Background Economy, velocity/power at maximal oxygen uptake (v(V) over dot O-2max/w(V) over dotO(2max)) and endurance-specific muscle power tests (i.e. maximal anaerobic running velocity; vMART), are now thought to be the best performance predictors in elite endurance athletes. In addition to cardiovascular function, these key performance indicators are believed to be partly dictated by the neuromuscular system. One technique to improve neuromuscular efficiency in athletes is through strength training.Objective The aim of this systematic review was to search the body of scientific literature for original research investigating the effect of strength training on performance indicators in well-trained endurance athletes-specifically economy, v(V) over dot O-2max/w(V) over dotO(2max) and muscle power (vMART).Methods A search was performed using the MEDLINE, PubMed, ScienceDirect, SPORTDiscus and Web of Science search engines. Twenty-six studies met the inclusion criteria (athletes had to be trained endurance athletes with >= 6 months endurance training, training >= 6 h per week OR (V) over dot O-2max >= 50 mL/min/kg, the strength interventions had to be >= 5 weeks in duration, and control groups used). All studies were reviewed using the PEDro scale.Results The results showed that strength training improved time-trial performance, economy, v(V) over dot O-2max/w(V) over dot O-2max, and vMART in competitive endurance athletes.Conclusion The present research available supports the addition of strength training in an endurance athlete's programme for improved economy, v(V) over dot O-2max/w(V) over dotO(2max), muscle power and performance. However, it is evident that further research is needed. Future investigations should include valid strength assessments (i.e. squats, jump squats, drop jumps) through a range of velocities (maximal-strength <-> strength-speed <-> speed-strength <-> reactive-strength), and administer appropriate strength programmes (exercise, load and velocity prescription) over a long-term intervention period (>6 months) for optimal transfer to performance.