Understanding The Purpose Of Interval Training Physical Education Essay

Interval training involves a repeated series of exercise work bouts interspersed with rest of relief periods. This is a popular method among athletes because it allows the athlete to exercise at higher relative intensities during the work interval than are possible with longer-duration, continuous training (Heyward 2002). The intensity can vary from between ‘all out’ to greater than competition intensity. Recovery periods can be from considerably less than the preceding work bout to complete recovery (recovery can be active or inactive). The duration can last from a few seconds to many minutes. The number of work bouts can obviously be from 2 to possibly 100 or more.

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Interval training is geared towards and dictated by the physiological variable-maximum oxygen consumption. With this in mind it might be more appropriate to refer to this type of training as vo2 max or aerobic capacity training since one trains at or very near the intensity which demands vo2 max of the system (Daniels and Scardina, 1984). Interval training can be referred to in a number of different ways. Fox (1977) refers to two types of interval training, low power output interval training (LPO-IT) and high power output interval training (HPO-IT). HPO-IT involves exercise and pause periods of less than one minute. Gibala and mcgee (2008) refer to High intensity training (HIT). This generally refers to repeated sessions of relatively brief intermittent exercise often performed with an ‘all out’ effort or at an intensity close to that which elicits VO2 peak (i.e >90% of vo2 peak). Depending on the training intensity, a single effort may last from a few seconds to up to several minutes with multiple efforts separated by up to a few minutes of rest or low intensity exercise (Gibala and McGee, 2008). Minimum volume of HIT may be necessary to increase VO2 peak and stimulate other adaptations such as an increase capacity for fat oxidation. On the other hand Astrand and Rodahl (1977) say that exercise bouts lasting 3-5 minutes each are the longest recommended and are considered optimum for training aerobic processes. The purpose of high intensity training is to repeatedly stress the physiological systems that will be used during specific endurance type exercise (Daniels and Scardina 1984) to a greater extent than which is actually required during a specific activity. At any level of exercise, duration frequency, programme length or initial fitness, intensity was the most important factor in producing improvements in aerobic power (Wenger and bell, 1986).
Interval training in the highly trained athlete
Landree (1997), lake and cavanagh (1996) and costill et al (1988) all report that an additional increase in submaximal exercise doesn’t appear to further improve endurance performance and associated factors such as VO2 max, anaerobic threshold, econonmy of motion and oxidative muscle enzymes. In highly trained individuals further improvements in performance can only occur via high intensity interval training (Landree 1997).
Interval training in the sedentary and recreationally active
It is generally believed that in sedentary (VO2 max 60 ml/kg/min) (Rowell 1993, ekblom 1969). In contrast to this a study by Hickson et al (1977) found that the vo2 max of eight sedentary and recreationally active people could be significantly increased after to 10 weeks of high intensity exercise training using cycling intervals.
Lauresen and Jenkins (2002) also report improved endurance performance. They reported that high intensity interval training in sedentary and recreationally active individuals improves endurance performance more than continuous sub maximal training alone. This improvement appears due to an up regulated contribution of both aerobic and anaerobic metabolism to the energy demand (Rodas et al 2000, MacDougall 1998). This could also be due to an improved capacity for aerobic metabolism through the increase in type 1 muscle fibres (Linossier et al 1993), cappiliristaion and oxidative enzyme activity.(Macdougall et al 1998, Essen et al 1977, chilibeck et al 1998). These adaptations are the most common due to High intensity interval training in untrainined or modertaley active.
Holoszy and booth (1976) and Holoszy and Coyle (1984) report that submaximal endurance training has little or no effect on gylcolytic enzyme activity whereas supramaximal high intensity training can elicit up regulation of both glycolytic and oxidative enzyme capacity, maximal short term power but most importantly can increase VO2 max in an untrainined individual.
Studies supporting increases in V02 max with interval training
Studies have shown that 6-12 weeks of moderate intensity exercise can increase aerobic capacity and mitochondrial enzyme activity (gollnick et al 1973, hickson et al 1977) but sprint interval training at very high outputs (150-300% VO2 peak) for 6-7 weeks also produces similar results (Macdougall et al 1998, Rodas et al 2000, Tabata et al 1996)
Tabata et al (1996) carried out a study involving 7-8 sets of 20 second high intensity exercise (170% of VO2 max) with 10 seconds rest between intervals. Post tests revealed a significant increase in VO2 max of 7ml.kg.min. This study concluded that adequate high intensity intermittent training may improve both anaerobic and aerobic energy systems significantly through imposing intensive stimuli on both systems.
