Medicine and Science in Sports

Stress experienced by young athletes (ages 11 to 23 years) during competition was studied by comparing urinary epinephrine (E) and norepinephrine (NE) excretion at rest, during bicycle exercise (55% max) and during a hockey game. Athletes were divided into four groups: 11, 12, 16, and 23 years olds with four subjects in each group. Urinary production rates were similar between experimental conditions and age groups. Both resting E and NE levels were constant across all ages. Game E levels were significantly higher (P less than 0.05) than resting and bicycle levels in both the 16 and 23 year old groups. Epinephrine excretion during hockey was also significantly higher (P less than 0.05) in the 23 year old athletes than in the 11 and 12 year olds and in the 16 year olds compared to the 11 year olds. Game NE was significantly elevated (P less than 0.05) above resting levels in the 16 and 23 year olds. Submaximal NE excretion was not significantly different from resting levels in any of the age groups (P greater than 0.05). Physical stress as reflected by NE excretion was constant across all ages within each experimental condition. Generally, sympathetic stimulation and NE excretion appeared to be related to intensity of physical activity, being greater during hockey than during submaximal exercise. Significant adrenal medullary activation and E excretion was evident only during hockey and then, only in the older athletes.

The purpose of this study was to describe cardiorespiratory alterations in a group of perviously untrained 9-to-11 year old children resulting from seven months of swimming training. Fifteen members of a competitive swim team served as subjects. A non-training group of fifteen children of similar age, height and weight were studied at the same times. All measurements were made on three separate days both before and after the training period. On Measurement Day One the subjects were measured for VC, FEV1.0, and MVV. On MEasurement Day Two they were measured for PWC170 and on MEasurement Day Three height (cm), weight (kg), VE max (1/min), Vo2 max (ml/kg.min) and HR max were determined. Results of the analyses indicated that: (1) the mean PWC170 change in the trained children (+80.00 kgm/min) was significantly greater than that in the reference group (+30.00 kgm/min) (P less than .05); (2) the mean Vo2 max change in the experimental group (+8.411 ml/kg.min) was significantly greater than in the reference group (2.21 ml/kg.min) (P less than .01); and the mean changes in VC, FEV1.0, MVV, VE max, and HR max were not greater than one would expect to see in normal children of similar age and body dimensions (P greater than .05).

The interrelationships and orthogonal factors of cardiac time components were studied at rest and 30 seconds after a standard one minute bench stepping exercise in 140 boys, 7 to 14 years of age. Cardiac time components were determined indirectly from simultaneous recording of the carotid pulse wave, phono-cardiogram, and electrocardiogram. The left ventricular intervals were found to be shorter in boys than those reported for middleaged men, with the largest difference being the isovolumetric contraction period, followed by tension period, mechanical and total systole, cycle time, diastole, ejection period and the least difference in the electromechanical lag. The intervals generally increased from age 7 to 14. The intervals shortened as a result of exercise, with lesser shortening in the 7 to 8 age range. Factor analysis of the variables yielded results similar to those reported for middle-aged men in other studies. Factor one represented left ventricular systole, with high loadings for ejection period, mechanical systole, and total systole; factor two represented left ventricular diastole and cycle time with high loadings for these two time components; factor three represented left ventricular tension period; and factor four represented electromechanical lag.

Investigations were conducted on the incorporation of 14C-proline into the Achilles tendons of control rats and rats who had performed a single exercise bout. The exercise rats received a single 30-minute bout of running on a motor-driven treadmill either 6 hours or 12 hours prior to being sacrificed, after which the Achilles tendons were removed and incubated in vitro with 14C-proline for two hours. After incubation, the quantity of tissue-free 14C-proline, the specific activity of 14C-proline and the specific activity of 14C-hydroxyproline were determined. No statistically significant differences were found among the two exercising groups and the control group in these parameters of 14C-proline anabolism. These results indicate no changes in proline anabolism after a single exercise.

