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.

[Comparative study of the effect of fasting during Ramadan on the glycaemia at rest in sportsmen and sedentaries]. / Etude comparative de l'effet du jeûne du ramadan sur la glycémie au repos chez des sportifs et des sédentaires.

The fast of Ramadan submits body to transient metabolic modifications; and decrease of glycaemia can be one of results. Physical exercise modifies rate of plasmatic hormones responsible for its regulation. The purpose of this study is to appreciate the influence of the fast on this biologic parameter in sportsmen and sedentaries. Thirty (30) healthy subjects (15 sportsmen of stamina and 15 sedentaries), with 25 years of average age were recruited. They have all a comparable diet. We excluded subjects having practised a physical exercise the day of the test. Capillary glycaemia was measured after weighed and physical exam, in 2 periods: in second Ramadan's fortnight, 15 minutes before food intake, two (2) months after Ramadan at least 4 hours at distance of the last meal. Comparisons were remitted in the test of Student, significant for p value lower than 0.05. During Ramadan, the glycaemia of the sportsmen at rest, is at one exception always superior or equal to that of the sedentaries. However, there is non significant difference as much during the fast as in normal food intake. Respective averages are 4.6 mmol/l, 0.15 and 4.5 mmol/l, 0.01 during Ramadan. They cross then in 4.8 mmol/l, 0.2 and 4.8 mmol/l, 0.4 in normal food intake. Landmark, the comparison of the averages from period to the other one in every group shows a significant difference only for the sedentaries. The return to normal food intake was expressed by an important gain in weight for all subjects. The fast of Ramadan has no notorious influence on sportsman's glycaemia contrary to that of sedentary. In other words, the sportsman administers better his stocks of glucose. Previous works however strongly advised against sports practice during Ramadan and more particularly the competitions, because, exercises of strong intensity can induce dehydration.

[Physical performance and thermoregulatory study of subjects with sickle cell trait during a sub-maximal exercise]. / Etude de la performance physique et de la thermoregulation des sujets porteurs du trait drepanocytaire au cours d'un exercice sous maximal.

The sickle cell trait is a genetic abnormality of red blood cells. It is due to the mutation of a parental gene, which rest Its to the substitution of glutamic acid by valin on beta globin chain of haemoglobin. The possibility for sickle cell trait carriers (SCT) to present any disturbance during predominantly anaerobic and aerobic exercises is unclear. Ten (10) subjects with sickle cell trait and 10 subjects control were studied during exercise test on cycloergometer. They were all students of the National Institute of Popular Education and Sport of Dakar. The mean of environmental temperature was 26 degrees C and humidity was 60 to 80%. After haematological analysis, a submaximal muscular exercise for one hour with 75% of maximal heart rate was done. We have determined heart rate, blood pressure, rectal and skin temperature during exercise. Haematological parameters shown any significant difference between the two groups. No significant difference was found in cardiocirculatory variables during maximal exercise in cycloergometer between control group and sickle cell trait group. The two groups have done submaximal exercise during 1 hour without particular difficulty. We have not observed a significant difference between the two groups in cardiovascular variables, rectal and skin temperature during exercise, and after 3 minutes of rest. These results show that subjects with SCT have physical capacity comparable with control subjects during a sub maximal exercise for 1 hour. We can assure that subjects with SCT in our country may participate in sports competition, as well as normal subjects (HbAA).

[Effects of water deprivation on rectal and skin temperature and on performance in sustained muscular exercise in a hot climate]. / Effets de la privation hydrique sur les températures rectale, cutanée et sur la performance lors de l'exercice musculaire de longue durée en climat chaud.

This study was performed on 16 Senegal young soldiers well trained in physical activities. Experimentation was done in tropical zone in Kedougou (Oriental Senegal) during Scorching period if the year, diurnal-room temperature 34 degrees 9 average. The subject had to ride on a cyclo ergometer to a force corresponding to 75% maximum. The central cutaneous temperature, the provided force, and the cardiac frequence were measured at the end of the muscular's exercise. For each subject that effort's test was once in normal alimentation and the other one after 24 hours' hydric privation. We noticed a significant low of the provided power for having 75% of the maximal cardiac frequence, after half hours (30 mn) of exercise during the hydric restriction compared to normal alimentation. In other respects, a regular increase was observed of the rectal temperature in the course of the activity in any case. That rise was more important to subject in hydric restriction. On the other hand there wasn't any significant difference of the cutaneous temperatures in both situations. The hydric privation has caused a hypohydration in origin of the significant decrease of the performance even if they remain moderated.

[Bicycle test: measure of anaerobic power, heart rate and blood lactic acid]. / Epreuve sur ergocycle: mesure de la puissance anaérobie, de la fréquence cardiaque et de la lactatémie.

