Strenuous Physical Training Research Articles

Regional Bone Mineral Density of the Tibia in Female Soldiers Following 16-Weeks of Recruit Training

The bone adaptation response to exercise is specific to the site being loaded, and may differ between regions of trabecular and cortical bone. It has been suggested that strenuous physical training may result in decreased bone mineral density (BMD) at regions susceptible to stress fracture. Additionally, individuals may respond uniquely to comparable exercise programs. PURPOSE: 1) To determine if regional BMD of the tibia decreases following 16 weeks of recruit training, and 2) to assess whether a change in tibial BMD is related to onset of lower extremity stress fracture. METHODS: 105 women (18.9 ± 0.5 yr) underwent DXA scanning before and after a 16-wk recruit training program in the Israeli Defense Forces. 57 women participated in a physically rigorous combat training program and did not sustain a stress fracture (no stress fracture), 10 participated in rigorous training and were diagnosed with a stress fracture (stress fracture), and 38 completed an academic program with light physical activity requirements (control). BMD was assessed at 5 regions of interest (ROI) at points 4, 33, 50, 66, and 95% from the distal end plate of the tibia. The 4 and 95% regions reflect predominantly trabecular bone; the 33, 50, and 66% sites reflect cortical bone. The 33 and 95% sites are the most frequent site of stress fracture. A total tibial BMD value was calculated as the mean of the five ROIs. Data were analyzed using a repeated measures ANOVA and Tukey post hoc testing. RESULTS: Stress fracture incidence was 14.9% in the combat training group, whereas there were no stress fractures in the control group. The following table presents tibial BMD (g/cm2) compared across groups for each ROI (mean±SD):Table 1Only the control group exhibited changes in tibial BMD over the study period, with increases evident at the 33% and 95% regions. CONCLUSION: Sixteen weeks of strenuous training did not result in decreased tibial BMD, whereas light physical training over the same period increased BMD at two regions, and resulted in a small but significant overall increase in tibial density.

Prevalence of iron deficiency and anemia among strenuously trained adolescents

Purpose There is a lack of awareness among physicians, dieticians, and public health planners as to the prevalence of iron deficiency and anemia among adolescents undergoing strenuous physical training. The aim of this study was to estimate the prevalence of iron deficiency and anemia among male adolescents undergoing such activity. Methods We studied 292 male adolescents on the day of entry into a volunteer military unit. Hemoglobin (Hb), mean corpuscular volume, ferritin, iron, iron-transferrin saturation, and soluble transferrin receptor (TfR) were measured, and TfR-F index was calculated. Results The mean Hb level (±SD) in the study population was 14.7 ± .9 g/dL (range, 10.8–16.8 g/dL), mean ferritin level was 50.6 ± 32.6 ng/mL (range, 5.4–162.5 ng/mL), and mean iron level was 97.1 ± 39.9 μg/dL (range, 24–267 μg/dL). The prevalence of anemia (Hb <14 g/dL) was 18.5%, and 3.4% had Hb concentrations less than 13 g/dL. Iron deficiency (ferritin <22 ng/mL) was present in 18% of the subjects, and 11.3% had ferritin levels less than 17 ng/mL. The mean soluble transferrin receptor concentration was 1.9 ± .8 mg/L, and the mean TfR-F index was 1.21 ± .57. Conclusions Nearly 19% of the study subjects had mild anemia at recruitment, and depletion of iron stores was observed among 18%. Overall, these changes were not accompanied by a significant increase in soluble TfR. This high prevalence is most likely the result of “sports anemia” due to the intense physical training regimen adopted prior to their recruitment.

Effect of 12 Weeks of Strenuous Physical Training on Hematological Changes

It is well known that sports and physical exercise affect the hemoglobin (Hb) concentrations; however, the factors affecting the hematological changes after intense exercise are still not fully elucidated. In the present study, we examined the hematological and biochemical parameters of nine young male soldiers participating in a 12-week ranger training program. The platelet counts before the training showed a strong in-verse correlation with the Hb concentrations after the training (r = -0.829, p < 0.01). Furthermore, the Hb concentrations of the subjects whose platelet counts were more than 25.0 x 10(4)/microL decreased significantly after the training (p < 0.05). Our findings suggest that an association exists between high platelet counts even within the normal range before strenuous physical training and the risk of a subsequent decrease in the Hb concentrations.

