I can say I ran for one hour. But how is the intensity of that one-hour run measured and expressed? In the first few years in a sport there is no doubt that increased duration is effective.
I came to realize quite early in my coaching that an ever-increasing weekly volume was not the path to take. At some point the return on investment plateaus and may even turn downward. I found that for the advanced and experienced athlete — usually starting around the fourth year of dedicated training — the focus needs to shift toward intensity. Making such a shift often keeps the positive performance slope steep for a few more seasons. How much? To be more clear, I believe that performance on race day is roughly 60 percent determined by recent training intensity and about 40 percent by workout durations weekly volume.
I know of no research that substantiates that ratio. But there is research that supports the notion that intensity is a better predictor of performance than is duration or volume, especially in the more experienced and advanced athletes. By clicking on the references you can read the abstracts. The bottom line here is that for the advanced athlete with about four or more years of dedicated and consistent training, the key to performance improvement shifts toward intensity as duration plays a somewhat lesser, but not unimportant, role.
Getting that balance right is more complicated than simply doing more weekly volume. Getting that balance right is the key to success. This is also a good time to point out that on TrainingPeaks you can express the intensity of a workout just as easily as you can its duration. That means that a single number gives you a pretty good idea of how much you accomplished in the workout relative to your current level of fitness. The CP model itself is not based on physiological measures, although it seems to have a physiological basis which was shown to be related to the maximal lactate steady state intensity Jones et al.
This concept however, does not include a differentiation of all intensity domains Meyer et al. Dekerle et al. From this point of view, a focus on optimization of both the low intensity-high volume and the high intensity-low volume parts of the training as well as concepts and models to prescribe both intensity and duration including physiologically relevant zones are required. Aim of the paper is to give a theoretical framework prescribing both intensity and duration for endurance training.
Guidelines recommend using percentages of maximal oxygen uptake VO 2max , maximal heart rate HR max , or maximal power output P max for setting exercise intensity Pescatello, , p. However, threshold or turn point concepts are suggested to be the gold standard for exercise intensity prescription in practice Meyer et al.
Actually, most authors agree to set training intensities by a three phase and two threshold model Meyer et al. Figure 1. Time course of ventilation VE , oxygen uptake VO 2 , carbon dioxide output VCO 2 , and lactate La as well as the first VT 1 and the second VT 2 ventilatory turn point during incremental cycle ergometer exercise in a well-trained cyclist B.
Several variables enable to discern three distinct phases of metabolism and cardio-respiratory responses which allow setting defined intensities for continuous or interval-type exercise Hofmann and Tschakert, ; Tschakert and Hofmann, According to the lactate shuttle theory Brooks, , the first lactate turn point LTP 1 is defined as the first increase in blood lactate concentration La accompanied by a first change of increase in ventilation VT 1 and distinct changes in other ventilatory variables.
The second lactate turn point LTP 2 is defined as the second abrupt increase in La accompanied by a sharp increase in ventilation VT 2 and distinct changes in other ventilatory variables Figures 1 , 2.
It has to be mentioned that the chosen incremental test protocol influences the accuracy of any threshold determination and the validity to prescribe constant load or intermittent-type exercise.
A careful choice of the protocol is accordingly substantial. A detailed discussion of this problem, however, is not within the scope of this article but discussed elsewhere McLellan, ; Amann et al. Figure 2. LTP 1 is the first increase above baseline. Lactate production within the muscle P M is equal to the elimination rate within the working muscle E M and, consequently, no La has to be shuttled to the system S. La within the system stays at resting level because the critical lactate clearance of the working muscle is not exceeded.
Above LTP 1 , blood La increases with increasing workloads. The critical La clearance rate of the system is not exceeded which gives a metabolically balanced situation zone II. The first and the second turn points are sub-maximal markers from incremental exercise which can be used to prescribe defined exercise workloads with distinct and defined metabolic, cardio-respiratory, and hormonal responses as shown recently by our working group for constant load and matched intermittent-type exercise Tschakert and Hofmann, ; Moser et al.
