Quick Answer
Types of speed work: strides, fartlek, tempo/threshold runs, VO2max intervals, hill repeats, and track intervals. How much: 1–2 sessions per week, representing 15–20% of total mileage. When to start: after 4–8 weeks of consistent easy running base. Most underused workout: strides — short controlled accelerations that build speed with minimal fatigue risk, suitable at any level. First speed session to try: fartlek — unstructured effort surges during an easy run, no track required.
Before Speed Work: The Base Requirement
Speed work only pays off when there’s an aerobic foundation underneath it. The aerobic base — built through weeks of consistent easy running — is what gives your body the oxygen delivery capacity to recover between hard efforts and absorb the stimulus from speed sessions. Without it, hard sessions produce disproportionate fatigue relative to fitness return, and connective tissue that hasn’t adapted to easy running is unprepared for the higher-impact demands of intervals and tempo runs.
The practical threshold: runners should be able to comfortably sustain 30+ minutes of easy running and be logging consistent weekly mileage before adding structured speed sessions. A minimum of 4–8 weeks of consistent base training before introducing intervals is the standard coaching guideline. Strides and gentle fartlek are appropriate earlier; structured VO2max intervals and continuous tempo runs require more base. Our guide on building an aerobic base covers what this foundational phase should look like and how long the adaptations genuinely take — relevant context before rushing into speed work.
The 80/20 principle also applies here. Speed work should represent roughly 20% of your training at most — the other 80% stays at easy, conversational pace. Getting this ratio right is as important as what type of speed work you do. Our guide on easy run effort covers what genuine Zone 2 running feels like, and our Zone 2 pace guide gives the numbers — because if your easy runs are actually moderate-hard, your speed sessions won’t have the recovery foundation they need.
The Five Main Types of Speed Work
| Type | Effort / heart rate | Duration | Recovery | Primary adaptation | Best for |
|---|---|---|---|---|---|
| Strides | ~90–95% max HR; mile effort, controlled | 20–25 sec (80–120m) per rep | Full walk-back recovery between each | Neuromuscular efficiency; leg turnover; fast-twitch recruitment | All levels; 2–3×/week after easy runs; race activation |
| Fartlek | Varies — moderate to hard surges within easy run | 30 sec–5 min fast segments; continuous run | Easy jogging between surges (no stopping) | Aerobic and anaerobic conditioning; mental toughness; pace flexibility | Beginners starting speed work; all levels; track-free training |
| Tempo / threshold | ~80–88% max HR; "comfortably hard" | 20–40 min continuous, or broken (e.g. 3 × 10 min) | 1–2 min recovery for broken tempo; none for continuous | Raises lactate threshold; sustain faster pace longer | Half marathon and marathon preparation; runners wanting to hold pace |
| VO2max intervals | ~95–100% max HR; 5km effort | 3–5 min per rep (typically 800m–1600m) | Equal or slightly shorter recovery (jog) | Raises aerobic ceiling (VO2max); improves oxygen utilisation | 5km and 10km racing; building speed for longer distances |
| Hill repeats | Hard — similar to VO2max effort | 30 sec–2 min uphill per rep | Walk or easy jog down | Leg strength, power, and running economy; reduced injury risk vs flat speed | All levels; especially useful without a track |
Strides: The Most Underused Speed Session
Strides are short controlled accelerations — 80 to 120 metres, roughly 20 to 25 seconds — run at approximately mile race effort. Not all-out. Fast, but controlled and smooth, with full walking recovery between each. Four to six strides after an easy run, two or three times per week, is one of the highest-value additions a recreational runner can make to their training.
The adaptation is primarily neuromuscular rather than cardiovascular. Strides teach your legs to move at a faster turnover, recruit fast-twitch muscle fibres that easy running never touches, and maintain the running mechanics associated with speed — upright posture, quick foot contact, relaxed arms — without generating meaningful fatigue. Because they’re short and the recovery is complete, they don’t produce the cumulative fatigue of interval sessions and can be added to easy run days without compromising the following day’s training.
Many runners who feel heavy-legged and “stuck at one pace” improve meaningfully by adding nothing more than strides after their easy runs for 4–6 weeks. The legs learn a faster gear without the body being overloaded. For runners beginning to introduce speed work, strides are the right starting point.
Fartlek: Speed Work Without a Track
Fartlek — Swedish for “speed play” — is the most accessible form of structured speed work. The concept is simple: during an easy run, insert surges of faster effort based on effort or landmarks, with easy jogging between them rather than stopping to rest. You decide the duration and intensity on the fly, based on how you feel and what’s around you. Run hard to the next lamppost, jog to recover, run hard again for 60 seconds, recover — whatever combination suits the day.
