Showing papers in "Medicine and Science in Sports and Exercise in 1983"
TL;DR: It is concluded that the ratings from the category-ratio scale correspond very well with glycogenolytic metabolism leading to lactate accumulation during exercise.
Abstract: The purpose of this investigation was to study the relationship between perceptual ratings from Borg's new category-ratio scale and some physiological variables during exercise. To accomplish this, scale ratings were related to blood and muscle lactate accumulation and heart rates during a progressive, maximal exercise test on the cycle ergometer. Ten physically active males were utilized as subjects; lactate data were recorded on only 7 of the 10 subjects. Three ratings of perceived exertion were made at each stage of the exercise test: leg effort (LE), cardiorespiratory effort (CE), and leg pain (LP). All ratings showed a positively accelerating increase with exercise intensity as did both blood and muscle lactate, while heart rate increased linearly. The exponents of the power functions describing the perceptual variation ranged from 1.63-1.67 compared to 2.2 for blood lactate and 2.7 for muscle lactate. Polynomial analysis revealed a similar quadratic trend for both perceptual and blood lactate data; however, muscle lactate demonstrated a cubic trend. No significant differences were found between CE and LE at 100, 200, and 300 W (P greater than 0.05). Subjects with the highest percentage of slow-twitch muscle fibers (mean ST%=51.14) rated LE and CE significantly lower ( mean of all power outputs, 0-300 W) than those with the lowest ST% (mean=34.52). It is concluded that the ratings from the category-ratio scale correspond very well with glycogenolytic metabolism leading to lactate accumulation during exercise.
636 citations
TL;DR: It is suggested that those with knee instability and those allowed to resume play with poorly rehabilitated or clinically unhealed injuries are more apt to sustain further injury.
Abstract: In order to study the incidence and mechanisms of injury in soccer and to recommend prophylactic measures, 180 players in a senior male soccer division were followed prospectively for 1 yr. Attendance records for games and practice sessions were kept, and all injuries were examined and treated by the same orthopaedic surgeon. One hundred twenty-four players incurred 256 injuries, mostly sprains and strains of the lower extremities. Of these, 62% were considered minor with ankle sprains being the most common (17%), while 11% were considered major with knee ligament sprains being the most frequent (32%). Overuse injuries were most frequent in the preseason training period. Traumatic leg injuries involved players with inadequate or no shin guards. Of the traumatic knee injuries, 11 of 18 (61%) occurred during a collision; non-contact knee injuries were frequently seen in those players with a history of knee injury and existing instability. Study of injury sequence disclosed that a minor injury was often followed within two months by a major one. In addition, with severe injuries incurred during fouls, the individual causing the penalty was injured. This prospective study suggested that those with knee instability and those allowed to resume play with poorly rehabilitated or clinically unhealed injuries are more apt to sustain further injury. Some injuries can be avoided by using better equipment and by observance of the rules.
600 citations
TL;DR: The regeneration of skeletal muscle is compared structurally and functionally with its embryonic development and the free muscle graft is used as a model to illustrate the integration of regenerating muscle with the rest of the body.
Abstract: Regeneration is a unique adaptation of skeletal muscle that occurs in response to injury. Following direct trauma or disease, regeneration results in restoration, to some degree, of the original structure and function of the muscle. Our purpose is to summarize the main features of the regeneration of skeletal muscle fibers and entire muscles with an emphasis on aspects of regeneration that may be important to the understanding and treatment of sports injuries. The regeneration of skeletal muscle is compared structurally and functionally with its embryonic development. The free muscle graft is used as a model to illustrate the integration of regenerating muscle with the rest of the body. Finally, the breakdown and regeneration of skeletal muscle fibers are discussed in relation to local anesthetics, sports injuries, and disease.
449 citations
TL;DR: It was concluded that the early change in strength may be accounted for largely by neural factors with a gradually increasing contribution of hypertrophic factors as the training proceeds.
