Effect of Various Training Modalities on Vertical Jump

Abstract

The purpose of the present investigation was to compare the effects of weight training, training with weights and plyometrics, and training with weights and the VertiMax® on vertical jump. Subjects were 37 intercollegiate athletes assigned to one of four training groups: strength (S), strength-plyometric (P), strength-VertiMax® without arms (VNA), and strength-VertiMax® with arms (VA). Each group completed a 6-week training program. There were no statistical increases in pre–post vertical jump within all groups. There were no significant differences for posttest vertical jump between the four training groups. Pre- and posttest effect sizes were minimal across all groups. The findings of this study demonstrate that there is no difference in vertical jump among strength training, plyometric training, and jump training over a 6-week timeframe.

KEYWORDS:

• jump training
• explosiveness
• power training
• weight training
• strength training

INTRODUCTION

The ability to generate lower body power is a key component for success in many sporting activities (Baker 1995; Haff and Potteiger 2001; Harman et al. 1990; Harris et al. 2000; Kemp 1997; Lyttle et al. 1996; Stone 1993). This is especially true for athletes who compete in activities that require sprinting and jumping (Lyttle et al. 1996). Power has been defined as the ability to apply force through a distance divided by the time of force application (Baker 1995). Various types of strength-training modalities have been utilized in order to improve lower body power, as can be measured by vertical jump (VJ). These modalities have been classified into three groups by Baker (1996): general, special, and specific. General strength-training exercises are utilized to increase the maximal strength of the muscles used in jumping (e.g., parallel squat). It has been shown that an increase in the 1 repetition maximum (1RM) of the squat leads to an increase in VJ performance (Harman et al. 1990). Special strength exercises are used in training for power, once strength levels have been increased. These types of exercises are effective at enhancing the stretch-shortening cycle (SSC), thus improving lower body power (Baker 1996; Harman et al. 1990; Harris et al. 2000; Kemp 1997). These modalities include explosive exercises as defined by having a maximal or near maximal initial rate of force development that is maintained throughout the selected range of motion (Baker 1995). For example, Olympic lifters are able to produce more forceful and powerful movements when compared with power lifters and sprinters (McBride et al. 1999). Specific strength exercises are those that produce a training stimulus similar to the actual activity being performed, such as jumping for height. Examples of specific strength exercises would include various types of plyometrics. A plyometric exercise program is also effective at improving the SSC (Adams et al. 1992; Fatouros et al. 2000; Gehri et al. 1998; Holcomb et al. 1996; Luebbers et al. 2003; Stone 1993; Wilson et al. 1993). Plyometric exercise is based on the idea that rapid lengthening of a muscle prior to contraction will result in a much stronger concentric contraction than could be generated during a concentric contraction from a static position not preceded by a stretch (Harman et al. 1990; Stone 1993). It has been defined as a quick, powerful movement using a prestretch, or countermovement that involves the SSC (Baechle and Earle 2000). Plyometrics also may enhance strength because muscles are trained under tensions greater than normal maximum tension due to the SSC (Holcomb et al. 1996). Both special and specific strength-training programs will also utilize the contribution of the upper extremities during training, particularly plyometric training. The usage of the arms during the performance of a jump has been shown to increase takeoff velocity, ground reaction forces, and the height of the center of gravity prior to takeoff (Fatouros et al. 2000, Luhtanen and Komi 1978; McBride et al. 2002). These contributions from the powerful flexion of the arms will thus contribute to power generation and jump height. Proper training of the upper extremities, in particular shoulder flexion, should be a part of a training program designed to increase jump height.

The effectiveness of plyometrics in combination with resistance training at improving lower body power has been investigated (Adams 1992; Baker 1996; Fatouros 2000). Baker (1996) concludes that the greatest improvements in VJ performance will be elicited when training both the contractile components of the muscle (utilized primarily by general strength exercises), as well as the SSC (utilized primarily by the special and specific strength exercises) rather than simply performing one type of training or the other. Additional research (Adams et al. 1992) also indicates that the combined method of training is more effective for enhancing vertical jump performance than either weight training or plyometric training alone (Harmon 1990). Fatouros et al. (2000) investigated how variables of vertical jumping performance were affected by a 12-week plyometric training program, a 12-week weight training program, and a 12-week combination training program. They concluded that both the individual plyometric and weight training programs increased vertical jumping performance, but the combination program showed the greatest improvement on vertical jumping performance. Lyttle et al. (1996) compared the performance benefits derived from maximal power training and a combined weight/plyometric training program. The researchers concluded that the two training modalities produced significant improvements in selected performance tests; however, the training groups did not differ significantly on any of these measures.

