covariates. RESULTS Nighttime HRV tended to decrease with the daily distance traveled. The more time the subjects spent in hyperglycemia, the lower the parasympathetic tone was. This result is striking given that hyperglycemic excursions progressively increased throughout the 9 days of the tour, and to a greater degree on the days a longer distance was traveled, while time spent in hypoglycemia surprisingly decreased. This phenomenon occurred despite no changes in insulin administration and a decrease in carbohydrate intake from snacks. CONCLUSIONS In sports enthusiasts with type 1 diabetes, multiday prolonged exercise at moderate-to-vigorous intensity worsened hyperglycemia, with hyperglycemia negatively associated with parasympathetic cardiac tone. Considering the putative deleterious consequences on cardiac risks, future work should focus on understanding and managing exercise-induced hyperglycemia.
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Power Profiles of Competitive and Noncompetitive Mountain Bikers.
Novak, AR, Bennett, KJM, Pluss, MA, Fransen, J, Watsford, ML, Dascombe, BJ
Journal of strength and conditioning research. 2019;(2):538-543
Abstract
Novak, AR, Bennett, KJM, Pluss, MA, Fransen, J, Watsford, ML, and Dascombe, BJ. Power profiles of competitive and noncompetitive mountain bikers. J Strength Cond Res 33(2): 538-543, 2019-The performance of Olympic distance cross-country mountain bikers (XCO-MTB) is affected by constraints such as erosion of track surfaces and mass start congestion which can affect race results. Standardized laboratory assessments quantify interseasonal and intraseasonal cycling potential through the assessment of multiple physiological capacities. Therefore, this study examined whether the power profile assessment (PPA) could discriminate between competitive XCO-MTB and noncompetitive mountain bikers (NC-MTB). Second, it aimed to report normative power profile data for competitive XCO-MTB cyclists. Twenty-nine male participants were recruited across groups of XCO-MTB (n = 14) and NC-MTB (n = 15) mountain bikers. Each cyclist completed a PPA that consisted of increasing duration maximal efforts (6, 15, 30, 60, 240, and 600 seconds) that were interspersed by longer rest periods (174, 225, 330, 480, and 600 seconds) between efforts. Normative power outputs were established for XCO-MTB cyclists ranging between 13.8 ± 1.5 W·kg (5-second effort) and 4.1 ± 0.6 W·kg (600-second effort). No differences in absolute peak power or cadence were identified between groups across any effort length (p > 0.05). However, the XCO-MTB cyclists produced greater mean power outputs relative to body mass than the NC-MTB during the 60-second (6.9 ± 0.8 vs 6.4 ± 0.6 W·kg; p = 0.002), 240-second (4.7 ± 0.7 vs. 3.8 ± 0.4 W·kg; p < 0.001), and 600-second (4.1 ± 0.6 vs. 3.4 ± 0.3 W·kg; p < 0.001) efforts. The PPA is a useful discriminative assessment tool for XCO-MTB and highlights the importance of aerobic power for XCO-MTB performance.
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Renal stress and kidney injury biomarkers in response to endurance cycling in the heat with and without ibuprofen.