Abstract: Fourteen male subjects (20-30 yr) accustomed to weight training went through progressive strength training of combined concentric and eccentric contractions three times per week for 16 wk. The training was followed by the 8-wk detraining period. The training program consisted mainly of dynamic exercises for leg extensors with the loads of 80-120% of one maximum concentric repetition. Significant improvements in muscle function were observed in early conditioning; however, the increase in maximal force during the very late training period was greatly limited. Marked improvements (P less than 0.001) in muscle strength were accompanied by significant (P less than 0.01) increases in the neural activation (IEMG) of the leg extensor muscles. The relationship between IEMG and high absolute forces changed (P less than 0.01) during the training period. The occurrence of these changes varied during the course of training. It was concluded that the early change in strength may be accounted for largely by neural factors with a gradually increasing contribution of hypertrophic factors as the training proceeds. It was suggested that the magnitudes and occurrence of these changes may vary due to the differences in conditioning periods, in individual muscles of muscle groups, in subject material, and in conditioning methods. During detraining, the decrease in muscle force seemed to be explainable also by the neural and muscular adaptations caused by the inactivity.
419 citations
TL;DR: A small portable accelerometer was developed to estimate the energy expenditure of daily activities and is reported to be an improvement over movement counters currently on the market.
Abstract: A small portable accelerometer was developed to estimate the energy expenditure of daily activities. The accelerometer is reported to be an improvement over movement counters currently on the market. The oxygen requirement of 14 different activities was measured in 21 subjects while each wore the accelerometer on the waist. A movement counter (mercury switch), which is available commercially, was also worn on the waist and another was worn on the left wrist. The reproducibility of the accelerometer readings was high (4 subjects, 14 activities; r = 0.94) and was superior to either the waist movement counter (r = 0.63) or the wrist movement counter (r = 0.74). In estimating oxygen requirement (VO2) the standard error of estimate, based on 21 subjects and 14 activities, was 6.6 ml X min-1 X kg-1 for the accelerometer. This was also better (smaller) than for the waist movement counter (9.2 ml X min-1 X kg-1) or for the wrist movement counter (7.9 ml X min-1 X kg-1).
339 citations
TL;DR: It is suggested that both delayed-onset muscular soreness and plasma enzyme activities are affected by structural changes in muscle tissue resulting from eccentric contractions.
Abstract: We tested the hypothesis that running down an incline, during which muscles primarily perform eccentric contractions, causes greater delayed-onset muscle soreness and greater increases in plasma enzyme activities than does running on the level, during which muscles perform similar amounts of concentric and eccentric contractions Subjective sensations of muscular soreness and plasma activities of CPK and LDH were assessed in seven subjects at 0, 24, 48, and 72 h after 45 min of running (one time on the level and a second time down a 10% incline) Following downhill running (57% of VO2max), significant delayed-onset soreness was experienced in gluteal, quadricep, anterior leg, and posterior leg muscles, and plasma CPK (but not LDH) activity was significantly increased (351% at 24 h) In contrast, following level running (78% of VO2max), no statistically significant soreness occurred in any muscle group, and plasma CPK and LDH activities were not elevated Thus, our results generally support the hypothesis Secondarily, we investigated whether delayed-onset soreness with downhill running is accompanied by increases in peripheral white blood cell counts suggestive of inflammation No such association was observed We suggest that both delayed-onset muscular soreness and plasma enzyme activities are affected by structural changes in muscle tissue resulting from eccentric contractions
313 citations
TL;DR: The state of the art within selected areas of body composition is discussed, identifying significant areas of controversy and proposing specific problems where research should be focused.
Abstract: Body composition has become a major field of interest for many exercise and sport scientists as well as clinicians who specialize in the prevention of and rehabilitation from hypokinetic diseases. This paper discusses the state of the art within selected areas of body composition, identifying significant areas of controversy and proposing specific problems where research should be focused. The areas addressed include the following: the use of body density to estimate relative body fat in selected populations, the use of anthropometric equations to estimate body composition, body composition assessment for profiling and counseling athletes, and alterations in appetite and body composition resulting from acute bouts of exercise and from exercise training.
223 citations
TL;DR: The effect of ammonia production during exercise and other conditions upon purposeful activity and the development of fatigued states are reviewed.