The VertiMax®, a resisted jump training apparatus similar to the specific strength exercises described above, appears to improve lower body power and vertical jump performance. The V6 model VertiMax® has the capability to train the arms via resisted shoulder flexion during the jumping to possibly improve the arms' contribution to power production and jump height. Although this resisted jump training has shown improvements anecdotally, few controlled studies have been implemented to determine the effectiveness of the apparatus. In addition, these studies differ in their conclusions about the effectiveness of VertiMax® training.

McClenton et al. (2008) compared the effects of a twice-weekly, 6-week depth jump training program vs. a VertiMax® basic training program with recreationally trained subjects. They concluded that the depth jump training program significantly increased their vertical jump, while the VertiMax® group did not. Conversely, Rhea, Peterson, Lunt, Ayllon, et al. (2008), using collegiate athletes in one study and high school athletes in a second, determined that the VertiMax® demonstrated an added benefit in conjunction with traditional preparatory strength and conditioning modalities, when compared with strength/power training alone. In both studies a substantial effect size was shown within the VertiMax® training groups, 0.54 and 0.95. The present study wishes to add to the current body of literature on the VertiMax® to substantiate its effectiveness as a training modality for improving vertical jump and, thus, lower body power.

It was the purpose of this study, therefore, to compare the effects of a weight training program, a combination program consisting of weight training and plyometric training, and two combination programs consisting of weight training and VertiMax® training on lower body power and vertical jump performance in off-season NCAA Division III athletes. We hypothesized that the combination training groups would outperform the weight training group, with the two VertiMax® groups showing the greatest improvement. This hypothesis is based on the work by Rhea, Peterson, Lunt, et al. (2008) and Rhea, Peterson, Oliverson, et al. (2008).

METHODS

Experimental Approach to the Problem

Four groups of male and female collegiate athletes participated in a 6-week training program. The four groups follow: (1) strength training (S), (2) strength training and plyometrics (P), (3) strength training and VertiMax® training without upper extremity resistance (VNA), and (4) strength training and VertiMax® training with upper extremity resistance (VA).

Subjects

Thirty-seven (15 men, 22 women) NCAA Division III athletes (basketball, soccer, volleyball) volunteered and gave written informed consent to participate in the study. The study was approved by the Institutional Review Board. Subjects were not in the competitive portion of their respective seasons. Our concern was not to determine differences between men and women across the training modalities. The influence of gender on the outcome of this study should be minimal. Deschenes and Kraemer (2002) state that relative performance improvements are similar in both men and women. The subjects were instructed not to take any dietary supplements during the study. This was not tracked by the researchers. Age and bodyweight for the men was 20.2 + 1.3 (years) and for the women was 19.8 + 1.0 (years) and mean value 69.5 + 7.2 (kg).

Design

This was a quasi-experimental (volunteer subjects) pre–post design with all subjects being randomly assigned to each of the four groups.

Methodology

Each subject underwent measurements of bodyweight and vertical jump. Pretesting was conducted the week prior to the initiation of the training period. Posttesting was conducted the week following training completion. Subjects were instructed to refrain from exercise for 48 hours and caffeine 24 hours prior to testing (Luebbers et al. 2003). Training intensity was reduced the final week of training to allow for sufficient recovery prior to posttesting.

Vertical jump height

Vertical jump height was measured by the stand and reach method using a Vertec® (Baechle & Earle 2000). All subjects completed the same 5-minute warm-up consisting of dynamic activities. A countermovement jump with arm swing was used in measuring vertical jump height (Luebbers et al. 2003). Subjects were allowed a minimum of 3 test jumps with a 30-second recovery between each jump. If subjects improved their jump height between the second and third jump, they then were allowed an additional jump. The highest jump recorded was used for data analysis.

Training protocols

Subjects then were randomly assigned to one of four training groups: strength (S), strength-plyometric (P), strength-VertiMax® without arms (VNA), and strength-VertiMax® with arms (VA). There were no statistical differences (P > 0.05) among the four groups for vertical jump prior to the commencement of the training program. The VNA group did not use the upper extremity attachments on the VertiMax® V6 unit, while the VA group did use the upper extremity attachments. It was the intent of this study to compare the effects of different types of strength and plyometric modalities, not to compare if these modalities improve lower body power versus no training. Also, the researchers, as well as the subjects' respective coaches, did not want the athletes to miss 6 weeks of training if placed into a control group that would do no training at all. As noted by Baker (1996), traditional strength training may not be sufficient to improve vertical jump in trained athletes. Also, the additional training load of subjects in groups P, VNA, and VA will elicit different neuromuscular responses than traditional strength training. So, while these additional exercises provide a greater training load, the stimulus it presents is different than traditional strength training. Additional strength or plyometric training was not allowed during the study. Aerobic training and participation in the subjects' respective sports was allowed. The subjects were instructed to continue their usual dietary habits throughout the study. All training was performed 3 days per week with 1 day of rest in between each training day.

