11 Half Marathon Workouts for Runners Who Know Their Paces
The half marathon lives in your lactate threshold zone: the hardest pace you can hold before fatigue starts snowballing. For elite runners, HM pace sits right at their threshold. For well trained amateurs, it falls just below it, somewhere between the aerobic and anaerobic thresholds. Either way, the relationship between your LT and your half marathon pace is tighter than at any other common race distance.
That’s what makes this distance so trainable. Your threshold can shift meaningfully in as little as 6 weeks of targeted work. Research (Noakes et al., 1990) found that speed at lactate threshold correlated at r = 0.90 with half marathon finishing time, making it one of the strongest lab measured predictors of HM performance alongside peak running speed.
So the workouts that matter most are the ones that push that threshold higher.
These sessions assume you have an established HM pace or a recent race result you can plug into the Jack Daniels VDOT calculator. All paces are based on current fitness, not goal pace. Train where you are and the paces will move forward on their own.
1. Alternating HM Pace
| Session | 4 x (3K @ HM pace / 1K float @ marathon pace) |
| Total quality | 16K (12K HM pace + 4K marathon pace) |
| When to use | Race specific phase, 4 to 8 weeks out |
The marathon pace floats aren’t recovery. They’re active clearance. You run 3K at HM pace, building lactate, then drop to marathon pace just long enough for your body to process it before the next rep hits. Four rounds of that and you’ve banked 16K of quality without ever fully stopping. This is one of the best race specific sessions you can do.
2. Sub and Over Threshold
| Session | 1K slightly below threshold / 1K slightly above threshold, repeat 6 to 8x continuous |
| Paces | “Below” = ~15K to HM pace. “Above” = ~10K pace. |
| When to use | Build phase through race specific |
You’re bouncing above and below your threshold the entire session. The faster kilometres push lactate production up. The slower kilometres force your body to clear it without stopping. No standing rest between reps. Thirty to sixty seconds jog max, and many coaches run this fully continuous. Start at 6 rounds and build to 8 as fitness develops.
3. Long Tempo + Pace Sharpening
| Session | 12K tempo @ marathon pace, then 3 x 1200m @ HM pace (90 to 120 sec jog recovery) |
| Total quality | ~15.6K |
| When to use | Race specific phase. Follow with an easy or off day. |
The 12K tempo is the setup, not the main event. You build a deep fatigue over marathon pace, then shift into HM pace for the 1200s. That’s where the adaptation lives. Locking in race pace on legs that already have 12K of work in them is exactly what kilometres 16 to 21 feel like on race day. Big session. Respect the recovery afterward.
4. Alternating Pace (Volume Variant)
| Session | 5 x (2K @ HM pace / 500m float @ marathon pace) |
| Total quality | 12.5K (10K HM pace + 2.5K marathon pace) |
| When to use | Midweek quality day, any phase |
Same concept as Workout 1, lower volume. This is your midweek option when the weekend long run is carrying the primary load and you need quality without the 16K commitment.
5. Broken Threshold (Cruise Intervals)
| Session | 6 x 6 min @ LT1 (marathon pace intensity) with 60 to 90 sec jog recovery |
| Total quality | 36 min at ~75% VO2max |
| When to use | Base phase and early build. Good re-entry session after a recovery week. |
This is your bread and butter aerobic builder. Marathon pace intensity for 6 minute chunks with short jog breaks. The effort should feel “comfortably hard.” You could get a few words out but you wouldn’t want to hold a conversation. Nothing flashy here. Just honest aerobic work that compounds over weeks.
6. Progressive Long Run
| Session | 6K steady / 6K @ marathon pace / 6K finishing @ HM pace |
| Total quality | 18K (plus warmup and cooldown) |
| When to use | Every other week during build and race specific phase. Replaces your normal long run. |
The Kenyan staple. Start slow, finish fast. By the time you hit the final 6K at HM pace, your slow twitch fibres are fatiguing and your body starts recruiting fast twitch fibres to keep up. Training those fibres under aerobic load is exactly what you need for the final third of your race. Alternate this with an easy long run on off weeks.
