Muscle Force-Length relationship and the specificity of adaptation

Chapter 9 in the latest edition of
Strength and Power in Sport which is edited by Paavo Komi. Chapter 9 is
written by Walter Herzog and Rachid Ait-Haddou from the University of
Calgary.

Research that Dr. Herzog has performed indicates that the force-length
relationship of a muscle will adapt to the particular activity the
individual performs. In runners, the in-vivo force-length relationship
of the Rectus Femoris muscle is exactly opposite that of a cyclist. In
runners, in-vivo measurements of the force-length relationship of the
Rectus Femoris muscle revealed a positive slope while for cyclists the
force-length relationship had a negative slope. This occurs because in
running the rf. muscle undergoes a SSC and larger force is required at
longer muscle lengths whereas for cyclists, the rf. muscle only shortens
and force is produced at shorter muscle lengths.

It was concluded that the specific mechanical muscle adaptations that
occur in response to chronic running versus chronic cycling would
prevent a champion in cycling from becoming a champion in running and
vice versa.