Should you be doing strides and sprints as a trail, fell or ultra runner?
Sprints and/or strides are common features in many running training plans, and are used extensively by athletes across a variety of ability levels and disciplines. They are also a popular choice for club interval training sessions, in part because they are easy to do with a mixed-ability group, can be performed in a relatively small space, and tend to be enjoyed by most runners.
In this article, we’ll take a detailed look at the evidence and theory supporting the use of sprints and strides in training, whether there are any particular risks, how these sessions might apply to fell, trail and ultra-running specifically, and finally provide some key tips for incorporating these sessions in your training.
Let’s start first with some definitions, so we’re all clear what we’re talking about…
What are sprints?
Sprints are hard efforts that last for 5-seconds to 30-seconds.
They are performed at an ‘all-out’ intensity, sometimes with a gentle build-up into the effort. This means you begin sprinting as fast as you can, and then aim to maintain this maximal pace for the full duration of the effort. You don’t hold anything in reserve for later in the effort.
A long recovery is employed between sprints (at least 5x the length of the sprint). This allows for full recovery, so that each sprint can be performed maximally.
What are strides?
Strides are ‘near-maximal’ efforts that typically last for 15-30 seconds.
They usually involve a gradual acceleration up to a 8-9/10 effort over the first ~5-10 seconds. This near-maximal speed is then maintained for another 5-10 seconds, before a gradual deceleration for 5-10 seconds.
In contrast to sprints, which aim to have you running as fast as possible, the focus of strides is on maintaining good running technique, form and a fast cadence. So you shouldn’t be running so fast that your form goes out the window.
A long recovery is employed between strides (at least 5x the length of the stride, and often more). This allows for full recovery, so that each stride can be performed with good technique.
Evidence of Training Benefits
Now we know what we mean by sprints and strides, lets look at what evidence exists to support their use…
Benefits of Sprints
1. Increased speed
Many studies show that sprint training is beneficial in improving running speed, particularly at high intensities.
For example, just 2 weeks of sprint training (3 sessions per week, including 4-7x 30-second all-out sprints with 4-min walking recovery, performed on the track) resulted in an improvement in ‘maximal aerobic speed’* of 2.3%. The time taken to complete a 3km time trial on the track was also reduced by 6%. This study involved a group of 16 moderately trained trail runners (Koral et al., 2018).
Another study (Skovgaard et al., 2018) showed that 10 sprint sessions over a 40 day period improved 10km running pace by 3-4% among 20 well-trained runners, showing that speed improvements also carry over to somewhat longer distances/durations too.
* Maximal aerobic speed is the speed reached in incremental test to exhaustion, where participants run in stages of increasing pace until they cannot maintain then target pace. It roughly translates to the maximum speed you’d be able to hold for 5-8 minutes.
2. Increased aerobic fitness
There are a whole host of studies that show that sprint training can help improve a wide variety of aerobic fitness attributes.
However, most of these studies compare athletes who perform sprint training with athletes who perform no exercise at all, and the participants are often untrained individuals. So, it’s not surprising that these studies show a benefit, and we need to be careful that we don’t over-exaggerate the benefits of sprint training.
Indeed, there is very little evidence that suggests sprint training enhances aerobic fitness more so than any other type of running training. It may just be training per se (at any intensity) that confers these benefits, rathe than the sprints themselves.
That said, there is one study in cyclists that showed that the addition of 3x 30-second sprints per hour (each sprint separated by 4-mins recovery) within a long ride might enhance aerobic adaptations above and beyond the adaptations from just riding at a low intensity (Almquist et al., 2021). The evidence here is very early-stage, since this study only looked at markers in the blood immediately after a training session to infer the likely adaptations that might take place. It did not implement a long-term training intervention to look at the actual real-world benefits. So further research is certainly needed in this area.
A review by Bishop et al. (2014) also shows the importance of high intensity training such as sprints in developing aspects of mitochondrial function, helping improve the capacity of existing mitochondria to process oxygen and produce energy. These adaptations seem to be stimulated mostly by high-intensity training, so sprints can help in this regard, though other forms of high-intensity training will also do the trick here.