McDermott, BP, Smith, CR, Butts, CL, Caldwell, AR, Lee, EC, Vingren, JL, Munoz, CX, Kunces, LJ, Williamson, K, Ganio, MS, et al
Journal of science and medicine in sport. 2018;(12):1180-1184
Abstract
UNLABELLED Exercise, especially in the heat, can contribute to acute kidney injury, which can expedite chronic kidney disease onset. The additional stress of ibuprofen use is hypothesized to increase renal stress. OBJECTIVES To observe the effects of endurance cycling in the heat on renal function. Secondarily, we investigated the effect of ibuprofen ingestion on kidney stress. DESIGN Randomized, placebo controlled and observational methods were utilized. METHODS Forty cyclists (52±9y, 21.7±6.5% body fat) volunteered and completed an endurance cycling event (5.7±1.2h) in the heat (33.2±5.0°C, 38.4±10.7% RH). Thirty-five participants were randomized to ingest a placebo (n=17) or 600mg ibuprofen (n=18) pre-event. A blood sample was drawn before and following the event. Serum creatinine was assessed by colorimetric assay. An ELISA was used to measure serum neutrophil gelatinase-associated lipocalin. Fractional excretion of sodium was calculated after urinary and serum electrolyte analyses. RESULTS Placebo versus ibuprofen groups contributed no significant difference in any variable (p>0.05). Serum creatinine significantly increased from pre- (0.52±0.14mg/dL) to post-event (0.88±0.21mg/dL; p<0.001). Serum neutrophil gelatinase-associated lipocalin significantly increased (pre: 68.51±17.54ng/mL; post: 139.12±36.52ng/mL; p<0.001) and fractional excretion of sodium was significantly reduced from pre- (0.52±0.24%) to post-event (0.27±0.18%; p<0.001). CONCLUSIONS Changes in renal biomarkers suggest mild acute kidney injury and reduced kidney function during a single bout of endurance cycling in the heat, without influence from moderate ibuprofen ingestion.
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Effects of long-term training cessation in young top-level road cyclists.
Maldonado-Martín, S, Cámara, J, James, DVB, Fernández-López, JR, Artetxe-Gezuraga, X
Journal of sports sciences. 2017;(14):1396-1401
Abstract
In cycling, it is common practice to have a break in the off season longer than 4 weeks while adopting an almost sedentary lifestyle, and such a break is considered to be long-term detraining. No previous studies have assessed the effect of training cessation with highly trained young cyclists. The purpose of the present investigation was to examine effects of 5 weeks of training cessation in 10 young (20.1 ± 1.4 years) male road cyclists for body composition, haematological and physiological parameters. After training cessation, body mass of cyclists increased (P = 0.014; ES = 0.9). [Formula: see text] (L · min-1 = -8.8 ± 5.0%, mL · kg-1·min-1 = -10.8 ± 4.2%,), Wmax (W = -6.5 ± 3.1%, W · kg-1 = -8.5 ± 3.3%,), WLT1 (W = -12.9 ± 7.0%, W · kg-1 = -14.8 ± 7.4%,), WLT2 (W = -11.5 ± 7.0%, W · kg-1 = -13.4 ± 7.6%,) and haematological (red blood cells count, -6.6 ± 4.8%; haemoglobin, -5.4 ± 4.3% and haematocrit, -2.9 ± 3.0%) values decreased (P ≤ 0.028; ES ≥ 0.9). Five weeks of training cessation resulted in large decreases in physiological and haematological values in young top-level road cyclists suggesting the need for a shorter training stoppage. This long-term detraining is more pronounced when expressed relative to body mass emphasising the influence of such body mass on power output. A maintenance programme based on reduced training strategies should be implemented to avoid large declines in physiological values in young cyclists who aspire to become professionals.
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Towards Upright Pedalling to drive recovery in people who cannot walk in the first weeks after stroke: movement patterns and measurement.
Hancock, NJ, Shepstone, L, Rowe, P, Myint, PK, Pomeroy, VM
Physiotherapy. 2017;(4):400-406
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Abstract
OBJECTIVES To examine whether people who are within 31days of stroke onset are able to produce controlled lower limb movement, and phasic activity in antagonistic lower limb muscle groups, during Upright Pedalling (UP). DESIGN Observational study. SETTING Acute stroke unit within a University Hospital. PARTICIPANTS Eight adults between 3 and 30days from stroke onset, with unilateral lower limb paresis and unable to walk without assistance. Participants were considered fit to participate as assessed by a physician-led medical team and were able to take part in UP for one, one minute session. INTERVENTION Participants took part in one session of instrumented UP at their comfortable cadence, as part of a feasibility study investigating UP early after stroke. OUTCOME MEASURES Reciprocal activation of lower limb muscles derived from muscle activity recorded with surface EMG, quantified using Jaccards Coefficient (J); smoothness of pedalling determined from standard deviations of time spent in each of eight 45° wheel position bins ("S-Ped"). Motor behavioural measures: Motricity Index, Trunk Control Test, Functional Ambulatory Categories. RESULTS Participants were all unable to walk (FAC 0) with severe to moderate lower limb paresis (Motricity Index score/100 median 48.5, IQR 32 to 65.5). Smooth pedalling was observed; some participants pedalling similarly smoothly to healthy older adults, with a variety of muscle activation patterns in the affected and unaffected legs. CONCLUSION These observational data indicate that people with substantial paresis early after stroke and who cannot walk, can produce smooth movement during UP using a variety of muscle activation strategies.