Abstract: Although fatigue is a well-known phenomenon and the phrase "exercised until exhaustion" is commonly understood, there is no unequivocal agreement on the fundamental nature of the fatigue process. Ammonia was linked to the development of fatigue as early as 1922, when ammonia production was observed from stimulated nerve and the question whether there could be a relationship between ammonia production and the muscle activity was raised. The immediate source of ammonia from muscle appears to be a result of the deamination of AMP and is more apparent in fast-twitch than in slow-twitch fibers. More recently, increases in blood ammonia levels have been reported in rats after swimming and in humans after arm work, maximal cycle ergometry, and treadmill exercise. Elevated blood ammonia has also been linked to a surprising variety of functional and metabolic neurological disturbances other than exercise and fatigue, including the development of hepatic coma, convulsions from ammonia toxicity precipitated by high-pressure oxygen breathing, epileptic seizures, and decreased neuronal excitability. In addition, a number of genetic disorders (inborn errors in metabolism, or IEMs) are characterized by elevated blood ammonia concentrations. Symptoms of neural disability in all of the above conditions have been related to the concentration of ammonia in blood. Although these studies do not relate to exercise or fatigue directly, it is conceivable that our understanding of the effect of high concentrations of blood ammonia in these clinical conditions may provide valuable insight into the effect of ammonia during exercise. This paper reviews the effect of ammonia production during exercise and other conditions upon purposeful activity and the development of fatigued states.
207 citations
TL;DR: It was determined that the highest serum enzyme activities and muscular soreness sensation occurred 8-24 h and 48 h post-exercise, respectively, and a positive relationship exists among exercise performed, serum enzyme activity 24 h post the exercise, and muscles soreness.
Abstract: The purposes of this study were to: 1) determine the time course of changes in serum enzyme activities and muscular soreness following muscular exercise, 2) quantify the relative amounts and importance of intensity and duration of muscular exercise in inducing elevated serum enzyme activities and muscular soreness in untrained individuals, and 3) determine the correlation between magnitude of soreness sensation and level of post-exercise serum enzyme activity. It was determined that the highest serum enzyme activities and muscular soreness sensation occurred 8-24 h and 48 h post-exercise, respectively. Intensity and duration of exercise were varied by adjusting the percent 10-repetition maximum (% 10RM) and number of contractions (NR) performed. Increasing intensity and duration of exercise resulted in corresponding increases in serum enzyme activities and muscular soreness. High-intensity, short-duration exercise (80% 10RM, 170 NR) resulted in greater serum enzyme activities and muscular soreness than long-duration, low-intensity exercise (30% 10RM, 545 NR). Most subjects experiencing high levels of muscular soreness were unable to lift resistances of 90% 1RM, 48 h post-exercise. These findings indicate that a positive relationship exists among exercise performed, serum enzyme activity 24 h post-exercise, and muscular soreness. Increased intensity and duration of exercise produced increased serum enzyme activities and muscular soreness, with intensity having the more pronounced effect.
192 citations
TL;DR: It was found that shoes with soft midsoles allowed significantly more maximum pronation (MP) and total rearfoot movement (TRM) than shoes with either medium (35 durometers) or hard (45 durometer) midsoles.
Abstract: Control of the amount and/or rate of pronation of the foot which occurs during distance running has been cited as an important consideration for runners when selecting a running shoe. In this study, high-speed movie film was taken from the rear while 10 subjects ran on a treadmill at a pace of 3.8 m X s-1. These subjects wore 36 different shoes in combinations of three midsole hardnesses, three heel flares, and four heel heights. The film data were digitized and used to determine the eversion or inversion of the heel relative to the lower leg throughout foot contact. Because eversion of the foot is a component of pronation it was used as a predictor of how much pronation was occurring. It was found that shoes with soft midsoles (25 durometer, Shore A scale) allowed significantly more maximum pronation (MP) and total rearfoot movement (TRM) than shoes with either medium (35 durometer) or hard (45 durometer) midsoles. Shoes with 0 degrees heel flare allowed significantly more MP and TRM than shoes with either 15 degrees or 30 degrees heel flares. Heel height was found to have no significant effect on either MP or TRM. These data provide guidelines for the construction of running shoes designed to limit rearfoot movement.
191 citations
TL;DR: Six trained middle-distance runners were studied under alkalotic (NaHCOa ingestion), placebo (CaCO3 ingestion), and control conditions and the effect of acute induced metabolic alkalosis on 800-m racing time was found to be positive.
Abstract: Six trained middle-distance runners wer studied under alkalotic (NaHCO3 ingestion), placebo (CaCO3 ingestion), and control conditions to determine the effect of an acute induced metabolic alkalosis on time to run an 800-m race. Pre-exercise, following NaHCO3 ingestion, pH and standard [HCO3-] were significantly higher. In the alkalotic condition, subjects ran faster (2.9 s) and the corresponding post-exercise values for blood [lactate] and extracellular H+ were higher than in the control and placebo conditions, suggesting an increased anaerobic energy contribution. These results support the speculation that the increase in extracellular buffering following NaHCO3 ingestion facilitated H+ efflux from the cells of working muscle, thereby delaying the decrease in intracellular pH and postponing fatigue. It is concluded that the ingestion of NaHCO3 by trained middle-distance runners prior to an 800-m race has an ergogenic benefit.
