Performance in middle-distance running in track and field is determined by aerobic and anaerobic capacities (18). The duration of the competitions in middle- and long-distance running points out the significance of aerobic capacity. In 800-m running, the athletes depend equally on both aerobic and anaerobic energies (31), whereas 80% of the energy needed in 1,500-m running comes from the aerobic energy system (31). This underlines the strong relationship between aerobic capacity and performance in middle-distance running. The athlete's endurance capacity is determined by the level of maximal oxygen consumption (o2max), fractional percentage of maximum oxygen consumption (%o2max), and running economy (RE) (24,26). Several studies (11,12,14,16) indicate a strong relationship between those parameters and performance in endurance sport. Furthermore, research on middle-distance runners (9,18,21) shows a high correlation between o2max and running performance. However, other researchers (14,23,26,37) have shown that there is a marked relationship between %o2max, RE, and running performance. Foster and Lucia (14) and Lucia et al. (26) showed the significance of RE as the critical factor determining performance in middle- and long-distance running (14,26). However, the study of Coyle (10) showed that the velocity at lactate threshold (vLT) has a higher correlation to running performance than o2max, %o2max, and RE (10). This is probably because of the fact that vLT is determined by o2max, %o2max, and RE (34). Recent research indicates, however, that velocity at maximal oxygen consumption (vo2max) has a stronger relationship to running performance in middle-distance running (5,18,22,34). The vo2max depends on an integrative contribution of aerobic and anaerobic energy abilities (9,11,22). Although several attempts have been made to construct a model of middle-distance training (800 and 1,500 m), a consensus of the optimal training volume and intensity distribution to maximize these adaptations remains elusive (3,9). Research shows that the development of training methods has traditionally been based on short-term studies among untrained or moderately trained individuals coupled with anecdotal evidence from experienced coaches and successful athletes (1,36). The physical adaptations that occur in untrained subjects remain unclear compared with highly trained subjects (25). Helgerud et al. (16) indicate that in endurance training, the intensity provides the best training response for moderate and untrained athletes (16). Newer studies applied on well-trained runners, however, indicate a higher correlation between higher training volume on lower intensities and performance than do training with higher intensities and performance (12,13,30). Furthermore, the reported studies indicate that training has to be performed with a relatively high volume on both high and low intensity to enhance performance in endurance athletes. No studies however have examined this relationship (combining training with low or high intensity) in a precompetition period with well-trained runners. Therefore, to enhance our knowledge of middle- and long-distance training, we need more specific information of how to periodize the distribution of the volume and the intensity in the daily training process in the different training periods (9,29). Studies show that the most successful middle-distance runners perform a total distance of 60-100 km·wk−1 in the different training periods (4,13). The amount of training performed with high and low intensity to enhance performance in the precompetition training however is openly discussed among coaches and researchers throughout the world. Presently, there have been no well-controlled studies to examine what is the most favorable model to enhance performance with well-trained runners. Therefore, the purpose of the present study was to examine the effect of 2 different intervention training regimes (high intensity-low volume [82-92% of o2max] and low intensity-high volume [65-82% of o2max]) on o2max, %o2max, vo2max, RE, vLT, and running performance on a group of well-trained male middle-distance runners in the precompetition training period. This study brings forward supplementary information about the periodization of training volume and intensity in the precompetition mesocycle (10 weeks) to reach the highest possible performance in a group of well-trained male middle-distance runners.