The physical work capacities of 43 (19 girls, 24 boys) competitive swimmers, 10-16 yr of age, were determined on a discontinuous steady state bicycle ergometer test. During the test heart rates were monitored each minute and oxygen uptakes were measured in the last minute of the final work load. Blood was collected before and after the exercise for measurement of blood lactates. These subjects represented a select group of young boys and girls, in that they took part regularly in a regimen of relatively vigorous swimming training. This included, on the average, 4 to 7 training sessions per wk for the year. The average distance completed in each training session varied from 2,118 to 3,194 yards depending on age and sex. The maximal oxygen uptakes ranged from 40.5 ml/kg min for the older girls to 56.6 ml/kg min for the older boys. The values for the boys are only slightly below those reported by others for champion swimmers. The values for P.W.C.170 (kgm/min) were much higher than those found in a general population of non athletic boys and girls (girls 683 to 844 kgm/min; boys 851 to 1285 kgm/min). In comparison with a relatively elite group of 22 yr old competitive swimmers the younger athletes had similar maximal oxygen uptake values (ml/kg min). The development of speed and endurance in outstanding swimmers appears to be primarily dependent upon the maintenance of aerobic capacity established in early prepubertal growth years and the subsequent development of strength, swimming skill and capacity for anaerobic metabolism as the young swimmer matures.

Six male subjects exercised on a bicycle ergometer until a heart rate of 180/min was attained five days per week for three weeks. The circadian rhythm of 17-Ketosteroid excretion was followed by colorimetric analysis of urine samples collected over four periods of each day. Headings were highest for the period 0730-1200 hours. Values for the last week of exercise were greater than those during the first and second weeks; differences between weeks were greatest over the period 1700-2300 hours, exercise being associated with development of a secondary peak of 17-KS excretion. Following completion of the exercise program, the diurnal rhythm returned to its pre-exercise pattern. (C)1974The American College of Sports Medicine

Skeletal age (SA) height, weight, PWC130, Vo2 at 130 heart rate (Vo130) and cardiorespiratory adaptation to work at 3 kgm-sec-1 were measured in 237 boys ranging in age from 8 to 18 years. Correlations for the total population for the variables of the study are generally higher with SA than with chronological age (CA), although there is no significant difference between the two sets of correlations. Analysis of linear trend indicate that significant nonlinear components are more frequent in the relationships between the variables and SA than with CA.Multiple regression analyses for each variate as dependent variable indicate that height and body weight generally contribute more to the explained variance, while SA is the next best predictor. CA is the least significant of the four independent variables. The total variance explained between any of the submaximal working capacity related measures acting as dependent variable and CA, height and weight is not significantly affected by the presence or absence of SA. The present study thus indicates that SA is not a significant factor in explaining submaximal working capacity, beyond CA, height and weight, when considered over the 8 to 18 year age span. However, when considering shorter age spans, or when considering the adolescent period (12-16 years), SA correlates better with PWC130 (.320 less than r less than .675) and with Vo130 (.299 less than r less than .772).

Twenty young males, all active in middle-distance running, were studied between January 1968 and May 1974 for the purpose of gathering longitudinal data regarding Vo2 during treadmil running. Vo2 submax (measured during the last 2 min of a 6-min run at 202 m/min) and Vo2 max values (measured during a 5-8 min increasing-speed run to exhaustion) were collected approximately every 6 months for 6 years. Different groups, starting at ages of 10, 12 and 13 years were followed for periods of 2 to 5 years continuously. In all longitudinal comparisons. Vo2 max (ml/min) changes peralleled changes in body weight; consequently, Vo2 max (ml/kg.min-1) did not show a significant change. In every group Vo2 submax (ml/kg.min-1) dropped significantly over time. All data were pooled by 1 yr age groups, providing cross-sectional data for active boys 10-18 yrs of age. Vo2 max ranged from 1933 ml/min for 10-yr olds to 4082 for 18-year olds. Concurrent changes in weight resulted in no significant differences in Vo2 max (ml/kg.min-1) from the overall mean of 61.5 Vo2 submax (ml/kg.min-1) was highest among 10-year olds (53.3) and lowest among 18-yr olds (42.5). Based on these longitudinal and cross sectional findings and significant improvements in times for 1- and 2-mile races, it was concluded that Vo2 max (ml/min) increases no faster than does body weight among moderately active growing boys and that both age and training contribute to a change in Vo2 submax; a factor which accounts greatly for improvements in middle-distance race performance.