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Active commuting and obesity in mid-life: cross-sectional, observational evidence from UK Biobank.
Flint, E, Cummins, S
The lancet. Diabetes & endocrinology. 2016;(5):420-35
Abstract
BACKGROUND Physical inactivity is a leading cause of obesity and premature mortality. We aimed to examine the relation between active commuting and obesity in mid-life using objectively measured anthropometric data from UK Biobank. METHODS Cross-sectional, observational data from UK Biobank were used. These were collected from individuals aged 40-69 years who visited 22 assessment centres across the UK between 2006 and 2010. Self-reported commuting method was operationalised into seven categories, ordered to reflect typical levels of physical exertion. The outcomes assessed were BMI (based on objectively measured weight and height) and percentage body fat. Hypothesised confounders were income, area deprivation, urban or rural residence, education, alcohol intake, smoking, leisure physical activity, recreational walking, occupational physical activity, general health, and limiting illness or disability. We used sex-stratified multivariate linear-regression models. FINDINGS Final complete case sample sizes were 72 999 men and 83 667 women for the BMI outcome and 72 139 men and 82 788 women for the percentage body fat outcome. Active commuting was significantly and independently associated with reduced BMI and percentage body fat for both sexes, with a graded pattern apparent across the seven commuting categories. In fully adjusted models, compared with their car-only counterparts, mixed public and active transport commuters had significantly lower BMI (men: β coefficient -1·00 kg/m(2) [95% CI -1·14 to -0·87], p<0·0001; women: -0·67 kg/m(2) [-0·86 to -0·47], p<0·0001), as did cycling or cycling and walking commuters (men: -1·71 kg/m(2) [95% CI -1·86 to -1·56], p<0·0001; women: -1·65 kg/m(2) [-1·92 to -1·38], p<0·0001). Similarly, compared with car-only commuters, mixed public transport and active commuters had significantly lower percentage body fat (men: -1·32% [95% CI -1·53 to -1·12], p<0·0001; women: -1·10% [-1·40 to -0·81], p<0·0001), as did cycling or cycling and walking commuters (men: -2·75% [95% CI -3·03 to -2·48], p<0·0001; women: -3·26% [-3·80 to -2·71], p<0·0001). INTERPRETATION This study is the first to use UK Biobank data to address the topic of active commuting and obesity and shows robust, independent associations between active commuting and healthier bodyweight and composition. These findings support the case for interventions to promote active travel as a population-level policy response for prevention of obesity in mid-life. FUNDING UK Medical Research Council.
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Self-report versus direct measurement for assessment of fluid intake during a 70.3-mile triathlon.
Wilson, PB, Rhodes, GS, Ingraham, SJ
International journal of sports physiology and performance. 2015;(5):600-4
Abstract
PURPOSE Self-report (SR) has been the primary method used to assess fluid intake during endurance events, but unfortunately, little is known about the validity of SR. The purpose of this study was to compare SR fluid intake with direct measurement (DM) during a 70.3-mile triathlon. METHODS Fifty-three (42 men, 11 women) individuals competing in a 70.3-mile triathlon participated in the study. On the 13.1-mile-run section of the triathlon, 11 research stations provided fluid in bottles filled with 163 mL of water or carbohydrate-electrolyte beverage (CEB). Participants submitted bottles 25 m past aid stations to be reweighed postrace. Participants also answered questions regarding fluid intake postrace. Bland-Altman plots and 95% limits of agreement were used to assess precision of the measures, while least-squares regression assessed linear agreement. RESULTS SR intakes during the run ranged from 0-1793, 0-1837, and 0-2628 mL for water, CEB, and total fluid, with corresponding DM intakes of 0-1599, 0-1642, and 0-2250 mL. DM and SR showed strong linear agreement for water, CEB, and total fluid (R2=.71, .80, and .80). Mean differences between the measures on the Bland-Altman plots were small (13-41 mL), but relatively large differences (±500 mL) between the measures were apparent for some participants. CONCLUSIONS SR is the predominant methodology used in field studies assessing hydration, despite little to no data confirming its validity. The results herein suggest that fluid-intake-assessment methodology should be chosen on a case-by-case basis and that caution should be used when interpreting data based on SR.
