Influence of Acetaminophen Consumption on Perceived Exertion at the Lactate Concentration Threshold

The purpose of this investigation was to study effects of acetaminophen consumption on ratings of perceived exertion and estimated time limit responses at the lactate threshold. 98 young regional to national level athletes performed a graded exhausting exercise on an outdoor running track to estimate their maximal aerobic velocity and the velocity associated with their lactate concentration threshold. Urine (30 mL) was collected during this test and analysed for numerous substances. During urinary screening for doping substances, 9 acetaminophen consumers (9.2%) among the 98 included athletes were detected. These acetaminophen consumers have significantly lower perceived exertion at velocity corresponding to the lactate concentration threshold than nonconsumers (11.9 ± 2.1 vs 13.6 ± 2.1, respectively) although they were at the same relative exercise intensity. This result shows that acetaminophen consumption may have mediated the perceived exertion response at the lactate concentration threshold. This may then suggest that the pain induced by training load could be a factor in use of self-prescribed pain relievers. Such consumption must be taken into account by medical staff, trainers, or educators who have to give information on the use and adverse effects of this substance and to propose palliative methods to their athletes.

Validity and Reliability of Perceptually-Based Scales during Exhausting Runs in Trained Male Runners

The purposes of this study were to test the validity of a recent scale based on the estimation of a time of exhaustion (entitled Estimated Time Limit scale) to predict a time limit (Tlim) and to regulate exercise intensity and to investigate the reliability of the Estimated Time Limit scale and the Ratings of Perceived Exertion (RPE) scale. 14 male runners performed one incremental test, one constant velocity test at 85% of Maximal Aerobic Velocity (MAV), one constant duration test and one retest of 15 min. on an outdoor track. The difference between Estimated Time Limit values obtained during the incremental test at 85% MAV and measured Tlim values during the constant velocity test were examined, the velocities at ETL = 13 (i.e., 15 min.) obtained during the incremental test were compared with measured velocities during the constant duration test or the retest (only the best performance was used), and RPE and Estimated Time Limit values during the constant duration test were compared with those measured during retest. The results have shown a nonsignificant correlation between Estimated Time Limit values at 85% MAV and measured Tlim values during constant velocity test. There was a significant correlation ( p < .02, r = .64) between velocities at ETL = 13 and measured velocities. However, the slope and y intercept value of this regression were significantly different from those of the identity line. There was no significant difference between constant duration test and retest for the values of RPE and Estimated Time Limit with high correlations (between r = .77 and .99 for RPE scale, and r = .74 and .99 for Estimated Time Limit scale). Moreover, the regression lines were close to the identity line. The RPE and Estimated Time Limit scales are reliable, but the lack of validity for the Estimated Time Limit scale suggests that more studies must be performed before using this scale to predict Tlim and regulate exercise intensity in male runners.

Influence of the Type of Training Sport Practised on Psychological and Physiological Parameters during Exhausting Endurance Exercises

The present purpose was to study the influence of the type of training sport practised (long distance running, sprinting, handball) on ratings of perceived exertion (RPE), estimation of time limit (ETL), and heart rate (HR) on running tests. It was hypothesised that these parameters would be related to the type of training sport practised. 31 trained women (10 endurance-trained runners, 10 sprinters, and 11 handball players) performed two exercises to exhaustion on an outdoor track. The first test was a graded run to estimate maximal aerobic speed (SMA), i.e., the minimal speed which elicited maximal oxygen uptake. The second test was a constant all-out run at speed delta 50 (SΔ50), which corresponded to the speed halfway between SMA and the speed at lactate threshold (SLT), to specify time to exhaustion at this intensity (TLIM). Sensations regarding RPE, ETL, and HR were recorded during these tests. SMA, SΔ50, and SLT, expressed in absolute values (km · hr.−1) were statistically significantly different between groups ( p<.05) whereas TLIM was not. The covariance analysis showed that endurance-trained runners perceived the exercise as lighter and presented lower HR than handball players and sprinters for a same running %SMA ( p<.05). Moreover, endurance-trained runners felt that they could endure more than the other groups at a given %SMA or relative exhaustion time (%TLIM). These results mean that the type of training sport which has been performed may mediate perceptual responses and influence physiological parameters during exhausting exercises. These results are likely in part related to sport-specificity of the exercise mode used in tests. This point must be taken into consideration by physical trainers who have to prescribe exercise intensities during athletic seasons for different groups of athletes.

