Improvement in running economy after 6 weeks of plyometric training

This study determined whether a 6-week regimen of plyometric training would improve running economy (i.e., the oxygen cost of submaximal running). Eighteen regular but not highly trained distance runners (age = 29 +/- 7 [mean +/- SD] years) were randomly assigned to experimental and control groups. All subjects continued regular running training for 6 weeks; experimental subjects also did plyometric training. Dependent variables measured before and after the 6-week period were economy of running on a level treadmill at 3 velocities (women: 2.23, 2.68, and 3.13 m.s(-1); men: 2.68, 3.13, and 3.58 m.s(-1)),VO(2)max, and indirect indicators of ability of muscles of lower limbs to store and return elastic energy. The last were measurements during jumping tests on an inclined (20 degrees ) sled: maximal jump height with and without countermovement and efficiencies of series of 40 submaximal countermovement and static jumps. The plyometric training improved economy (p < 0.05). Averaged values (m.ml(-1).kg(-1)) for the 3 running speeds were: (a). experimental subjects-5.14 +/- 0.39 pretraining, 5.26 +/- 0.39 posttraining; and (b). control subjects-5.10 +/- 0.36 pretraining, 5.06 +/- 0.36 posttraining. The VO(2)max did not change with training. Plyometric training did not result in changes in jump height or efficiency variables that would have indicated improved ability to store and return elastic energy. We conclude that 6 weeks of plyometric training improves running economy in regular but not highly trained distance runners; the mechanism must still be determined.     

Longitudinal associations between anaerobic threshold and distance running performance

Longitudinal alterations in anaerobic threshold (AT) and distance running performance were assessed three times within a 4-month period of intensive training, using 20 male, trained middle-distance runners (19-23 yr). A major effect of the high intensity regular intensive training together with 60- to 90-min AT level running training (2 d X wk-1) was a significant increase in the amount of O2 uptake corresponding to AT (VO2 AT; ml O2 X min-1 X kg-1) and in maximal oxygen uptake (VO2max; ml O2 X min-1 X kg-1). Both VO2 AT and VO2max showed significant correlations (r = -0.69 to -0.92 and r = -0.60 to -0.85, respectively) with the 10,000 m run time in every test. However, further analyses of the data indicate that increasing VO2 AT (r = -0.63, P less than 0.05) rather than VO2max (r = -0.15) could result in improving the 10,000 m race performance to a larger extent, and that the absolute amount of change (delta) in the 10,000 m run time is best accounted for by a combination of delta VO2 AT and delta 5,000 m run time. Our data suggest that, among runners not previously trained over long distances, training-induced alterations in AT in response to regular intensive training together with AT level running training may contribute significantly to the enhancement of AT and endurance running performance, probably together with an increase in muscle respiratory capacity.     

Kenyan dominance in distance running

Critical physiological factors for performance in running are maximal oxygen consumption (VO(2max)), fractional VO(2max) utilization and running economy. While Kenyan and Caucasian elite runners are able to reach very high, but similar maximal oxygen uptake levels, the VO(2max) of black South African elite runners seems to be slightly lower. Moreover, the studies of black and white South African runners indicate that the former are able to sustain the highest fraction of VO(2max) during long distance running. Results on adolescent Kenyan and Caucasian boys show that these boys are running at a similar percentage of VO(2max) during competition. Kenyan elite runners, however, appear to be able to run at a high % of VO(2max) which must then have been achieved by training. A lower energy cost of running has been demonstrated in Kenyan elite runners and in untrained adolescent Kenyan boys compared to their Caucasian counterparts. In agreement with this are the results from studies on black South African elite runners who have shown similar low energy costs during running as the Kenyan elite runners. The good running economy cannot be explained by differences in muscle fibre type as they are the same in Kenyan and Caucasian runners. The same is true when comparing untrained adolescent Kenyan boys with their Caucasian counterparts. A difference exists in BMI and body shape, and the Kenyans long, slender legs could be advantageous when running as the energy cost when running is a function of leg mass. Studies comparing the response to training of Kenyans and Caucasians have shown similar trainability with respect to VO(2max), running economy and oxidative enzymes. Taken all these data together it appears that running at a high fractional VO(2max) and having a good running economy may be the primary factors favouring the good performance of endurance athletes rather than them having a higher VO(2max) than other elite runners. In addition to having the proper genes to shape their bodies and thereby contributing to a good running economy, the Kenyan elite runners have trained effectively and used their potential to be in the upper range both in regard to VO(2max) and to a high utilization of this capacity during endurance running.     