TL;DR: The purpose of this paper is to briefly review some of the effects of reduced muscle use on the structure and function of human and animal skeletal muscle.
Abstract: The purpose of this paper is to briefly review some of the effects of reduced muscle use on the structure and function of human and animal skeletal muscle. A loss in muscle strength has been observed in astronauts after space flight. On Earth joint fixation of human limbs results in losses in muscle mass, in the cross-sectional area of both fiber types, and in the activities of mitochondrial enzymes. Methods that reduce muscular activity of animals also produce muscle atrophy. Fixation of the limb joints in position where the muscles are maintained less than resting length results in an atrophy in slow-twitch muscle. Associated with this atrophy are decreases in sarcomere number, fiber cross-sectional area, protein synthesis, and insulin responsiveness for the uptake of 2-deoxyglucose by muscle. Suspension of animals in a horizontal or head-down position is also a method being used currently for unloading muscles and producing alterations in development. In the future, the animal and human model should identify the mechanisms responsible for a decrease in muscle function when the muscle undergoes a decrease in usage.
TL;DR: The physiological factors that relate to 20-km performance were studied in eight competitive racewalkers and data indicate that the velocity at LT correlates closely to performance in racewalkingers and that the factor of submaximal economy is related more to performance ability in Racewalking than was previously observed in running.
Abstract: The physiological factors that relate to 20-km performance were studied in eight competitive racewalkers. The racewalking velocity at the blood lactate threshold (LT) during steady-state exercise was highly correlated to racewalking pace (r = 0.94) and predicted performance times to within 0.6%, which agrees with previous observations on runners. The two factors that contribute to velocity at LT are O2 uptake at LT (VO2 at LT) and submaximal racewalking economy (measured as the VO2 at a standard velocity). Oxygen uptake at LT was significantly correlated (r = 0.89) to performance in the racewalkers in the present investigation, which agrees with previous observations of runners. Submaximal economy was significantly correlated to performance in the racewalkers (r = -0.82). Maximal oxygen uptake measured during racewalking was not significantly correlated (r = 0.62) to performance. These data indicate that the velocity at LT correlates closely to performance in racewalkers and that the factor of submaximal economy, which partly determines velocity at LT, is related more to performance ability in racewalking than was previously observed in running.
TL;DR: It was argued that strength training may cause an increased ability to raise motoneuron excitability during voluntary effort.
Abstract: Two healthy females and twelve healthy males, aged 19-24 yr, underwent strength training for periods of 9-21 wk. The muscles trained included extensor digitorum brevis (N = 3), soleus (N = 7), brachioradialis (N = 4), and the hypothenar muscles (N = 3). The effect of training on motoneuron excitability was measured as the degree to which two reflex responses (V1 and V2) were potentiated by voluntary effort. Strength training was found to increase V1 and V2 potentiation by 49.7 and 38.9%, respectively, (P less than 0.01) for pooled muscle comparisons with the exception of the soleus V2 wave, which was rarely seen and excluded from this analysis. There was a positive correlation (r = 0.83, P less than 0.01) between the change in the V1 and V2 potentiation. It was argued that strength training may cause an increased ability to raise motoneuron excitability during voluntary effort.
TL;DR: Data suggest that the moving treadmill belt reduces the energy requirements of the runner by bringing the supporting leg back under the body during the support phase of running.
Abstract: Selected variables were measured to examine differences in overground and treadmill running at sprinting speeds of maximal effort. Five college-varsity sprinters volunteered to run 100-yd sprints in both overground and treadmill running conditions. After a minimum of 10 training sessions on the treadmill, the subjects were filmed (75 fps) sprinting 100 yd and expired respiratory gases were collected during an 18-min recovery period. The oxygen debt of the overground condition, means = 47.86 ml X kg-1, was 36% greater than the treadmill running condition, means = 30.64 ml X kg-1. Regardless of individual running style, the major biomechanical differences between treadmill and overground running conditions occurred during the support phase and were observed in the supporting leg. During treadmill running, the leg of the supporting lower extremity was less erect at contact (means = 83.9 vs 88.3 deg) and moved through a greater range of motion (means = 60.6 vs 54.5 deg) with a faster overall angular velocity (means = 566.36 vs 478.07 deg X s-1). The thigh of the supporting lower extremity was more erect at contact (means = 67.1 vs 61.1 deg) and moved with a slower overall angular velocity (means = 435.14 vs 528.77 deg X s-1). Data suggest that the moving treadmill belt reduces the energy requirements of the runner by bringing the supporting leg back under the body during the support phase of running.