Ultimately, sprint training is probably useful in developing aerobic fitness as part of a well-rounded training plan, and can provide important high-intensity training that may be needed to fully optimise aerobic fitness, though it’s certainly not essential to achieve this.
3. Improved running economy/efficiency
One of the most commonly-cited benefits of sprint training is that it helps improve running economy. Running economy is a measure of the amount of oxygen it takes to run at a given speed. Having a good running economy is important for most fell, trail and ultra races, because it allows you to run at a faster speed for the same aerobic fitness level, and because it may allow you to conserve more fuel (i.e. muscle glycogen) over longer events (more on this below…).
There is good evidence that the inclusion of sprints within training can help improve running economy across a range of running intensities. This is true when efforts are performed both on the flat (Skovgaard et al., 2018) and on hills (Ferley et al., 2014).
For example, a study of 20 well-trained male and female runners found that 40 days of ‘speed endurance’ training, involving 10 sessions of 6-10x 30-second all-out sprints** alongside a 36% reduction in usual training volume, resulted in a 2% improvement in running economy both when running at 60% VO2max (roughly a Zone 2 intensity) and at 10km pace (Skovgaard et al., 2018).
The root cause of this improvement in improved economy is unknown, and it’s likely multi-factorial.
There is some evidence that this improvement in economy may at least partly come from an improvement in mitochondrial efficiency, meaning that there is less energy-wastage by the mitochondria when generating energy (Skovgaard et al., 2018).
It may also be partly attributable to improved biomechanics and neuromuscular activation, meaning that muscle fibres can be activated more efficiently (e.g. with motor neurons firing in synchrony for stronger force development), and to support a more efficient running form. Indeed, the benefits of sprint training in forging stronger and more effective neuromuscular connections is well known (Creer et al., 2004; Mero et al., 1992).
** The first and last session included 6 sprints. All other sessions included 10 sprints. Sprints were separated by 3.5 minutes of walking recovery. All other running was a moderate intensity (roughly Zone 3).
4. Aerobic Priming
Finally, another benefit of sprints seems to be that they help to ‘prime’ the aerobic system ahead of a race.
Research shows that including sprints within a training session 1-3 days before a race can help speed up so-called ‘VO2 on-kinetics’ on race day (Iannetta et al., 2022). This means your aerobic system ramps up it’s contribution to energy production more rapidly at the start of a race. The faster the aerobic system ramps up, the less you have to rely on anaerobic energy sources that cause a build-up of fatiguing metabolites. Or in other words, quicker VO2 on-kinetics means less fatigue! This is particularly important for shorter races (e.g. 30-mins or less), or races that start hard (e.g. with a hill).
If you want to learn more about VO2 kinetics and the importance of priming, then check out our article on our cycling site here.
Benefits of Strides
Strides are an extremely common feature of running training plans, and are used by professional and amateur runners alike. They have been around for decades. However, we are not aware of any scientific literature specifically looking at the benefits of strides.
We have seen articles that use evidence from sprinting studies to support use of strides in training. However, strides are really quite different, since they are not performed at an all-out intensity.
Mechanistically, performing an all-out sprint results in rapid and severe deoxygenation in muscle capillaries, and a high level of muscle fibre recruitment. These are likely to be important stimuli for many of the benefits of sprint training (e.g. improved mitochondrial efficiency and capacity, aerobic priming, neuromuscular developments). It’s not clear whether the intensity of strides is sufficient to bring about these same training benefits, and we certainly cannot look to sprint studies to support the use of strides.
That said, there is a great deal of anecdotal evidence that strides do seem to have a benefit.
In our view, these benefits are probably largely biomechanical and neuromuscular, helping teach the muscles to fire effectively, and helping improve running efficiency, form and stride rate. Running form is inherently better when running at a faster pace, and so repeating strides may help build muscle memory for good running form. Since strides are short, it’s also possible to focus closely on correcting any known weaknesses in running technique while you perform these drills.
There’s even an argument that strides might be better than sprints for developing running form, since the intensity is lower, and your biomechanics will more closely resemble the biomechanics of normal fell, trail or ultra-running. This hasn’t been shown in research, but the theory makes sense.