[Effects of intermittent walk program on the body mass and composition in obese women]

The obese patients adhere weakly to rehabilitation programs; therefore the expected gains are often disappointing. This is possibly linked to the monotony of constant velocity exercises frequently proposed. Consequently, other less monotonous exercises such as the intermittent walk may be more appropriated.

OBJECTIVES

The main objectives of this study were to determine if the obese women prefer a constant velocity walk or an intermittent walk, and to analyze the effects of a rehabilitation program based on the intermittent walk.

MATERIALS AND METHODS

Twenty obese women were recruited. To determine the preferred walk modality, 10 obese women performed a constant velocity walk and an intermittent walk (with a similar duration and velocity) on a treadmill. The preferred walk modality was determined by lower ratings of perceived exertion. Then, these same 10 women participated in a rehabilitation program of 10 weeks (three days per week) consisting of intermittent walks. The 10 other women did not participate in a training program.

RESULTS

The ratings of perceived exertion were not significantly different between the two walk modalities. However, the women who participated in a training program increased their maximal distance during a 6 min walking test and they have stabilized theirs anthropometric data. Meanwhile, the untrained women have increased their body mass, body mass index and percentage of body fat.

CONCLUSION

The obese patients preferred similarly the constant velocity walk and the intermittent walk, and a rehabilitation program based on an intermittent walk is effective in avoiding the obesity aggravation.

Perceptual responses in free vs. constant pace exercise

The purpose of the present investigation was to study the influence of free versus constant pace on perceived exertion (RPE) and estimated time Limit (ETL). Ten athletes performed a graded test aimed to determine maximal oxygen uptake (VO2max) and the velocity associated with VO2max (vVO2max), a constant run to exhaustion at 90 % vVO2max to determine the time and distance to exhaustion at this relative velocity, a free paced run over the distance to exhaustion set by the time to exhaustion at 90 % vVO2max. Oxygen uptake and velocity during constant pace and free pace runs were both averaged throughout the entire period of exercise and without the last lap. The results did not show any significant effect of free versus constant pace on RPE and ETL. Averaged oxygen uptake between free and constant pace runs was not significantly different, whereas averaged vVO2max, % vVO2max and time to exhaustion was significantly higher for free pace runs only for the entire exercise. Consequently, compared to the constant pace run, the free pace one only allowed athletes to finish the run by a sprint which was effective in increasing performance, but not to perceive the free pacing run as being less strenuous than the constant pace one.

Factors associated with perceived exertion and estimated time limit at lactate threshold

The purpose was to identify the most predictive parameters for perceived exertion and estimated time limit responses at the velocity corresponding to the lactate concentration threshold. The former scale concerns the subject's current status (how hard he feels the exercise currently is) whereas the latter scale deals with a subjective prediction of how long the current exercise level can be maintained. Multiple regression equations were developed among physiological, psychological, nutritional, and individual parameters (subjects' characteristics and performances) as independent variables, and perceived exertion or estimated time limit as dependent variables. Independent variables were collected before or during an incremental running field test. 94 regional to national level athletes (47 endurance-trained runners, 11 sprinters, and 36 handball players) participated. Multiple stepwise regression showed that Rating of Perceived Exertion and Estimated Time Limit at the lactate threshold were mainly mediated by factors relative to the performance expressed in percentage of the maximal aerobic velocity. Secondary factors which contribute significantly as perceptual predictors were related to various classes of factors except for psychological factors.

Training content and potential impact on performance: a comparison of young male and female endurance-trained runners

The purpose of the present investigation was to compare the content of 8 weeks of training in young endurance-trained male and female runners and study the potential impact of this training content on performance. Fourteen men and 11 women performed two criterion exercises until exhaustion on an outdoor track before and after the 8-week training period. The first test was a graded exercise to determine maximal aerobic velocity (Mav), the velocity at the lactate concentration threshold (v-Tlac), and the velocity at delta 50 (v delta50: the velocity halfway between Mav and v-Tlac). The second test was a constant run at v delta50 to determine the time to exhaustion at this velocity (tlimv delta50). Training logs were used to monitor the self-directed training sessions. The results showed that the women had a lower training volume but trained at higher exercise velocities than the men. However they presented similar values as the men for expected temporary performance capacity and did not improve their performance (Mav and tlimv delta50) over the 8-week period. After the training period, only v-Tlac (absolute and relative values) was slightly but significantly increased by training. These results could be due to the fact that both men and women did not train more than 10% of the total distance run at exercise velocities equal to or higher than their Mav and did not increase their training load during the 8-week training period. We suggest that changes in training content during the season, such as severe (long-duration or high-intensity) training sessions, may have improved their performance capacity.

