A marathon is 42.195 km. Almost no one runs 42.195 km on race day. They run 42.4. Or 42.7. Or, if they were running near the back at Mumbai in January, 43.1. The course is measured on the shortest legal line. You ran somewhere else.
That extra distance has a name. It is called not running the tangents. It is the single most preventable mistake in marathon racing. Fix it and you save two to four minutes for free. No extra training. No new shoes. Just lines on a road.
What a tangent is
A marathon course is measured by a certified surveyor along the shortest possible legal path. That path is called the measured line. On a perfectly straight road, the measured line runs down the middle. On a road that bends, the line cuts the inside of the corner.
If you bend with the road, you run extra distance. If you cut across to meet the next bend on its inside, you run less. The line you cut across is the tangent.
Why it matters
One small bend taken wide costs you 5 metres. Across 42 km, with 30 to 60 turns on a typical city course, that adds up. Elite athletes do not run 200 extra metres at the World Marathon Majors. Recreational runners routinely do. Some run 800 extra metres.
You trained for a marathon. You did not train for a marathon plus a 5K of extra zigzag.
The maths is brutal
At 5:30/km, every extra 100 metres costs you 33 seconds. 200 extra metres is over a minute. 400 extra metres is two and a half minutes. Sub-4 marathon goals have been missed by this margin alone.
How to actually run a tangent
Tangents are not a trick. They are a habit. The habit takes practice. Most runners learn it badly because they only think about it at kilometre 30, when they are already too tired to choose their line.
Look ahead, not down
Most runners stare at their feet. The runner who cuts tangents looks 50 to 100 metres ahead. They see the next bend before the bend sees them. They start the line change while the road is still straight.
Find the inside line
On a road that bends right, the shortest line hugs the right edge of the running surface. On a road that bends left, hug the left edge. Use the inside, not the centre. The barricades and cones are usually placed along the racing line for elites. Run beside them, not in the middle of the road.
S-shapes are the enemy
The classic mistake. Right bend, then left bend, 100 metres apart. The wrong way is to take the inside of the right bend, drift back to the centre, then take the inside of the left bend. The right way is a single diagonal line cutting from the inside of bend one straight to the inside of bend two. Two corners. One line.
The Tata Mumbai Marathon, specifically
The course at the Tata Mumbai Marathon is a well-known tangent test. Marine Drive's gentle arc, the Bandra-Worli Sea Link's long bend, Worli Sea Face's coastal curves — none are sharp, but all are continuous. A runner who drifts wide on every curve from Bandstand to Peddar Road can easily add 300 to 500 metres.
The Sea Link, treat it like one giant tangent
The Sea Link bends. You can see the entire span ahead. Pick your line at the entry, hold it to the exit. Do not chase the centre of the road. Do not chase the camera drones. Pick the inside line of the bend and stay there.
Marine Drive, the long deceiver
Marine Drive looks straight. It isn't. The Queen's Necklace arcs. The smart line follows the kerb on the seaward side from Nariman Point until the road straightens at the back end. Many runners stay in the middle. They pay for it.
What stops people from running tangents
Three things, in order of frequency.
Other runners
The line you want is occupied by a slower runner. You have a choice. Go around — and run wide. Or fight for the line — by surging briefly to pass on the inside. The inside line is yours if you can take it.
Aid stations
Aid stations sit on one side of the road. You drift across. You drift back. Two drifts per aid station, ten aid stations, 20 line changes you didn't plan for. The fix is to commit to one side of the road before the aid station and accept that you will lose one or two cups of water. Plan your fuelling so you don't depend on every station.
Tunnel vision in the late race
The last 10 km is where the wheels come off. Form deteriorates. Eyes drop. The runner stops choosing lines and starts surviving. This is when you must choose lines. Late-race tangent discipline is worth more than late-race surges, because it is free.
What to do in training
You can practise tangents on any road run that has bends. Pick the inside line on every corner. Make it instinct. By race day, you should not have to think about it.
You can also practise it mentally. Pull up a satellite map of your goal race. Trace the shortest legal path with your finger. Notice where the bends are. Notice where the line crosses the road. Then on race day, the picture is in your head before your feet are on the road.
The numbers that matter
If you wear a GPS watch, look at the recorded distance after the race. If your watch says 42.6 km and the course is certified at 42.195 km, you ran 405 extra metres. That's a minute or two you gave away.
A well-tangented marathon, on a watch with decent GPS, reads between 42.20 and 42.30 km. A poorly tangented marathon reads 42.50 to 43.00. The gap is your bonus distance. Free time, given back.
One last thing
Running tangents is not aggressive. It is not unsporting. It is the line every elite athlete runs, on every certified course, in every race. The certification of the course assumes you run that line. Anything else is paying tax on a course the surveyor never asked you to run.
If you have a goal race coming up, build your weekly mileage and pace work with our plan generator and check your race-day pace targets on the calculators. Once race week is here, the nutrition guide will sort your final 72 hours of eating. Everything else lives at the Running Lab.