Seven sportsmen, 100 meters and 400 meters runners are submitted to an effort test of 30 seconds. The subjects are on average 23.7 +/-2 years old. The purpose of our work is to study on the one hand the evlution of the anaerobic power. the heart rate and the lactic acid in blood during and after a bicycle test. and their relation, and on the other hand. to know the suitable pratical importance of the heart rate and the lactic acid in blood in connection with the intermittent efforts recovery aiming the anaerobic power developpement. These physiological parameters have been measured by a Monark bicycle 864, a sport-tester PE 3000 and a spectrophotometer JASCO 7800 UV/VIS. The power and the heart rate increase quickly in the 5 first seconds. Our subjects reach their average maximal anaerobic power at the 10th second, and then this power decreases progressively, while the heart rate continues to increase, without being maximal at the end of te test. Five minutes later it decreases in a half, while the lactic acid level calculated at the 30th second is continuing significantly. We have not found a significant relation between the measured parameters at the test stopping and during the recovery period (except between the lactic acid and the recovery index of the heart rate at the 25th minute). The lactic acid in blood would inform better about a good recovery during an interval training effort.

[Rectal temperature trends during 24 hours in a hot climate with and without nutritional support]. / Evolution de la température rectale sur 24 heures en climat chaud avec et sans apport nutritionnel.

A group of 22 young subjects staying in rest was studied in the aim to follow the nycthemeral evolution of the rectal temperature, according to two situations: 1) normal feeding, 2) absence of feeding. The use of drinking water was not limited. The experimentation was carried out in tropical area, Kédougou (Eastern Senegal), during a high period of temperature. The mean of day temperature was 38 degrees C and the night temperature, 22 degrees C. The skin and rectal temperature, the arterial pressure and the cardiac frequency were measured every three hours. The results showed a significant difference in the nycthemeral rythm of the rectal temperatures. The nocturnal temperatures were not different in the two conditions. We observed a significant elevation (delta = 0.31 +/- 0.18 degree C) of the diurne post prandial temperature. The results supported that the thermic modification observed during the experience were linked to the feed.

[Method for recovering and concentrating lactic acid during interval training]. / Mode de récupération et concentration d'acide lactique au cours d'un entraînement par intervalles.

Sixteen athletes were divided into 2 equal groups, A and B. Then, they were put through a series of repetitive trial exercises consisting in a sequence of 400 m races run to a sub-maximum speed (75% of maximum speed) and with pauses of a length of time equal to race time, and repeated to exhaustion, i.e., inability to keep up required speed. Recuperation in between races varied: Group A was completely passive, motionless; Group B was still going, albeit rather slowly. The parameters measured included blood concentration of lactic acid at rest and on completion of exercise and overall distance covered. At rest, there was a significant difference of lactatemia between the two groups. During the exercise, the distance run by Group B was longer (by 187.5 m) that that covered by Group A, though the difference was not significant (0.05 < P < 0.10), but his lactatemia was significantly much lower (P < 0.05). On average, the race speed and the time for recuperation which were alternatively measured were just the same for the two groups.

[Comparative study of repolarization in professional footballers and in sedentary black senegalese]. / Etude comparative de la repolarisation chez le footballeur de haut niveau et le sedentaire noirs senegalais.

The objective of this work is to study the EKG of Senegalese black football players in comparison with sedentary adults of the same age by focusing on repolarization.100 high-level football players and 50 Senegalese black sedentary adults have each had 12 classic recordings.The ST segment elevation or depression presented no significant difference between both groups. Without taking into account the amplitude of the T wave, the frequency of the negative T waves in each recording was significantly higher in the soccer player's than in the sedentary group.Early repolarization is more frequent in the sportsmen's compared to the sedentary but without significant statistical difference. As for the QTc interval, no significant difference between the two groups was noted.

L'objectif de ce travail est d'étudier l'ECG de footballeurs noirs sénégalais en comparaison avec des sédentaires de même âge en se focalisant sur la repolarisation.Cent footballeurs de haut niveau et 50 sédentaires noirs sénégalais ont bénéficié chacun d'un enregistrement de 12 dérivations classiques.Le segment ST sus décalé ou sous décalé ne présentait aucune différence significative chez les deux groupes.Sans tenir compte de l'amplitude de l'onde T, la fréquence des ondes T négatives dans chacune des dérivations était significativement plus élevée chez les footballeurs que chez les témoins.La repolarisation précoce est plus fréquente chez les sportifs par rapport aux sédentaires mais sans différence statistique significative. Quant à l'intervalle QT corrigé, nous n'avons pas noté de différence significative entre les deux groupes.

Maximal power and torque-velocity relationship on a cycle ergometer during the acceleration phase of a single all-out exercise.

Seven subjects pedalled on a Monark cycle ergometer as fast as possible for approximately 7 s against four different resistances which corresponded to braking torques (TB) equal to 19, 38, 57 and 76 N.m at the crank level. Exercise periods were separated by 5-min recovery periods. Pedal velocity was recorded every 50 ms by means of a disc with 360 slots fixed on the flywheel, passing in front of a photo-electric cell linked to a microcomputer which processed the data. Every 50 ms, the time necessary to perform half a pedal revolution (t1/2) was computed by adding the 50-ms periods necessary to reach 669 slots (the number of slots corresponding to half a pedal revolution). To measure t1/2 to an accuracy better than 50 ms, this time was computed by a linear interpolation of the time-slot number relationship. Power (P) was averaged during t1/2 by adding the power dissipated against braking torque and the power necessary to accelerate the flywheel. The torque-velocity (T-v) relationship was studied during the acceleration phase of a sprint against a single TB by computing every 50 ms the relationship between v and T (N.m), equal to the sum of TB and the torque necessary to accelerate the flywheel at the same time. The T-v relationships calculated from the acceleration phase of a single all-out exercise were linear and similar to the previously described relationships between peak velocity and braking force.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of aerobic exercise on the torque-velocity relationship in cycling.

