The influence of high-intensity interval training on endurance performance in well trained cyclists

Laursen, P. B. (2004). The influence of high-intensity interval training on endurance performance in well trained cyclists PhD Thesis, School of Human Movement Studies, The University of Queensland.

       
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Author Laursen, P. B.
Thesis Title The influence of high-intensity interval training on endurance performance in well trained cyclists
School, Centre or Institute School of Human Movement Studies
Institution The University of Queensland
Publication date 2004
Thesis type PhD Thesis
Supervisor Dr. David G. Jenkins
Jeff Coombes
Total pages 309
Collection year 2004
Language eng
Subjects L
321401 Exercise Physiology
750203 Organised sports
Formatted abstract Note: The symbol for Mean average value of xi has been substituted with ‘x bar’ and the symbol for volume per time of oxygen with ‘VO2’


In contrast to the volume of data relating to the physiological adaptations that occur following high-intensity interval training (HIT) in previously sedentary and recreationally active individuals, relatively little is available pertaining to the training adaptations that occur in already highly trained endurance athletes following HIT. Information relating to HIT programme optimisation in endurance athletes, in terms of exercise intensity, frequency, and duration, is also sparse. Preliminary work using the velocity at which VO2max is achieved (Vmax) as the interval intensity, and fractions (50-75%) of the time to exhaustion at Vmax (Tmax) as the interval duration have elicited improvements in performance in long-distance runners. However, Vmax and Tmax have not been used with cyclists. Instead, HIT research with cyclists has revealed that repeated supramaximal sprinting may be just as effective as lower intensity intervals for eliciting improvements in endurance performance. Consequently, the aim of this series of studies was to extend this work and more fully describe the influence of HIT on endurance performance and the associated physiological adaptations in already well trained cyclists.

The purpose of the study described in Chapter Three was to investigate the acute responses that occur following a brief HIT programme in well trained cyclists. This study examined the effects of four HIT sessions performed over two weeks on peak volume of oxygen uptake (VO2peak), the first and second ventilatory thresholds (VT1, VT2) and peak power (PP) in well trained cyclists. Fourteen well trained male cyclists (x bar ± SD; V02peaK= 67.5 ± 3.7 ml kg-1min-1) performed a ramped cycle test to determine VO2peak. VT1, VT2, and PP. Subjects were divided equally into a HIT group and a control group. The HIT group performed four HIT sessions (20 x 60 s at PP, 120 s recovery); the VO2peak test was repeated <1 wk after the HIT programme. Control subjects maintained their regular training programme and completed the same tests, at the same time, as the HIT subjects. There was no change in VO2 peak for either group, however, the HIT group showed a significantly greater increase in VT1 (+22% vs. -3%), VT2 (+15% vs. -1%) and PP (+4.3 vs. -0.4%) compared to controls (all P < 0.05). This study demonstrated that HIT can improve VT1, VT2, and PP, following only four HIT sessions in already well trained cyclists.

In preparation for examining HIT programme optimisation, four studies were undertaken (Chapters Four, Five, Six, and Seven; methods decribed in Appendix B). It has previously been suggested that intervals performed at VO2 peak may be the most effective means of improving the VO2peak and endurance ability of already well trained athletes; the study presented in Chapter Four therefore examined temporal aspects of the VO2 response to exercise at the cycling power output at which well trained cyclists achieve their VO2peak (i.e. Pmax). Following a progressive exercise test to determine VO2peak. forty-three well trained male cyclists (x bar ± SD; age = 25 ± 6 yr; mass = 75 ± 7 kg; VO2peak = 64.8 ± 5.2 ml kg-1min-1) performed two Tmax tests one-week apart. Fatigue was defined as the Inability to maintain a cadence of ≥ 60 rev•min-1 and values expressed are the mean of these two tests. VO2peak during the Tmax test was achieved after 176 ± 40 s (74 ± 12% of Tmax) and was maintained for 66 ± 39 s (26 ± 12% of Tmax). Additionally, 95% of VO2peak was achieved after 147 + 31 s (62 ± 8% of Tmax) and maintained for 95 ± 38 s (38 ± 8% of Tmax). These findings suggest that 60% to 70% of Tmax is an appropriate exercise Intensity for well trained cyclists to attain VO2peak during Interval training. However, the variable VO2 response to exercise at Pmax suggests that intervals might best be prescribed according to an athlete's individual VO2 response to exercise at Pmax-