The winning times of men’s international rowing championships have been collected over a period of 79 years (1893-1971). The regression for the relation-ship between winning time and year was calculated for each of seven events: Pair, Pair with Cox, Four, Four with Cox, Eight, Single, and Double Sculls. The average slope of the regression lines was -0.7 sec per year. This reflects a 40% improvement in “work-output” through the 79 year period. The increase of “work-output” is explained by an increasing height of the general population (10&), better selection and training of oarsmen (15%), and better boats and rigging of the boats (15%). The expected time for rowing 2000 m 1972 could be calculated as follows; 7.03, 7.34, 6.29, 6.37, 6.01, 7.21, and 6.41 (min-sec) respectively. Equivalent speed and time per boatlength are presented. The values are considered die optimal times (records) for the year of the regatta eliminating the influence of wind and current on the results. II is suggested to compare actual obtained regatta results to these estimates instead of the now available course rec-ords, which are all very dependent on water and wind conditions.

The results from swimming, track, and field events of the 1972 Olympic Games at Munich were compared to those from past Games. The winning times or distances were expressed as a percent difference from records which existed at the time of the Games. The average winning times in both men’s and women’s swimming were.55% better than the world records. This degree of improvement in performance during an Olympics has been seen before only in women’s running at Mexico City in 1968. Although the results in women’s running and field events at Munich were not significantly better than the world records, they were better than performances in Olympic competition between 1904 and 1964. In men’s field and track winning distances and times were poorer than world marks, but this pattern conforms to that seen in other Olympics. These comparisons provide a quantitative evaluation of the competition which exists in each sport at different times. Winning times of four individuals exceeded the listed work record by more than 2.0%. Spitz broke four men’s individual swimming records by an average of 0.54%. Gould was credited with breaking three women’s swimming records by an average of 0.81%. In both running and swimming, the winning times of women were 1.13 greater than those for men at equal distances.

Age at menarache, family size, and birth order in 145 athletes at the Montreal Olympic Games, 1976, were determined through interview. The athletes represented 27 countries, but 76% came from Canada, Great Britain and the United States. On the average, athletes attained menarche later than the general population in their respective countries, the mean age at menarche for the sample of 139 athletes who had attained menarche at the time of the survey being 13.66 +/- 0.12 years. Six athletes had not yet attained menarche at the time of the survey. Gymnasts, runners and rowers attained menarche significantly later than swimmers, but gymnasts, runners, rowers and jumpers/hurdlers did not differ significantly among themselves in the age at menarche. Correlations between age at menarche and family size and birth order were significant, but low to moderate in magnitude. Athletes from larger families tended to have, on the average, later menarche than those from smaller families, this trend being more apparent in rowers and track and field athletes.

The effect of exercise, either long or short term, on levels of 2,3-DPG and P50 are at present controversial. The present study compared the effects of shortterm maximal exercise (average time 5 min 35 sec, maximal group) on levels of 2,3-DPG and P50 to those after a 10 mile road race (average time 51 min 36 sec, endurance group). The resting levels of 2,3-DPG of both groups of athletes were significantly higher (P < 0.01) than the mean for a group of sedentary males simultaneously determined. The resting P5o value for endurance group athletes was also significantly elevated. After short-term maximal exercise (maximal group), a mean 15% increase in DPG with an increase of in vitro Pso(7.4;37c) from 27.2 ± 0.5 to 30.0 ± 0.9 mmHg was observed. On the other hand after prolonged endurance exercise (endurance group), a small but significant (P < 0.05) decrease in DPG and a decrease of in vitro Pso(7.4;37c) from an elevated resting level of 28.9 ±1.5 mmHg to the normally determined sedentary value (26.7 it 1.5 mmHg) resulted. Different stimuli are involved in short-term anaerobic maximal exercise compared to prolonged aerobic exercise and a model is presented to account for the alterations in 2,3- DPG and oxy-Hb affinity in the two types of exercise.

Concurrent with the study of performance and aerobic power of 12 highly trained, superior middle distance runners before, during and after 3 wk of strenuous training at 2,300 m altitude, observations were made pre and post altitude on blood volume (BV), plasma volume (PV), cell volume (CV), hematocrit (Hctv), and the concentration and amount of hemoglobulin (Hb). For comparative purposes, the same components were measured in 21 non athletic young men at or near sea level. Similar data on 27 black and white sharecroppers also were available for comparison. Since CV did not change at altitude, Hctv values obtained on 8 occasions at altitude were used to calculate PV at altitude. The mean Hctv increased 3.7% at altitude, which corresponds to a decrease of 6.6% in PV. The mean decrease in body weight, BW, was 2.1. In the runners BV in relation to BW was 21% greater than in 48 non athletes. Approximately one third of this larger BV is accounted for by the lower body fat of the runners. Cell volume, PV and total Hb, all in relation to BW, were greater in the runners than in the non athletes by 18, 24 and 16%, respectively. Consistent with the difference in PV and in CV, Hb concentration was 4% lower in the runners. It is concluded that endurance athletes have thin blood but so much of it that their total Hb exceeds that of non athletes. Aerobic power was dependent in part on Hb/kg not only in the runners but also in girl swimmers.

