Cisse F

Effects of hydration and dehydration on blood rheology in sickle cell trait carriers during exercise

This study compared the hemorheological responses of a group of sickle cell trait (SCT) carriers with those of a control (Cont) group in response to 40 min of submaximal exercise (exercise intensity, 55% aerobic peak power) performed in two conditions: one with water offered ad libitum, i.e., the hydration (Hyd) condition, and one without water, i.e., the dehydration (Dehyd) condition. Blood and plasma viscosities, as well as red blood cell rigidity, were determined at rest, at the end of exercise, and at 2 h recovery with a cone plate viscometer at high shear rate and 37 degrees C. The SCT and Cont groups lost 1 +/- 0.7 and 1.6 +/- 0.6 kg of body weight, respectively, in the Dehyd condition, indicating a significant effect of water deprivation compared with the Hyd condition, in which body weight remained unchanged. Plasma viscosity increased with exercise and returned to baseline during recovery independently of the group and condition. As previously demonstrated, resting blood viscosity was greater in the SCT carriers than in the Cont group. Blood viscosity increased by the end of exercise and returned to baseline at 2 h recovery in the Cont group in both conditions. The blood viscosity of SCT carriers did not change in response to exercise in the Dehyd condition and remained elevated at 2 h recovery. This extended hyperviscosity, in association with other biological changes induced by exercise, could be considered as a risk factor for exercise-related events in SCT carriers, similar to vasoocclusive crises, notably during the recovery. In contrast, the Hyd condition normalized the hyperviscosity and red blood cell rigidity of the SCT carriers, with blood viscosity values reaching the same lower values as those found in the Cont group during the recovery. Adequate hydration of SCT carriers should be strongly promoted to reduce the clinical risk associated with potential hyperviscosity complications.

Are athletes able to self-select their optimal warm up?

This study aimed to examine whether athletes are able to self-select their optimal warm up and to propose a methodological approach in investigating the effects of warm up on performance. Nine male subjects underwent a free field warm up (FWU) at a self-selected intensity and duration during which heart rate (HR) and rectal temperature (Tre) were monitored. The intensity of this warm up was subsequently estimated from the HR obtained during an incremental test to determine maximal power (Pmax). Performance (cycle time to exhaustion at Pmax), HR and Tre, were then examined following either: NWU (no warm up); RWU (reference warm up based on FWU); RWU-10 (warm up intensity diminished by 10% compared to RWU); and RWU+10 (warm up intensity increased by 10% compared to RWU). Results showed no significant difference in HR (P = 0.37) and Tre increase (P= 0.77) between FWU and RWU. Performance improvement after warm up conditions gave RWU (56%; ie, 5/9 subjects) >RWU-10 (33%; ie, 3/9) >RWU+10 (11%; ie, 1/9) >NWU with significant differences between RWU and NWU (P < 0.01); RWU and RWU+10 (P < 0.01); RWU-10 and NWU (P < 0.01). A warm up intensity ranging from 54-72% Pmax, and inducing an increase in heart rate to 80 +/- 6% HRmax, was found to be optimal. While most athletes were able to self-determine the intensity of their optimal warm up, for others there is still a need for control.

Effects of hydration and water deprivation on blood viscosity during a soccer game in sickle cell trait carriers

The present study compared the changes in blood viscosity, hydration status, body temperature and heart rate between a group of sickle cell trait (SCT) carriers and a control (Cont) group before and after a soccer game performed in two conditions: one with water offered ad libitum (hydration condition; Hyd) and the other one without water (dehydration condition; Dehyd). Blood viscosity and haematocrit per blood viscosity ratio (HVR; an index of red blood cell oxygen transport effectiveness) were measured before and at the end of each game. Resting blood viscosity was greater in the SCT carriers than in the Cont group. The increase of blood viscosity over baseline at the end of the game in the Cont group was similar in the two conditions. In contrast, the change in blood viscosity occurring in SCT carriers during soccer games was dependant on the experimental condition: (1) in Dehyd condition, blood viscosity rose over baseline; (2) in Hyd condition, blood viscosity decreased below resting level reaching Cont values. The Cont group had higher HVR than SCT carriers at rest. HVR remained unchanged in the Cont group at the end of the games, whatever the experimental condition. Although HVR of SCT carriers decreased below baseline at the end of the game performed in Dehyd condition, it increased over resting level in Hyd condition reaching the values of the Cont group. Our study demonstrated that ad libitum hydration in exercising SCT carriers normalises the blood hyperviscosity.