In order to assess performance and adaptations to training, any tests that are used must be reliable. The purpose of the study presented in Chapter Five, therefore, was to examine the reproducibility of Tmax at the power output equal to that attained at VO2peak during a progressive exercise test. Forty-three well trained male cyclists performed two Tmax tests one week apart. While the two measures of Tmax were strongly related (r = 0.88; P < 0.001),Tmax from the second test (245 ± 57 s) was significantly higher than that of the first (237 ± 57 s; P = 0.047; two-tailed). Within-subject variability in this study was calculated to be 6 ± 6%, which was lower than that previously reported for Tmax in sub-elite runners (25%). The mean Tmax was significantly (P < 0.05) related to both VT2 (r = 0.38) and to VO2peak (r = 0.34). Despite a relatively low within-subject coefficient of variation (CV), these data demonstrated that the second of two Tmax scores was significantly greater than the first. Moreover, the data showed that Tmax in well trained cyclists is moderately related to VT2 and VO2peak.

The purpose of the study presented in Chapter Six, was to examine the reproducibility of laboratory-based 40-km cycle time-trial (TT40) performance on a stationary wind-trainer. Each week, for three consecutive weeks, and on different days, forty-three well trained male cyclists performed: 1) a VO2peak test, and 2) a TT40 on their own racing bicycle mounted to a stationary wind-trainer (Cateye - Cyclosimulator). Data from all tests were compared using a one-way analysis of variance. Performance on the second and third TT40 tests were highly related (r = 0.96; P < 0.001), not significantly different (57:21 ± 2:57 vs 57:12 ± 3:14 min:s), and displayed a low CV (0.9 ± 0.7%). Although the first TT40 test (58:43 ± 3:17 min:s) was not significantly different from the second and third tests (P = 0.06), inclusion of the first test in the assessment of reliability increased within-subject CV to 3.0 + 2.9%. Mean TT40 speed (km•h-1) was significantly (P < 0.001) related to PP (W; r = 0.75), VO2peak (L•min-1 r = 0.53), and the VT2 (L•min-1; r= 0.68) measured during the progressive exercise tests. These data demonstrated that the assessment of TT40 performance in well trained endurance cyclists on a stationary wind-trainer is reproducible, provided the athletes perform a familiarisation trial.

The purpose of the study presented in Chapter Seven, was to cross-sectionally examine the cycling performance ability of well trained cyclists and triathletes. Each week for three weeks, and on different days, 25 well trained male cyclists and 18 well trained male triathletes performed: 1) an incremental exercise test on a cycle ergometer for the determination of VO2peak. PP. VT1 and VT2, followed, 15 minutes later by a sprint to fatigue at 150% (TF150) of PP, 2) a Tmax at Pmax, and 3) a TT40 test. There were no differences found between the groups in VO2peak. PP. Tmax, and TF150. However, the cyclists completed the TT40 in a significantly faster time (56:18 ± 2:31 min:s) compared with the triathletes (58:57 ± 3:06 min:s; P < 0.01), which could be partially explained (r = 0.34-0.51; P < 0.05) by a significantly higher VT1 (3.32 ± 0.36 vs. 3.08 ± 0.36 L•min-1) and VT2 (4.05 ± 0.36 vs. 3.81 ± 0.29 L•min-1 both P < 0.05) in the cyclists versus the triathletes, respectively. In conclusion, the study found that cyclists had an improved ability to perform a cycling time-trial compared with triathletes, and that this may have been due to differences in VT1 and VT2.