The kinetics of the torque-velocity (T-omega) relationship after aerobic exercise was studied to assess the effect of fatigue on the contractile properties of muscle. A group of 13 subjects exercised until fatigued on a cycle ergometer, at an intensity which corresponded to 60% of their maximal aerobic power for 50 min (MAP60%); ten subjects exercised until fatigued at 80% of their maximal aerobic power for 15 min (MAP80%). Of the subjects 7 exercised at both intensities with at least a 1-week interval between sessions. Pedalling rate was set at 60 rpm. The T-omega relationship was determined from the velocity data collected during all-out sprints against a 19 N.m braking torque on the same ergometer, according to a method proposed previously. Maximal theoretical velocity (omega zero) and maximal theoretical torque (Tzero) were estimated by extrapolation of the linear T-omega relationship. Maximal power (Pmax) was calculated from the values of Tzero and omega zero (Pmax = 0.25 omega zero Tzero). The T-omega relationships were determined before, immediately after and 5 and 10 min after the aerobic exercise. The kinetics of omega zero, Tzero and Pmax was assumed to express the effects of fatigue on the muscle contractile properties (maximal shortening velocity, maximal muscle strength and maximal power). Immediately after exercise at MAP60% a 7.8% decrease in Tzero and 8.8% decrease in Pmax was seen while the decrease in omega zero was nonsignificant, which suggested that Pmax decreased in the main because of a loss in maximal muscle strength. In contrast, MAP80% induced a 8.1% decrease in omega zero and 12.8% decrease in Pmax while the decrease in Tzero was nonsignificant, which suggested that the main cause of the decrease in Pmax was probably a slowing of maximal shortening velocity. The short recovery time of the T-omega relationship suggests that the causes of the decrease of torque and velocity are processes which recover rapidly.

Effect of fatigue on maximal velocity and maximal torque during short exhausting cycling.

A group of 24 subjects performed on a cycle ergometer a fatigue test consisting of four successive all-out sprints against the same braking torque. The subjects were not allowed time to recover between sprints and consequently the test duration was shorter than 30 s. The pedal velocity was recorded every 10 ms from a disc fixed to the flywheel with 360 slots passing in front of a photo-electric cell linked to a microcomputer which processed the data. Taking into account the variation of kinetic energy of the ergometer flywheel, it was possible to determine the linear torque velocity relationship from data obtained during the all-out cycling exercise by computing torque and velocity from zero velocity to peak velocity according to a method proposed previously. The maximal theoretical velocity (v(0)) and the maximal theoretical torque (T(0)) were estimated by extrapolation of each torque-velocity relationship. Maximal power (P(max)) was calculated from the values of T(0) and v(0) (P(max) = 0.25v(0)T(0). The kinetics of v(0), T(0) and P(max) was assumed to express the effects of fatigue on the muscle contractile properties (maximal shortening velocity, maximal muscle strength and maximal power). Fatigue induced a parallel shift to the left of the torque-velocity relationships. The v( 0), T(0) and P(max) decreases were equal to 16.3 percent, 17.3 percent and 31 percent, respectively. The magnitude of the decrease was similar for v(0) and T(0) which suggested that P max decreased because of a slowing of maximal shortening velocity as well as a loss in maximal muscle strength. However, the interpretation of a decrease in cycling v(0) which has the dimension of a maximal cycling frequency is made difficult by the possible interactions between the agonistic and the antagonistic muscles and could also be explained by a slowing of the muscle relaxation rate.

Biological activity of the shrubBoscia senegalensis (PERS.) LAM. ex Poir. (Capparaceae) on stored grain insects.

Biological activity of leaves, fruits and extract of the African shrubBoscia senegalensis (PERS.) LAM. ex Poir. was evaluated against five stored-grain insects. When added to cowpeas at 2-4% (w/w), fresh ground fruits and leaves caused 80-100% mortality inCallosobruchus maculants (F.) adults and significantly reduced both emergence and damage of the F1 progeny. Acetone fruit extract exhibited a potent fumigant effect onProstephanus truncatus HORN, C.maculatus, andSitotroga cerealella OLIV.; with LT50 values of 3.8, 2.3, and below 1.5 hr, respectively. LC50 determination forB. senegalensis fruits and leaves as well as pure methylisothiocyanate (MITC) onTribolium castaneum HERBST,Sitophilus zeamais MOTSCH. andC. maculatus showed a differential response of the insects to plant parts or MITC. Quantitative dosage ofBoscia active components and LC50 values obtained for the plant tissues, compared to those of pure molecules, indicate that the biological activity ofB. senegalensis is due to the liberation of MITC from a glucosinolate precursor glucocapparin contained inBoscia fruits and leaves.