Because the recovery segments are jogged rather than walked or stopped, the overall heart rate stays higher than track intervals — your cardiovascular system is working continuously even as you recover from each surge. This makes fartlek a genuinely dual-mode workout: it develops both aerobic endurance and anaerobic speed within a single session, in a format that’s adaptable to any terrain and requires no track, watch, or precise pacing.
A structured fartlek option that works well for runners building from easy training into quality sessions: after a 10-minute easy warm-up, alternate 1 minute at hard effort (roughly 5km effort) with 2 minutes easy jogging, repeated 6–8 times, followed by a 10-minute easy cool-down. Total session around 40–45 minutes. The effort during the surges should feel hard but not maximal — you should be able to complete each rep at similar quality. If the later reps feel significantly harder than the first, the surges were too fast.
Tempo Runs: The Cornerstone of Race Preparation
Tempo runs target the lactate threshold — the intensity at which lactate begins accumulating in the muscles faster than it can be cleared. Training at and slightly above this threshold raises it over time, meaning you can run faster before lactate accumulation becomes limiting. For half marathon and marathon runners especially, raising the lactate threshold is the most direct route to a faster race time.
The effort is distinctive and recognisable: comfortably hard. You’re breathing steadily and working, but it’s sustainable. You could say a few words, but not hold a flowing conversation. Heart rate sits between 80 and 88% of maximum. Running coach descriptions often call it the “threshold pace” or sometimes “marathon pace plus a bit” for well-trained runners. In practice, most recreational runners run their tempo pace somewhere between 10km and half marathon race pace.
The classic tempo run: 10–15 minutes easy warm-up, 20–40 minutes at threshold effort, 10 minutes easy cool-down. Total session 40–65 minutes. For runners who find sustained tempo effort difficult, broken tempo intervals work the same adaptation: 3 × 10 minutes at threshold effort with 2-minute easy recoveries, for example. Same stimulus, more manageable structure. The continuous version is better preparation for race-day sustained effort; the broken version allows better quality control on the threshold effort for newer speed workers.
For runners training for a half marathon or marathon, tempo work is particularly high-value. Our half marathon training plans and marathon training plans both build threshold work into the weekly structure as the primary quality session during the build phase. The running pace calculator can help you find your tempo pace based on recent race times — threshold pace for most recreational runners is approximately 25–35 seconds per kilometre slower than their 5km race pace.
VO2max Intervals: Raising Your Ceiling
VO2max intervals are the hardest sessions in most runners’ programmes — short, fast repetitions at 5km race effort or slightly faster, targeting the aerobic ceiling rather than the threshold floor. The adaptation is an increase in VO2max itself: your heart pumps more blood per beat, your muscles extract more oxygen, and your capacity for sustained fast running improves.
The effort is clearly hard — breathing is heavy, you can’t speak, and you’re working close to your limit. The sessions are short by necessity: 3 to 5 minutes per repetition, with recovery jogging of equal or slightly shorter duration. Classic structures include 5 × 1000m with 90-second jog recovery, or 6 × 800m with 2-minute recovery.
The key coaching principle for VO2max intervals: if you can’t maintain the same pace and effort on the final rep as the first, the pace was too fast or the recovery too short. These sessions should be challenging but executable. Starting conservatively is always correct — the adaptation comes from hitting the stimulus consistently, not from going to absolute maximum on the first rep and deteriorating through the session.
VO2max intervals are most appropriate 8–12 weeks before a goal race, in the sharpening phase after the base and threshold work is established. They’re typically not the right starting point for speed work — tempo and fartlek build the threshold foundation that makes VO2max intervals productive.
Hill Repeats: The Track Alternative
Hill repeats produce similar cardiovascular demands to VO2max intervals with lower impact stress on the joints. Running uphill naturally shortens stride length, reduces ground contact time, and increases muscular effort — you get a hard workout with less of the braking force that creates injury risk on flat fast running.
A simple hill repeat session: find a moderate hill (6–8% grade) that takes 60–90 seconds to run hard. After a 10–15 minute warm-up, run hard uphill for the full repeat, walk or jog back down as recovery, and repeat 6–8 times. The effort uphill should be hard — genuinely hard, like the end of a 5km race. The down recovery should be complete enough that each uphill rep is hit with similar quality.
Hill repeats are particularly useful for runners without track access, runners who find track intervals mentally difficult, and runners who want to build leg strength alongside cardiovascular conditioning. They’re also appropriate earlier in a training cycle than flat VO2max intervals, as the lower impact means lower injury risk during periods when connective tissue is still adapting to running volume.