Changes In Parameters Of Bone And Body Composition In Females Undergoing U.S. Army Basic Training

U.S. Army initial entry training (IET) requires soldiers to undergo a vigorous nine week basic training course designed to enhance physical strength, endurance and function to prepare them for combat operations. However, there is little known about the effect of this type of training on bone parameters. PURPOSE To observe the response of bone and lean tissue mass (LM) to strenuous physical training in a cohort of IET soldiers, and to explore the association between LM and bone area (BA), bone mineral content (BMC), and bone mineral density (BMD). METHODS 151 female soldiers (age 21.4 ± 3.4 years) underwent dual x-ray absorptiometry scanning before and after nine weeks of basic training. A total body scan provided BA, BMC, BMD and LM measures for the total body (TB), the upper extremities (UE), and the lower extremities (LE). Data were analyzed using paired sample t-tests and Pearson's correlation coefficients. RESULTS Total body BMD decreased from 1.20 ± 0.08 to 1.19 ± 0.08 g/cm2 (p<0.001). Total body LM increased from 39.38 ± 4.30 to 41.84 ± 4.42 kg (p<0.001), and was not significantly correlated with parameters of bone. Total body BMC and BA did not change significantly. Extremity data are presented in the following table:TableThe observed changes in LM were positively correlated with changes in BA for the UE (r=.52) and LE (r=.32) (both p<0.001). CONCLUSION This study provides evidence for the influence of physical training on bone acquisition in the skeletally mature female. Lower extremity bone area increases in response to short term, strenuous, weight bearing activity without a concomitant increase in BMD or BMC. Increases in bone area in the extremities are positively associated with increases in lean tissue mass. At this time it is unknown if significant changes in soft tissue composition result in artifactual variability in measures of bone.

Heat acclimation and physical training adaptations of young women using different contraceptive hormones

Although endogenous and exogenous steroid hormones affect numerous physiological processes, the interactions of reproductive hormones, chronic exercise training, and heat acclimation are unknown. This investigation evaluated the responses and adaptations of 36 inactive females [age 21 +/- 3 (SD) yr] as they undertook a 7- to 8-wk program [heat acclimation and physical training (HAPT)] of indoor heat acclimation (90 min/day, 3 days/wk) and outdoor physical training (3 days/wk) while using either an oral estradiol-progestin contraceptive (ORAL, n = 15), a contraceptive injection of depot medroxyprogesterone acetate (DEPO, n = 7), or no contraceptive (EU-OV, n = 14; control). Standardized physical fitness and exercise-heat tolerance tests (36.5 degrees C, 37% relative humidity), administered before and after HAPT, demonstrated that the three subject groups successfully (P < 0.05) acclimated to heat (i.e., rectal temperature, heart rate) and improved muscular endurance (i.e., sit-ups, push-ups, 4.6-km run time) and body composition characteristics. The stress of HAPT did not disrupt the menstrual cycle length/phase characteristics, ovulation, or plasma hormone concentrations of EU-OV. No between-group differences (P > 0.05) existed for rectal and skin temperatures or metabolic, cardiorespiratory, muscular endurance, or body composition variables. A significant difference post-HAPT in the onset temperature of local sweating, ORAL (37.2 +/- 0.4 degrees C) vs. DEPO (37.7 +/- 0.2 degrees C), suggested that steroid hormones influenced this adaptation. In summary, virtually all adaptations of ORAL and DEPO were similar to EU-OV, suggesting that exogenous reproductive hormones neither enhanced nor impaired the ability of women to complete 7-8 wk of strenuous physical training and heat acclimation.

Plasma Insulin-Like Growth Factor-I and High Affinity Growth Hormone-Binding Protein Levels Increase After Two Weeks of Strenuous Physical Training

The high affinity growth hormone-binding protein (GHBP) circulates in human blood and represents the extracellular domain of the growth hormone (GH) receptor. It is well known that repetitive bouts of endurance type exercise result in increased integrated GH secretion. As the effects of chronic exercise on plasma GHBP levels have never been studied systematically, we investigated the effect of 2 weeks of intense endurance training on plasma GHBP as well as on plasma insulin-like growth factor (IGF)-I levels in 10 healthy, young, non-obese men. IGF-I was measured as an indicator of the effects of GH release. We also studied 10 control subjects matched for sex, age and activity, who were instructed not to change their customary activities. GHBP was determined by FPLC size exclusion chromatography and subsequent Scatchard plot analysis of the binding data; IGF-I levels were measured by RIA. The results showed that plasma IGF-I and GHBP levels were increased in the subjects who followed the training program. IGF-I and GHBP changed from 252 +/- 56 ng/ml and 912 +/- 59 pmol/l before training, to 344 +/- 61 ng/ml (p < 0.01) and 1020 +/- 48 pmol/l (p < 0.01), respectively. Another effect of the training was that the aerobic capacity of these subjects was better utilized and endurance was improved. In contrast, plasma IGF-I, GHBP, utilization of aerobic capacity and endurance did not change significantly in the control subjects. We conclude that two weeks of strenuous endurance training lead to increased plasma IGF-I and high affinity GHBP levels.

