Acute Effects of Plyometric Exercise on Maximum Squat Performance in Male Athletes
This study examines the acute effects of plyometric exercise
on 1 repetition maximum (RM) squat performance in trained
male athletes. Twelve men (mean age SD: 20.5 1.4 years)
volunteered to participate in 3 testing sessions separated by
at least 6 days of rest. During each testing session the 1RM
was assessed on back squat exercise. Before all 3 trials sub-
jects warmed up on a stationary cycle for 5 minutes and
performed static stretching. Subjects then performed 5 sub-
maximal sets of 1–8 repetitions before attempting a 1RM lift.
Subjects rested for at least 4 minutes between 1RM trials.
During the first testing session (T1) subjects performed a
series of sets with increasing load until their 1RM was de-
termined. During the second and third testing sessions sub-
jects performed in counterbalanced order either 3 double-leg
tuck jumps (TJ) or 2 depth jumps (DJ) 30 seconds before each
1RM attempt. The average 1RM lifts after T1 and testing
sessions with TJ or DJ were 139.6
29.3 kg, 140.5
25.6
kg, and 144.5
30.2 kg, respectively (T1
DJ; p
0.05).
These data suggest that DJ performed before 1RM testing
may enhance squat performance in trained male athletes.
Postactivation Potentiation Response in Athletic and Recreationally Trained Individuals
The response to a heavy resistance exercise stimulus
designed to elicit postactivation potentiation appears
to depend on training status. Recreationally trained
individuals may exhibit fatigue in the 5 minutes fol-
lowing an acute heavy resistance exercise stimulus. In
athletically trained individuals, however, this stimulus
enhances power performance for 5 to 18.5 minutes.
This method of postactivation potentiation appears to
be a viable means of acutely enhancing explosive
strength performance in athletes, but not recreation-
ally trained individuals. The results of this study may
be applicable to sports with brief, discrete, maximal
efforts, such as weightlifting and sports involving
short sprints, jumping, or throwing actions.
To determine if training status directly impacted the re-
sponse to postactivation potentiation, athletes in sports re-
quiring explosive strength (ATH; n
7) were compared to
recreationally trained (RT; n
17) individuals. Over the
course of 4 sessions, subjects performed rebound and con-
centric-only jump squats with 30%, 50%, and 70% 1 RM
loads. Jump squats were performed 5 minutes and 18.5 min-
utes following control or heavy load warm-ups. Heavy load
warm-up consisted of 5 sets of 1 repetition at 90% 1 RM
back squat. Jump squat performance was assessed with a
force platform and position transducer. Heavy load warm-
up did not have an effect on the subjects as a single sample.
However, when percent potentiation was compared between
ATH and RT groups, force and power parameters were sig-
nificantly greater for ATH (p
0.05). Postactivation poten-
tiation may be a viable method of acutely enhancing explo-
sive strength performance in athletic but not recreationally
trained individuals
The Acute Effects of Heavy Loads on Jump Squat
Performance: An Evaluation of the Complex and
Contrast Methods of Power Development
The purpose of this investigation was to examine power per-
formance in jump squats when using the complex and con-
trast training methods. Eleven (n
11) women participated
in a familiarization session and in three randomly ordered
testing sessions. One session involved completing sets of
power exercises (jump squats) before sets of half squats (tra-
ditional method). The second session involved sets of half
squats before sets of jump squats (complex method). A third
session involved the alternation of sets of half squats and
jump squats (contrast method). No significant difference in
jump squat performance between each of the training meth-
ods was found. There was a significant difference (p
0.05)
in the first set of each session, with the complex method
having a significantly lower peak power. Further, there was
a significant difference (p
0.05) in performance changes
between the higher and lower strength groups, with the
higher strength group having a greater improvement in per-
formance using the contrast training method compared with
the traditional method. It was concluded that contrast train-
ing is advantageous for increasing power output but only for
athletes with relatively high strength levels.