Sex-related differences in ratings of perceived exertion and estimated time limit

The purpose of the present investigation was i) to study the effect of sex on ratings of perceived exertion (RPE) and estimation of time limit (ETL) during runs to exhaustion at both absolute and relative physical and physiological reference criteria, ii) to propose some recommendations for exercise intensity prescription from both RPE and ETL according to sex. Eight male and eight female middle-distance endurance-trained runners performed two exercises until exhaustion on an outdoor track. The first test was a graded exercise to determine maximal aerobic velocity (vV.O2max), the velocity at the lactate threshold (vLT), and the velocity at delta 50 (vDelta50: the velocity halfway between vV.O2max and vLT). The second test was a constant all-out run at vDelta50 to determine the time to exhaustion at this intensity (tlim). The results of this study showed that the female runners perceived exercise as being harder, felt that they could endure less and had higher heart rate values than males for a given absolute velocity (km.h-1) whereas there were no difference between males and females for a given relative velocity (%vV.O2max). Moreover, the female runners perceived exercise as lighter and felt that they could endure more than the males for a given absolute time period (in s) whereas there was no difference between males and females for a given relative time period (%tlim). This result may be explained by the fact that the same exercise intensity or duration corresponded to higher %vV.O2max and lower %tlim for the females compared to the males. Consequently, physical trainers can prescribe the same perceived ratings for a given percentage of vV.O2max or tlim both in male and female athletes.

Use of acetaminophen in young subelite athletes

AIM

The purpose of the present investigation was to look for other drugs besides doping substances in the urine of subelite athletes submitted to heavy training.

METHODS

One hundred and forty-one young subelite athletes (in sprint, cycling, middle distance running and handball) were included in the study, with a control group of 89 high school pupils. Drugs were researched by high performance liquid chromatography using a diode array detector.

RESULTS

Among the 212 subjects who agreed to give a urine sample, acetaminophen was detected: 9.5% for the subelite athletes versus 1.3% for the control group with a greater difference for sprint and cycling training (26.7% and 20%, respectively). Acetaminophen is used to treat both acute and chronic pains. It relieves pain by elevating the pain threshold.

CONCLUSIONS

The use of acetaminophen has to be taken into account by medical staff, trainers and educators.

Influence of aerobic fitness level on measured and estimated perceived exertion during exhausting runs

The purpose of the present investigation was 1) to study the effects of fitness level on perceived exertion (RPE) and estimated time limit (ETL) scales during exhausting runs, and 2) to predict time to exhaustion from RPE or ETL values collected during a constant run exercise. Eight high-fitness level and twelve moderate-fitness level endurance trained males performed two exhausting exercises on a 400-m running track. The first test was a graded exercise using a portable metabolic system to determine maximal oxygen uptake (V.O (2)max), the velocity associated with V.O (2)max (vV.O (2)max), the velocity at the lactate threshold (vLT) and the velocity at delta 50 (vDelta50 : the velocity halfway between vV.O (2)max and vLT). The second test was a constant run exercise at vDelta50 to determine the time to exhaustion at this intensity (tlimvDelta50). Moderate-fitness level athletes perceived exercise to be relatively more strenuous and felt that they could continue for less time than high-fitness level athletes at similar relative velocities. There was no effect of fitness level on perceived exertion for a given relative exercise duration. RPE corresponding to vLT was not statistically significantly different between the two levels groups. For the two groups, measured and predicted exhaustion time values, which were calculated from linear extrapolation of RPE and ETL values collected during the first 4 minutes of a submaximal constant run exercise, were not statistically significantly correlated. These results indicate that the aerobic fitness level seems to influence perceived exertion only during graded exercise. Consequently, if RPE is used to prescribe an exercise intensity, the prescription must be individualised regarding the aerobic fitness level of the athlete except for exercise intensities corresponding to vLT. Moreover, the perceived exertion pattern at the beginning of a submaximal constant run exercise could not be considered as a sensitive predictor of the point of self-imposed exhaustion whatever the fitness level of the athletes.