Field and laboratory studies were made on 16 trained distance runners to determine the relationship between selected metabolic measurements and distance running performance. Measurements were made for oxygen consumption, heart rate, and blood lactate accumulation during submaximal and maximal treadmill running. Several days after the laboratory test all of the runners competed in a 10-mile road race. The correlation between max[latin capital V with dot above]o2 (ml/kg x min) and performance in the 10-mile race (min) was -0.91 At a selected speed (268 m/min) the % max[latin capital V with dot above]o2 and % max HR were found to be highly related to distance running performance (r = -0.94 and 0.98, respectively). At all running speeds above 70% max[latin capital V with dot above]o2 the faster runners were found to accumulate less blood lactate than the slower runners at similar speeds and relative percentages of their aerobic capacities. The findings suggest that successful distance running is dependent on the economical utilization of a highly developed aerobic capacity and the ability to employ a large fraction of that capacity with minimal accumulation of lactic acid. (C)1973The American College of Sports Medicine

Subjects walked one hour out of every six on a self-paced treadmill, during two separate 31 hour test periods, carrying either a 15 or 30 kg pack. During the 31 hour period each subject walked for 6 one hour periods (or walked 4.8 km each period) without sleep during the intervening five hour periods. The average times with the 15 kg load for each 400 m at each experimental hour only showed significantly faster times for hours 7 and 13 compared to hour 25. No differences at all existed for the heavier 30 kg load. The time to complete 400 m during each walk with the 15 kg load showed slower walk times from 0-400 m and from 3200 to 4000 m than for all others; no differences were observed with the 30 kg load. The relationship between heart rate and reported perceived exertion level was not significant, but this perhaps reflected the narrow range of the heart rate data. Furthermore, there was clearly a progressive increase in the perceived exertion level reported for both loads, but the differences were not significant. It appears that an extended 31 hour operation, without sleep, is not sufficient to measurably change the voluntarily selected "hard work" rate. However, the subjective evaluation of perceived exertion level may very well increase despite constant work and physiological responses. (C)1973The American College of Sports Medicine

Eight male subjects exercised on a bicycle ergometer for one half to one hour at loads demanding 52 to 59% of Vo2max on two separate occasions, once with ambient temperature held at 0 degrees C and once in a 35 degrees C environment. Throughout exercise and during recovery in a 25 degrees C environment, measurements were made of oxygen consumption, ventilation, heart rate, muscle-rectal-skin temperatures, and blood lactic acid. In the hot condition significant increases in heart rate, blood lactates, sweat loss, muscle, rectal and skin temperature responses were observed. At 0 degrees C Vo2 was significantly elevated during exercise over that in the 35 degrees C condition. Despite the elevated Vo2 response in the cold, higher body temperatures measured in the heat were associated with a significantly higher (P less than .025) recovery Vo2 (x = 866 ml), which was of the magnitude predicted by the van't Hoff-Arrhenius relationship.

The study was designed to investigate possible influences of 18 selected anthropometric measures and ratios on velocity attained by 107 "untrained" college women during the last thirty-five yards of a fifty-yard run. Weight and weight-related variables such as the leg girth measurements and bi-trochanteric diameter appeared to exert a negative influence on the ability to run rapidly. The relationship between velocity and height and between velocity and other linear measurements used in this study appeared to be masked by weight and the weight-related variables. Obliquity of the femur, lateral hip displacement, the crural index, and the three measures and ratios reflecting the position of the calf muscle showed little or no relationship to velocity on the run through all procedures of analysis. (C)1971The American College of Sports Medicine

It is well accepted that hyperventilation before breath hold swimming and diving makes it possible for a person to extend the time under water. Less well known is the fact that this maneuver can cause loss of consciousness due to hypoxia. This accident happens almost exclusively to males (56 cases). The most common age group was 16-20 years (range 12-33 years). All were known to be good swimmers or divers. Approximately 80% of the cases occurred in guarded pools. Thirty-five subjects survived the accident and of the twenty-three fatalities, there was only one good autopsy report. In this instance the findings were those associated with classical drowning preceded by hypoxia and hypercapnia. Breath holding experiments indicated that the times between loss of consciousness and death may be no longer than 2.5 minutes. The patterns associated with these cases suggest that those who are responsible for aquatic safety as supervisors or guards of pools could prevent most accidents by watching for young male swimmers who are practicing hyperventilation and underwater swimming in competition with themselves or with others.