Influence of plasma catecholamines on the lactate threshold during graded exercise

This investigation examined the relationship among plasma catecholamines, the blood lactate threshold (TLa), and the ventilatory threshold (TVE) in highly trained endurance athletes. Six competitive cyclists and six varsity cross-country runners performed a graded exercise test via two different modalities: treadmill running and bicycle ergometry. Although maximal oxygen consumption (VO2 max) did not differ significantly for the cyclists for treadmill running and cycling (64.6 +/- 1.0 and 63.5 +/- 0.4 ml O2.kg-1-min-1, respectively), both TLa and TVE occurred at a relatively earlier work load during the treadmill run. The opposite was true for the runners as TLa and TVE appeared at an earlier percent of VO2max during cycling compared with treadmill running (60.0 +/- 1.7 vs. 75.0 +/- 4.0%, respectively, TLa). The inflection in plasma epinephrine shifted in an identical manner and occurred simultaneously with that of TLa (r = 0.97) regardless of the testing protocol or training status. Although a high correlation (r = 0.86) existed for the shift in TVE and TLa, this relationship was not as strong as was seen with plasma epinephrine. The results suggest that a causal relationship existed between the inflection in plasma epinephrine and TLa during a graded exercise test. This association was not as strong for TVE and TLa.     

Oxygen uptake during running as related to body mass in circumpubertal boys: a longitudinal study

To investigate the effect of endurance training on physiological characteristics during circumpubertal growth, eight young runners (mean starting age 12 years) were studied every 6 months for 8 years. Four other boys served as untrained controls. Oxygen uptake (VO2) and blood lactate concentrations were measured during submaximal and maximal treadmill running. The data were aligned with each individual's age of peak height velocity. The maximal oxygen uptake (VO2max; ml.kg-1.min-1) decreased with growth in the untrained group but remained almost constant in the training group. The oxygen cost of running at 15 km.h-1 (VO2 15, ml.kg-1.min-1) was persistently lower in the trained group but decreased similarly with age in both groups. The development of VO2max and VO2 15 (l.min-1) was related to each individual's increase in body mass so that power functions were obtained. The mean body mass scaling factor was 0.78 (SEM 0.07) and 1.01 (SEM 0.04) for VO2max and 0.75 (SEM 0.09) and 0.75 (SEM 0.02) for VO2 15 in the untrained and trained groups, respectively. Therefore, expressed as ml.kg-0.75.min-1, VO2 15 was unchanged in both groups and VO2max increased only in the trained group. The running velocity corresponding to 4 mmol.l-1 of blood lactate (nu la4) increased only in the trained group. Blood lactate concentration at exhaustion remained constant in both groups over the years studied. In conclusion, recent and the present findings would suggest that changes in the oxygen cost of running and VO2max (ml.kg-1.min-1) during growth may mainly be due to an overestimation of the body mass dependency of VO2 during running.(ABSTRACT TRUNCATED AT 250 WORDS)     

Oxygen uptake kinetics and time to exhaustion in cycling and running: a comparison between trained and untrained subjects