TL;DR: Cardiorespiratory responses to progressive incremental arm cranking and wheelchair ergometry and upper limb strength and peak Vo2 in the two tests increased progressively in athletes categorize physically disabled athletes.
Abstract: We investigated the cardiorespiratory responses to progressive incremental arm cranking (AC) and wheelchair ergometry (WCE) and upper limb strength in 72 elite male (N=61) and female (N=11) physically disabled athletes. Peak Vo2 in the two tests increased progressively in athletes categorize
TL;DR: Coaching behaviors accounted for about half of the variance in post-season attitudes toward the coach and the sport, but for significantly less variance in measures of team solidarity and self-esteem.
Abstract: To define the characteristics and dimensional patterning of coaching behaviors, 15,449 behaviors of 31 youth basketball coaches were coded in terms of a 10-category system Post-season attitude and self-esteem data were obtained from players on 23 teams and were related to the behavioral measures Compared with rates of reinforcement, encouragement, and technical instruction, punitive responses occurred relatively infrequently Factor analysis of the coaching behaviors indicated that supportive and punitive behavioral dimensions were orthogonal or statistically independent of one another rather than opposite ends of the same dimension Punitive and instructional categories were part of the same behavior cluster The relationship between coaching behaviors and the various player attitudes were highly specific in nature Coaching behaviors accounted for about half of the variance in post-season attitudes toward the coach and the sport, but for significantly less variance in measures of team solidarity and self-esteem Surprisingly, the rate of positive reinforcement was unrelated to any of the attitudinal measures Punishment was negatively related to liking for the coach In general, technical instruction categories were the strongest predictors of basketball player attitudes
TL;DR: Exhaustion was not a result of hypoglycemia or central nervous system dysfunction and that glucose polymer supplements may enhance endurance capacity, and plasma glucose did not fall below the pre-exercise level and was significantly higher than the C plasma glucose concentration at exhaustion.
Abstract: The effect of glucose polymer (GP) ingestion upon endurance performance during walking exercise at 45% VO2max was examined. Also, performance on a battery of psychomotor tests was assessed to determine if exhaustion from endurance exercise was related to central nervous system dysfunction. Ten trained male subjects ingested approximately 120 g of GP in four equally-divided dosages 60, 90, 120, and 150 min following the start of exercise. This treatment significantly increased time to exhaustion by 11.5% as compared to the control (C) group (GP=299.0 +/- 9.8 min; C=268.3 +/- 11.8 min). No difference in VO2 (1 X min-1) or perceived exertion was noted between treatments. As a result of the GP feedings the rate of carbohydrate utilization during the GP trial was 0.53 g X min-1 greater than during the C trial. However, during the GP trial plasma glucose did not fall below the pre-exercise level and was significantly higher than the C plasma glucose concentration at exhaustion. No differences in psychomotor performance between treatments or between rested and exhausted states for either the C or GP treatments were noted. These data suggest that exhaustion was not a result of hypoglycemia or central nervous system dysfunction and that glucose polymer supplements may enhance endurance capacity.
TL;DR: It was concluded that exercising at LI (30-45% HRR) is an adequate training stimulus in older individuals and produces changes in VO2max that are comparable to those elicited by HI (60-75%HRR) training.
