1. Optimization and gaits in the locomotion of vertebrates;Alexander;Physiol Rev,1989
2. Perceived exertion as an indicator of somatic stress;Borg;Scand J Rehabil Med,1970
3. Relationships between perceived exertion, HR and HLA in cycling, running, and walking;Borg;Scand J Sports Set,1987
4. The pace of life;Bornstein;Science,1976
5. Mechanical work in terrestrial locomotion: two basic mechanisms for minimizing energy expenditure;Cavagna;Am J Physiol,1977