The objective of the present study was to compare pulmonary gas exchange kinetics (VO2 kinetics) and time to exhaustion (Tlim) between trained and untrained individuals during severe exercise performed on a cycle ergometer and treadmill. Eleven untrained males in running (UR) and cycling (UC), nine endurance cyclists (EC), and seven endurance runners (ER) were submitted to the following tests on separate days: (i) incremental test for determination of maximal oxygen uptake (VO2max) and the intensity associated with the achievement of VO2max (IVO2max) on a mechanical braked cycle ergometer (EC and UC) and on a treadmill (ER and UR); (ii) all-out exercise bout performed at IVO2max to determine the time to exhaustion at IVO2max (Tlim) and the time constant of oxygen uptake kinetics (tau). The tau was significantly faster in trained group, both in cycling (EC = 28.2 +/- 4.7s; UC = 63.8 +/- 25.0s) and in running (ER = 28.5 +/- 8.5s; UR = 59.3 +/- 12.0s). Tlim of untrained was significantly lower in cycling (EC = 384.4 +/- 66.6s vs. UC; 311.1 +/- 105.7 s) and higher in running (ER = 309.2 +/- 176.6 s vs. UR = 439.8 +/- 104.2 s). We conclude that the VO2 kinetic response at the onset of severe exercise, carried out at the same relative intensity is sensitive to endurance training, irrespective of the exercise type. The endurance training seems to differently influence Tlim during exercise at IVO2max in running and cycling.     

Physiological correlates of middle-distance running performance. A comparative study between men and women.

To compare the relative contributions of their functional capacities to performance in relation to sex, two groups of middle-distance runners (24 men and 14 women) were selected on the basis of performances over 1500-m and 3000-m running races. To be selected for the study, the average running velocity (v) in relation to performances had to be superior to a percentage (90% for men and 88% for women) of the best French v achieved during the season by an athlete of the same sex. Maximal O2 consumption (VO2max) and energy cost of running (CR) were measured in the 2 months preceding the track season. This allowed us to calculate the maximal v that could be sustained under aerobic conditions, va,max. A v:va,max ratio derived from 1500-m to 3000-m races was used to calculate the maximal duration of a competitive race for which v = va,max (tva,max). In both groups va,max was correlated to v. The relationships calculated for each distance were similar in both sexes. The CR [0.179 (SD 0.010) ml.kg-1 x m-1 in the women versus 0.177 (SD 0.010) in the men] and tva,max [7.0 (SD 2.0) min versus 8.4 (SD 2.1)] also showed no difference. The relationships between VO2max and body mass (mb) calculated in the men and the women were different. At the same mb the women had a 10% lower CR than the men; their lower mb thus resulted in an identical CR.(ABSTRACT TRUNCATED AT 250 WORDS)     

Square-wave endurance exercise test (SWEET) for training and assessment in trained and untrained subjects. III. Effect on VO2 max and maximal ventilation

The effect of training on VO2 max, endurance capacity (EC) and ventilation during maximal exercise (VE max) were studied in 17 normal subjects aged 21--51 years. At the beginning of the study 11 of the subjects (eight women and three men) were untrained (U) and six others (three women and three men) trained regulatory (T). A maximal intensity exercise (on a cycle ergometer) which could be sustained for 45 min (MIE45) was performed three times per week for 6 weeks; the total mechanical work (TMW) corresponding to the MIE45 per session varied between 3.14 and 9.24 kJ . kg-1. Before training, VO2 max (a), VEmax (b), and TMW (c) were higher in T than in U subjects. Training increased these variables in most of the subjects; the increase being significantly higher (mean +/- SEM) in U (a = +29.9 +/- 3.8%; b = 49.6 +/- 6.5%; c = 47 +/- 6.9%) than in T subjects (a = 6.6 +/- 3.8%; b = 17.5 +/- 3.6+; c = 19.1 +/- 2.8%). In all but three cases the % increase of TMW was higher than that of VO2 max, suggesting a higher sensitivity of TMW in measuring EC. The significant increase in VE max, maximal voluntary ventilation, peak flows (inspiratory and expiratory) and static maximum voluntary ventilation, peak flows (inspiratory and expiratory) and static maximum pressures indicate that this training protocol improves in healthy subjects the performance of respiratory muscles as well.     