Experimental Approach to the Problem
All the physical tests were performed on a treadmill (Woodway ELG 2, Weil am Rhein, Germany). The treadmill was calibrated for inclination and speed and had a gradient degree from 0 to ±30% with a maximum speed of 30 km·h−1. An inclination of 1.7% was used for all physical capacity measurements to equalize the air resistance on the treadmill compared with running on the track. The inclination of 1.7% is a Norwegian standard for testing lactate threshold (LT) on the treadmill (8,17). Lactate was analyzed by taking blood samples into a capillary tube and thereafter injecting them into a lactate analyzer having a mixing chamber (1500 Sport, YSI Inc., Yellow Springs Instruments, Yellow Springs, OH, USA) with the help of a standard injector (20-μL pipette). To monitor heart rate (HR), a pulse transmitter (Polar Sport Tester S610, Polar Electro OY, Kempele, Finland) was attached around the participant's chest. The pulse belt sent HR signals to a pulse watch (Polar accurex Plus, Polar Electro OY). The o2 was measured through a 2-way mouthpiece (Hans Rudolph Instr., Shawnee, KS, USA) and a sling connected to O2 and CO2 analyzer (Oxygen Champion, Jaeger Instr; Hoechberg, Germany). The expired volume was measured with turbine (Triple V volume transducer, Leipzig, Germany).
The participants were matched according to their pretest results in the performance test. Then they were randomly assigned into 1 of 2 groups, a high-volume (70 km) low-intensity (65-82% of HRmax) training group (HVLI-group); and a high-intensity (82-92% of HRmax) low-volume (50 km) training group (HILV-group). The intensity zones used in this study were based on the elite endurance athletes' individual LT zone that is around 85-90% of HRmax (5). Systematic testing of top athletes in endurance events at the Norwegian Olympic training center for the last 30 years shows that the individual LT is about 87-88% of HRmax (1). Therefore, training in the intensity zone 65-82% of HRmax is recommended as a low-intensity training regime, whereas training from 82-92% is considered as a high-intensity training regime around LT.
The study took part in the precompetition phase of the training program for the participants. The length of the mesocycle was 10 weeks. The pretests and the posttests were conducted on 2 separate days with 2 days rest in between. On test day 1, LT and o2max were tested, and the individual vo2max, vLT, and RE were calculated. On test day 2, a continuous performance time-trial test on the treadmill was conducted at the athletes' vo2max.
Twenty-six young well-trained male middle-distance runners (mean ± SD) aged 19.9 ± 6.1 years, body mass 69.8 ± 5 kg, and stature 179.4 ± 5 cm volunteered to participate in the present study. The participants were all highly committed to training and running 90 ± 14 km·wk−1. The personal records for the participants in 800 m (mean ± SD) was 2.03 ± 0.04 minutes, 1,500 m was 4.17 ± 0.07 minutes, and 3,000 m was 9.06 ± 0.18 minutes. The length of training for the participants was 3.8 ± 6.2 years. All participants gave their written voluntary informed consent, and the local ethics committee at the Norwegian School of Sport Sciences approved the study.
Test-retest performance reliability was conducted on all participants on 2 consecutive days (test day 1 and test day 2), 1 week before the actual testing took place. The test-retest was applied on those tests that we believe would have an influence on the results because of the learning effect (vo2max, vLT, and the performance test, respectively). Furthermore, to increase reliability and strengthen the validity of the testing procedures, the athletes were instructed to prepare mentally like they would do before important competitions and to keep up their normal routines for meals, sleep time, and use of running equipment. The tests were performed under standard laboratory conditions. No actual training was performed on the day before the test day.
The exercise protocol on the first test day started with a 10-minute warm-up by running on a motorized treadmill at a speed of 9 km·h−1 to establish a baseline value of o2, HR, and blood lactate concentration (La). Then, a 6 × 5-minute submaximal incremental running test was performed at 10, 11.5, 13.0, 14.5, 16.0, and 17.5 km·h−1, with 30 seconds of rest between stages. Heart rate and o2 were measured during each running period. Blood samples from fingertips were taken 10 seconds after finishing each of the 6 standardized running velocities. These values were used to calculate the LT and vLT. The LT was determined as the vLT that corresponded with 3-mmol lactate. A fixed value of 3-mmol lactate was shown to have the best correlation with direct LT measurement (8). The RE was calculated by measuring the o2 from 2 to 3.5 minutes during the lactate profile test. The mean o2 presented in ml·kg−1·min−1was the measure of the RE for the athlete (17). The RE was determined by measuring o2 during the final 1.5 minutes of all standardized intensities.