During exercise below LTP 1 , no increase in La above baseline level was detected for constant load exercise, and it was shown recently that this intensity can be sustained for a very long duration of up to 24 h in trained ultra-distance athletes Pokan et al. Increasing the workload above LTP 1 leads to an increase in La above baseline, but after several minutes a La steady state is built up.
Although mLaSS intensity can be determined rather precisely, time to exhaustion at the mLaSS still can vary distinctively between athletes. Faude et al. This is also reflected in the response of adrenaline and noradrenaline Moser et al. Figure 3 shows schematically the time course of La for the three different exercise intensity zones. Figure 3. Intensities below LTP 1 give a lactate steady state at resting level because the critical lactate clearance rate within the working muscle is not exceeded zone I.
For intensities above LTP 2 , some La produced within the muscle is shuttled to the system but La clearance is high enough to establish an equilibrium, the so called systemic La steady state LaSS zone II. Above LTP 2 , no equilibrium can be established and La increases with time with early termination of exercise due to non-sustainable acidosis zone III. These authors suggested distinct fatigue mechanisms for each intensity domain. A paucity of fatigue-related mechanistic studies was shown for the moderate and high-intensity domains but lee attention has focused on the low intensity part so far.
As can be seen in Figure 3 , an intensity slightly above LTP 1 already increases La which indicates that the critical lactate clearance rate for the working muscle has been exceeded, and therefore, different hormonal and cardio-respiratory responses are suggested for this intensity level Moser et al.
In very prolonged exercise with blood lactate remaining at resting level throughout exercise it was prescribed that only after several hours fatigue occurs and increases with time until the limit of tolerance Burnley and Jones, It has to be mentioned that energy stores play a substantial role regarding the maximal duration until the point of fatigue Johnson et al.
The prescription of intermittent exercise is somehow more complicated compared to continuous exercise as the number of variables is higher. In addition to the workload intensity for the intervals P peak , the total duration t total number of intervals , the duration of the single workloads t peak as well as recovery intensity P rec and duration t rec and the corresponding mean load P mean have to be considered Buchheit and Laursen, a , b ; Tschakert and Hofmann, Similar to constant load exercise CLE , the mean intensity and total duration are main markers of the overall workload, but P mean is influenced by the aforementioned variables with respect to the degree and the kind of fatigue and recovery Burnley and Jones, In addition, we could recently show that aerobic high-intensity interval exercise HIIE with short workload durations and P mean -matched constant load exercise produced similar acute metabolic, hormonal and cardio-respiratory responses Moser et al.
This indicated that strictly planning interval-type exercise respecting all variables allows the regulation and the predictability of the acute physiological responses Tschakert et al.
In a recent paper we could show that even with a high-intensity running speed, short 10 s intervals, 20 s passive recovery but a very low mean load below LTP 1 , lactate levels were only slightly higher than resting level, and 30 min of exercise was clearly below the maximal duration which was, however, not obtained in this study Wallner et al. Similar to constant load exercise Chidnok et al. As long as there is a metabolically balanced situation aerobic interval training , we may treat this problem similar to constant load exercise.
In case of increasing La anaerobic interval training , the optimal number of intervals may be set similar as it is performed in resistance-type exercise Richens and Cleather, Again there is urgent need to identify any markers of optimal duration for both constant load and interval-type exercise.
It is a fact that any certain intensity has its own critical time limit which is dependent on the type of exercise and the kind of athletes, but may be used as an individual diagnostic tool to prescribe exercise duration Vanhatalo et al. Figure 4A shows the running speed for all endurance-type world records in continuous running from m to marathon distance which has been described as a most perfect logarithm relationship for both men and women Nikolaidis et al.
A similar relationship can be shown for free style swimming Figure 4B. The relationship between speed and distance is linear applying a logarithmic x-axis within this wide range of race distances. It is obvious that no speed-distance pairs above the linear line are possible Burnley and Jones, This speed-distance or power-duration relationship can therefore be applied to detect the maximal speed or power output for any distance or duration but, no less importantly, to detect any maximal duration or distance for an arbitrarily chosen speed or power on an individual basis.