Investigation of Vertical Jump Performance After Completing Heavy Squat Exercises
Mangus, B.C., M. Takahashi, J.A. Mercer, W.R. Holcomb, J.W. McWhorter, and R. Sanchez. Investigation of vertical jump performance after completing heavy squat exercises. J. Strength Cond. Res. 20(3):597–600. 2006.—The purpose of this study was to determine whether vertical jump height was influenced by completing a half squat or quarter squat exercise prior to jumping. Ten male subjects experienced with the squat exercise performed 4 warm up squat sets followed by 1 repetition with the weight of 90% of 1 repetition maximum of the half squat or quarter squat. No difference in jump heights after any of the 3 conditions, including a control group (F = 3.096, p = 0.070), was found. Correlations between the relative strength ratio and the difference in averaged jump heights before and after the half and quarter squat conditions were also tested, and no correlation was found (r = −0.128, p = 0.724, and r = −0.189, p = 0.601, respectively). Although statistical significance at the 0.05 level was not observed for the comparison of jump heights between conditions, we did observe a trend (i.e., p = 0.07). Therefore, we examined the individual responses to the exercises and determined that 5 of the subjects did increase their vertical jumps after both squat exercises. It may be that the influence of prejump exercise on jump performance may be individualized. Nevertheless, the use of a strength ratio does not appear to predict who will benefit from posttetanic potentiation in this type of exercise situation.
Influence of recovery time on post-activation potentiation in professional rugby players
Following a bout of heavy resistance training, the muscle is in both a fatigued and potentiated state with subsequent muscle performance depending on the balance between these two factors. To date, there is no uniform agreement about the optimal acute recovery required between the heavy resistance training and subsequent muscle performance to gain performance benefits. The aim of the present study was to determine the recovery time required to observe enhanced muscle performance following a bout of heavy resistance training. Twenty professional rugby players performed a countermovement jump at baseline and ∼15 s, 4, 8, 12, 16, 20, and 24 min after a bout of heavy resistance training (three sets of three repetitions at 87% one-repetition maximum squat). Power output, jump height, and peak rate of force development were determined for all countermovement jumps. Despite an initial decrease in countermovement jump performance after the heavy resistance training (P < 0.001), participants' performance increased significantly following 8 min recovery (P < 0.001) (i.e. jump height increased by 4.9%, s = 3.0). The findings suggest that muscle performance during a countermovement jump can be markedly enhanced following bouts of heavy resistance training provided that adequate recovery (∼8 min) is allowed between the heavy resistance training and the explosive activity.
The Effects of Postactivation Potentiation on Muscular Strength and Power
Abstract;The purpose of the present study was to examine the effects of postactivation potentiation on muscular strength and power after the different intensity of half squat and how long that effects are remained. Eight healthy men (21.+-.2 years old), who are able to squat a minimum load (1.5*body mass), participated in a familiarization session with the test of one repetition maximum (1RM) and in two testing sessions. 80% of 1RM and 40% of 1RM with more than 1 week interval were used as the preload. The magnitude increase in height of loaded (30% of 1RM) counter movement jump (LCMJ) was no difference between 40%1RM and 80% 1RM preload. However, an increase in force parameter during LCMJ was appeared in 80%1RM preload but not in 40%1RM. Moreover, an increase in power parameter with 80%1RM preload was remained longer than that of 40% 1RM. These results suggest that the effects of postactivation potentiation on muscular strength and power and its time course of recovery may be different from the intensity of preload. (author abst.)
The Acute Effects of a Resistance Training Warmup on Sprint Performance
Twenty male rugby union players were tested to determine the acute effect of a resistance training warmup on subsequent 20-m sprint performance. The study consisted of a repeated measures design with two experimental conditions. During the control (C) condition, the participants performed a 20-m sprint, rested for 10min, and then repeated the 20-m sprint. During the experimental (E) condition, the second sprint was preceded by five repetitions of a back-squat with a load equal to each participant's five repetition maximum (5RM). Sprint times were recorded using New Test digital recording equipment. The results showed a mean improvement of 0.098s (p<0.0001) when the second sprint was preceded by the back squats. This amounted to a 3.3% improvement on the precondition time. During the control condition, no improvement was observed between the first and second sprint. The improved sprint times observed during the E condition probably were due to a temporary increase in the efficiency of neuromuscular activation following the performance of heavy-load back squats.