The role of the knee brace in the prevention of anterior knee pain syndrome.

Our prospective study evaluates the use of a knee brace with a silicon patellar support ring as a method of preventing anterior knee pain from developing in young persons undergoing strenuous physical exercise. We studied 60 young athletes, who qualified for a strenuous physical training course and who had not suffered from anterior knee pain previously. Twenty-seven subjects were in the brace group and 33 were in the nonbrace control group. The incidence of anterior knee pain syndrome increased with the intensity of exertion as the study progressed; i.e., subjects ran 6 km in the 1st week, gradually increasing each week up to 42 km/week at the 8th week. Yet, there was a significant reduction in the incidence of the syndrome at the end of the study in male athletes who had applied the braces before exercise sessions and in the brace group as a whole, compared with the control group. Prophylactic use of the brace, as described, did not reduce the ability of the athletes who wore braces to improve their physical fitness parameters in response to exercise. These data indicate that the use of a brace may be an effective way to prevent the development of anterior knee pain syndromes in persons participating in strenuous and intensive physical exercise.

Longitudinal Exercise-Heat Tolerance and Running Economy of Collegiate Distance Runners

To evaluate the effects of strenuous physical training on the exercise-heat tolerance (EHT) and running economy (RE) of endurance athletes, 5 male collegiate distance runners performed three strenuous 20-min exercise trials in a hot environment during the winter (Tl) indoor track and field season and during the latter stages (T2 and T3) of the outdoor track and field season. EHT was highest at Tl and did not change during 17.5 wks of training and competition. Similarly, RE was not significantly enhanced from Tl to T3. RE was strongly correlated with the change in rectal temperature pre- to postexercise, suggesting that RE may be an important factor in the development of hyperthermia during exercise in the heat. The runners did not significantly improve their EHT and RE during training and competition. However, the magnitudes of change in mean RE and in sweat rate suggest that these training related adaptations may have been physiologically though not statistically significant.

Effect of physical exercise on the phagocytic function of peritoneal macrophages from Swiss mice

The influence of strenuous physical exercise (swimming until exhaustion) or physical training (swimming 90 min daily during 20 days) on different aspects of phagocytic function of peritoneal macrophages from Swiss mice was studied. The adherence capacity was not modified by strenuous or training exercise. The spontaneous mobility, chemotaxis, spontaneous attachment and ingestion of Candida albicans and of inert particles (latex beads) were also not modified by the strenuous physical activity, but increased significantly with training. The attachment and ingestion of opsonized C. albicans, as well as the nitroblue tetrazolium (NBT) reduction in the absence (oaxidative metabolism measure) or presence (microbicidal capacity measure) of ingested material ( C. albicans with and without serum or latex beads), were increased by both the strenuous and the training physical exercises. Moreover, significantly higher values were found for training activity compared with those found for strenuous physical exercise. The advantageous effects of physical exercise in the phagocytic function of macrophages are discussed.

Strenuous exercise simulating hepatic injury during vaccine trials

Three healthy young men participating in phase 1 clinical vaccine trials had unexplained increases in their serum transaminase levels. Retrospective analysis indicated that these volunteers had participated in strenuous physical training 2–5 days prior to the noted elevations. The pattern of serum enzyme elevations, initially thought to be consistent with hepatic injury, were associated with parallel increases in creatine phosphokinase. One individual consented to repeat his exercise regimen. This was followed by a recurrence of the same pattern of increases in serum enzymes, including creatine phosphokinase. Thus, in trials where serum enzymes will be measured, it may be prudent to encourage subjects to refrain from increasing their activity above that which they normally perform.