Reliability of rating scales of perceived exertion and heart rate during progressive and maximal constant load exercises till exhaustion in physical education students

The purpose of this study was to assess the reliability of ratings of perceived exertion (RPE) and estimation of time limit (ETL) scales, and heart rate in physical education students during standardised and replicated progressive and constant load exercises till exhaustion realised on a track. Three groups of ten physical education students who present the same anthropometrical characteristics performed an incremental exercise to determine their maximal aerobic velocity (MAV) on an indoor track. Thereafter, group 1 performed an identical incremental exercise whereas groups 2 and 3 performed two identical exercises to exhaustion: a constant load exercise up to exhaustion at 90 and 100 % MAV, respectively, to determine the time to exhaustion at each intensity (tlim 90 and tlim 100). The results of this study were that MAV, tlim 90 and tlim 100 were not significantly different between the two trials. Moreover, the individual Pearson correlation coefficients between test and retests were very high (0.94 to 1). The slope and y intercept values of the relationships between test and retest perceived exertion ratings were not significantly different from the identity line. Moreover, test-retest differences in HR values fell within the 95 % LoA analysis. Consequently, HR values, RPE and ETL scales are reliable during standardised and replicated progressive and constant load exercises till exhaustion performed on a track with physical education students.

The ratio HLa : RPE as a tool to appreciate overreaching in young high-level middle-distance runners

The purpose of the present investigation was to study the effects of eight weeks of intensive training at the beginning of the athletic season on perceived exertion and on the ratio of blood lactate concentration to ratings of perceived exertion (HLa : RPE) in young runners. Eight high-level middle-distance runners performed two exhausting exercises on an indoor track before and after eight weeks of training. The first test was an incremental exercise to determine their maximal oxygen uptake (VO(2) max), the velocity associated with VO(2) max (vVO(2) max), the velocity of the lactate concentration threshold (vLT) and the velocity delta 50 (vDelta50 : the velocity halfway between vVO(2) max and vLT). The second test was a constant-load all-out run at vDelta50 to determine the time to exhaustion at this intensity (tlim vDelta50). There were five training sessions a week with interval training twice a week. After eight weeks of training, vVO(2) max, vLT and tlim vDelta50 were not significantly different. The athletes perceived exercise as being harder after training than before at a same given relative velocity in the incremental test. During the all-out run at vDelta50, they felt that, at the same given relative time, they could endure less after than before training. Moreover, the HLa : RPE ratio was significantly lower after intensive interval-training performed immediately after the holidays. Consequently, two interval-training sessions per week would induce an overreaching state that is not yet characterized by a decrease in performance and physiological values whereas perceived exertion (RPE, ETL) and especially the HLa : RPE ratio allows the detection of changes in young high-level middle-distance runners.

Does perceived exertion depend on glycemic index of foods ingested throughout three hours before a one-hour high-intensity exercise?

The purpose of this study was to assess the relationships between perceived exertion (RPE) and plasma glucose concentrations or hunger feelings during a 1-hr. bicycle submaximal exercise after ingestion of pre-exercise test foods with a different glycemic index. Each of endurance-trained male triathletes ingested three different glycemic index (GI) foods (HighGI: glucose, LowGI: whole-wheat biscuit or water) throughout the 3 hr. before exercise at 80% maximal oxygen uptake (VO2 max). RPE values increased as a logarithmic function of time. This result is opposite to results obtained with longer exercise bouts up to 3 hr. duration. RPE and hunger ratings were not significantly different for the three test foods whatever the time. Moreover, RPE did not correlate with plasma glucose concentrations during exercise. Consequently, RPE did not depend on the GI of the pre-exercise test foods during a 1-hr. exercise at 80% VO2 max. Physiological and psychological factors other than glycemic index may have mediated the perceptual responses during a 1-hr. high-intensity exercise. It is possible that during endurance exercise of longer duration, the level of blood glucose mediates the intensity of peripheral exertional perceptions arising from active skeletal muscle during prolonged exercise.

