Glucose pulse. A simple method to estimate the amount of glucose oxidized during exercise in type 1 diabetic patients

In type 1 diabetic patients, exercise contributes to enhance insulin sensitivity and may help, together with diet and insulin therapy, to achieve and maintain better metabolic control. Fat and carbohydrates are the main substrates for energy production in skeletal muscle during aerobic exercise in well-fed humans, with their relative contribution to total energy production being a function of exercise intensity. Below the anaerobic threshold, both oxygen consumption and heart rate during exercise increase linearly as a function of exercise intensity. On the basis of these relationships, the aim of the present study was to verify the possibility of using heart rate to estimate the amount of glucose oxidized during exercise in type 1 diabetic patients as well as in a control group of healthy subjects. This study shows that heart rate can be a useful physiological parameter to be used to estimate the amount of glucose oxidized during exercise

Energy cost differences between marathon runners and soccer players: Constant versus shuttle running

Purpose: In the last decades, the energy cost assessment provided new insight on shuttle or constant running as training modalities. No study, though, quantified the benefit of constant/shuttle running in soccer-players and runners. Therefore, the aim of this study was to clarify if marathon runners and soccer players present specific energy cost values related to their training experience performing constant and shuttle running.Methods: To this aim, eight runners (age 34 ± 7.30y; training experience 5.70 ± 0.84y) and eight soccer-players (age 18.38 ± 0.52y; training experience 5.75 ± 1.84y) were assessed randomly for 6’ on shuttle-running or constant-running with 3 days of recovery in-between. For each condition, the blood lactate (BL) and the energy cost of constant (Cr) and shuttle running (CSh) was determined. To assess differences for metabolic demand in terms of Cr, CSh and BL over the two running conditions on the two groups a MANOVA was used.Results:V·O2max were 67.9 ± 4.5 and 56.8 ± 4.3 ml·min−1 kg−1 (p = 0.0002) for marathon runners and soccer players, respectively. On constant running, the runners had a lower Cr compared to soccer players (3.86 ± 0.16 J kg−1m−1 vs. 4.19 ± 0.26 J kg−1 m−1; F = 9.759, respectively; p = 0.007). On shuttle running, runners had a higher CSh compared to soccer players (8.66 ± 0.60 J kg−1 m−1 vs. 7.86 ± 0.51 J kg−1 m−1; F = 8.282, respectively; with p = 0.012). BL on constant running was lower in runners compared to soccer players (1.06 ± 0.07 mmol L−1 vs. 1.56 ± 0.42 mmol L−1, respectively; with p = 0.005). Conversely, BL on shuttle running was higher in runners compared to soccer players 7.99 ± 1.49 mmol L−1 vs. 6.04 ± 1.69 mmol L−1, respectively; with p = 0.028).Conclusion: The energy cost optimization on constant or shuttle running is strictly related to the sport practiced

MECHANICAL EFFICIENCY, WORK AND HEAT OUTPUT IN RUNNING UPHILL OR DOWNHILL

Heat output in running, per unit distance and body mass, was evaluated from published data on the corresponding energy cost (Cr). Cr is independent of the speed and is a function incline (i); between i = - 0.45 and + 0.45, it is described by Cr = 155.4 i5 - 30.4 i4 - 43.3 i³ + 46.3 i² + 19.5 i + 3.6, where 3.6 J/(kg m) is the cost on flat terrain (Minetti et al., 2002). Since the mechanical work performed against gravity is proportional to it, this equation allows one to calculate the efficiency (η) of work performance against gravity: η increases with i to attain a value of about 0.23 for i > 0.25. When running downhill, η becomes negative to attain a value of about - 1.0 for i = - 0.25 or steeper. Cr is transformed into mechanical work (w) and/or dissipated as heat (h): Cr = w + h. Since η = w/Cr, h, per unit mass and distance, can be calculated for any given slope and speed (h = Cr - w = Cr (1 - η)). The minimum Cr (2.28 J/(kg m)) is attained for i = - 20 %, whereas the minimum h (3.53 J/(kg m)) for i = - 8 %. Furthermore, since both Cr and h are independent of the speed, the ratio h/Cr, which ranges from about 2 (for i = - 0.40) to 0.77 (for i = + 0.40), at any given speed is equal to the ratio of heat output to metabolic power rates

A BRIEF HISTORY OF HUMAN POWERED FLIGHT: FROM PHYSIOLOGY TO PHILOSOPHY

The development of a scientific theory (T) can be separated into successive phases: i) Fantasy, to conceive T ii) Analysis to couch T into formal language iii) Action, to apply in practice the predictions of T. The history of human powered flight, in which case the three phases are stretched over several thousand years, allow us to better appreciate their intrinsic characteristics. Fantasy, dating back to the myth of Ikarus, must be experimentally testable, as indeed were Daedalus’ wings. Analysis must state in quantitative terms the laws governing the matter at stake. Action, from Leonardo’s unsuccessful attempts to the crossings of the British Channel in 1979 and of the arm of the sea separating Crete from mainland Greece in 1988, has the aim of shaping the world according to our will. The kernel of any “proper” T is a formal system wherein a set of operational rules allows us to manipulate a set of symbols, representing the objects of T, on the bases of a limited number of axioms. In such formal systems, “theorem” is a string of symbols that can be arrived at in a finite number of steps from the axioms, applying the canonical operational rules. However, as Kurt Gödel showed in 1931, it is possible to demonstrate that, within a sufficiently powerful formal system, there exists demonstrably true strings of symbols that are not theorems. Thus, even in an ultra-powerful theory of everything, there will still be truths that can not be arrived at within the theory

Can the P/O2 ratio be estimated in vivo in humans?

3nonenoneFrancescato M.P.; Cettolo V.; di Prampero P.E.Francescato, Maria Pia; Cettolo, Valentina; DI PRAMPERO, Pietro Enric