[Evaluation of erythrocyte deformability in subjects with sickle cell trait during a soccer game: effect of hydration ad libitum].

This study compared erythrocyte changes between a group of subjects with sickle cell trait (SCT) and controls (subjects without hemoglobinopathy) during a soccer game in two conditions: with and without hydration. Erythrocyte deformability of subjects was assessed by the coefficient of erythrocyte rigidity (Tk) which was calculated before and after football match. Our results showed a significant increase in erythrocyte rigidity (Tk) in SCT at the end of physical activities without hydration; however when water was provided ad libitum their Tk decreased significantly, reaching values of controls. And adequate hydration is recommended in subjects with sickle cell trait during and after exercise.

Évaluation de la déformabilité érythrocytaire des sujets porteurs de trait drépanocytaire au cours d’un match de football : effet de l’hydratation ad libitum

This study compared erythrocyte changes between a group of subjects with sickle cell trait (SCT) and controls (subjects without hemoglobinopathy) during a soccer game in two conditions: with and without hydration. Erythrocyte deformability of subjects was assessed by the coefficient of erythrocyte rigidity (Tk) which was calculated before and after football match. Our results showed a significant increase in erythrocyte rigidity (Tk) in SCT at the end of physical activities without hydration; however when water was provided ad libitum their Tk decreased significantly, reaching values of controls. And adequate hydration is recommended in subjects with sickle cell trait during and after exercise.

Cardiopulmonary Response to Exercise in COPD and Overweight Patients: Relationship between Unloaded Cycling and Maximal Oxygen Uptake Profiles

Cardiopulmonary response to unloaded cycling may be related to higher workloads. This was assessed in male subjects: 18 healthy sedentary subjects (controls), 14 hypoxemic patients with chronic obstructive pulmonary disease (COPD), and 31 overweight individuals (twelve were hypoxemic). They underwent an incremental exercise up to the maximal oxygen uptake (VO2max), preceded by a 2 min unloaded cycling period. Oxygen uptake (VO2), heart rate (HR), minute ventilation (VE), and respiratory frequency (fR) were averaged every 10 s. At the end of unloaded cycling period, HR increase was significantly accentuated in COPD and hypoxemic overweight subjects (resp., +14 ± 2 and +13 ± 1.5 min−1, compared to +7.5 ± 1.5 min−1 in normoxemic overweight subjects and +8 ± 1.8 min−1 in controls). The fR increase was accentuated in all overweight subjects (hypoxemic: +4.5 ± 0.8; normoxemic: +3.9 ± 0.7 min−1) compared to controls (+2.5 ± 0.8 min−1) and COPDs (+2.0 ± 0.7 min−1). The plateau VE increase during unloaded cycling was positively correlated with VE values measured at the ventilatory threshold and VO2max. Measurement of ventilation during unloaded cycling may serve to predict the ventilatory performance of COPD patients and overweight subjects during an exercise rehabilitation program.

Évaluation de la déformabilité érythrocytaire des sujets porteurs de trait drépanocytaire au cours d'un match de football : effet de l'hydratation ad libitum Evaluation of erythrocyte deformability in subjects with sickle cell trait during a soccer game: effect of hydration ad libitum

This study compared erythrocyte changes between a group of subjects with sickle cell trait (SCT) and controls (subjects without hemoglobinopathy) during a soccer game in two conditions: with and without hydration. Erythrocyte deformability of subjects was assessed by the coefficient of erythrocyte rigidity (Tk) which was calculated before and after football match. Our results showed a significant increase in erythrocyte rigidity (Tk) in SCT at the end of physical activities without hydration; however when water was provided ad libitum their Tk decreased significantly, reaching values of controls. And adequate hydration is recommended in subjects with sickle cell trait during and after exercise.