Potentiation and Recovery Following Low- and High-Speed Isokinetic Contractions in Boys

The objective of this study was to examine the response and recovery to a single set of maximal, low and high angular velocity isokinetic leg extension-flexion contractions with boys. Sixteen boys (11-14 yrs) performed 10 isokinetic contractions at 60 degrees.s(-1) (Isok60) and 300 degrees.s(-1) (Isok300). Three contractions at both velocities, blood lactate and ratings of perceived exertion were monitored pretest and at 2, 3, 4, and 5 min of recovery (RI). Participants were tested in a random counterbalanced order for each velocity and recovery period. Only a single contraction velocity (300 degrees.s(-1) or 60 degrees.s(-1)) was tested during recovery at each session to remove confounding influences between the recovery intervals. Recovery results showed no change in quadriceps' power at 300 degrees.s(-1), quadriceps' power, work and torque at 60 degrees.s(-1) and hamstrings' power and work with 60 degrees.s(-1). There was an increase during the 2 min RI in hamstrings' power, work and torque and quadriceps' torque with isokinetic contractions at 300 degrees.s(-1) suggesting a potentiating effect. Performance impairments during recovery occurred for the hamstrings torque at 60 degrees.s(-1) and quadriceps work with 300 degrees.s(-1). In conclusion, 10 repetitions of either low or high velocity isokinetic contractions (Isok60 or Isok300) resulted in full recovery or potentiation of most measures within 2 min in boys. The potentiation effect predominantly occurred following the hamstrings Isok300 which might be attributed to a greater agonist-antagonist torque balance and less metabolic stress associated with the shorter duration higher velocity contractions.