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Bike and run pacing on downhill segments predict Ironman triathlon relative success.
Johnson, EC, Pryor, JL, Casa, DJ, Belval, LN, Vance, JS, DeMartini, JK, Maresh, CM, Armstrong, LE
Journal of science and medicine in sport. 2015;(1):82-7
Abstract
OBJECTIVES Determine if performance and physiological based pacing characteristics over the varied terrain of a triathlon predicted relative bike, run, and/or overall success. Poor self-regulation of intensity during long distance (Full Iron) triathlon can manifest in adverse discontinuities in performance. DESIGN Observational study of a random sample of Ironman World Championship athletes. High performing and low performing groups were established upon race completion. METHODS Participants wore global positioning system and heart rate enabled watches during the race. Percentage difference from pre-race disclosed goal pace (%off) and mean HR were calculated for nine segments of the bike and 11 segments of the run. Normalized graded running pace (accounting for changes in elevation) was computed via analysis software. Step-wise regression analyses identified segments predictive of relative success and HP and LP were compared at these segments to confirm importance. RESULTS %Off of goal velocity during two downhill segments of the bike (HP: -6.8±3.2%, -14.2±2.6% versus LP: -1.2±4.2%, -5.1±11.5%; p<0.020) and %off from NGP during one downhill segment of the run (HP: 4.8±5.2% versus LP: 33.3±38.7%; p=0.033) significantly predicted relative performance. Also, HP displayed more consistency in mean HR (141±12 to 138±11 bpm) compared to LP (139±17 to 131±16 bpm; p=0.019) over the climb and descent from the turn-around point during the bike component. CONCLUSIONS Athletes who maintained faster relative speeds on downhill segments, and who had smaller changes in HR between consecutive up and downhill segments were more successful relative to their goal times.
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Case study: beverage temperature at aid stations in ironman triathlon.
Burdon, CA, Johnson, NA, Chapman, PG, Munir Che Muhamed, A, O'Connor, HT
International journal of sport nutrition and exercise metabolism. 2013;(4):418-24
Abstract
PURPOSE The aim of this study was to measure the effect of environmental conditions and aid-station beverage- cooling practices on the temperature of competitor beverages. METHODS Environmental and beverage temperatures were measured at three cycling and two run course aid stations at the 2010 Langkawi, Malaysia (MA), and Port Macquarie, Australia (AU), Ironman triathlon events. To measure the specific effect of radiant temperature, additional fluid-filled (600 ml) drink bottles (n = 12) were cooled overnight (C) and then placed in direct sun (n = 6) or shade (n = 6) near to a cycle aid station at AU. RESULTS During both events, beverage temperature increased over time (p < .05) as environmental conditions, particularly radiant temperature increased (p < .05). Mean beverage temperature ranged between 14-26°C and during both events was above the palatable range (15-22°C) for extended periods. At AU, bottles placed in direct sunlight heated faster (6.9 ± 2.3 °C·h-1) than those in the shade (4.8 ±1.1°C·h-1, p = .05). CONCLUSION Simple changes to Ironman aid-station practices, including shade and chilling beverages with ice, result in the provision of cooler beverages. Future studies should investigate whether provision of cool beverages at prolonged endurance events influences heat-illness incidence, beverage-consumption patterns, and competitor performance.