Fox (1973) and (1977) compared low power output training compared to high power output training. It observed no differences in Vo2 max gain with low power output training versus high power output training. This suggested that in long exercise repeats oxygen transport demands would be greater with vo2 max achieved in each exercise phase while in sprint repeats the high intensity may result in greater muscle hypoxia stimulating adaptations in muscle oxidative capacity.
HIIT over a longer period of time (4-6wk) has been reported to increase high-intensity exercise performance, muscle buffering capacity, whole body exercise fat oxidation
rates, and aerobic capacity (Edge et al 2005, Laursen and Jenkins 2002, Weston et al 1997)
Talanian et al (2007) found that after 2 weeks of high intensity aerobic intervak training vo2 peak increased by 13%.
Rodas et al (2000) conducted a study to evaluate the changes in aerobic and anaerobic metabolism produced by a newly devised short training programme. The training involved fourteen training sessions everyday for two weeks. Training consisted of a number of 15 second all out sprints with 45 second rest and also a number of 30 second ‘all out’ sprints with 12 minute rest periods. The participants involved were moderately active individuals. Results found an increase in vo2 peak pre and post training from 57.3 +2.6 to 63.8 + 3.0 ml.min.kg following a progressive exercise test.
Macdougall et all 1998 conducted a study involving 30 second maximum sprint effort interspearsed by 2-4 minutes of recovery performed 3 times per week for 7 weeks. The program began with four intervals with four minutes recovery per session to 10 intervals with 2.5 minutes. The effect of the training program on VO2max was that it increased from 3.73 + 0.13 to 4.01 + 0.08l/min (P # 0.05). Because there were no significant
changes in body mass over the training program, V O2max relative to body mass also increased significantly from 51.0 + 1.8 to 54.5 ml·kg-1 ·min-1.
Gorostiaga et al (1991) compared high intensity training, using repeated 30 second sprints with 30 second rest, to continous training at 50% of VO2 max. All participants cycled 30 minutes per day, 3 days a week for 8 weeks. Both groups were exercising at the same mean intensity. Post training incremental tests revealed an increase in VO2 max, exercising work rate and peak power more so in the high intensity training group (9-16% improvement) compared to the continous training group ( 5-7% improvement).
Studies by Edge et al (2005), Laursen and Jenkins (2002) and Weston et al (1997) have found that High intensity interval training for 4-6 weeks improved high intensity exercise performance, increased muscle buffering capacity, increased whole body fat oxidation rates and also improved aerobic capacity.
Gibala and Mcgee (2008) reviewed the high intensity training intervention the wingate test which involves 30 seconds of all out maximal cycling. This is also the method being used in this study. Protocols involved 4-6 wingates with 4 minutes of recovery between each one. A total of 2-3 minutes of intense exercise per session with 3 sessions per week for 2-6 weeks( Burgomaster et al 2008,2007,2006 and Gibala et al 2006 ). There was no measurable change in VO2 peak after 2 weeks of interval training wingates as the intervention. This suggests that peripheral adaptations improved exercise capacity. On the other hand studies by ( Rodas 2000 and talanian et al 2007) found increases in vo2 max after just 2 weeks of high intensity training.
Bailey et al (2009) also used the wingate based model for their training intervention. Particpants performed all out 30 seconds wingate with 4 in week one progressing to 6 and 7 in week 5 and 6. Each wingate was separated by 4 minutes of rest. Post intervention testing showed a significant increase in VO2 max. Pre testing participants had a vo2 max of 3.06+ 0.60 l/min which increased post testing to 3.29+0.65 l/min. Also VO2 max increased in relative terms from 42+6 to 45+6 ml.kg.min. The other two other groups of participants one performing endurance training and the other a control group showed no increase in V02 max.