7. Cut Down Tempo
| Session | 5K @ marathon pace / 4K @ HM pace / 3K @ 10K pace / 2K @ 5K pace (continuous, no recovery) |
| Total quality | 14K across the full aerobic spectrum |
| When to use | Sharpening phase, 3 to 5 weeks out |
Descending distance, ascending intensity, no rest. Each segment gets shorter as the pace increases, so no single block buries you. You touch every energy system in one continuous run and you finish the session at your fastest. There’s a real psychological benefit to that. Finishing fast on tired legs builds the kind of confidence that pays off at kilometre 19 when your brain starts negotiating.
8. HM Specific Repeats
| Session | 4 x 3K @ HM pace with 2 min jog recovery |
| Total quality | 12K at race pace |
| When to use | Build through race specific. Versatile enough to use weekly. |
Sometimes simple is the right call. Twelve kilometres at race pace, broken into manageable 3K chunks. The only goal is precision. Hit the pace. Run smooth. Don’t drift faster, don’t drift slower. The half marathon is a pace discipline race, and this is how you train that discipline.
9. Short Rep Alternations
| Session | 8 x (1K @ HM effort / 1K float 30sec/km slower than HM pace), continuous |
| Total quality | 16K (8K HM effort + 8K float) |
| When to use | Race specific phase, 5 to 6 weeks out |
Same alternation principle as Workouts 1 and 4, but with shorter 1K reps and more rounds. The faster turnover between efforts means you never fully settle into either pace. You’re constantly switching gears, which trains the neuromuscular and metabolic systems to handle pace changes without panic. The float is defined by feel (30sec/km slower) rather than a fixed pace like “marathon pace,” which makes this more intuitive on hilly or variable terrain. Good option for runners who find the 3K reps in Workout 1 mentally heavy.
10. Descending HMP Intervals
| Session | 3 x (4K @ HM effort / 1K easy jog). Rep 1: 2 to 4 sec/km slower than HMP. Rep 2: at HMP. Rep 3: 2 to 4 sec/km faster than HMP. |
| Total quality | 12K at or near HM pace + 3K easy |
| When to use | Race specific phase, 4 to 6 weeks out |
The descending pace structure is the key here. You start conservatively, find your rhythm on the second rep, then push slightly past race pace on the third. This teaches you to run negative splits under fatigue, which is exactly how a well executed half marathon should feel. The 1K easy jogs between reps give you enough recovery to maintain quality across all three. The 4K rep length is long enough to force honest pacing. You can’t fake 4K.
11. Per Kilometre Progression
| Session | 18K continuous, getting faster every single kilometre. Start very easy, finish at 10K pace. Aim to increase by 5 to 10 sec/km each kilometre. |
| Total quality | 18K (plus 2K cooldown jog) |
| When to use | Race specific phase. Replaces your long run. |
This is the most demanding progression run in the collection. Unlike Workout 6 where you shift pace in 6K blocks, here you’re making a deliberate pace increase every single kilometre for 18 consecutive kilometres. The early kilometres should feel almost too easy. That’s the point. You’re building an aerobic reserve that you’ll spend in the final 4 to 5K when you’re running at 10K effort on legs with 14K of accumulated fatigue. The per kilometre discipline also trains pacing awareness better than any other session. If you can nail this workout, you know your fitness is there.
Programming Guide
All workouts include 15 to 20 minutes warmup (easy jog plus drills) and 10 to 15 minutes cooldown. Standard week: 2 quality sessions + 1 long run. Remaining days easy.
| Phase | Weeks | Primary Sessions |
|---|---|---|
| Base | 1 to 4 | Broken Threshold (#5) + easy long runs |
| Build | 5 to 8 | Sub/Over Threshold (#2) or Alternating Pace (#4) midweek. Progressive Long Run (#6) every other weekend. |
| Race Specific | 9 to 14 | Alternating HM Pace (#1 or #9), Long Tempo (#3), HM Repeats (#8), or Descending HMP Intervals (#10). Per Kilometre Progression (#11) or Progressive Long Run (#6) on weekends. |
| Sharpening | Final 2 to 3 | Volume drops, intensity stays. Cut Down Tempo (#7). |
Your threshold responds to specificity. Run these sessions at the paces your fitness dictates today, and those paces will be faster by the time you toe the line.
One gap these workouts do not cover: what you do on the days you are not running. Threshold work makes you fast. Strength work keeps you durable enough to absorb it, and the research on concurrent training shows the two do not interfere when structured correctly.
The FLEX Program handles that side: structured strength, hypertrophy, and mixed conditioning you can slot alongside run training. And if you want the fundamentals behind these sessions, start with the complete running guide.