Androgenic Response to Long-Term Physical Training in Male Subjects

An increase in endogenous androgen production has been observed following long-term physical training and the beneficial effects of training have been attributed in part to this phenomenon. Other investigators, however, found, in contrast lower testosterone levels in trained compared with untrained subjects. The purpose of the present study was to follow the long-term changes in total testosterone (T) and cortisol (C) levels in intensely training individuals. The changes in the body's anabolic state, induced by intense long-term physical training, were determined using the plasma resting T/C ratio. T and C levels of 35 young untrained subjects were measured at 6 week intervals during 18 weeks of strenuous physical training. All samples were drawn within one half hour of awaking (05.30-06.00). Mean serum T levels increased significantly at 6 weeks (28.7%, p less than 0.02) and decreased significantly at 12 weeks (20.6%, p less than 0.02), but did not differ at 18 weeks compared with levels before training was commenced (mean +/- SE, 16.9 +/- 0.2, 21.8 +/- 0.3, 12.8 +/- 0.2 and 17.3 +/- 0.2 nmol/l at 0, 6, 12, and 18 weeks, respectively). Mean serum C was increased significantly (21.3%, p less than 0.005) at 18 weeks (463.5 +/- 19.3, 507.7 +/- 22.1, 480.1 +/- 19.3, and 565.6 +/- 22.1 nmol/l). T/C ratio decreased significantly after 12 and 18 weeks of training. Our results do not support an association between reduced total testosterone levels and prolonged training. However, hypercorticolism with a relative catabolic state may occur.

The Possible Involvement of Endogenous Opioid Peptides and Catecholestrogens in Provoking Menstrual Irregularities in Women Athletes

It is well known that women athletes engaged in strenuous physical exercise and endurance training may develop "athletic menstrual irregularities" (AMI). Although many studies have appeared dealing with the immediate endocrinological and physiological changes in these women, the underlying mechanisms have remained unknown to date. A number of hypotheses have been put forward, the most well-known among them, for example, defending the existence of a critical percent of body fat necessary to trigger or maintain normal menstruation. All these theories have, however, their own, sometimes numerous, methodological inaccuracies and a teleological way of investigation. Spectacular, and perhaps promising new developments concern the possible involvement of endogenous opioid peptides and catecholestrogens in these processes. In basal circumstances beta-endorphin, the most well-known endogenous substance with opiate-like activity, may decrease LH levels by suppressing hypothalamic GnRH. This phenomenon is, however, only observed during the estrogen-dominant late-follicular and mid-luteal phases. As for catecholestrogens, it appears essential to differentiate between, for example, the 2- and 4-hydroxy derivatives of both estrone and estradiol. While some of these catecholestrogens obviously seem to suppress LH levels, others seem to potentiate and induce the LH surge. In any case, similar to beta-endorphin, these activities of catecholestrogens appear to depend upon the essential presence of a sufficiently estrogenic environment. In addition, both endogenous opioid peptides and some of the catecholestrogens appear to be able to suppress prolactin release, probably by interfering with its inhibiting factor dopamine. Other effects of catecholestrogens may include the control of the luteolysis-potent prostaglandin F2 alpha. Although a number of studies have investigated the behaviour of beta-endorphin during and post-exercise, similar studies investigating catecholestrogens as to their relation to physical exercise are almost nonexistent. This, in association with the numerous methodological inaccuracies of various studies, makes it difficult to draw any firm conclusion. As to formulate new hypotheses, the only reasonable suggestion considers the possible existence of a complex feedback system including catecholestrogens and endogenous opioid peptides. Furthermore, recommendations made in this survey may be helpful in designing new, perhaps more firmly supported and appropriate future studies.

Indentation stiffness of young canine knee articular cartilage—Influence of strenuous joint loading

The indentation stiffness of knee articular cartilage subjected to strenuous physical training (SPT: treadmill running 20 km day −1 for 15 weeks, n = 6) of young Beagles was tested and compared to that obtained from age-matched (55 weeks, n = 9) controls. The mathematical solution for the shear modulus, as determined from indentation of an elastic layer bonded to a rigid half space, was extended to small Poisson's ratios and applied to the analysis of cartilage response after a step stress (0.39 MPa) application. In these measurements with an impervious, plane-ended indenter, the equilibrium deformation was systematically greater than values predicted from the instant response by the linear biphasic theory. Therefore, the accurate determination of Poisson's ratio from the creep curves was not possible. The mean shear modulus (calculated by using the deformation at 900 s after load application and assuming a constant Poisson's ratio of 0.40 for the matrix) of canine knee articular cartilage was 0.37 MPa. While the cartilage thickness was not affected by SPT, the cartilage of the lateral tibial plateau was stiffer (13.3%, p<0.05) than that in controls. However, in the femoral condyles, the stiffness was at the control level or even below. Our results on cartilage structure and properties suggest that SPT, in contrast to our previous findings with moderate training, does not necessarily improve the biological properties of articular cartilage in young animals.