Studies not showing improvement in VO2 max performance
Franch et al (1998) compared the effects of a continous training programme and a high intensity training programme in recreational runners. All participants were split into three groups. The first training group was a short high intensity training group which involved 30-40 15 second runs at 20.4km/h with 15 seconds rest between intervals. The second training group involved a long high intensity training programme which was 4-6 4 minute runs at 16.6km/h with 2 minutes of inactive rest. The final group did a continous traning programme with 15km/h for 26 minutes. All groups trained three times per week for six weeks . The results of this study found that continous and long high intensity interval training improved VO2 max than short high intensity training.
Burgomaster et al (2006) and (2005) used a wingate based training intervention for their study. 4-7 all out 30 second wingates were carried out over a 2 week period. Post testing revealed no significant difference in VO2 peak (pHypothesis
From reviewing previous studies and studies using similar methodology I hypothesise that VO2 max will increase in post testing. I also hypothesise that peak wattage in the incremental test will increase and also time to exhaustion. The reason for under taking this study is that I feel that other studies have looked at other factors rather than specifically focusing on VO2 max.
Method
Subjects
16 healthy males from the University of Exeter Rugby Union Club volunteered to participate in this study (mean age weight and height and SD). The participants were contacted via email and also verbally The subjects regularly took part in exercise, usually involving 4 training sessions a week, two being skills based and the other two being resistance sessions. Participants were asked to carry one with normal training before any testing had began and were asked to maintain their normal diet throughout the duration of the study although participants were asked to refrain from alcohol 24 hours before any testing.
Ethical procedure
Before any testing could be done the study had to be ethical approved by the University of Exeter School of sport and health sciences ethics board. Prior to the study all participants were informed fully about the study including all risks and all procedures involved verbally and in writing. All participants volunteered to be in the study and filled out informed consent forms in accordance with the ethics committee of the University of Exeter. Particpants were informed they had the right to withdraw from the study at any point. All results gained from the study were kept confidential and stored privately.
Experimental design
Subjects in the testing group were required to attend the laboratory on ten occasions over a 4 week period and control group on two occasions. All tests were separated with at least twenty four hours of recovery. All subjects undertook pre and post training incremental tests to ascertain Vo2 peak. Testing group then participated in a series of ‘all out’ 30 second wingate tests over a four week training period.
Screening
Participants were asked to fill out a PAR-Q (a physical activity readiness questionnaire) to make sure there were no underlying medical problems. A risk factor count was also undertaken which involved blood pressure measurement using a sphygmomanometer. Particpants were weighed (in kg) and height measured (in cm) and recorded. Weight being most important as this data was need to eastablish weight applied during the wingate tests.
Incremental tests
Both before and after the training intervention all subjects performed ramp incremental tests to determine VO2 max. The ramp incremental tests were performed on an electronically braked cycle ergometer (Lode Excalibur Sport, Gronigen, The Netherlands). Subjects performed 3 minutes at 50 watts after which the wattage increased 1 watt every 2 seconds until volatile exhaustion. Subjects were asked to cycle at a constant rate of 80rpm. When the rpm dropped below 80rpm participants were encouraged to increase the rpm back up and the test was ended when participants reached below 70rpm. Saddle and handlebar height was adjusted to suit each subject and then recorded for future reference in post testing. Verbal encouragement was used throughout to encourage participants to last as long as physically possible to obtain accurate data. Gas exchange data was collected continuously using cortex gas analyser. VO2 max was taken from the highest value before the subjects volatile exhaustion. Heart rate was measured minute by minute using polar heart rate monitor. After volatile exhaustion the end wattage and time at exhaustion was recorded.
Training intervention
After completing pre testing, the testing group performed a series of “all out” 30 second sprints (Wingate tests) twice a week over a four week period. The Wingate tests were performed against a resistance equivalent to 0.075kg/kg body mass on a mechanically braked cycle ergometer (model 814E bicycle ergometer, Monark, Stockholm, Sweden). All wingates were interspersed with 4 minutes rest. In week one of testing participants were asked to perform 3 Wingate’s interspersed with four minutes of rest twice a week. This then increased by one Wingate per week (i.e week one three wingates, week two four wingates, week three five Wingate’s and week four six wingates).All participants were provided with a warm up on the cycle ergometer against no resistance. Having weighed the participants the relevant weight was added to the basket. Five seconds before each Wingate participants were asked to generate high pedalling speed in order to create a rolling start for when the weight was dropped. Participants were told when there was 10 and 5 seconds left of the test, so they could work at their maximal capacity for the duration of the test. During the rest periods participants were asked to cycle at a low cadence against no resistance. The computer program wingate 30 provided data on peak power, mean power and fatigue rate. Verbal encouragement was given throughout the winagates to encourage maximal effort and water was provided during each rest interval.