To regulate these distances we apply the concept of Platonov who differentiated four domains of durations with selective adaptation Viru, , p. Figure 4. Speed-duration relationship of endurance-type world records in running from m to marathon race distance A and swimming B was shown to be linear in a logarithmic scale for male and female athletes. Table 1. Definition of specific duration domains for endurance-type exercise modified from Platonov, Platonov , p.
Figure 6 shows an example of the recovery of heart rate variability HRV after maximal, sub-maximal, moderate, and low duration exercise with the same intensity applied unpublished results. HRVwas shown to be sensitive for intensity and duration of exercise Kaikkonen et al. Figure 5. Relationship between duration of exercise and fatigue modified from Platonov, Figure 6.
From this concept Platonov, , p. To prescribe these duration domains one needs the maximal duration for at least 2—3 different intensities to draw the power-duration relationship as can be seen in Figure 7 which shows the same athlete as Figure 1. Figure 7. Example of exercise intensity-duration relationship in a single well-trained cyclist. As described in Figure 1 , for any individual athlete, a plot of maximal speed and distance relationships can be drawn describing the maximal distance for any specific velocity or power output or the maximal velocity or power output for any chosen distance.
Earlier approaches such as the model from Garcin and Billat applied a perceived exertion scale to attest both intensity and duration, but the optimal duration may not be obtained from this model. As can be seen in Figures 7 , 8 , the power output or speed to time or distance relationship allows discerning these specific durations for any intensity of interest by using four different duration domains according to Platonov in Viru, , p. As shown in Table 1 , zone 1 is defined as low, zone 2 as moderate, zone 3 as sub-maximal, and zone 4 as maximal workload each producing different states of fatigue and, consequently, different effects of adaptation, which is in line with recent data from Tremblay et al.
In this combined exercise prescription model, the setting of work intensities should also be individualized and physiologically based by using turn point intensities as discerning markers for distinctly different metabolic, hormonal and cardio-respiratory responses Tschakert and Hofmann, ; Moser et al.
Figure 8. In addition, it allows a retrospective analysis of distances covered with given intensities in the past. It is, however, important to note that some authors also use fixed reference values for lactate such as 2 and 4 mmol. Our own results showed that La at LTP 1 was found at 1. As a consequence, high-volume training set above LTP 1 may get too close to a fatigue state that avoids repeating high volumes on a regular daily basis.
In addition, for low intensity exercise training, it is usually NOT intended to reach maximal duration t max but to apply a certain percentage of t max Table 1 in order to avoid fatigue and to guarantee the ability to repeat high volumes of training on a daily basis. However, we like to point out that dependent on the aim of a specific training period specific types of micro-cycles need to be structured combining exercise type, intensity, and duration.
Beside the attractiveness of the concept, several open questions and limits have to be addressed. Firstly, the chosen percentages of maximal duration are just marginally evidenced. To discern the low regenerative zone from a moderate zone without fatigue, a zone with compensated fatigue and finally zone 4 with clear fatigue needs to be taken with caution.
Carefully conducted studies and retrospective analysis of distances covered at defined intensities are needed to identify the stability or variability of these percentages for athletes with different age, training status and sex, and individual physiological markers are needed to guide the training. As could be shown in a pilot test Figure 6 , heart rate variability might be a potential parameter to identify these cut-off points for duration as discussed recently Kaikkonen et al.
Additionally, ratings of perceived exertion RPE scales may be helpful to identify these reference markers on a daily individual basis Garcin and Billat, ; Seiler and Sjursen, ; Coquart et al. A second important limit is the method to derive the power-duration or velocity—distance relationship. The intensity of your workout may also determine the duration of an exercise session.
Most people can maintain a brisk walk for a longer time than they can an all-out running pace, for example. The CDC notes that one minute of intense, or vigorous, activity equals about two minutes of more moderate activity. If you have aspirations to run a marathon or participate in a century bike ride, you'll have to endure long exercise sessions during training.
These long exercise duration sessions prepare you for these extreme events, but are not necessary if your goals are simply to stay healthy and fit. If you wish to lose weight, you may also need to undergo longer duration exercise sessions.
Harvard School of Public Health reports that to maintain weight loss, you may need to commit to at least an hour a day of exercise.
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