The 40 km to 50-mile time trial
Ride below CP by an amount the base cannot fix, so set the target from rehearsal in the race position, hold it evenly on flat roads, lean only modestly into climbs and headwinds, and fuel and cool the longer ones
The question it answers
What power, position, pacing, fuelling and heat plan for an individual TT of roughly 50-120 min (40 km / 25 mi to 80 km / 50 mi), and which sessions and taper lead to it. Shorter TTs, hill climbs, the P = CP + W′/t model and priming are in SYNTH-48. Inference (arithmetic): 40 km at 35 km/h takes ~69 min, 80.5 km at 40 km/h ~2:01; plan from the athlete's expected time, not the distance.
Default (what to prescribe first)
Target below TT-position CP, set from a rehearsal, not a table. At CP, 7 trained men lasted 20-41 min (REF-750, B) and REF-168 (B+) cites "approximately 20-30 min" only as the premise of a view it disputes; its body reports time to the limit at CP as highly variable (~15-40 min, occasionally ~60 min) and calls "how long" CP lasts an ill-conceived question (corrected 2026-10-12); the CP model predicts nothing about duration at or below CP (REF-751, B+).
No entry gives the % of CP for 50-120 min.
Test and rehearse on the TT bars. In 7 trained cyclists TT-position power was lower in every trial, more so the longer the trial (3 → 12 min); CP was lower, W′ unchanged (REF-201, B).
Even power on flat, steady courses; modest extra power on climbs and into headwinds on rolling or windy ones.
Fuel from ~90 min: 60-90 g/h for an amateur (base practice, SYNTH-02); 30-60 g/h or a mouth rinse below that.
In heat: pre-cool, start euhydrated and lower the target (sources in the heat table; how much to lower is not in the base).
Decision
Target intensity by planned duration. Not from a study; the base's own practice for the starting points below: ~1 h, roughly 90-95% of TT-position CP; ~2 h, roughly 85-90%. Then adjust from a race-duration rehearsal. What the entries do support:
| Planned duration | What the base supports | Source |
|---|---|---|
| ~50-70 min (40 km) | Below CP and below FTP20 for most riders. Median time to exhaustion at FTP20 was 35 min (recreational), 42 (trained), 47 (well-trained), 51 (professional), n=87, wide spread (REF-747, B); its entry advises hour-long efforts below FTP20. How far below is not in the base | REF-747, REF-750, REF-751 |
| Pros, long TT (>40 km) | Heart rate averaged 89 ± 5% of HR at OBLA and 103 ± 8% of HR at the lactate threshold, against 100 ± 3% and 114 ± 8% in prologues (<10 km); the authors name HR at LT as the marker for events of 30 min or more (REF-792, B, 18 world-class pros, heart rate only, no power in the abstract). Male pro TTs ~400-420 W short (near OBLA), ~370-390 W long (near LT) (REF-174, B+, 2001 narrative, race heart rate). Transfer: professionals to amateurs; do not convert these heart rates into a watts target | REF-792, REF-174 |
| World-class 1 h (track) | The hour record was ridden at an estimated 509.5 W, slightly above the 497.25 W at the rider's OBLA oxygen uptake (power at OBLA 505 W lab, 500.6 W track) (REF-843, C+, n=1, Tier 5, power estimated). Inference: an all-out hour sits at or just above an OBLA-type threshold only in a world-class rider; most amateurs' 40 km lasts longer and sits lower (REF-792) | REF-843 |
| ~80-120 min (50 mi) | Inference: lower again. After heavy-intensity cycling, CP (3-min test) was unchanged at 40 and 80 min and fell 9% at 2 h on placebo (260 → 236 W); 60 g/h carbohydrate negated the fall (254 W). W′ fell 18% by 80 min and 23% by 2 h, and carbohydrate did not restore it (REF-145, B+, n=16, training status not in the abstract). Inference: a fuelled 2-h TT keeps roughly its fresh ceiling but less reserve for surges; the magnitudes come from one preload protocol (SYNTH-32) | REF-145, SYNTH-32 |
Position vs power (numbers only as the abstracts give them)
| Question | What the base supports | Source |
|---|---|---|
| Does a lower torso cost power? | Yes: in 19 well-trained men at five torso angles, every maximal value, peak power included, fell as the torso got lower (P < 0.001); the flat-back 0° position cost significantly more than all others; at the same %PPO, physiological strain was higher in lower positions. No magnitudes in the abstract | REF-793, B+ (lab ergometer; frontal area, not drag) |
| Does position work cut drag? | In a wind tunnel, position changes cut drag 14% in 5 professionals; drag area while pedalling at race pace was 31% higher than static; the aero helmet was not favourable for all. No absolute CdA values | REF-794, B (n=5) |
| Net time: is the lower position faster? | No ridden test in the base. In 12 participants, 20-min self-paced TT power was higher at a 24° torso than at 12° or 0°, drag not measured (REF-845, B). A model fed by 19 TT cyclists' measurements puts the break-even by speed: aero losses outweigh the power cost only above 46 km/h, a more upright TT position is better below 30 km/h, a fully flat torso is never optimal (REF-844, C, not ridden). The road power-speed model is validated (R² = .97, SE 2.7 W; REF-846, B), so a net figure needs the rider's own drag and power in each position (REF-490, B+). Inference: at amateur speeds the power side weighs more than in pros; retest power in any lower position | REF-845, REF-844, REF-846; net time a gap |
| Holding the position for 1-2 h | Untested. Inference: REF-201's gap grew with duration up to 12 min; whether it keeps growing past an hour is unknown | gap |
Inference from REF-793, REF-794, REF-201: judge a position while pedalling at race effort, retest power in it, and change it well before race week.