Abstract: A program of physical activity for people over 60 yr of age was developed to determine whether exercising at lower intensities (LI) is a significant conditioning stimulus. In addition, differences in aerobic capacities (VO2max) elicited by training at LI, as opposed to training at higher intensities (HI), were evaluated. Thirty-two volunteers over 60 yr of age (mean = 67.8 yr) participated in a 9-wk exercise program. After initial testing of VO2max on a cycle ergometer, subjects were assigned randomly to the HI, LI, or control group. Endurance training of the two exercise groups on cycle ergometers was maintained at 30-45% (N = 14) or 60-75% (N = 14) of the range (HRR) between the subject's resting and maximum heart rate for 25 min during each exercise session. These training intensities represented 57 and 70% of the VO2max of the LI and HI groups, respectively. Participants averaged three exercise sessions per week. Non-exercising volunteers served as control subjects. A one-way ANOVA with repeated measures was utilized for comparisons of retest, groups, and interaction. As a result of the exercise program, significant changes (P less than 0.005) in absolute (VO2max, 1 X min-1) and relative (VO2max, ml X min-1 X kg-1) aerobic capacities were realized within each training group while initial and post-training VO2max were not significantly different between the two groups. Similar changes were documented by a reduction in heart rate at submaximal exercise intensities and during recovery. It was concluded that exercising at LI (30-45% HRR) is an adequate training stimulus in older individuals and produces changes in VO2max that are comparable to those elicited by HI (60-75% HRR) training.
TL;DR: Equations by Durnin and Womersley, Jackson and Pollock, and Lohman for estimating body density purportedly overcome the problem of specificity by accounting for age and/or the curvilinear relationship between skinfolds (SF) and BD are evaluated.
Abstract: Equations by Durnin and Womersley [(D-W), Br. J. Nutr. 32:77, 1974], Jackson and Pollock [(J-P), Br. J. Nutr. 40:497, 1978], and Lohman [(L), Human Biol., 53:181, 1981] for estimating body density (BD) purportedly overcome the problem of specificity by accounting for age and/or the curvilinear relationship between skinfolds (SF) and BD. Their equations were validated on 265 male athletes against percent fat measured by underwater weighing [(UWW); mean +/- SD = 9.2 +/- 4.4%]. Equations by Sloan [(S), J. Appl. Physiol. 23:311, 1967], Katch and McArdle [(K-M), Human. Biol. 45:445, 1973], and Forsyth and Sinning [(F-S), Med. Sci. Sports 5:174, 1973] were included as "linear regression models" to compare to the curvilinear models of J-P, D-W, and L. Differences between UWW and estimated mean values ranged from -1.1 to +5.9%; correlations ranged from 0.58 to 0.85; SEE ranged from +/- 2.41 to +/- 3.61% and total error (E) ranged from 2.38 to 6.97%. The seven D-W equations overestimated mean percent fat by from 3.9 to 5.9%. The K-M, S, and L equations overestimated by 1.3, 0.5, and 1.7%, respectively. The F-S equations overestimated by 2.4 to 3.8%. Of the 21 equations evaluated, only 3 by J-P gave estimates not significantly different from UWW percent fat. Regression analyses of the relationship between UWW (y) and estimated (x) percent fat values from those equations were: y = 1.037x - 0.08 +/- 2.38, E = 2.38, r = 0.84; 0.869x + 1.36 +/- 2.45, E = 2.51, r = 0.83; 1.107x - 1.14 +/- 2.51, E = 2.53, r = 0.82.(ABSTRACT TRUNCATED AT 250 WORDS)
TL;DR: The purposes of this study were to describe the pattern of segmental coordination used in vertical jumping and to determine if skilled jumpers displayed distinguishing patterns of coordination, and to assess the extent of simultaneity.
Abstract: HUDSON, J. L. Coordination of segments in the vertical jump. Med. Sci. Sports Exerc., Vol. 18, No. 2, pp. 242–251, 1986. Three general patterns of segmental coordination (i.e., sequential [SEQ], simultaneous [SIM], and modified simultaneous [MSIM]) have been hypothesized for jumping. The pur
TL;DR: It was concluded that for men and women similarly trained, the average sex difference in 12-min run performance is primarily due to differences in percent fat and cardiorespiratory capacity.
Abstract: The extent to which differences between men and women in cardiorespiratory capacity (VO2max in ml X min-1 X kg FFW-1), percent fat, and running economy (VO2 in ml X min-1 X kg BW-1 at 188 m X min-1) account for the sex difference in 12-min run performance was investigated in 34 male and 34 female recreational runners, 19-35 yr of age. Men differed significantly (P less than 0.05) from women in VO2max (68.6 vs 65.1 ml X min-1 X kg FFW-1), percent fat, (10.8 vs 19.8%), and 12-min run performance (3294 vs 2747 m), but not in running economy (39.0 vs 39.1 ml X min-1 X kg BW-1). Simple and multiple regression and correlation analyses indicated that relations of the biological variables to 12-min run performance were similar within groups of men and women. Multiple regression analysis revealed that percent fat, VO2max (ml X min-1 X kg FFW-1), and running economy accounted for 74, 20, and 2% of the average sex difference in 12-min run performance, respectively. It was concluded that for men and women similarly trained, the average sex difference in 12-min run performance is primarily due to differences in percent fat and cardiorespiratory capacity. If the observed differences between men and women on these variables are truly a function of sex, results of this study provide a biological basis for different distance running performance expectations for men and women.