Statistical analysis
All pre and post incremental gas analysis was exported to Microsoft Excel. Standard statistical equations were carried out to calculate standard deviations and averages. The data was then input into SPSS (PC program, version 16 for windows) to calculate if the training intervention has a significant effect upon VO2 max. For the analysis a 2(testing v control) x 2 (pre v post) MANOVA ( three dependant variables, vo2 ml/kg/min, VO2 l/min and peak wattage) will be used. All data is represented in mean and standard deviation. The statistical significance level is set at PValidity and reliability
Validity is described as whether the researcher truly measures that which it was intended to measure or how truthful the research results are. In a scientific experiment the aim is to manipulate a independant variable to produce an outcome on a dependant variable or variables. Once the researcher can confidently say that the changes in the dependant variable have been cause by the independant variable and no other factor the experiement is said to be internally valid (Levine et al 1994).
This study is a valid and reliable study and several measures have been used to make sure of this Firstly a control, group was used. The reason being that it shows that it was the intervention that caused an increase in Vo2 max and peak wattage and no other outside factor and can provide a comparison. Another measure is that all participants were told not to alter any current training regimes so this would not affect pre or post test results. Proper calibration of gas analyzer was carried out to make sure Vo2 max values were precise. Throughout the wingate tests verbal encouragement was used to ensure that participants were giving their maximum effort into the training to obtain the best results. This intervention has been carried out before and shows that it is a protocol which is reliable and valid.
Results
All participants completed the 4 week training intervention. Each participant reported that they did not change their current training regimes outside of the intervention which may alter the results. The data was collected and then analysed. Results show that mean VO2 max in l/min, ml/kg/min and also peak wattage increased in the testing group after the intervention. Whereas the control groups data stayed similar due to no training intervention.
Table 1.0: Mean VO2 MAX ML/KG/MIN, VO2 MAX L/MIN AND PEAK WATTAGE for Testing and control group.
GROUP
VO2 max ml/min/kg
Vo2 max l/min
Peak wattage
Testing
PRE
45.875
3.91
383.5
POST
50.125
4.315
396.125
Control
8.5%
9.4%
3.2%
PRE
49
4.040
395.5
POST
48.875
4.050
397.125
Graph 1.0: Mean VO2 ml/kg/min pre and post training of testing and control groups.
After the four week wingate training intervention, Vo2 max (ml/kg/min) in relative terms increased during the incremental vo2 max test. The mean difference in the testing group from pre to post tesing was 4.25 ml/kg/min, compared to the control groups mean difference of -0.125 ml/kg/min so the control groups mean relative Vo2 max decreased. Taking into account body weight this measure can be affected over time. One participant in the testing group started off with a weight of 118kg, at the end of the programme his weight dropped to 116kg, this caused the participant to have one of the biggest increases in relative VO2 max from 32 ml/kg/min to 41 ml/kg/min.
Graph 1.1: Mean VO2 max l/min pre and post training for testing and control groups.
Absolute Vo2 max (l/min) also increased in the testing group during the incremental Vo2 max test following the four week intervention. The mean difference pre and post testing in the training group was 0.405 l/min increase. Whereas the control group stayed the same with a 0.01 l/min increase.
Graph 1.2: Peak wattage (w) pre and post training for testing and control groups.
Mean peak wattage in the incremental Vo2 max test also increased following four weeks of wingate training in the testing group. This shows that participants who took part in the training programme could last longer during the post training Vo2 max test compared to the pre testing. This meant the time to exhaustion increased in the testing group. Mean peak wattage (w) increased from 383.5w to 396.125w showing a mean increase of 12.625w in the testing group. The control groups mean post peak wattage stayed similar with a mean increase of only 1.625w which was to be expected
The data gathered from pre and post incremental test was input into the statistics programme SPSS to see if the increased found were statistically significant. The statistical test used was a 2×2 MANOVA. This test allowed me to compare groups (control and testing) and time (pre and post) to my three dependant variables (VO2 max ml/kg/min, l/min and peak wattage). Due to the three dependant variables a multi analysis of variance (MANOVA) had to be used.
