Effects of Alternating Unilateral vs. Bilateral Resistance Training on Sprint and Endurance Cycling Performance in Trained Endurance Athletes: A 3-Armed, Randomized, Controlled, Pilot Trial
Participants
n=24 trained triathletes and cyclists (age 31.1 ± 8.1 years; VO2max 57.6 ± 7.1 ml/kg/min), randomly assigned to:
AUL: alternating unilateral resistance training
BIL: simultaneous bilateral resistance training
CON: control — usual training, no resistance training
Group sizes of 8 per arm: full text; not checked against the abstract
Protocol
Duration: 10 weeks of resistance training in AUL and BIL, 4 sets × 4-10RM
Strength tests: maximal isometric leg extension, leg curl and leg press, in unilateral and bilateral conditions
Cycling tests: determinants of cycling performance (economy at submaximal intensities, sprint peak power and acceleration index) and time to exhaustion at 105% of the estimated anaerobic threshold (the "time trial" outcome)
Full text; not checked against the abstract: sessions 2×/week; exercises squat, leg press, calf raise (each leg alternating in AUL, both legs simultaneously in BIL)
Key Findings
| Parameter | AUL | BIL | CON | Significance |
|---|---|---|---|---|
| Maximal leg strength | ~+27% | ~+28% | ~+6% (p > 0.54) | AUL & BIL: p < 0.01 |
| Time to exhaustion at 105% AT ("time trial") | +67% | +43% | +37% (p = 0.43) | AUL & BIL: p < 0.05 |
| Cycling economy (submaximal) | ~+3% (p > 0.24) | ~+8% | ~+3% (p > 0.24) | BIL: p < 0.05 |
| Sprint peak power | no decline reported | no decline reported | −6% | CON: p < 0.05 |
| Sprint acceleration index | +20% (d = 0.5) in favour of AUL | — | −15% | CON decline p < 0.05; AUL improvement d = 0.5 |
Both strength modes raised maximal leg strength (~27-28%) and time to exhaustion at 105% AT vs control
BIL improved economy (~8%, p < 0.05) — AUL and CON did not (~3%)
AUL favoured sprint acceleration (+20%, d = 0.5, medium) — reported as an effect size, not a significance test
Without strength training → decline: CON lost sprint peak power (−6%) and acceleration (−15%, p < 0.05) over 10 weeks
Authors' conclusion: resistance training matters for endurance cycling performance and leg strength independent of movement pattern; whether sprint cycling benefits from AUL needs corroboration
Mechanisms (interpretation, not measured)
BIL → economy: bilateral exercises closer to pedaling biomechanics may transfer better to economy (inference, not tested)
AUL → acceleration: unilateral execution develops force production per leg independently, which may transfer to sprint starts (inference, not tested)
CON decline: ten weeks without a strength stimulus coincided with sprint losses in trained endurance athletes; the fibre-level cause was not measured
Practical Application
10 weeks of 4 × 4-10RM resistance training in n=24 trained triathletes/cyclists (VO2max 57.6): maximal leg strength +27% (alternating unilateral) / +28% (bilateral) vs +6% control (p < 0.01); time to exhaustion at 105% of anaerobic threshold +67% / +43% vs +37% control (p < 0.05 for both training groups); cycling economy +8% only with bilateral lifting (p < 0.05); sprint acceleration +20% (d = 0.5) in favour of unilateral; the no-strength control lost 6% sprint peak power and 15% acceleration — a pilot, small groups.
Match the modality to the goal: bilateral lifting when economy and sustained power are the priority (long climbs, time trials); alternating unilateral when sprint acceleration is — the two did not substitute for each other here, though the authors call the sprint finding preliminary.
A small unilateral add-on at the end of a bilateral session is a reasonable hedge for leg imbalance, but that combination was not tested.
The control arm is the warning: ten weeks of endurance-only training in trained athletes eroded sprint power. Keep some strength stimulus in every phase; the maintenance dose comes from REF-149, not from this pilot.
Limitations
Pilot trial with a small sample split across three arms — underpowered for the between-group comparisons it reports, and the authors label it a pilot.
Trained amateur endurance athletes (VO2max ~58), not elite; conclusions apply to trained amateurs.
The endurance outcome is time to exhaustion at 105% of an estimated anaerobic threshold, a high-variance test (control rose 37% without significance), not a race or a fixed-distance time trial.
Short intervention; strength transfers to cycling performance over months, not weeks, so a null or a win at this duration is weak either way.
Sprint and endurance cycling outcomes measured in the laboratory; no race performance.
No women reported separately; the unilateral-versus-bilateral question has no reason to be sex-neutral and was not tested as such.
How this entry was checked and changed
Why this level
(pilot, small sample)
Content correction 2026-09-27
Tier "mixed→Tier 4-5 (review, predominantly this population)" -> Tier 2, trained amateurs; this is an RCT pilot, not a review.
"1RM" -> maximal isometric leg strength (leg extension, leg curl, leg press); "cycling TT" -> time to exhaustion at 105% of estimated anaerobic threshold.
Session frequency, exercise list and 8-per-arm group sizes -> not in the abstract; marked full text. Mechanisms labelled interpretation.
Cross-reference descriptions checked against the cited entries' current content; wrong years, wrong entries and claims the cited entry does not make were corrected.