Another benefit of strides can be in helping introduce newer runners to higher-intensity running. Since the duration is short, and intensity is moderate (relative to the interval length), they are relatively low-risk. They can therefore be a good way to begin to build higher-intensity running into your plan if you’ve not done much of this before, allowing chance to condition muscles and ligaments for higher-intensity running.
Strides may also be useful during a warm-up before a race or high-intensity training session, since they will help to activate higher-power (Type II) muscle fibres and may help to prime the aerobic system ahead of the main session or race.
It’s worth reiterating that these benefits are based on theory rather than hard evidence, but we do feel there’s a likely benefit to using strides in these contexts.
Hills vs flat?
A question that arises when it comes to both sprints and strides is whether they should be performed on the flat, or on an incline.
Studies show that improvements in running economy are seen when sprints are performed both on the flat (Skovgaard et al., 2018) and on hills (Ferley et al., 2014), and there’s likely to be a lot of overlap between the benefits you’ll get from hill sprints vs flat sprints.
However, there are some biomechanical differences, and it’s worth thinking about what you’re hoping to achieve from the efforts, as well as your own individual weaknesses and risk factors when deciding where to perform your efforts.
Sprinting or striding up hills tends to elicit lower overall speeds, and demands more force over a longer time-frame from each leg strike than running at the same intensity on the flat. Thus, sprints and strides on an incline are often said to be better for developing muscular strength when compared to running on the flat. That said, there are far better methods for developing strength (i.e. lifting heavy weights). So we don’t think this is a particularly strong argument for choosing hill sprints/strides over flat sprints/strides.
It’s also easier to hit a higher overall intensity (in terms of oxygen consumption and metabolic demand) when running on a hill. This is because running on the flat is often limited more by how powerfully you can contrast your muscles (a combination of force and speed), rather than your aerobic abilities. Since hill sprints are performed at a slower speed, with the hill providing additional resistance, it’s easier to reach a higher aerobic intensity. So the aerobic benefits of hill sprints/strides might be higher.
In contrast, sprints and strides on the flat tend to be performed at a higher speed, with a shorter ground contact time (meaning higher impact), and lower overall exercise intensity. Thus sessions on the flat might have a bigger neuromuscular and biomechanical benefit, especially if you’re looking to develop leg speed and power.
When we think about which terrain might be best, it’s also good to think about your injury risk. It’s often said that hill efforts are safer than flat efforts because the absolute speeds and level of impact are lower.
However, as fell, trail and ultra-runners, we’re already often completing a lot of milage on hills, and we may already have a predisposition for hill-related injuries (e.g. injured calves and achilles tendons, which tend to be worked harder on hills). Therefore, if you already have a niggle or injury in these areas, then flat sprints and strides might actually be a lower-risk option (provided you condition yourself appropriately, as we’ll come onto below…).
Relevance to trail, fell and ultra running
In almost all research that explores the benefits of sprint training, running tests have been performed either on a treadmill or on a flat track. Given most trail, fell and ultra races involve considerable climbing, and all involve uneven terrain, this begs the question of whether and how the benefits translate over to fell, trail and ultra-running.
Based on the evidence and theory, there are several key ways that sprints and strides may help:
1. Faster cadence for improved descending speed
Having quick leg turnover is very important for fast descending off-road, since it allows you to place your feet closer to your centre of gravity and reduce your risk of slipping. Sprints and strides both probably help in this regard, and you could even try doing some strides on a slight down-hill gradient to make these efforts more trail-specific.
If your main goal is to improve cadence for descending, then we’d recommend using strides rather than sprints, since the injury risk is lower.
2. Better leg power for jumping bogs/obstacles, and ascending steep gradients
Sprint training (and possibly strides) improve the ability to recruit high-power (particularly Type IIx) muscle fibres, and this translates to an improvement in leg power - i.e. the ability contract your muscles forcefully and quickly. This can be very useful in off-road running, and particularly fell running, where you often need to hop from tussock to tussock, or maybe even leap a wall! It may also help with powering up short sections of particularly steep gradient quickly.
We’d recommend a mixture of sprint-based sessions to develop leg power, incorporating a mixture of flat sprints (which will probably help develop power and contraction speed best) and hill sprints (which will activate muscles in a more race-specific way).