The study presented in Chapter Eight Investigated the Influence of three different HIT regimens on endurance performance in well trained endurance cyclists. Before and after two and four weeks of training, thirty-eight cyclists and triathletes (x bar ± SD; age = 25 ± 6 yr; mass = 75 ± 7 kg; VO2peak = 64.5 ± 5.2 ml•kg-1min-1) performed: 1) a progressive cycle test to measure VO2peak and PP, 2) a Tmax test at Pmax, and 3) a TT40 test. Subjects were matched and assigned to one of four training groups (G1, N=8, 8 x 60% Tmax at Pmax, 1:2 work:recovery ratio; G2. N=9, 8 x 60% Tmax at Pmax, recovery at 65% HRmax; G3, N=10, 12 x 30 s at 175% PP, 4.5 min recovery; GCON, N=11). In addition to G1, G2, and G3 performing HIT twice per week, all athletes maintained their regular low-intensity male cyclists and 18 well trained male triathletes performed: 1) an incremental exercise test on a cycle ergometer for the determination of VO2peak. PP. VT1 and VT2, followed, 15 minutes later by a sprint to fatigue at 150% (TF150) of PP, 2) a Tmax at Pmax, and 3) a TT40 test. There were no differences found between the groups in VO2peak. PP. Tmax, and TF150. However, the cyclists completed the TT40 in a significantly faster time (56:18 ± 2:31 min:s) compared with the triathletes (58:57 ± 3:06 min:s; P < 0.01), which could be partially explained (r = 0.34-0.51; P < 0.05) by a significantly higher VT1 (3.32 ± 0.36 vs. 3.08 ± 0.36 L•min-1) and VT2 (4.05 ± 0.36 vs. 3.81 ± 0.29 L•min-1 both P < 0.05) in the cyclists versus the triathletes, respectively. In conclusion, the study found that cyclists had an improved ability to perform a cycling time-trial compared with triathletes, and that this may have been due to differences in VT1 and VT2. The study presented in Chapter Eight Investigated the Influence of three different HIT regimens on endurance performance in well trained endurance cyclists. Before and after two and four weeks of training, thirty-eight cyclists and triathletes (x bar ± SD; age = 25 ± 6 yr; mass = 75 ± 7 kg; VO2peak = 64.5 ± 5.2 ml•kg-1min-1) performed: 1) a progressive cycle test to measure VO2peak and PP, 2) a Tmax test at Pmax, and 3) a TT40 test. Subjects were matched and assigned to one of four training groups (G1, N=8, 8 x 60% Tmax at Pmax, 1:2 work:recovery ratio; G2. N=9, 8 x 60% Tmax at Pmax, recovery at 65% HRmax; G3, N=10, 12 x 30 s at 175% PP, 4.5 min recovery; GCON, N=11). In addition to G1, G2, and G3 performing HIT twice per week, all athletes maintained their regular low-intensity training throughout the experimental period. All HIT groups improved TT40 performance (+4.4 to +5.8%) and PP (+3.0 to +6.2%) significantly more than GCON (-0.9 to +1.1%; P < 0.05). Furthermore, G1 (+5.4%) and G2 (+8.1%) improved their VO2peak significantly more than GCON (+1.0%; P < 0.05). In conclusion, this study showed that when HIT incorporates Pmax as the interval intensity and 60% of Tmax as the interval duration, already well trained cyclists can significantly improve their 40-km time trial performance. Moreover, the present data confirmed prior research, in that, repeated supramaximal HIT can significantly improve 40-km time trial performance. Using the same training regimes presented in Chapter Eight, the study present in Chapter Nine examined the influence of the three HIT regimens on VT1, VT2, anaerobic capacity (ANC), and plasma volume (PV) in well trained endurance cyclists. VT1, VT2, and ANC all significantly increased in G1, G2, and G3 (P < 0.05), but not in GCON. However, PV did not change in response to the four week training program. Changes in TT40 performance were modestly related to the changes in VO2peak. VT1, VT2, and ANC (r = 0.41, r = 0.34, r = 0.42, r = 0.40, respectively; all P < 0.05). In conclusion, the significant improvements in TT40 performance reported in Chapter Eight were related to significant increases in VO2peak, VT1, VT2, and ANC, but did not appear to be accompanied by significant changes in PV. These findings suggest that peripheral metabolic adaptations are largely responsible for the improved performance usually observed following HIT in already well trained athletes training throughout the experimental period. All HIT groups improved TT40 performance (+4.4 to +5.8%) and PP (+3.0 to +6.2%) significantly more than GCON (-0.9 to +1.1%; P < 0.05). Furthermore, G1 (+5.4%) and G2 (+8.1%) improved their VO2peak significantly more than GCON (+1.0%; P < 0.05). In conclusion, this study showed that when HIT incorporates Pmax as the interval intensity and 60% of Tmax as the interval duration, already well trained cyclists can significantly improve their 40-km time trial performance. Moreover, the present data confirmed prior research, in that, repeated supramaximal HIT can significantly improve 40-km time trial performance.