Perceived exertion scales attest to both intensity and exercise duration

The present purpose was to study the relationships between perceived exertion (RPE, ETL) and exercise duration for all-out runs eliciting vVO2 max. 12 endurance-trained men performed three exhausting exercises on an indoor track. The first test was an incremental exercise to measure their maximal oxygen uptake (VO2 max), the velocity associated with VO2 max (vVO2 max), the velocity of the lacate concentration threshold (vLT) and the velocity delta 50 (vdelta50: the velocity halfway between vVO2 max and vLT). The second and third tests were a constant load all-out run at vVO2 max and vdelta50 to measure the time to exhaustion at these intensities (tlim vVO2 max and tlim vdelta50, respectively). vdelta50 corresponded to 90.1 +/- 2.5% vVO2 max; tlim vVO2 max and tlim vdelta50 were equal to 286 +/- 71 sec. and 547+/- 157 sec., respectively. For a same given relative time (%tlim), athletes perceived exercise as harder and felt that they could endure less for vVO2 max than vdelta50. When subjects began to perceive exercise as "hard" (RPE = 15), they had run for only 36.4 +/- 26.8%tlim at vVO2 max, whereas they had run for 46.1 +/- 15.7 %tlim at vdelta50. These results indicate that RPE and ETL scales were a combined subjective estimation of both intensity and exercise duration for all-out runs at 90 and 100% vVO2 max. Therefore, this scale could be used to assess duration as well as intensity of exercise for the practical application in sport. Moreover, it could be suggested that exercise duration can be prescribed as a function of perceived exertion for healthy normal people. Consequently, perceived exertion could be an important tool to individualize the prescription of a training program.

RPE responses during arm and leg exercises: effect of variations in spontaneously chosen crank rate

The aim of this study was two-fold. First, the rating of perceived exertion (RPE) was compared between two different upper and lower body exercises. Subjects (n = 12) performed with spontaneously chosen crank or pedal rates: (i) incremental maximum power tests (Test 1), with an initial work rate of 50% of maximal power followed by increases of 10% at each 120-sec. work stage and (ii) tests (Test 2) with exercise bouts set at 20, 40, 60, and 80% of maximal power separated by passive recovery periods. Second, the effects of variations in spontaneously chosen crank rate on RPE was analysed using the second test performed only with upper body. Subjects performed Test 2 three times with crank rates spontaneously chosen by the subjects, set at plus or minus 20% of spontaneously chosen crank rate. During both Tests 1 and 2 for upper or lower body, RPE increased linearly (p<.01) with power output. No significant difference was noticed between upper and lower body tests; however, RPE was significantly different (p<.05) between Test 1 results for upper and lower body at 70, 80, 90, and 100% of maximal power. The greater RPE at high power output could be linked to the important effect of fatigue during upper body exercise. Among the three crank-rate conditions, no significant difference in RPE was noticed. The choice of crank rate does not seem to influence the perception of exertion in upper body cycling exercise.

A new rating scale of perceived exertion based on subjective estimation of exhaustion time: a preliminary study

Perceived exertion has been investigated during incremental exercise to exhaustion with athletes, according to the 6-20 scale proposed by Borg (RPE, 1970) and a new scale based on the estimation of exhaustion time (t(lim)) (Estimated Time Limit or ETL, from 1 to 20; ETL= 21 - 2 n, with n = log2t(lim)). ETL increased linearly with the percentage of maximal aerobic power (%MAP) up to the ventilatory threshold (VT). Beyond VT, an inflection of the ETL-%MAP relationship was observed. RPE and ETL calculated at VT were equal to 15 +/- 1.7, i.e. an exercise intensity perceived as "hard", and 10 +/- 2.3, i.e. an estimated exhaustion time equal approximately to 45 minutes. Standard deviations for RPE and ETL at VT were too large for an accurate estimation of this threshold. The results of the present study suggest that RPE and ETL should be used in addition to physiological data, but not replace them in the prescription of a training program.