The influence of weekly training distance on fractional utilization of maximum aerobic capacity in marathon and ultramarathon runners

This study was designed to examine the interrelationships between performance in endurance running events from 10 to 90 km, training volume 3-5 weeks prior to competition, and the fractional utilization of maximal aerobic capacity (%VO2max) during each of the events. Thirty male subjects underwent horizontal treadmill testing to determine their VO2max, and steady-state VO2 at specific speeds to allow for calculation of %VO2max sustained during competition. Runners were divided into groups of ten according to their weekly training distance (group A trained less than 60 km X week-1, group B 60 to 100 km X week-1, and group C more than 100 km X week-1). Runners training more than 100 km X week-1 had significantly faster running times (average 19.2%) in all events than did those training less than 100 km X week-1. VO2max or %VO2max sustained during competition was not different between groups. The faster running speed of the more trained runners, running at the same %VO2max during competition, was due to their superior running economy (19.9%). Thus all of the group differences in running performance could be explained on the basis of their differences in running economy. These findings suggest either that the main effect of training more than 100 km X week-1 may be to increase running economy, or that runners who train more than 100 km X week-1 may have inherited superior running economy.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cardiovascular changes associated with decreased aerobic capacity and aging in long-distance runners

Fifty-five male runners aged between 30 to 80 years were examined to determine the relative roles of various cardiovascular parameters which may account for the decrease in maximal oxygen uptake (VO2max) with aging. All subjects had similar body fat composition and trained for a similar mileage each week. The parameters tested were VO2max, maximal heart rate (HRmax), cardiac output (Q), and arteriovenous difference in oxygen concentration (Ca-Cv)O2 during graded, maximal treadmill running. Average body fat and training mileage were roughly 12% and 50 km.week-1, respectively. The average 10-km run-time slowed significantly by 6.0%.decade-1 [( 10-km run-time (min) = 0.323 x age (years) + 24.4] (n = 49, r = 0.692, p less than 0.001]. A strong correlation was found between age and VO2max [( VO2max (ml.kg-1.min-1) = -0.439 x age + 76.5] (n = 55, r = -0.768, p less than 0.001]. Thus, VO2max decreased by 6.9%.decade-1 along with reductions of HRmax (3.2%.decade-1, p less than 0.001) and Q (5.8%.decade-1, p less than 0.001), while no significant change with age was observed in estimated (Ca-Cv)O2. It was concluded that the decline of VO2max with aging in runners was mainly explained by the central factors (represented by the decline of HR and Q in this study), rather than by the peripheral factor (represented by (Ca-Cv)O2).     

Rate of decline in blood lactate after cycling exercise in endurance-trained and -untrained subjects

The purpose of this study was to compare the rate of decline in blood lactate (La) levels in nine trained men [maximal O2 consumption (VO2max) 65.5 +/- 3.3 ml.kg-1.min-1] and eight untrained men (VO2max 42.2 +/- 2.8 ml.kg-1.min-1) during passive recovery from a 3-min exercise bout. Trained and untrained subjects cycled at 85 and 80% VO2max, respectively, to produce similar peak blood La concentrations. Twenty samples of arterialized venous blood were drawn from a heated hand vein during 60 min of recovery and analyzed in an automated La analyzer. The data were then fitted to a biexponential function, which closely described the observed data (r = 0.97-0.98). There was no difference in the coefficient expressing the rate of decline in blood La for trained and untrained groups (0.0587 +/- 0.0111 vs. 0.0579 +/- 0.0100, respectively). However, trained subjects demonstrated a faster time-to-peak La (P = 0.01), indicative of a faster efflux of La from muscle to blood. Thus the rate of decline in blood La after exercise does not appear to be affected by training. The faster decline previously reported for trained subjects may be due to the use of a linear rather than a biexponential curve fit.     