Using the same training regimes presented in Chapter Eight, the study present in Chapter Nine examined the influence of the three HIT regimens on VT1, VT2, anaerobic capacity (ANC), and plasma volume (PV) in well trained endurance cyclists. VT1, VT2, and ANC all significantly increased in G1, G2, and G3 (P < 0.05), but not in GCON. However, PV did not change in response to the four week training program. Changes in TT40 performance were modestly related to the changes in VO2peak. VT1, VT2, and ANC (r = 0.41, r = 0.34, r = 0.42, r = 0.40, respectively; all P < 0.05). In conclusion, the significant improvements in TT40 performance reported in Chapter Eight were related to significant increases in VO2peak, VT1, VT2, and ANC, but did not appear to be accompanied by significant changes in PV. These findings suggest that peripheral metabolic adaptations are largely responsible for the improved performance usually observed following HIT in already well trained athletes.

In order to gain insight into the metabolic adaptations that occur in response to increases in exercise intensity and volume in the training programmes of already well trained athletes, the final study presented in Chapter Ten examined the Influence of HIT and high-volume training (HVT) on the activities of skeletal muscle citrate synthase (CS) and phosphofructokinase (PFK) of already well-trained rats. At four weeks of age, 56 Wistar rats were divided into sedentary (N=18) and exercise training groups (N=38). Following a ten-week preliminary training program (reaching 4 d•wk-1, 90 min•d-1,30 m•min-1 18% grade), the trained rats were divided randomly into three further groups (HIT, HVT, CON) that performed four additional weeks of training [HIT (N=12) = 15x2 min, 60 m•min-1 20% grade, 2 min recovery; HVT (N=12) = 25 m•min-1 18% grade, 180 min; CON (N=14) = 90 min•d-1 30 m•min-1 18% grade]. A timed run to fatigue test (Tlim) was used to examine exercise capacity (30 m•min-1 20% grade) and muscles of the lower limb (soleus, red and white gastrocnemius, red and white vastus lateralis) were removed 48 h following the final Tlim test for the analysis of PFK and CS activities. There were no differences in Tlim between any of the training groups (50 + 10, 56 ± 13; and 48 ± 12 min, for HIT, HVT, and CON, respectively). While CS activity in the soleus and red vastus lateralis muscles was significantly higher in all three training groups compared with SED (P < 0.05), there were no differences in CS activity between training groups. However, CS and PFK activities for white vastus lateralis were 60% and 24% higher, respectively, in the HIT group compared with the HVT group (both P < 0.05). The present data suggest that HIT, compared with HVT, in already well-trained rats results in a greater recruitment of fast-twitch muscle fibres that In turn lead to higher oxidative and glycolytic enzyme activities In those particular fibres. HIT had no influence on the activities of CS and PFK in slow-twitch fibres compared with the other training groups.
In summary, the present series of studies established that i) four HIT sessions over two weeks can result in significant increases in VT1, VT2 and PP in already well trained cyclists, ii) HIT performed at Pmax. and using fractions of 60 to 70% of Tmax, appear to be appropriate for prescribing HIT sessions when the goal is to train at VO2peak. iii) the CV between two Tmax scores is relatively low (6 ± 6%), however, the second of two Tmax scores may be significantly greater than the first, iv) the repeatability of two 40-km time trials on a stationary wind trainer (Cateye - Cyclosimulator) is highly reliable (CV = 0.9 ± 0.7%) when a familiarisation test precedes the first test, v) well trained cyclists may be able to perform significantly better in time trial events compared with triathletes as a result of having a significantly higher VT1 and VT2, vi) HIT performed at Intensities of Pmax and durations of 60% of Tmax is an effective means for enhancing TT40 performance and PP, and VO2peak in well trained cyclists, repeated supramaximal training can significantly enhance PP, VO2peak. and TT40 performance in well trained cyclists, viii) the significant improvements in TT40 performance were related to significant increases In V02peak. VT1, VT2, and ANC, but were not accompanied by significant changes in PV, and ix) HIT, compared with HVT, in already well trained rats may result in a greater recruitment of fast twitch-muscle fibres that in turn leads to higher oxidative and glycolytic enzyme activities in those particular fibres; this adaptation may help to explain the improved endurance performance commonly observed following HIT in already well trained athletes.
Keyword Cyclists -- Physical training
Cyclists -- Physiological aspects
Additional Notes
Missing page 198 in the original thesis.

Document type: Thesis
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