title: Postactivation potentiation can counteract declines in force and power that occur after stretching.
abstract: Stretching can decrease a muscle's maximal force, whereas short but intense muscle contractions can increase it. We hypothesized that when combined, postactivation potentiation induced by reactive jumps would counteract stretch-induced decrements in drop jump (DJ) performance. Moreover, we measured changes in muscle twitch forces and ankle joint stiffness (KAnkle) to examine underlying mechanisms. Twenty subjects completed three DJs and 10 electrically evoked muscle twitches of the triceps surae subsequent to four different conditioning activities and control. The conditioning activities were 10 hops, 20s of static stretching of the triceps surae muscle, 20s of stretching followed by 10 hops, and vice versa. After 10 hops, twitch peak torque (TPT) was 20% and jump height 5% higher compared with control with no differences in KAnkle. After stretching, TPT and jump height were both 9% and KAnkle6% lower. When hops and stretching were combined as conditioning activities, jump height was not different compared with control but significantly higher (11% and 8%) compared with stretching. TPTs were 16% higher compared with control when the hops were performed after stretching and 9% higher compared with the reverse order. KAnklewas significantly lower when stretching was performed after the hops (6%) compared with control, but no significant difference was observed when hops were performed after stretching. These results demonstrate that conditioning hops can counteract stretch-related declines in DJ performance. Furthermore, the differences in TPTs and KAnklebetween combined conditioning protocols indicate that the order of conditioning tasks might play an important role at the muscle-tendon level.
authors.affiliation: Sensorimotor Performance Lab, Department of Sport Science, University of Konstanz, Konstanz, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Kümmel
authors.affiliation: Sensorimotor Performance Lab, Department of Sport Science, University of Konstanz, Konstanz, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Kramer
authors.affiliation: Neuromuscular Research Center, Department of Biology of Physical Activity, University of Jyväskylä, Jyväskylä, Finland.
authors.forename: N J
authors.initials: NJ
authors.lastname: Cronin
authors.affiliation: Sensorimotor Performance Lab, Department of Sport Science, University of Konstanz, Konstanz, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Gruber
mesh_terms: D000328:Adult; D000843:Ankle Joint / Q000502:physiology; D001696:Biomechanical Phenomena; D004558:Electric Stimulation; D004576:Electromyography; D006801:Humans; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D052580:Muscle Stretching Exercises; D018482:Muscle, Skeletal / Q000502:physiology*; D019415:Torque; D055815:Young Adult
keywords: conditioning activity; muscle-tendon unit; stretch-shortening cycle