Gain in mass density of bone following strenuous physical activity.

A group of 223 military recruits aged 18-21 years underwent strenuous physical training for a period of 14 weeks. The absolute bone density of the distal tibia in both lower limbs was measured before the training period and at its end. The density was determined by the Compton scattering technique, which has been developed in our laboratory; this method provides the bone mass of all bone constituents per unit volume. The distribution curve of the bone density in both tibiae shifted to higher values at the end of the training period. The mean bone density in the right and left tibia increased significantly by 7.5%. This study indicates that following an intensive physical exercise regime, a significant increase in the mass density of bone can be obtained in young adults within a short period.

Effect of intense physical activity on the bone-mineral content in the lower limbs of young adults.

The effect of intense physical training on the bone-mineral content of young adults who are unaccustomed to physical activity has not yet been established. In this study, 268 male recruits, eighteen to twenty-one years old, were evaluated before and after fourteen weeks of strenuous physical training. The bone-mineral content of both legs at the level of the distal third of the tibia in each individual was measured using single-beam photon absorptiometry. The subjects started their training with equal values for bone-mineral content in both legs. During the training period, the average bone-mineral content of the left leg increased by 11.1 per cent and that of the right leg, by 5.2 per cent. In the group of subjects who did not complete the training course, mainly because they incurred stress fractures, the increase in bone-mineral content was significantly less than the increase in those who completed the program. This study indicated that in young adults a high level of loading of bone results in either a stress fracture or a rapid increase in bone-mineral content.

Pulsatile Secretion of Gonadotropins and Prolactin in Male Marathon Runners. Relation to the Endogenous Opiate System

We tested the hypothesis that sustained, strenuous physical training alters the neuroendocrine regulation of pulsatile gonadotropin and/or prolactin secretion in men. Blood was sampled at 20-minute intervals over 8 hours in five endurance-trained men after a 10-15 mile run in the middle of the active training season, and in 11 nonendurance trained normal controls. In these two groups, basal patterns of physiologically pulsatile secretion of LH, FSH, and prolactin (PRL) were not significantly different in relation to the following parameters: mean serum concentration of each of the three hormones (N = 25 samples); areas under the hormone concentration vs. time curves; fractional, incremental, and absolute pulse amplitudes; and pulse frequency, or periodicity. To test for enhanced suppressive effects of endogenous opiates in trained male marathon runners, subjects were administered the potent opiate-receptor antagonist, naltrexone (1 mg/kg). This antagonist significantly stimulated pulsatile LH secretion by increasing mean serum LH values from 10.94 to 13.58 mIU/ml (P = 0.007); area under the LH concentration vs. time curve increased from 5370 to 6510 mIU/ml X 8 hours (P = 0.05) and, pulse frequency rose from 2.8 to 4.9 pulses/8 hours (P = 0.006). Naltrexone also enhanced pulse frequency of FSH secretion from 3.4 to 5.4 pulses/8 hours (P = 0.009), but did not alter serum prolactin concentrations. None of these responses differed significantly from those in normal sedentary controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Pulsatile secretion of gonadotropins and prolactin in male marathon runners. Relation to the endogenous opiate system.

We tested the hypothesis that sustained, strenuous physical training alters the neuroendocrine regulation of pulsatile gonadotropin and/or prolactin secretion in men. Blood was sampled at 20-minute intervals over 8 hours in five endurance-trained men after a 10-15 mile run in the middle of the active training season, and in 11 nonendurance trained normal controls. In these two groups, basal patterns of physiologically pulsatile secretion of LH, FSH, and prolactin (PRL) were not significantly different in relation to the following parameters: mean serum concentration of each of the three hormones (N = 25 samples); areas under the hormone concentration vs. time curves; fractional, incremental, and absolute pulse amplitudes; and pulse frequency, or periodicity. To test for enhanced suppressive effects of endogenous opiates in trained male marathon runners, subjects were administered the potent opiate-receptor antagonist, naltrexone (1 mg/kg). This antagonist significantly stimulated pulsatile LH secretion by increasing mean serum LH values from 10.94 to 13.58 mIU/ml (P = 0.007); area under the LH concentration vs. time curve increased from 5370 to 6510 mIU/ml X 8 hours (P = 0.05) and, pulse frequency rose from 2.8 to 4.9 pulses/8 hours (P = 0.006). Naltrexone also enhanced pulse frequency of FSH secretion from 3.4 to 5.4 pulses/8 hours (P = 0.009), but did not alter serum prolactin concentrations. None of these responses differed significantly from those in normal sedentary controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Nature and causes of injuries in women resulting from an endurance training program.