Ratings of perceived exertion (RPE) during cycling exercises at constant power output

The purpose of the present investigation was to study the overall rating of perceived exertion (RPEov) according to the 6-20 scale proposed by Borg (1970) and muscular RPE (RPEmu) in exercises at constant load. The relationship between RPE and heart rate for three different loads was studied during exhausting exercises in 10 participants. Whether the drift of RPE during a 20 min exercise at constant load could be an index of the endurance time during long-lasting exercises at constant load was also investigated. At 1-week intervals, the participants performed cycling exercises up to exhaustion at 60, 73, and 86% maximal aerobic power (MAP) measured during an incremental test. Heart rate, RPEov, RPEmu and exhaustion time (tlim) were measured. The upward shift of the HRmax-RPE regressions was significant between 86, 73 and 60% MAP (p < 0.001) for RPEov and RPEmu. This result suggests that the equation HR = 10 x RPE proposed by Borg (1973) for incremental exercise is not valid for long-lasting exercise at constant load until exhaustion because the heart rate corresponding to a given RPE depends on load and time. Mean RPE increased linearly with time up to exhaustion. Unexpectedly, the relationships between RPEmu or RPEov and percentage of exhaustion time were similar for exercises at 60 and 73% MAP although the exhaustion times were very different (79.40 +/- 30.64 min versus 36.19 +/- 15.99 min, respectively) (p < 0.001). Consequently, it is likely that RPE was a subjective estimation of the hardness of exercise rather than the intensity of exercise. The RPE pattern at the beginning of long-lasting exercises at constant load (60 and 73% MAP) cannot be considered as a sensitive predictor of the point of self-imposed exhaustion for individuals. Indeed, the errors in the estimation of exhaustion time from extrapolation of RPE at the beginning of exercise were very large. Moreover, at 60% MAP, a steady-state in RPE was observed during 20 min in five subjects whose tlim were not longer than tlim of the other subjects. In addition, the data of the present study indicate that RPEmu could be more useful than RPEov in cycling.

Ratings of perceived exertion (RPE) as an index of aerobic endurance during local and general exercises

The main purpose of this study was to assess the correlations of RPE with indicators of endurance (critical power), exhaustion time and the electromyographic activity of a relevant muscle during general and local exercises. Eight healthy subjects participated in the study. During the first session, Maximal Aerobic Power (MAP) was measured by means of an incremental cycling exercise on a Monark ergometer. At 1-week intervals the participants performed a general or local exhausting exercise, which consisted of a cycle exercise (60, 73, 86 or 100% MAP) and a knee extension exercise (lifting a load between 17.5 and 32.5 kg every 3 s), respectively. The critical powers corresponding to cycling (CPcycling) and knee extension (CPknee) were calculated from the slope of the linear relationship between exhaustion time (tlim) and work. Rate of perceived exertion, concerning the whole body (overall RPE [RPEov]), RPE concerning the exercising muscles (muscular RPE [RPEmu]) and exhaustion time were measured. During the last session, the integrated electromyogram of the right Vastus Lateralis (iEMG s-1) was measured during short (20 s) cycling and knee extension non-exhausting exercises, with the same electrode location, at the different power outputs used during the exhausting exercises. The relationships between RPEmu at the fifth minute and log tlim and between iEMG% (percentage of the iEMG s-1 corresponding to 100% MAP during cycling) and log tlim were similar for the cycling and knee extension exercises. The mean values of RPEmu at the fifth minute of exercise calculated for CPcycling and CPknee were almost equal (12.3 +/- 1.7 versus 12.2 +/- 0.9). Similarly, the mean values of iEMG% corresponding to CPcycling and CPknee were equal (78.44 versus 79.02%). These results suggest that RPEmu is related to aerobic endurance and that the possibility of sustaining a high percentage of maximal aerobic power during a general exercise is mainly related to local muscular factors.

Use of physiological criteria for improving physical work conditions

Physical work is still present in many countries, specially in developing ones. The physiological analysis of the work load could be conducted through two different ways, referring to his energetic cost and/or to the mechanical power of the human motor. The purpose of ergonomics is to organize any physical professional task in order to maintain the workers as much as possible inside the limits of a fatiguing activity. The process of fatigue affects differently a "general activity" and a "local work." If a worker is engaged in a general hard activity, like carrying a load or pushing a trolley, an increase of oxygen consumption or/and an acceleration of the heart rate could be observed. This latter, allowing to estimate the oxygen cost of the work, is more affected if the work is performed in a hot environment. In order to establish the ratio between the data observed at the work place and the maximal working capacity of the organism, it is possible to experiment with the physiological effects of transitory increases of the work stress, by increasing the load or/and the frequency of the repetition of the "unit" of work done. When the task could be described in terms of local work, the correct methodology is based upon the general rules established respectively for the static and the dynamic work. In both the cases, it is possible to determine the critical rate of the muscular activity, the part of the muscular capacity engaged at the work place and the probable time for local exhaustion, in order to limit the duration of each period of work. It should be remembered that 50 years ago, Lucien Brouha proposed that heart rate determinations at work be used as a criteria for a better organization of human work by a non-sophisticated method.