Strength training

Group S (n = 8) performed strength training only. Week 1 training was performed at an intensity of ∼60%–65% of 1RM. Three sets of 10 repetitions were completed for each exercise for the 6-week training period. Days 1 and 3 exercises included back squat, bench press, lat pull, hamstring curl, shoulder press, seated row, elbow curl, and extension. Day 2 exercises included lunge, dumbbell bench press, lat pull, hamstring curl, shoulder press, seated row, elbow curl, and extension. Exercise resistance was increased at weeks 3 and 5. Volume of training was not changed. During the sixth week of training each subject decreased intensity to Week 1 levels to prepare for posttesting the following week.

Strength training plus plyometric training

Group P (n = 9) performed strength training and plyometric training. The strength-training program was the same as the strength-training protocol described previously. The plyometric program was identical to the exercises performed with the VertiMax® training protocol without the use resistance provided by the VertiMax®. This was done to insure that the plyometric group would have the same number of foot contacts and exercises as the resisted jump-training groups. The plyometric exercises were varied at week 3, but the exercises chosen were selected based on the take-off and landing protocols of the jumps being consistent with that of the jumps used on the VertiMax®. At week 6, the plyometric exercises were returned to the same exercises performed at the start of the training program. Volume and intensity of plyometric training was not altered during the 6-week program. Instructions and protocol provided to the subjects in this group were identical to the instructions and protocol given to the two VertiMax® groups.

Strength training plus VertiMax® training with no upper extremity resistance training

Group VNA (n = 12) performed strength training and VertiMax® training. The VertiMax® training followed the manufacturer's suggested basic training program, as shown in Table 1. Cord resistances were increased one-half of a band at weeks 3 and 5. These lesser resistances were selected as the VertiMax® was a novel training modality for the subjects; thus, the researchers did not want to introduce too large of a training stimulus via added resistance. Cord resistances were returned to beginning levels at week 6. The manufacturer suggests a cord intensity that will not significantly alter jumping and landing kinematics. On the resistance cords are marker bands that are positioned approximately 6 inches apart over the length of the cord. When the cord is stretched or released to change resistance, these marker bands can be used to objectively provide resistance on the cords.

TABLE 1 VertiMax® Training

Training Jumps	Cord Configuration	Resistance	# of Sets	# of Reps
Warm up Jumps	No Resistance	-	1	10
Half Quick	Single Cord	≥ 1	2	10
Quarter Quick	Single Cord	≥ 1	4	10
Contrast Jumps	No Resistance	-	1	6

Warm-up jumps (quarter-quicks) consisted of the subject beginning in a standing position then bending the knees until the thigh was 45 degrees to the horizontal. The subject initiated the jump from this position. Upon landing, the subject resumed the starting position and pushed off for the next attempt. The half quick jumps consisted of the subject beginning in a standing position then bending the knees until the thighs were approximately parallel to the floor. The subject initiated the jump from this position. Upon landing, the subject returned to the standing position prior to the initiation of the next jump. The contrast jumps were of the same protocol as the quarter quick jumps but with no resistance being applied via the VertiMax®.

Strength training plus VertiMax® training with upper extremity resistance

Group VA (n = 8) performed the same training as Group SVNA with the addition of the arm training on the VertiMax®. Resistance cords were attached to the wrists with the provided wrist wraps, and the same training as described above was performed. Arm resistance began at 1 band, was increased one-half of a band at week 3, and returned to 1 band at week 6. The manufacturer suggests that the resistance on the arms remains relatively light for the best results. Even though the resistance applied to the arms was relatively light, the subjects were still instructed to use the arms as forcefully as possible, similar to what they would do when performing a simple vertical jump. All subjects within both VertiMax® groups were able to change cord resistance accordingly and did not have to change their normal jumping mechanics. This was determined via visual observation by the researchers.

Statistical Analyses

A two-way mixed-factor repeated measures analysis of variance (ANOVA; 2 [times] × 4 [groups]) was used to determine statistical differences between the four groups. Significant within-subjects factors were followed up using protected dependent t tests. Effect sizes were calculated by determining the difference between pre- and posttest means, divided by the pretest SDs (Rhea et al. 2008). Statistical significance was set at P < 0.05 for all tests except for the protected dependent t tests (P < 0.025). SPSS 14.0 was used to perform all statistical analyses.

RESULTS

Training Compliance

There were 18 training sessions over the 6-week training program. There was no significant difference among the four groups for training compliance. Attendance in each group was S: mean value 15, s = 2.7; P: mean value 14, s = 2.8; VNA: mean value 15, s = 1.1; VA: mean value 14, s = 2.1. The primary reason for missing a training session was due to the subjects' academic requirements.

Body Mass

There were no pre- or posttest body mass differences within or between (P = 0.347) the groups.