Mutlivariate analysis using pillails trace showed no significant difference in group (testing and control) on the Vo2 max in ml/kg/min, l/min and peak wattage, V=0.145, F(3,26)=0.145, P>0.05. Seperate Univariate ANOVA’s were carried out on each variable and revealed no significant difference in group on VO2 max ml/kg/min F(1,28)=0.134, P>0.05. No significant difference was found in group on VO2 max l/min F(1,28)=0.094, P>0.05. Also no significant difference was found in group on peak wattage F(1,28)=0.364, P>0.05. This shows there was no significant difference in testing and control groups in terms of the three variables.
Multivariate analysis using pillails trace showed no significant difference in time (pre and post) on the Vo2 max in ml/kg/min,l/min and peak wattage V=0.034, F(3,26)=0.306, P>0.821. Seperate univariate ANOVAS revealed no significant difference in time on Vo2 ml/kg/min F(1,28)=0.646, P>0.05, on Vo2 l/min F(1,28)=0.437, P>0.05 and on peak wattage F(1,28)=0.903, P>0.05. This shows there was no significant difference in pre and post results of the three variables.
Multivariate analysis using pillais trace showed no significant difference in group (testing and control) x time(pre and post) on Vo2 max ml/kg/min, l/min and peak wattage V=0.037, F(3,26)=0.334, P>0.05. Univariate ANOVAS revealed no significant difference of group x time on Vo2 max ml/kg/min, F(1,28)=0.727, P>0.05. No significant difference was found for group x time on Vo2 max l/min, F(1,28)=0.822, P>0.05. Also no significant difference was found for group x time on peak wattage F(1,28)=0.261, P>0.05. This shows that testing group pre and post and control pre and post results were not statistically significant.
Although these results did not show statistical significance, it cannot be ignored that they did show an increase. Despite that fact that the results were not significant all three variables increased following post testing. Results still show that the 4 week training programme was successful and the desired increases in Vo2 max (ml/kg/min, l/min) and peak wattage were achieved. Vo2 max in l/min saw the highest increase after the 4 week training intervention. Vo2 max l/min increased 9.4% in the testing group which is quite a considerable considering only 4 weeks of training was undertaken.
Discussion
Over the 4 week training programme all sprints were carried out at a maximal intensity with participants verbally encouraged to do so. This led the testing to be very uncomfortable and severely demanding, despite this the when adding up total cycle time at maximal intensity , participants only cycled for 18 minutes over the four weeks. Despite the fact that the intervention did not prouduce statistically significant results it did show that the intervention worked and increase the three variables. . This shows that with only 18 minutes of intense cycling through wingate tests can increase Vo2 max in relative an absolute terms and peak wattage by 3-10% in an incremental vo2 max test.
Analysis of the evidence and relation to previous literature
These results are similar to Bailey et al (2009) who used a similar intervention to the one use in this study. Bailey et al(2009) used one more wingate per session that this study (4 in week one increasing by one each week up to 7) and 4 minutes recovery time between each wingate. Results from this study showed a similar increase in Vo2 max, Bailey et al (2009) reported an increase in Vo2 peak of 8% which compared to the increase of 8.4% (ml/kg/min) and 9.5% (l/min) is very similar. This study’s training programme may have had a slightly larger increases due to the 4 week programme compared to the 2 week training programme in Bailey et al’s (2009) study. Studies by Macdougall et al (1998)and Burgomaster et al (2008) also have reported increases of 7-8% in Vo2 max. Madougall et al (1998) also used the wingate based intervention but over a longer duration with a 7 week training programme and with 1 more session a week than the present study. Their results found a 7% increase in absolute Vo2 max and a 6.4% increase in relative Vo2 max. This is quite interesting considering the length and amount of sessions compared to the present study. The present study produced higher values in absolute and relative Vo2 max over four weeks. Macdougall et al (1998) also went up to 10 training intervals by the end of the study. This could potentially show that optimal time to obtain training adaptations could be around 4 weeks. Burgomaster et al (2006) also used a winagte protocol as its training intervention. Thier results are similar to what is found in this study. Vo2 max did increase after the 2 week training programme but after statistical analysis is was shown that this increase was not significant which is the same in the present study. Rodas et al (2000) also showed increases in Vo2 max after a short term interval training programme constsing of a mixture of 15 seconds and 30 second all out sprints which increase in number of the two week training programme. After the training programme maximal progressive test were carried out to obtain post test value of Vo2 max (ml.min.kg) and peak wattage, two of the variables being testing in this study. Results showed an increase of around 10% in Vo2 max (ml.kg.min) and a 9% increase in peak wattage in the maximal progressive test. This increase of the 2 weeks is similar to the data reported in this study. This increases the validity of the present study that two out of the three variables measured in this study are also reported in Rodas et al (2000) study.