Physiological strains while pushing or hauling

An experiment has been designed to compare two ways of load moving: pushing with a bar or hauling with a pelvic belt, against the same resistances, at the same speeds. This study has been carried out in the laboratory on a treadmill, using two groups: 15 healthy sedentary men and 10 endurance trained male athletes. The task consisted of pushing or hauling against the same resistance (3, 5 and 7 kg for the first group and 6, 8, 9 and 10 kg for the second) at two walking speeds (3 and 4 km. h-1 for the first group and 3.7 and 4.7 km.h-1 for the second). The physiological strains were studied by measuring heart rate (HR) and oxygen consumption (VO2) in both experiments. In addition, perceived exertion was estimated in the second group according to a rating scale of perceived exertion (RPE). Analysis of variance showed that pushing with the arms was more strenuous than hauling with a pelvic belt with regard to HR, VO2 and RPE (P < 0.01). When resistances and speeds were grouped, the differences between pushing and hauling were equal to 3 beats min-1, 0.85 ml. min-1. kg-1 for HR and VO2, respectively, for the first experiment (sedentary subjects), whereas the differences were equal to 11.4 beats. min-1, 1.66 ml.min-1.kg-1 and 2.15 for HR, VO2 and RPE, respectively, for the second experiment (trained endurance athletes). In the endurance athletes, there was a parallel upward shift of the VO2-HR linear relationship for pushing (covariance analysis, P < 0.01), which suggested that an element of static work (pushing with the upper limbs) added to the dynamic work could explain the higher physiological cost during pushing.

Melanotic neurofibroma: a case report with ultrastructural study

The authors report a case of a solitary melanotic neurofibroma involving the temporomalar area in a 17-year-old man. Light-microscopic study reveals a benign neurofibroma including melanin deposits. Electron microscopy shows typical premelanosomes and melanosomes within Schwann cell cytoplasm. The literature is reviewed, and theories of histogenesis for this unusual tumor are discussed.

[The treatment of laryngeal stenosis in the child. 156 cases (author's transl)]

156 cases of laryngeal stenosis in the child were seen over a 10 year period. 40 were congenital and 116 acquired, chiefly after intubation. Congenital stenosis improved spontaneously in 60 % of cases. When tracheotomy was necessary, treatment was similar to that of acquired stenosis. For post-intubation stenosis analysis of the underlying pathology revealed the existence of risk factors: coma, cardiac surgery with extracorporeal circulation, laryngaeal pathology being responsible in 75 % of cases. Awareness of these risk factors was felt to be one of the essential elements in the prevention of post-intubation stenosis. Treatment varied in accordance with the degree of progression of the stenosis. In recent progressive forms medical and endoscopic treatment (51 cures without treacheotomy, 11 after tracheotomy for 2 to 10 weeks). In forms with scar tissue, tracheotomy associated with endolaryngeal calibration (21 cases) or laryngotracheal enlargement surgery (21 cases). A number of precautions are suggested in order to improve the prevention of stenosis with scar tissue. Indications of the various therapeutic methods are discussed according to whether the stenosis is due to scar tissue or is congenital. With regard to procedures involving laryngotracheal widening (28 in all : 21 for stenosis after intubation and 7 for congenital stenosis), emphasis placed upon the need to select amongst several types of operation according to the site and extent of the lesions.

Microsurgical approach to the cerebellopontine angle

Various sections of the IXth, Vth, vestibular and cochlear nerves have been performed on twenty patients. The technique we used was an 'a minima' approach to the cerebellopontine angle. This operation is atraumatic and quick to perform, and the postoperative period is always excellent. It seems very useful for patients with Ménière's disease or intractable pains in the glossopharyngeal or trigeminal fields. It can be used for diagnosis if a small neurinoma in the cerebellopontine angle is suspected.