Vertical Jump

There were no significant differences between the groups for pretest vertical jump heights (P = 0.234) and posttest vertical jump heights (P = 0.349). Tests of within-subjects effects for time showed significant differences (P = 0.001). Post-hoc within-group analyses protected dependent t tests indicated groups P (P = 0.04), VNA (P = 0.03), S (P = 0.167), and VA (P = 0.219) groups did not increase their vertical jump from pre- to posttest (Table 2). Reliability analysis resulted in an intraclass correlation coefficient of 0.97 between pre- and posttesting across all four training groups.

TABLE 2 Results

Group	VJ pre-test (cm)	VJ post-test (cm)	ES
S	58.0  ±  11.6	59.8 ± 8.8	0.17
P	54.7  ±  8.9	∗56.4  ±  9.2	0.35
VNA	59.2  ±  1.6	∗61.6  ±  1.5	0.16
VA	65.9  ± 1.1	68.0  ±  1.0	0.20
ES = pre/post effect size; S = strength group; P = plyometric group; VNA = VertiMax no arms group; VA = VertiMax with arms group
∗Significant difference from pre-test scores (p < 0.05).

DISCUSSION AND CONCLUSIONS

The current investigation compared the effects of a weight-training program, a combination program consisting of weight training and plyometric training, and two combination programs consisting of weight training and resisted jump training on vertical jump and predicted lower body power. The findings of this investigation were that there were no significant mean differences for pretest and posttest vertical jump between the training groups or within each training group. Training compliance across all four groups was 80% throughout the 6-week training program. There were no statistical differences, however, with training compliance across the four groups. We felt that we did all that was reasonably possible to insure attendance at the training sessions. We had hypothesized that the plyometric and resisted jump-training groups would show the greatest amount of change in vertical jump (Adams et al. 1992; Fatouros et al. 2000; Harman et al. 1990). The results of the present study did not support these previous findings. Our findings would concur with those of McClenton et al. (2008) in that the VertiMax training does not improve vertical jump more so than traditional strength or plyometric training. Rhea, Peterson, Lunt, et al. (2008) and Rhea, Peterson, Oliverson (2008), in his two studies utilizing the VertiMax®, did find substantial effect size differences between VertiMax® training and other training modalities. This may be partially explained by the fact that the training protocol utilized by Rhea was twice as long as the current study's training.

Practical applications

Resistance training may elicit positive change in the functional components of the neuromuscular system, such as strength, power, and local muscular endurance (Deschenes & Kraemer 2002). Based on our findings, when training athletes for improvement in vertical jump and lower body power, the chosen training modality is negligible. What may be of more importance is that an appropriate training stimulus is present that could lead to neuromuscular adaptation, i.e., motor unit recruitment, motor unit firing rate, and cocontraction of antagonists (Hammett and Hey 2003).The chosen training must also satisfy the specificity component of training (Baechle and Earle 2000). Thus, if the practitioner wishes to improve lower body power, programs and exercises must be selected to elicit such a response from the neuromuscular system. Plyometrics and training devices such as the VertiMax® may be an appropriate selection, provided they elicit the desired training stimulus. In the present study, we did not find this to be the case, however, possibly due to the short duration of the training. This 6-week program may have been too short to elicit performance changes in previously trained athletes.

Another possible explanation for the lack of practical posttest improvement in the VertiMax® groups was postulated by McClenton et al. (2008). They stated that their VertiMax® training group did not increase their posttest vertical jump because of the possible increase in amortization time due to the band set up utilized on the VertiMax®.

Neuromuscular adaptations have been noted to occur, however, within as little as 4 weeks of training. Hammett and Hey (2003) found a change in neurological adaptation through 4 weeks of training using trained athletes as subjects. They concluded that neurological adaptation can take place at any point during one's training cycle, provided an adequate stimulus is present. The noted trends in our study would concur with the findings of Hammett and Hey (2003). A training protocol of this duration and with this level of athlete may promote neuromuscular adaptation. This positive response to training would be beneficial to the practitioner who may have limited time to prepare athletes for competition. It also may be utilized as a meso- or micro-cycle during the training year.

Last, three athletic teams, which involved some of our subject pool, began their spring training sessions halfway through our training study. While we limited our subjects to not performing any additional specific agility or explosiveness training, we were not able to limit their time spent with their respective teams in a practice environment. This may have influenced the results from two perspectives. First, this added training volume may have initiated a greater neuromuscular response. On the other hand, the added training volume may have limited the effort that the subject was able to give when participating in the study itself. While a member of the research team was present at all sessions, we were not able to control for the amount of effort that was given. Finally, we concluded that the findings of this study suggest there is no difference in vertical jump improvements between strength training, plyometric training, and jump training utilizing the VertiMax®.

The authors acknowledge Genetic Potential for their assistance with the purchase of the VertiMax® used in this investigation.