After a 15-minute rest period, the o2max was measured. The participants started to run at their vLT with a stepwise increase in velocity of 1 km·h−1·min−1 until a plateau in their o2 was observed. If the participants could no longer continue and a plateau was not observed, the following criteria were set to accept the test result for further analyses: An R value over 1.10, flattening of o2 for the last 30 seconds of measuring, and HR closer to 5-8 beats below the athletes' maximal HR (19). The duration of the test was 6-7 minutes.
On test day 2, the participants warmed up on the treadmill for 15 minutes at 9 km·h−1. Then the performance test was started after a 3-minute rest. The test was performed by running at a speed corresponding to the athlete's individual vo2max (11,20). The duration of the test was between 5 and 6 minutes.
The Training Intervention
The training volume and distribution of intensity in the intervention period (10 weeks) were thoroughly calculated and matched for total work and frequency. The difference in distribution of training intensity in the 2 intervention groups was compensated by the HVLI-group running some more kilometers per week at a slower pace than the HILV-group. The HILV-group ran a mean of 50 km·wk−1, and the HVLI-group ran a mean of 70 km·wk−1. The participants in both groups were running 6 training sessions per week. The HILV-group performed 33% of the total training volume at 82-92% of HRmax, and 67% was performed at 65-82% of HRmax. The HVLI-group performed 13% of the total training volume at 82-92% of HRmax, and 87% was performed at 65-82% of HRmax. Furthermore, the HILV-group performed 3 intensive workouts per week at 82-92% of HRmax, and the HVLI-group performed 1 intensive workout per week. The Polar pulse watches were adjusted to beep if the intensity (HR) was more than ±5 b·min−1 from the planned intensity target zone.
Raw data were transferred to SPSS 13.0 for Windows and Microsoft Excel for analysis. Intraclass correlation coefficient (ICC) was assessed on the data to examine reliability of performance. To detect differences in measures between pre and posttest, paired t-test was performed to test for a difference in central location (mean) between the paired samples (within group). To test for a difference in central location (mean) between groups, the independent sample t-test was applied. Differences were considered significant at p ≤ 0.05, and the results are expressed as mean and SD. The 95% confidence interval (95% CI) was also calculated for all measures.
Differences within groups and between groups of a variety of physiological measures are shown in Table 1. The results indicate that there were no differences within the HVLI-group from pre to posttest on all measured variables. Furthermore, the results indicate that there was a notable improvement within the HILV-group on velocity at o2max and velocity at LT. A comparison between groups indicates that there were no notable differences between the 2 groups at either pretest or posttest.
The HLVI-group had a notable decrease in o2 at running velocities of 10, 11.5, 13, 14.5, and 16 km·h−1 (Table 2). This indicates a notable improvement in RE for the HVLI-group for those velocities. No change was observed at 9 km·h−1. Furthermore, the results show that the HILV-group also had a notable improvement in RE on all tested velocities except 11.5 km·h−1. When comparing the 2 groups, no marked differences were observed between them at pretest or at posttest.
Within the HVLI-group, no differences from pre to posttest were observed for the 3 performance test measure variables (Table 3). The HIVL-group had only a marked increase in the lactic acid concentration when compared with the pretest for the same group. When comparing between groups, there were no marked differences observed between groups at pretest or at posttest.
The day-to-day reliability of measurements gave an ICC of 0.88 for mean vo2max, 0.92 for mean vLT, and 0.91 for mean performance test.