How to Structure Speed Work in Your Week
The placement of speed sessions within the week matters as much as the sessions themselves. The basic principles:
Never two hard sessions back-to-back. A quality session on Tuesday means the next quality session should be Thursday at the earliest — 48 hours minimum between hard efforts. This applies to both running speed sessions and other demanding activities like heavy strength training.
The long run is also a quality session. If your week has a long run on Saturday, that’s one quality commitment for the week. Adding a second quality session on Tuesday (not Wednesday or Friday) is the reliable structure: hard Tuesday, easy Wednesday, hard (long run) Saturday, easy everything else.
Strides don’t count as quality sessions in the same sense — they can be added to easy run days without disrupting this structure. They’re metabolic cost is low enough that they don’t require the same recovery window as tempo or intervals.
| Runner type | Speed work per week | Recommended structure |
|---|---|---|
| Beginner (building base) | Strides only; no structured intervals yet | 4–6 strides after 2–3 easy runs per week |
| Intermediate (consistent runner, some races) | 1 quality session + strides | Tuesday fartlek or tempo; strides after 2 easy runs; Saturday long run |
| Advanced (racing, structured plan) | 2 quality sessions + strides | Tuesday threshold/tempo; Thursday VO2max or hills; strides midweek; Saturday long run |
For runners following a structured marathon or half marathon plan, speed work is periodised — threshold work dominates the build phase, VO2max work sharpens form in the final 6–8 weeks, and speed work reduces to maintenance during the taper. Our guide on building marathon mileage safely covers how quality sessions integrate into a progressive mileage plan without overloading the training week.
Common Speed Work Mistakes
Going too fast on intervals. If the last rep is significantly slower than the first, the pace was too fast. CorrerJuntos’s coaching guidance puts it well: if you can’t maintain the same pace on the last rep as the first, you started too hard. Start conservatively — you can always push harder on subsequent sessions once you know the session is manageable.
Skipping the warm-up. A minimum of 10–15 minutes of easy jogging before any speed session, ideally followed by 4–6 strides. Cold muscles don’t respond to fast running the way warm muscles do, and the injury risk at the start of a session without warm-up is meaningfully higher. The warm-up isn’t optional time you can abbreviate when you’re short on time — it’s the part that makes the session productive and safe.
Adding speed work without the base. Speed work on an aerobic base that isn’t established yet produces a high fatigue-to-adaptation ratio. You feel the sessions. You don’t feel the benefit. And connective tissue that’s still adapting to easy running is at genuine injury risk from the higher-impact demands of track intervals. Build the base first.
Too many quality sessions. More than two quality sessions per week is only appropriate for runners who have been training consistently for years at significant volume. For most recreational runners, two hard sessions per week is already the edge of what’s productive. A third hard session typically produces fatigue accumulation without proportional fitness return.
No cool-down. 10 minutes of easy jogging after the main set clears metabolic waste products from the muscles, begins the recovery process, and reduces next-day soreness. It’s not optional.
For older runners, the speed work principles are the same but recovery between sessions takes longer. An extra recovery day between quality sessions — Tuesday quality and Friday quality rather than Tuesday and Thursday — often produces better adaptation than the shorter window that works for younger runners. Our guide to speed training for older athletes covers how speed work should be adapted for runners over 50, including how to maintain fast-twitch muscle function that becomes increasingly important with age.
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FAQ: Speed Work for Runners
How often should runners do speed work?
1–2 quality sessions per week for most recreational runners. Allow 48 hours between hard sessions. Speed work should represent 15–20% of total weekly mileage. More than two quality sessions per week is only appropriate for runners with a substantial training history at high volume.
What is a tempo run?
A sustained effort at your lactate threshold pace — comfortably hard, where you could say a few words but not hold a conversation. Run for 20–40 minutes continuously or as broken intervals. The primary adaptation is a higher lactate threshold, which improves 10km to marathon performance directly.
What is the difference between intervals and tempo runs?
Tempo runs are sustained at threshold pace for 20–40 minutes with minimal recovery. Intervals are shorter, faster efforts (typically 800m–1600m at 5km effort) separated by structured recovery jogs. Tempo targets the threshold; intervals target VO2max. Both are valuable at different points in a training cycle.
When should I start doing speed work?
After 4–8 weeks of consistent easy running base at 15–20 miles per week. New runners should start with strides and fartlek before progressing to structured intervals and tempo runs. Adding speed work before the base is established produces more injury risk than fitness benefit.
What are strides in running?
Short controlled accelerations of 80–120m at mile effort, with full walking recovery between each. Done 4–6 times after an easy run, 2–3 times per week. The most accessible and underused speed session — they build neuromuscular efficiency and leg turnover without generating meaningful fatigue.
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