TL;DR: The level of lipoprotein lipase activity measured in postheparin plasma nearly doubled after the race, demonstrating that vigorous exercise acutely increases this enzyme activity.
Abstract: We investigated the acute effects of prolonged exercise on lipoprotein metabolism. Serum lipid and lipoprotein concentrations and plasma postheparin lipolytic activity were measured in ten well-trained men (ages 21 to 39) the day before and after a 42 km foot race. LDL cholesterol decreased by 10% (113 +/- 31 to 103 +/- 32 mg/dL, P less than 0.01) and total HDL-cholesterol levels increased by 9% (65 +/- 18 to 71 +/- 19 mg/dL, P less than 0.01) the day after the race. No changes in the concentration of apolipoprotein A-I or A-II occurred. Triglyceride levels decreased by 39% (95 +/- 38 to 58 +/- 23 mg/dL, P less than 0.001). Two days after the race, total HDL cholesterol (74 +/- 21 mg/dL, P less than 0.05) and the HDL2 subfraction (37 +/- 19 mg/dL, P less than 0.05) remained significantly elevated compared to pre-race values. Most dramatically, the level of lipoprotein lipase activity measured in postheparin plasma nearly doubled after the race, demonstrating that vigorous exercise acutely increases this enzyme activity. The increase in lipoprotein lipase activity probably mediated the fall in serum triglycerides after exercise and may also account for the increase in HDL cholesterol.
TL;DR: The HR response and percent maximal HR (%HRmax) at the AT in 20 young women indicated that heart rate may be used to regulate activity intensity above or below the anaerobic threshold.
Abstract: Although heart rate (HR) cannot be used to identify the anaerobic threshold (AT), it may be used to regulate activity intensity above or below AT. This study examined the HR response and percent maximal HR (%HRmax) at the AT in 20 young women. The AT, VO2max, and HRmax were assessed during i
TL;DR: The forces and movement at the feet during the golf swing were studied using force platform and three-dimensional cinematography techniques, with special consideration given to implications for golf shoe design.
Abstract: The forces and movement at the feet during the golf swing were studied using force platform and three-dimensional cinematography techniques, with special consideration given to implications for golf shoe design. Ground reaction forces and center-of-pressure patterns were obtained by alternat
TL;DR: It is suggested that when the flight phase is included in the mechanical energy calculations, the measured efficiency for the positive work reaches a high but constant value in running at low-to-moderate speeds.
Abstract: To investigate the possible role of elastic potentiation on mechanical efficiency, three male marathon runners were filmed while running on a treadmill at various steady-state speeds ranging from 7.0-22.0 km X h-1. Kinematic and mechanical energy analyses were performed from the film. Expired air was collected for energy expenditure determination. The analysis disclosed that during contact on the treadmill the knee and ankle joints initially had a phase of negative (flexion) angular velocity, followed by a positive velocity. In the hip joint the stretch-shortening cycle of the extensor muscles occurred primarily during the flight phase. The mean vertical and horizontal forces of the negative and positive phases of the contact period increased linearly with the increase in the running speed. The calculated mechanical efficiency of positive work was high but relatively constant (55.1 +/- 12.7%) across all speeds. The absolute contribution of the extra work, which comes from the stored elastic energy to the positive work, increased with running speed; however, its relative value (0.61 +/- 0.09 J X min-1 X kg-1) remained constant at all measured speeds. It is suggested, therefore, that when the flight phase is included in the mechanical energy calculations, the measured efficiency for the positive work reaches a high but constant value in running at low-to-moderate speeds.
TL;DR: The results suggested that although the exercise program was strenuous enough to increase significantly the physical working capacity of the exercise group, it did not alter their serum lipid and lipoprotein levels during the 8-wk period.