Effect of endurance exercise training on ventilatory function in older individuals

To evaluate the effect of endurance training on ventilatory function in older individuals, 1) 14 master athletes (MA) [age 63 +/- 2 yr (mean +/- SD); maximum O2 uptake (VO2max) 52.1 +/- 7.9 ml . kg-1 . min-1] were compared with 14 healthy male sedentary controls (CON) (age 63 +/- 3 yr; VO2max of 27.6 +/- 3.4 ml . kg-1 . min-1), and 2) 11 sedentary healthy men and women, age 63 +/- 2 yr, were reevaluated after 12 mo of endurance training that increased their VO2max 25%. MA had a significantly lower ventilatory response to submaximal exercise at the same O2 uptake (VE/VO2) and greater maximal voluntary ventilation (MVV), maximal exercise ventilation (VEmax), and ratio of VEmax to MVV than CON. Except for MVV, all of these parameters improved significantly in the previously sedentary subjects in response to training. Hypercapnic ventilatory response (HCVR) at rest and the ventilatory equivalent for CO2 (VE/VCO2) during submaximal exercise were similar for MA and CON and unaffected by training. We conclude that the increase in VE/VO2 during submaximal exercise observed with aging can be reversed by endurance training, and that after training, previously sedentary older individuals breathe at the same percentage of MVV during maximal exercise as highly trained athletes of similar age.     

Calculation of record-time in the 800-meter run: predictive value of Margaria's equation

Margaria's equation (1976)--describing the relationship between the minimum time necessary to cover a distance equal or longer than 1,000 m (record-time TR) and the maximal oxygen consumption (VO2 max)--has been modified in order to be applied to the calculation of TR in the 800 m foot race. Fifteen subjects participated in this study (VO2 max = 63 +/- 3.5 ml O2 X kg-1 X min-1, measured TR = 131 +/- 10 seconds). It has been found the TR calculated from Margaria's equation (TRc) are underestimated (TRc = 104 +/- 10 seconds). By taking into account the actual energy cost of running (0.19 ml O2 X kg-1 X m-1) and the kinetics of VO2 at the onset of exercise, TRc averaged 133 +/- 8.5 seconds. Moreover, the relationship between TRc and measured TR (TRm) is highly significant (TRc = 50.4 + 0.65 TRm; r = 0.75; P less than 0.01). These results validate Margaria's equation modifications.     

Comparison of cardiorespiratory responses of moderately trained men and women using two different treadmill protocols

In practice, the Bruce protocol is the most commonly used treadmill protocol to assess maximal oxygen consumption (V(.-)O2max). It has been suggested that a running protocol (e.g., Astrand) may elicit a comparatively higher V(.-)O2max and different cardiorespiratory responses when applied to moderately trained runners. Thus, the purpose of this study was to compare V(.-)O2max and other cardiorespiratory responses as elicited by the standard Bruce and a modified Astrand treadmill protocol in moderately trained runners. Fifteen women (age = 21 years, height = 171.5 cm, weight = 63 kg, and body fat = 18%) and 15 men (age = 26 years, height = 177 cm, weight = 72 kg, and body fat = 9%) who were moderately trained runners completed a standard Bruce and modified Astrand protocol (random order), separated by approximately 7 days. Heart rate, Borg ratings of perceived exertion, blood pressure, and pulmonary gas exchange variables were measured during the exercise tests using standard laboratory procedures. This study revealed V(.-)O2max values between the Bruce protocol (51.3 +/- 11.6 ml x kg(-1) x min(-1)) and modified Astrand (51.5 +/- 10.9 ml x kg(-1) x min(-1)) were not significantly different in either the men or the women. However, the Bruce protocol elicited significantly higher maximum treadmill time in men and maximum respiratory exchange ratio (RERmax) and maximum minute ventilation (VEmax) values in both genders. Conversely, the modified Astrand elicited a higher HRmax. These data suggest that V(.-)O2max in both moderately trained men and women runners is independent of treadmill protocol despite differences in HRmax, RERmax, and VEmax.     

Effects of standing cycling and the use of toe stirrups on maximal oxygen uptake

Twenty-eight subjects (6 normal men, 14 distance runners, and 8 rowers) were tested for maximal oxygen uptake (VO2max) and associated physiological measures during bicycle ergometer exercise with toe stirrups while standing (BEts) and during treadmill exercise (TM). Correlation between BEts VO2max and TM VO2max was high (r = 0.901, p less than 0.05). No significant difference existed between the two VO2max values (60.3 +/- 8.9 vs. 60.5 +/- 9.7 ml.kg-1.min-1; n = 28). No differences were found even when three different subgroups were separately compared. It is concluded that the higher VO2max elicited during BEts as compared with normal sitting cycling may be attributed to the increased muscle blood flow and/or involvement of a larger muscle mass, the latter being partly evidenced by the observation of greater electromyographic activity during BEts.     