The results show that only the participants of the HILV-group markedly increased their vLT (Table 1). The vLT increased from 14.6 km·h−1 in pretest to 15.2 km·h−1 in posttest. Because of the small intervention period in this study, it can be said that the improvement in the HILV-group was large. Furthermore, research (24,33) shows that improvements of the vLT are caused by development of o2max, %o2max, or RE. The improvement in vLT in this study could be explained by the improvement of RE and %o2max. This indicates that specific training close to the LT will result in favorable improvements of the vLT. Similar results were found in the literature (6,35). In this study, the improvement in vLT could not be caused by improvement in o2max because there was no notable improvement in o2max (Table 1).
Neither group improved their o2max (Table 1). The reason could be because of the intensity of the training (7,16,36). The results indicate, however, that this is not the probable explanation, because the training resulted in a marked improvement in anaerobic capacity. Another explanation could be that the period of intervention was too short for the participants to improve their o2max. Furthermore, the participants in this study could have reached their o2max potential after many years of extensive training. Longitudinal studies show that o2max is developed fast and that elite athletes reach their highest values in their early twenties (20). Furthermore, progress made in the twenties is mainly caused by improved %o2max, RE, and increased anaerobic capacity (20). Despite the fact that o2max did not increase; the HILV-group improved markedly on vo2max (Table 1). The vo2max increased from 16.0 to 16.8 km·h−1. The improvement is probably explained by the marked progress the participants made on RE and anaerobic capacity. This indicates that training around the LT is favorable for elite athletes to develop vo2max. Because o2max is a parameter that correlates well with the ability to perform, training around the LT can be an effective intensity to develop performance in elite middle-distance runners (5,11).
The results showed that neither group had any marked change in their %o2max at vLT (Table 1). The HILV-group decreased in their %o2max at vLT; this decrease could be caused by training sessions that were too short. Results from various studies indicate that elite athletes, with long competition times, often train more hours and have a higher %o2max than athletes whose competition times are shorter (2). The vLT of elite marathon athletes has been reported to be approximately 90% o2max. Another explanation can be that the marathon athletes train more and have longer workouts around the LT than athletes whose competition time is under 5 minutes. In future studies of elite middle-distance athletes, one should study what effect the length of the training sessions and the intensity of training has on %o2max.
Both the HILV-group and the HVLI-group markedly improved their RE at most of the speeds during the LT test (Table 2). The progress was unexpected, because studies of elite athletes show that it takes months and years to develop high RE (20). It is important to improve the RE to develop the ability to make progress over years, and often that is the specific factor which can explain the differences in performance between successful endurance athletes on an elite level (14,20,28). Research indicates that to a large degree, the total length of workout can explain progress made in RE. This training can lead to transforming Type II fibers to Type I fibers and thus better the RE (3). Another conceivable effect is that many hours spent doing 1 specific form of activity can be necessary to develop running technique and with that RE. However, the results from this study do not indicate that there is such a connection. That could be a result of the intervention period being too short, and that the differences in intensity and training time between the groups too small. Other researchers have found that performing strength, plyometrics, and speed training helps improve the RE in typical endurance sports (27,32). In the future, one should carry out longitudinal studies where one studies the long-term effect of endurance training with high and low intensity and compares those results with that with strength, plyometric, and speed training.
The results show no notable progress in the performance test (Table 3). This was surprising, because there is a good connection between vLT and the ability to perform in running (15). Furthermore, the results show that both groups on average run between 54 and 98 seconds longer at the posttest (Table 3). Possibly a greater number of participants would result in performance test differences. In future surveys, one could work hard to complete similar training studies with more participants.
The main findings in this study were that training close to the LT (HILV-group) resulted in better training effect among male middle-distance runners than training with low intensity (HVLI-group). The HILV-group had markedly improved in vo2max and vLT, anaerobic capacity, and RE. The HVLI-group had only a notable improvement in their RE. As for all measured parameters in this study, there were no marked differences between the 2 groups before and after the intervention period. Future research should focus on the effect of endurance training with high and low intensity on a longer period. This could increase the understanding of the significance of intensity to develop aerobic and anaerobic capacities, and whether endurance training is more effective than strength, plyometrics, and speed to improve the performance of middle-distance runners.
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