The effect of an aerobic training program on the electrical remodeling of the heart: high-frequency components of the signal-averaged electrocardiogram are predictors of the maximal aerobic power

Increased heart rate variability (HRV) and high-frequency content of the terminal region of the ventricular activation of signal-averaged ECG (SAECG) have been reported in athletes. The present study investigates HRV and SAECG parameters as predictors of maximal aerobic power (VO2max) in athletes. HRV, SAECG and VO2max were determined in 18 high-performance long-distance (25 ± 6 years; 17 males) runners 24 h after a training session. Clinical visits, ECG and VO2max determination were scheduled for all athletes during thew training period. A group of 18 untrained healthy volunteers matched for age, gender, and body surface area was included as controls. SAECG was acquired in the resting supine position for 15 min and processed to extract average RR interval (Mean-RR) and root mean squared standard deviation (RMSSD) of the difference of two consecutive normal RR intervals. SAECG variables analyzed in the vector magnitude with 40-250 Hz band-pass bi-directional filtering were: total and 40-æV terminal (LAS40) duration of ventricular activation, RMS voltage of total (RMST) and of the 40-ms terminal region of ventricular activation. Linear and multivariate stepwise logistic regressions oriented by inter-group comparisons were adjusted in significant variables in order to predict VO2max, with a P < 0.05 considered to be significant. VO2max correlated significantly (P < 0.05) with RMST (r = 0.77), Mean-RR (r = 0.62), RMSSD (r = 0.47), and LAS40 (r = -0.39). RMST was the independent predictor of VO2max. In athletes, HRV and high-frequency components of the SAECG correlate with VO2max and the high-frequency content of SAECG is an independent predictor of VO2max.

The Prevalence of Anemia in Recreational Runner

OBJECTIVE: To evaluate the prevalence and characteristics of anemia in the long distance runners. METHOD: Subjects included 61 long distance runners and 40 control. The 61 subjects averaged 39.9+/-4.5 years of age. Long distance runners has been training for at least 6 months. Hemoglobin, iron, total iron binding capacity, reticulocyte count, peripheral blood smear, urine hemosiderin were evaluated. WHO criteria cut off value of hemoglobin for the diagnosis of anemia was used, 13 g/dl in men and 12 g/dl in women. Iron deficiency was defined as the percent transferrin saturation less than 15. The percent transferrin saturation was calculated by dividing the serum iron level by the total iron-binding capacity. RESULTS: Anemia occurred in only 2.0% and 9.0% of the male and female long distance runners respectively and other laboratory findings supported diagnosis of iron deficiency anemia. The percentage of iron deficiency anemia was lower than normal control. Iron deficiency was evident in 6.0% and 18.1% of the male and female long distance runners respectively. CONCLUSION: Recreational long distance runners were at no greater risk for developing a frank anemia than the non-exercising population.

Difference in physiological responses to an incremental running test between middle- and long-distance runners / 体力科学

To obtain a viewpoint concerning evaluation of endurance type of athletes, we investigated the difference in physiological responses between middle- and long-distance runners in an incremental running test. Measurements were VO<SUB>2</SUB>max and time of its appearance, change of VO<SUB>2</SUB> from 1.5 min before exhaustion to exhaustion (ΔVO<SUB>2</SUB>), heart rate (HR), and blood lactate after exhaustion.<BR>Results were as follows.<BR>(1) The time of VO<SUB>2</SUB> max appearance in the middle distance runners was earlier than in the long distance runners.<BR>(2) VO<SUB>2</SUB>max was significantly higher in the long distance runners than in the middle distance runners.<BR>(3) Blood lactate after exhaustion and HRmax were significantly higher in the middle distance runners than in the long distance runners.<BR>(4) Blood lactate after exhaustion was significantly related to ΔVO<SUB>2</SUB> (r =-0.660, P<0.05) .<BR>These findings suggest that the endurance type of athletes could be evaluated from the time of VO<SUB>2</SUB>max appearance, blood lactate after exhaustion and HRmax in incremental running, and that VO<SUB>2</SUB>max appearance may be effected by high blood lactate accumulation.

THE RELATIONSHIPS BETWEEN THE PEAK RUNNING VELOCITY, AND AEROBIC AND ANAEROBIC CAPACITY DURING INCREMENTAL RUNNING TEST / 体力科学

The purpose of the present study was to investigate the relationships between the peak running velocity, and aerobic and anaerobic capacity in incremental running in pre- and post-competitive season using eight long distance runners. Measurements were peak running velocity, VO<SUB>2max</SUB>, running velocity and VO<SUB>2</SUB> at respiratory exchange ratio (RER) 1.0, and blood lactate after exhaustion in the incremental running test. Correlation analysis revealed that pre-season velocity at RER 1.0 and post-season blood lactate were both related to peak running velocity. Furthermore, change in peak running velocity was related to change in blood lactate between pre-and post-season. These results suggest that factors that probably influenced running performance change from aerobic capacity in the pre-season to anaerobic capacity in the post-season, and that running performance during the competitive season may be highly dependent upon anaerobic capacity.

Relationship between muscle fiber composition, capillary supply, oxidative enzyme activity and aerobic work capacity in middle- and long-distance runners / 体力科学

It was the purpose of this study to examine the property of skeletal muscle fiber in middle- and long-distance runners, and to evaluate the relationship between the property of skeletal muscle fiber and aerobic work capacity.<BR>Biopsy samples were taken from M, vastus lateralis of 23 middle- and long-distance runners, and analyzed for muscle fiber composition, capillary supply and SDH activity. Aerobic work capacity was measured on a treadmill with continuous method.<BR>The mean value for % ST in M. vastus lateralis was 61.3%, and the muscle fiber distribution showed the tendency of slow type. The crosssectional area of ST and FT fibers ranged approximately from 3, 000 μm<SUP>2</SUP> to 13, 000 μm<SUP>2</SUP>, and the cross-sectional area of ST fiber tended to be larger than that of FT fiber. The mean values for CD, C/F ratio, and CC (/ST) as capillary supply were 279/mm<SUP>2</SUP>, 1.62 and 5.7, respectively. The mean value for SDH activity was 5.86 μmoles/g/min, and was lower than reported previously for elite runners. In addition, SDH activity correlated with % ST and CC (/ST) (r=0.480, p<0.05, r=0.640, p<0.01) . On the other hand, the mean value for VOG<SUB>2</SUB>max was 68.5 ml/ kg/min (4, 066 ml/min), while VO<SUB>2</SUB>@AT averaged 45.9 ml/kg/min (2, 756 ml/min) . And it was found that VO<SUB>2</SUB>max and VO<SUB>2</SUB>@AT correlated significantly with % ST, CC (/ST) and SDH activity. Particular, VO<SUB>2</SUB> max was most strongly related to SDH activity (r=0.612, p<0.01) .<BR>The results of this study suggest that in regard to middle- and long-distance runners, structural characteristics of the ST fiber and capillary are some of the indispensable factors to regulate such a functional property as SDH activity and that the distinctive characteristics of the skeletal muscle fiber might possibly influence aerobic work capacity to a great extent.