The role of anaerobic ability in middle distance running performance

The purpose of this study was to assess the relationship between anaerobic ability and middle distance running performance. Ten runners of similar performance capacities (5 km times: 16.72, SE 0.2 min) were examined during 4 weeks of controlled training. The runners performed a battery of tests each week [maximum oxygen consumption (VO2max), vertical jump, and Margaria power run] and raced 5 km three times (weeks 1, 2, 4) on an indoor 200-m track (all subjects competing). Regression analysis revealed that the combination of time to exhaustion (TTE) during the VO2max test (r2 = 0.63) and measures from the Margaria power test (W.kg-1, r2 = 0.18; W, r2 = 0.05) accounted for 86% of the total variance in race times (P less than 0.05). Regression analysis demonstrated that TTE was influenced by both anaerobic ability [vertical jump, power (W.kg-1) and aerobic capacity (VO2max, ml.kg-1.min-1)]. These results indicate that the anaerobic systems influence middle distance performance in runners of similar abilities.     

Cardiovascular responses to lower body negative pressure in trained and untrained older men.

To determine whether aerobic conditioning alters the orthostatic responses of older subjects, cardiovascular performance was monitored during graded lower body negative pressure in nine highly trained male senior athletes (A) aged 59-73 yr [maximum O2 uptake (VO2 max) = 52.4 +/- 1.7 ml.kg-1 x min-1] and nine age-matched control subjects (C) (VO2 max = 31.0 +/- 2.9 ml.kg-1 x min-1). Cardiac volumes were determined from gated blood pool scintigrams by use of 99mTc-labeled erythrocytes. During lower body negative pressure (0 to -50 mmHg), left ventricular end-diastolic and end-systolic volume indexes and stroke volume index decreased in both groups while heart rate increased. The decreases in cardiac volumes and mean arterial pressure and the increase in heart rate between 0 and -50 mmHg were significantly less in A than in C. For example, end-diastolic volume index decreased by 32 +/- 4 ml in C vs. 14 +/- 2 ml in A (P < 0.01), mean arterial pressure declined 7 +/- 5 mmHg in C and increased by 5 +/- 3 mmHg in A (P < 0.05), and heart rate increased 13 +/- 3 beats/min in C and 7 +/- 1 beats/min in A (P < 0.05). These data suggest that increased VO2 max among older men is associated with improved orthostatic responses.     

Short-term plyometric training improves running economy in highly trained middle and long distance runners

Fifteen highly trained distance runners VO(2)max 71.1 +/- 6.0 ml.min(-1).kg(-1), mean +/- SD) were randomly assigned to a plyometric training (PLY; n = 7) or control (CON; n = 8) group. In addition to their normal training, the PLY group undertook 3 x 30 minutes PLY sessions per week for 9 weeks. Running economy (RE) was assessed during 3 x 4 minute treadmill runs (14, 16, and 18 km.h(-1)), followed by an incremental test to measure VO(2)max. Muscle power characteristics were assessed on a portable, unidirectional ground reaction force plate. Compared with CON, PLY improved RE at 18 km.h(-1) (4.1%, p = 0.02), but not at 14 or 16 km.h(-1). This was accompanied by trends for increased average power during a 5-jump plyometric test (15%, p = 0.11), a shorter time to reach maximal dynamic strength during a strength quality assessment test (14%, p = 0.09), and a lower VO(2)-speed slope (14%, p = 0.12) after 9 weeks of PLY. There were no significant differences in cardiorespiratory measures or VO(2)max as a result of PLY. In a group of highly-trained distance runners, 9 weeks of PLY improved RE, with likely mechanisms residing in the muscle, or alternatively by improving running mechanics.