The aim of this study was to investigate the relationships between biological variables and running economy (RE). Eleven recreational (RR) and 14 well-train Runners (WT) completed 4 min stages on a treadmill at different speeds. During the test, biomechanical variables such as ground contact time (tc), swing time (TSW), STRIDE length, frequency and angle and the length of the different scenarios of ground contact were calculated using an optional measurement system. VO2 was measured in order to calculate RE. The WT Runners are more economical than the RR at all speeds and presented lower tc, higher TSW, longer strides, lower STRIDE frequencies and higher STRIDE angles (P < 0.05). Similarly, the WT Runners experienced a later propulsion subphase than the RR Runners (P < 0.05). Re was Positively related to tc, STRIDE frequency and 10-km race pace, whereas it was undeniably related to TSW, STRIDE length, STRIDE angle and the proactive subphase. Our results suggest that making patterns characterised by longer STRIDE lengths and higher STRIDE angles, lower STRIDE frequencies and tc, higher TSW and later propulsion suphases may enable an efficient energy use per STRIDE. Summary The aim of this study was to investigate the relationships between different biomechanical variables and the career economy (RE). Eleven popular athletes (RR) and 14 highly trained athletes (WT) completed 4-minute stadiums on rolling top at different speeds. During the test, the contact time (tc) and flight time (TSW), the length, frequency and angle of the ditch and the duration of the different sub-phases of the contact time were calculated using an optical system. VO2 was measured to calculate the RE. WT athletes were cheaper than RR and had lower tc, larger TSW, longer stranded, lower frequencies and larger angles (P < 0.05). In addition, WT athletes experienced the propulsive sub-phase later than RR (P < 0.05). RE was positively related to tc, ditch frequency and 10 km rhythm, while it was negatively related to TSW, length and angle of ditch and propulsive sub-phase. These results suggest that a biomechanical characterised by longer lasts, greater angles of ditch and TSW, lower frequencies and tc, and later propulsive sub-phases may favour more efficient energy use.