Gibala and Mcgee (2008) reviewed the wingate based training intervention with studies of 4-6 wingates per session with 4 minute rest intervals which is similar to the present study. This review also concluded no changes in Vo2 max after the training intervention in studies by burgomaster 2005, 2006. One reason being why no reported increase in Vo2 max was seen is due to the length of the training programme. Gibala and Mcgee actually report this in their review. They compare the work load of Burgomaster (2005) which they review and state that studies by rodas et al (2000) and talanian et al (2007) had a greater work load than Burgomaster (2005) which could be one reason for no change in Vo2 max. Iaia et al (2008) also showed no increase Vo2 max following a 4 week training intervention. As you can see there is mixed evidence towards the wingate based protocol as a training intervention to elicit improvements in VO2 max performance. Although some of these studies did not show increases in VO2 max, other performance based improvements occurred. For example burgomaster et al (2005,2006) showed increases in time trial performance following four weeks of wingate based interval training.
Despite some evidence to the contrary and statistical analysis showing the data in this study to not be significant, the fact that percentage increases in VO2 max are very similar to what has been reported in other studies. There can be many reasons to why high intensity interval training can increase VO2 max. The wingate test can be a very demanding test and is primarily used as a measurement of anaerobic capacity, showing peak power, average power and fatigue rates. Macdougall (1998) states that oxidative metabolism has a minor contribution to the energy delivered during each wingate test, although slievert at al (1995) says that the contribution of oxidative metabolism probably increased with every interval. The fact that using a wingate test with repeated intervals, participants can reach 140-210% Vo2 max during each interval, this shows that training at intensities above Vo2 max can be more important than the volume of training and can stimulate increases in muscle oxidative potential (Macdougall et al 1998). Common responses to HIT in moderately active individuals is the expression of type 1 fibres, capillirisation and oxidative enzyme activity (linossier et al 2003, Mcdougall et al 1998).
The recovery phase of the wingate based training programme can have an important part to play in obtaining improvements in Vo2 max and other performance parameters. Passive recovery during the rest periods between each interval has been reviewed by billat (2001), because high levels of lactate develop during interval training performed at an intensity above the lactate threshold, active recovery facilitates this removal (hermansen and stensvold 1972). This removal allows althletes to tolerate heavy work rates for longer period of time ( Billat et al 2000). The rest days between each wingate session are also important. Rodas et al (2000) found significant increases in oxidative and glycolytic enzyme activity after two weeks of sprint training but this was no change in wingate performance after only one days rest. This improves the validity my results as partipants had more than one days rest between each wingate training session.
Critical evaluation of the method
One factor that could affect the amount of increase in Vo2 max could be baseline levels of Vo2 max. Participants with low baseline Vo2 are going to see larger increases than participants who already have higher fitness levels. Although as I have mentioned before Landree (1997) states in highly trained individuals further improvements in performance can only occur via high intensity interval training. One major reason why the results of this study did not prove significant is the standard deviation. Participants with low baseline levels before the intervention may have showed an improvement in VO2 max and peak wattage but this improvement may still not have got them to the level of another participants baseline level. For example one participant increased their Vo2 max (ml.kg.min) from a baseline level of 39 ml.kg.min to a post intervention score of 50 ml.kg.min but this increase still did not get their Vo2 max level to the same as 4 other participants baseline. This variety in different peoples Vo2 max could be a reason why significant results were not obtained.
A good comparison can be made between this study and Bailey et al (2009) due to similar participants being used. Their study used young adults with a mean age of 21 SD 4 which is a similar age to the participants in this study. One factor that could have been improved in this study is a larger sample s