Women entering the Army are exposed to considerable physical stress due to the intense physical training program encoun tered. At the beginning of a basic training cycle, a prospective study was initiated to identify exercise-related injuries and performance-limiting conditions that resulted from an 8-week physical training program and to identify some of the factors that may contribute to their occurrence. Four hundred women recruits (age 18 to 29 years) participated in the study. All had passed an initial physical examination and were without any limiting disabilities. An initial assessment of physical fitness was accomplished to determine the current status of body composition, strength of the major muscle groups (e.g., legs, trunk, arms, and upper torso), aerobic capacity, previous ath letic history, self-perception of physical fitness, and psychoso matic predisposition. The training and conditioning program (1 hr daily, five to six times a week) involved a series of standard warm-up calisthenics and stretching exercises fol lowed by a run, beginning at 3/4 mile at a 10 min per mile pace and increasing to 2 miles at 9½ min per mile by the end of training. Extensive road marches and military training activities were also included. At the end of training, a self-report injury questionnaire was used to collect injury data. These data were documented with the records from the unit dispensary and data provided by the installation physical therapy, orthopaedic, and podiatry clinics. Fifty-four percent (215) of the women sustained some reportable injury. These injuries resulted in an average training time loss of 13 days. Forty-one percent of these injuries prevented participation in all activity, 31% resulted in only limited participation. Early training "overuse syndrome" ac counted for 42% (92) of the reported injuries. Significant injuries were: tibial stress fracture (45), chondromalacia of the patella (21), hip or neck of femur stress fracture (20), sprains (12), Achilles tendinitis (10), calcaneous or metatarsal stress fracture (8), and fascial and anterior compartment strains (6). The injury data were correlated with prior-fitness measures. The results indicated that a major cause of injury in women can be attributed to the lack of prior conditioning, greater body weight and fat percent, and limited leg strength. These factors, coupled with some inherent physiologic characteristics of women (i.e., wide pelvis, less strength, and greater joint flexi bility), probably contributed to the increased risk of injury in these women. It is concluded that susceptibility to these poten tial orthopaedic and medical conditions can be identified before the beginning of training and minimized through proper reme dial activity before a strenuous physical training program is initiated.

身体鍛練者と非鍛練者の激運動時における赤血球数, ヘマトクリット値, エリトロポエチン濃度の変化の比較

In an attempt to compare changes in erythrocyte count, hematocrit and erythropoietin levels of athletes induced by strenuous physical training with those of nonathletes, twenty three male well trained university athletes and 12 male nonathletic university students were subjected to exercise on a Monark bicycle ergometer with a working intensity of about 8 in relative metabolic rate for 2 hours for successive 7 days during summer. The results obtained were as follows: The mean values of decrease in erythrocyte count and hematocrit after one week's strenuous muscular exercise for non-athletes were greater than those for athletes. In both athletes and nonathletes, subjects with higher value of hematocrit showed a tendency of greater fall in hematocrit after physical training. Nonathletes showed smaller mean value of reticulocyte count before physical training than the athletes. The former showed an increase in reticulocyte count after physical training, while the latter showed essentially no change in reticulocyte count. Nonathletes showed lower erythropoietin levels before physical training than the athletes. Nonathletes showed no change in erythropoietin levels after physical training, while the athletes showed a marked increase in this variable after the training. These results suggest that there were marked differences between athletes and nonathletes in the state of destruction and production of erythrocyte before and after the strenuous physical training which lasted for 7 successive days. While the rate of erythrocyte production for nonathletes might be slower than that for athletes at any time, the rate of erythrocyte destruction for nonathletes might be slower before the physical training and might be faster during and after the physical training than that for the athletes.

Effect of strenuous physical training of rats on content and biosynthesis of ubiquinone in their skeletal muscles

The ubiquinone content was determined in the skeletal muscles and muscle mitochondria of rats after undergoing strenuous physical training for 2.5–3 months. The incorporation of the labeled precursor acetate-1-14C into ubiquinone and sterols by thin slices of skeletal muscles was investigated at the same time. An increase in the ubiquinone content and production of mitochondrial protein was observed in the muscles of the trained animals. Incorporation of the radioactive label into ubiquinone by thin muscle slices from trained rats was considerably increased, whereas its incorporation into sterols was unchanged.