Integra

Introduction
Ballistic exercise, such as loaded squat jumps, is used for the improvement of vertical jump performance. This type of
exercise, however, may be applied for the development of anaerobic performance using short term (5-10 sec) and
medium term (15-30 sec) sets of anaerobic training by modifying exercise set duration and the rest intervals between
sets. The purpose of the study was to examine the effects of exercise set duration and rest intervals during the
performance of loaded squat jumps (LSJ) sessions oriented for the improvement of anaerobic performance.

Methods
Seven male physical education students (age: 22.5 ± 2.4 yrs, height: 174.1 ± 4.8 cm, and weight: 73.6 ± 7.1 kg)
performed LSJ with two set durations, 5 sec and 15 sec. Each set was performed with two different exercise to rest
ratios i) 1:3 (i.e. 5sec exercise: 15sec rest and 15sec exercise: 45sec rest) and ii) 1:6 (i.e. 5sec: 45sec and 15sec: 90sec)
on two separate occasions. On each occasion the subjects performed 4 sets of loaded squat jumps with a load 30% of
the 1-RM in the semi-squat exercise (knee angle 90°). The heights of a countermovement jump (CMJ), a squat jump
(SJ), and a drop jump from 40cm (DJ) were measured before (pre) and after (post) the LSJ session. The average height
(cm) of each set of LSJ was measured using a force resistive platform (Ergojump, Psion XP, MA.GI.CA. Rome, Italy).
Blood lactate concentrations were measured 4 min after the end of each LSJ exercise session.

Results
When the exercise to rest ratio was 1:3, average jump height at each set decreased (p<0.05) progressively from the 1st to
4th set whether exercise set duration was 5 or 15 sec. When the exercise to rest ratio was 1:6, average jump height
decreased only when set duration was 15 sec. The rate of decrease of the average height at each set was greater (p<0.05)
with the 1:3 ratio than with the 1:6 ratio with both exercise set durations. Average height at each set was lower (p<0.05)
when set duration was 15 sec than 5 sec whether the exercise to rest ratio was 1:3 or 1:6. The height of the SJ, the CMJ,
and the DJ decreased more (p< 0.05) when set duration was 15 sec while the exercise to rest ratio did not affect the
magnitude of decrease except for the DJ with the 5 sec and only with the 1:3 exercise to rest ratio. Blood lactate values
were higher (p< 0.05) with the 15 sec exercise sessions while rest interval did not affect lactate values at both exercise
durations (1:3: 8.61±1.61 vs 12.59±2.53 mmol/L for 5sec and 15sec, respectively; 1:6: 7.5±2.18 vs 13.05±1.46 mmol/L
for 5sec and 15sec, respectively).

Discussion/Conclusion
It appears that when the duration of repeated exercise sets increases, performance decrement is greater regardless if the
exercise to rest ratio is kept the same. The higher activation of anaerobic metabolism requires probably, a longer
exercise to rest ratio for the restoration of the intra-muscular environment at a level comparable to that achieved with a
shortest exercise duration and rest interval. Performance in a single maximal effort, like a countermovement jump, does
not appear to be affected by the exercise to rest ratio. However, in repeated efforts, such as sets of continues vertical
jumps, the shortest the rest interval the greatest the decrease in performance.

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