Abstract: This study was designed to measure the effect of physical conditioning on the serum lipid and lipoprotein levels of white male adolescents. Fifty white males, ages 11–17 yr, underwent pre-test evaluations including physical measurements, physical activity levels, nutritional intake, physical working capacity, and fasting serum lipid and lipoprotein levels. Each subject was randomly assigned to a physical conditioning group or to a control group. There were no statistically significant differences in pre-test measurements. The physical conditioning group participated in an 8-wk progressive aerobic exercise program 30 min/d for 4 d each wk. The pre-test measurements were then repeated for both groups. Based on Student's t-test, the physical conditioning group had a significantly higher physical working capacity on the post-test than the control group. An analysis of covariance test showed no differences between the groups in the post-test serum lipid and lipoprotein levels. The results suggested that although the exercise program was strenuous enough to increase significantly the physical working capacity of the exercise group, it did not alter their serum lipid and lipoprotein levels during the 8-wk period.
TL;DR: Specific changes include alterations in hydration status, resulting in a relative dehydration, loss of body calcium stores with a concomitant increase in urinary hydroxyproline, skeletal muscular atrophy, and a negative energy balance after prolonged space flight.
Abstract: The absence of hydrostatic forces, which results in body fluid shifts, and the absence of deformation forces on normally load-bearing tissues, appear to cause the principal disturbances found during and after space flight in the cardiovascular, fluid and electrolyte, erythropoietic, musculoskeletal, and metabolic systems. These alterations produce reduced body fluid volume, reduced musculoskeletal mass, and alterations in basal metabolism, resulting in the following consistent findings of space flight: weight loss, altered body composition, decreased orthostatic tolerance, and a compromised ability to deal with physical activity after returning from a space-flight environment. Specific changes include alterations in hydration status, resulting in a relative dehydration, loss of body calcium stores with a concomitant increase in urinary hydroxyproline, skeletal muscular atrophy, and a negative energy balance after prolonged space flight. Numerous endocrine changes have been determined during space flight, but more sensitive assays developed recently will allow careful determination of other hormone levels, and measurement of some of the primary changes that occur during the first hours of space flight. These results will be integrated into a working systems model of the physiologic response to weightlessness.
TL;DR: Examination of the relationships of marathon performance time (MPT) to maximal aerobic power (VO2 max), physical characteristics, and training indices recorded for 12 weeks prior to a race in 35 female distance runners found MPT was positively correlated to body mass index, and body fat but negatively related to VO2 max.
Abstract: The purpose of this study was to examine the relationships of marathon performance time (MPT) to maximal aerobic power (VO2 max), physical characteristics, and training indices recorded for 12 weeks prior to a race in 35 female distance runners. The marathon experience of the subjects ranged from two to fifteen races. Physical and aerobic power characteristics (mean +/- S.D.) were: age, 35.7 +/- 8.5 yr; height, 166.4 +/- 5.7 cm; weight, 55.1 +/- 5.7 kg; body fat, 15.7 +/- 5.0%; VO2 max, 56.5 +/- 6.2 ml . kg-1 . min-1. Marathon time for this race averaged 227.0 +/- 31.6 min. Records from individual training diaries indicated the runners averaged 71.0 +/- 10.0 workout days, 10.0 +/- 10.0 two X day-1 workouts, 81.0 +/- 8.0 total workouts, 12.3 +/- 1.8 mean km . workout-1, 5402.8 +/- 1302.6 total training min, 187.0 +/- 18.0 m . min-1 training pace, 112.2 +/- 32.1 max km . wk-1, 83.1 +/- 23.4 mean km . wk-1, 998.8 +/- 282.6 km . 12 wk-1 and 13.8 +/- 2.4 mean km . day-1. MPT was positively correlated to body mass index (r = 0.52), and body fat (r = 0.52) but negatively related to VO2 max (r = -0.65). MPT was also negatively related to previous marathons completed (r = -0.47), workout days (r = -0.47), two X day-1 workouts (r = -0.52), total workouts (r = -0.56), mean km . workout-1 (r = -0.58), total training min (r = -0.56), m . min-1, training pace (r = -0.66), max km . wk-1 (r = -0.70), mean km . wk-1 (r = -0.74), km . 12 wk-1 (r = -0.74), and mean km . day-1 (r = -0.77). MPT for our population of runners may be predicted (r = 0.82, R2 = 0.68) by the following equation: MPT, (min) = 449.88 - 7.61 (-/x km.day-1 run) - 0.63 (m.min-1, training pace); SEE = +/- 18.4 min.