The Acute Effects of Heavy-Load Squats and Loaded Countermovement Jumps on Sprint Performance
McBride, J.M., S. Nimphius, and T.M. Erickson. The acute effects of heavy-load squats and loaded countermovement jumps on sprint performance. J. Strength Cond. Res. 19(4):893– 897. 2005.—The purpose of this investigation was to determine whether performing high force or explosive force movements prior to sprinting would improve running speed. Fifteen NCAA Division III football players performed a heavy-load squat (HS), loaded countermovement jump (LCMJ), or control (C) warm-up condition in a counterbalanced randomized order over the course of 3 weeks. The HS protocol consisted of 1 set of 3 repetitions at 90% of the subject's 1 repetition maximum (1RM). The LCMJ protocol was 1 set of 3 repetitions at 30% of the subject's 1RM. At 4 minutes post–warm-up, subjects completed a timed 40-m dash with time measured at 10, 30, and 40 m. The results of the study indicated that when preceded by a set of HS, subjects ran 0.87% faster (p ≤ 0.05) in the 40-m dash (5.35 ± 0.32 vs. 5.30 ± 0.34 seconds) in comparison to C. No significant differences were observed in the 10-m or 30-m split times between the 3 conditions. The data from this study suggest that an acute bout of low-volume heavy lifting with the lower body may improve 40-m sprint times, but that loaded countermovement jumps appear to have no significant effect.
Acute neuromuscular and hormonal responses during contrast loading: Effect of 11 weeks of contrast training
The purpose of this study was to assess (1) acute neuromuscular and endocrine responses during a contrast loading protocol and (2) how these acute responses are possibly influenced by 11 weeks of contrast training. Contrast loading tests consisting of 4 sets of 80% 1 RM back squat and 4 sets of squat jump (SJ) were performed before and after training. Bilateral isometric leg extension (LE) assessed the impact of loading on isometric variables pre-, mid-, and post-loading. Potentiated SJ performance was observed in set 2 (4.6%, P<0.05), before training only. Greater indications of fatigue were observed in SJ, isometric force, and vastus lateralis (VL) activation after training (P<0.05). Training-induced improvements in SJ height, 80% 1 RM squat load, and maximum isometric LE force were observed (12%, 10%, and 7.7%, P<0.05). In conclusion, potentiated SJ performance occurred during a typical contrast loading protocol before the training period. However, potentiated SJ performance may alter through training, and therefore, the responsiveness of the individual should be periodically monitored and training protocols updated when necessary.
Acute Effects of Heavy- and Light-LoadSquat Exercise on the Kinetic Measures of Vertical Jumping
Hanson, E.D., S. Leigh, and R.G. Mynark. Acute effects of heavy- and light-load squat exercise on the kinetic measures of vertical jumping. J. Strength Cond. Res. 21(4):1012– 1017. 2007.— This study examined the acute performance enhancing effects of a single light-load, high-velocity or heavy-load, low-velocity squat intervention set (SIS) on stimulating activity-dependent postactivation potentiation and thereby increasing vertical jumping performance. Jump performance was assessed using 4 dependent variables: net impulse, time of ground contact, and normalized peak and normalized minimum vertical ground reaction force. Resistance-trained subjects (n = 30) attended 3 independent sessions separated by 3 to 7 days. The first session served for familiarization and to determine each subject's 1 repetition maximum (1RM) in the squat. In the 2 testing sessions, subjects performed 2 countermovement jump (CMJ) sets, followed by a single SIS and then a final CMJ set. A CMJ set consisted of 3 maximal effort jumps. The testing sessions were identical except for SIS intensity, which was 40% of 1RM for 1 session and 80% of 1RM for the other. The order of the 2 testing sessions was counterbalanced within subjects. The 4 dependent variables were reduced for every jump. No significant changes were observed from pre- to post-testing in either SIS condition, nor were there any differences between the heavy and light SIS loading condition. Reasons for the lack of performance enhancement can be attributed to postactivation potentiation stimulated by the SIS being insufficient in magnitude or dissipating before post-testing. This may have been due to a submaximal workload of 50% during the SIS, insufficient movement pattern specificity between the squat exercise and a CMJ, or rest intervals of excess duration. A single SIS provides no benefit to a warm-up protocol under the current conditions.