3. Faster running speed up to ~1-hour of racing
Sprints seem to help improve running speed in efforts lasting ~1-hour or less, which is relevant to many fell and trail races. They seem to be particularly beneficial over shorter efforts, so might be especially relevant in hilly races, where you’re intermittently running hard for shorter bursts of time.
We’d recommend using hill sprints over flat sprints to develop running speed if you generally participate in hilly races, or flat sprints if you’ll generally be competing on flatter terrain. This will allow you to activate your muscles in the most race-specific way. It’s unclear whether strides would be beneficial in developing running speed to the same extent as sprints. The biggest benefit of strides is probably in helping increase cadence, which may be useful for improving speed in flatter fell and trail races.
4. Better endurance (perhaps)
Since sprints (and perhaps strides) seem to improve running economy, there’s an argument that they might help develop endurance, since an improvement in economy should mean less fuel is required to run at a given pace. As endurance is mainly limited by the body’s glycogen (i.e. carbohydrate) stores, and more particularly its ability to conserve these stores, then a better economy might help with glycogen conservation.
It’s not quite as simple as this though, since the ability to conserve glycogen also depends on the ability of the body to use fats for fuel, and it’s unclear if and how sprint training might affect this. A large amount of sprint training would tend to increase your propensity for glycolysis and decrease your propensity for fat oxidation.
Moreover, interestingly, the improvement in economy seen in Skovgaard et al. (2018) was only observed when muscles were high in glycogen. In a glycogen-depleted state, as you’d typically begin to see towards the end of any race lasting 2-hours or more, there was no measurable improvement in economy, which might suggest that sprint training doesn’t translate over to longer duration events quite so well (though there was still an improvement in 10km pace even in the glycogen-depleted state).
Ultimately the benefits of sprints and strides for races lasting more than ~3-hours is less clear.
5. Better Race Starts
As mentioned above, sprints can help ‘prime’ the aerobic system and improve the speed of ‘VO2 on-kinetics’, or in other words, how quickly the aerobic system ramps up at the start of a race. This is directly relevant to many off-road races, such as those that start with a hill (common for many short fell races!), or those where a fast start is useful to avoid getting caught up in any bottlenecks.
Flat or hill sprints will do the trick here, and these efforts can be included in any session 1-3 days ahead of a race. Strides are probably not intense enough to have the same priming effect.
Top tips for performing strides
Generally, you’ll want to perform between 4-10 strides per session, taking a full recovery between each effort (at least 2.5 minutes) either walking or jogging very lightly depending on fitness level.
It’s not necessary to time strides accurately. Beginners can start by accelerating over 5 seconds, simply counting this up in your head, then maintaining pace for 5-seconds, and finally decelerating over 5 seconds. As you become more familiar with these efforts, you can extent the main portion of your strides to roughly 15-20 seconds.
Focus on form and keep your upper body relaxed with shoulders and arms loose. Your shoulders shouldn’t be tensed up towards your ears, and you shouldn’t be driving your arms hard like you would with a sprint. The optimal running form is very individual, so just try to keep your body position that feels natural and similar to the way you’d run if you were racing a 5km, for example. Focus on fast, light feet so you can work on increasing your ability to run at higher cadences.
Strides are best performed on the road or a section of smooth trail, so that you can focus completely on your form, and not the technical features ahead. You can choose to do these efforts on a slight down-hill, flat or up-hill depending on your injury risk and the specific adaptations you’re looking to get from the session.
Since strides add minimal fatigue, they can be included up to 4x per week, either as part of a warm-up for a main session, or towards the beginning or end of a steady endurance run.
Top tips for performing sprints
Only perform sprints once you’re familiar with strides, and have been performing strides regularly for at least a month.
Don’t perform sprints if you have any existing injuries, since they are high-risk, and consider whether hill or flat sprints might be more appropriate for your own personal injury history/predispositions.
You should warm up thoroughly before doing any sprinting, with at least 20-minutes of gentle running, some strides and optionally some mobility drills.
Sprints are best performed on the road or non-technical trail to reduce the risk of tripping. Impact on the road will be higher, which might be beneficial if looking to specifically develop leg power.