Pacing
| Course | Prescription | Source and how sure |
|---|---|---|
| Flat, steady wind | Even power at target | Even pacing optimal > 4 km in steady conditions (REF-490, B+); more even pacing may improve times in events > 2 min (REF-010, B+) — both narrative |
| Natural wobble | ±5% is free | In 8 trained men, 1 h at 78% VO₂max with ±5% alternations every 5 min cost the same VO₂, HR, lactate and RPE as constant power (REF-241, B) |
| Rolling or windy | Harder uphill and into headwinds, easier downhill and with tailwinds, same mean | Rule in REF-490 (B+). Riders: on an undulating 4-km field course, power varied with the gradient was 12 ± 8 s (2.9%) faster than attempted constant power at the same normalised mean (20 experienced cyclists, REF-848, B+); over a simulated 16.1-km TT with a headwind then a tailwind half, 5% more power into the headwind saved ~12 s and even power ~10 s against self-pacing, same mean, lowest RPE (7 men, REF-849, B, lab; self-paced trial always first, variable and even power 2 s apart). Both are far shorter than 40 km. Models (C, no riders): ±10% saved 26 s on a standard 40-km TT, 51 s on a windy 40 km and 126 s on a hilly 10 km at 289 W (REF-795); on hilly 40-km courses ±15% in step with 6% gradients saved 188.89 s at 200 W, out of step cost up to 43.90 s (REF-847). Direction also in REF-126 (C) |
| Size of the swings | Keep them modest and rehearsed | In 15 elite cyclists, 15% swings every 2 min at 70% and 95% of LT raised VO₂ and lactate vs constant power (HR higher in the abstract, no main effect in the Results (corrected 2026-10-12)), with similar whole-bout RPE at 95% LT (REF-252, B+, submaximal, not a TT). Inference: ±5% cost nothing measurable in one study, 15% cost more in another; ±10% is untested in riders |
| Technical corners | Carry speed | Time lost in slow sections was not won back on straights (40-km simulation, REF-125, C) |
| Late in a 50-mile TT | Keep late surges small | W′ was 18% lower by 80 min and 23% by 2 h (REF-145, B+); its entry: pace the finish by CP |
Settle into target over the first few minutes rather than starting hard: self-paced riders opened 14% above their mean over the first 1.61 km of a 16.1-km TT and then faded (REF-849, B, 7 men).
Not from a study; the base's own practice: heart rate lags early and drifts late, so pace by power and use HR as a cross-check (REF-792's entry), with HR zones set in the TT position (REF-201). Warm-up: a 20-min TT was no better after one than without (REF-278, B+, 15 trained men); Inference: a short, easy warm-up is enough for longer TTs.
Fuel, fluid and heat for the longer ones
| Situation | Do | Source |
|---|---|---|
| < 90 min, cool | 30-60 g/h, or a mouth rinse | Duration matrix is base practice (SYNTH-02); mouth rinse raised mean power (SMD 0.25) but not completion time (REF-483, A-); no gain in a 15-min time trial in 12 male amateur cyclists (REF-957, B; shorter than this event) |
| 90 min-2 h | 60-90 g/h (amateur), multiple-transportable above ~60 g/h, gut trained first | SYNTH-02 (base practice); 60 g/h negated the 2-h CP fall (REF-145, B+) |
| Caffeine | 3-6 mg/kg, tested in training | TT +3.2 ± 4.3%, range −0.3 to +17.3% across 21 studies (REF-083, A) |
| Hot day | Expect a large loss and less fuel used; lower the power target and pace by RPE/HR | 10 trained men, 2 h + ~15-min TT at 32 vs 19 °C with airflow: TT 15% slower, exogenous glucose oxidation −14-15% (REF-461, B) |
| Hot day, pre-cooling | Pre-cool before; cool during where possible | Endurance-trained athletes, TT: +3.7% (4 studies); heat +6.6%, moderate +1.4% (REF-112, A-). Prolonged exercise d = 1.91, per-cooling d = 0.76 in the heat (REF-111, A-) |
| Hot day, fluid | Start euhydrated; drink during the longer ones (house practice; the study shows only the cost of a deficit) | ~2.4% hypohydration cut 15-min work ~8% at 34 °C (7 active men, blinded, REF-226, B) |
| Hot season ahead | Heat acclimation, ~8-10 exposures | SYNTH-04 (base prescription); heat impairs aerobic performance, countermeasures are acclimation, cooling, hydration (REF-002, B+) |
How to progress / periodise
When NOT to use it / red flags
What the evidence does and does not show
Evidence gaps
How this entry was checked and changed
(intensity from B/B+ CP-boundary work plus one B heart-rate field study in professionals; position from B+/B laboratory and wind-tunnel studies with no net trade-off; pacing from B+ narrative reviews, one B+ field and one B lab trial on short courses, and C models; fuel and heat from A-/B+/B)