One hundred and two sedentary and forty- six active adult Japanese females, whose ages ranged from 20-62 years, were tested for maximal oxygen intake (Vo2 max) on a bicycle ergometer. The active females participated in a regular physical conditioning program. For the sedentary females, the mean Vo2 max’s in ml/kg • min were 32.4 for 20-29 years, 27.9 for 30-39 years, 26.0 for 40-49 years and 24.4 for 50-62 years. For active females, the average Vo2 max values were 37.5 for 20-29 years, 31.9 for 30-39 years, 28.8 for 40-49 years and 27.3 for 50-59 years. Vo2 max was significandy higher at all ages in the active group (p < 0.05). The rate of decline of V02 max as a function of increasing age after the twenties was 0.283 ml/kg-min per year for sedentary females and 0.316 ml/kg • min per year for active females; the respective regression equations being Y = —0.283 X -f 38.5, and Y = -0.316 X + 43.3.

The purpose of this investigation was to gain insight, through measuring various performance, cardiopulmonary, and anthropometric parameters, to the upper functional limits for man in the eighth decade of life. The subject holds age-group record times for 16.1, 40.2, 80.5, and 171.4 km. Remarkable aerobic power was exhibited while cycling on a bicycle ergometer depicted by high values for VO2 max 4.7 1/min (STPD) and 59.9 ml/kg BW-min (STPD), VE 159 1/min (BTPS), O2 pulse 0.36 ml/kg/beat and heart rate max 166 beats/min. VO2 max is the highest value reported for a man over 70 years of age. To provide inference to the aging process and to training, comparisons were made with data from the normal population of similar age and with data from young and endurance athletes. Cardiopulmonary data and body composition measures equalled that for similar age athletes and were comparable to younger endurance athletes. The findings have significant implications in determining upper functional standards for well-trained older males.

This study was designed to determine the intensity and duration of EMG muscle action potentials in the upper and lower segments of the rectus abdominis (RA) muscle during four abdominal exercises: the conventional sit-up, the hook sit-up, the arched back sit-up, and the double leg raise. Integrated muscle action potentials were analyzed for both intensity (maximum pen deflection) and duration (amount of time during the contraction in which a moderate degree of activity was present). All three types of sit-ups elicited significantly greater intensity of contraction than the leg lift exercise in both the upper and lower RA. The three sit-up exercises did not differ significantly from each other. Since the intensity of the leg lift exercise was seldom sufficient to allow a duration measurement to be taken, only the three sit-up exercise were included in the analysis of duration. In duration the arched back sit-up significantly surpassed the hook and conventional sit-up for both the upper and lower rectus muscle. The hook and conventional sit-up did not differ significantly from each other. In every subject, for both intensity and duration, the readings were much higher in the upper rectus than in the lower rectus. (C)1970The American College of Sports Medicine

A method of measuring impact absorbing capacity of athletic playing surfaces is described. Four impact parameters were measured of grass fields, asphalt and Astro Turf. It is concluded that the new Astro Turf surface approximates, but does not equal a grass field in impact absorption capability. The 5 yr old Astro Turf surface has significantly decreased ability to absorb impact compared to the new Astro Turf layer. Replacing the Astro Turf surface layer significantly improves the impact quality of the field; therefore the diminished impact absorbing quality of the field appears to be directly related to the alterations in the grass like surface layer secondary to continued use and exposure to atmospheric conditions.

The conditions during which the most common serious and fatal football injuries occur were simulated and the impact absorption characteristics of various types of football headgear were compared during these conditions. The head and neck were simulated using a plastic headform and a flexible metallic rod, respectively, attached to a sled. Impacts were delivered to the occiput to simulate the acute subdural hematoma and to the vertex to imitate the broken neck. Considerable differences between commercially available as well as custom fabricated headgear were noted on such testing. (C)1971The American College of Sports Medicine