Some coaches recommend beginning with hill sprints earlier in the training cycle and then transitioning to flat sprints later in the cycle. This is because hill sprints are often considered to have a lower injury risk, allowing you to condition muscles and ligaments to all-out running in a more progressive way. However, as mentioned above, if your training already involves a lot of hill running and you are predisposed to hill-related injuries, then flat sprints might actually be safer (provided you’ve done some flat strides to begin conditioning your muscles and ligaments as mentioned above).
Sprints should be included no more than 2x per week, with 6-10 sprints per session. Take at least 5x the length of the sprint as recovery.
Try to include sprint training only at appropriate points in the year (such as in the lead—up to key races). The study by Skovgaard et al. (2017) showed that 10 sprint sessions over 40 days was enough to improve 10km performance, and that continuing sprint training beyond this period, even when increasing the frequency of sprint to every other day, didn’t result in any additional improvement. In this study, performance over shorter durations did continue to improve with a further 20 sessions. So depending on your race goals, something between 10-20 sprint sessions over 2-4 months should be enough to maximise training benefits.
To reduce injury risk, you should build into your sprint over the first 5-seconds. Then aim for the maximum pace you can hold for the remainder of the effort. Don’t worry if you start to slow down toward the end of the sprint.
Finally, if you’re doing sprints regularly, we would suggest that you don’t also need to be doing strides. Your energy is probably best spent doing something different so that your training remains well-rounded and varied!
Conclusion
In summary, both sprints and strides have potential benefit to trail, fell and ultra runners.
Although strides have minimal scientific evidence to support their use, they create very little fatigue and have a low risk, while allowing activation of higher-power (Type II) muscle fibres that are not usually worked during lower-intensity running. In our view they are worth including in a running program for all off-road disciplines, since the potential benefits seem to outweigh the risks for most runners.
Sprints probably confer additional benefits above and beyond those provided by strides, but there is a risk tied with these, and they cause considerably more fatigue. So we’d only recommend using sprints if there is a specific benefit for the types of racing you do. Sprints are probably not the most optimal session choice if you are mainly targeting races that last longer than ~3-hours.
References
Almquist, N. W., Ellefsen, S., Sandbakk, Ø., & Rønnestad, B. R. (2021). Effects of including sprints during prolonged cycling on hormonal and muscular responses and recovery in elite cyclists. Scandinavian Journal of Medicine & Science in Sports, 31(3), 529-541.
Creer, A. R., Ricard, M. D., Conlee, R. K., Hoyt, G. L., & Parcell, A. C. (2004). Neural, metabolic, and performance adaptations to four weeks of high intensity sprint-interval training in trained cyclists. International journal of sports medicine, 25(02), 92-98.
Bishop, D. J., Granata, C., & Eynon, N. (2014). Can we optimise the exercise training prescription to maximise improvements in mitochondria function and content?. Biochimica et Biophysica Acta (BBA)-General Subjects, 1840(4), 1266-1275.
Ferley, D. D., Osborn, R. W., & Vukovich, M. D. (2014). The effects of incline and level-grade high-intensity interval treadmill training on running economy and muscle power in well-trained distance runners. The Journal of Strength & Conditioning Research, 28(5), 1298-1309.
Iannetta, D., Inglis, E. C., Maturana, F. M., Spigolon, G., Pogliaghi, S., & Murias, J. M. (2022). Transient speeding of V̇O2 kinetics following acute sessions of sprint interval training: similar exercise dose but different outcomes in older and young adults. Experimental Gerontology, 164, 111826.
Koral, J., Oranchuk, D. J., Herrera, R., & Millet, G. Y. (2018). Six sessions of sprint interval training improves running performance in trained athletes. Journal of strength and conditioning research, 32(3), 617.
Mero, A., Komi, P. V., & Gregor, R. J. (1992). Biomechanics of sprint running: A review. Sports medicine, 13, 376-392.
Skovgaard, C., Almquist, N. W., & Bangsbo, J. (2017). Effect of increased and maintained frequency of speed endurance training on performance and muscle adaptations in runners. Journal of applied physiology, 122(1), 48-59.
Skovgaard, C., Christiansen, D., Christensen, P. M., Almquist, N. W., Thomassen, M., & Bangsbo, J. (2018). Effect of speed endurance training and reduced training volume on running economy and single muscle fiber adaptations in trained runners. Physiological reports, 6(3), e13601.
