Mechanical energy contributions derived fromjoint muscle and joint force powers were computed for the right lower extremity in 12 male cyclistsriding at five different conditions of cycling cadence and power output. The knee was found to dominate in its contribution to system energy, power derived from hip joint reaction forces was significant, and the distribution ofenergy generation and dissipation was sensitive to bicycle power output and, within the range of conditions studied, insensitive to cadence.

Three energy models were developed to characterize energetic advantages associated with appropriate actions oftwo-joint muscles. Two energy models estimated mechanical energy expenditure (MEE) associated with hypothetical single-joint muscle (no intercompensation) and multi-joint muscle (unlimited intercompensation) conditions. A third model (MEELIC) used a fully deterministic algorithm to apportion joint muscle powers to single- and two-joint muscles and muscle groups in accordance with minimum energy expenditure criteria. The results indicated that intercompensations primarily involving simultaneous actions of the gastrocnemius and hamstrings muscles potentially reduce the energy dissipated to non-transferable sources during pedalling to less than 6.0 J per limb, and the corresponding MEE associated with single-joint muscle actions by up to 14 percent Furthermore, muscle actions predicted by the MEELIC algorithm agreed remarkably well with previously reported muscle activation patterns during cycling. Slight differences between MEELIC model predictions and published activation patterns could be attributed to passive element energetics and energy transport mechanics using antagonist muscle actions. These findings were used to suggest (a) that MEE minimization can be achieved by appropriate actions ofsingle- and two-joint muscles and muscle groups, and (b) that unlike walking and running, stretch-shorten cycle actions ofmuscle-tendon units observed during cycling are not necessary to reduce mechanical energy expenditure.