Low velocity (LV) resistance training is a method of resistance-training consisting of a 10-second concentric muscle action and a 4- to 10-second eccentric muscle action (6). It has been purported to be safer than traditional resistance training as well as giving superior results for muscular fitness, cardiovascular health, and sports performance (6). It was the aim of this study to determine the validity of these claims under carefully controlled conditions.
Many studies have evaluated velocity specificity of resistance training using isokinetic training and testing (22). However, most athletes and nonathletes train using dynamic constant external resistance (DCER). A few studies have investigated the effects of different DCER training velocities on various performance-related measures (19,20,30). Performing DCER training at a high velocity compared to a traditional velocity has been shown to increase strength to a greater degree (19,20) and also to improve maximum rate of force development (30) showing that high velocity resistance training can be a beneficial adjunct to a resistance-training program (22). In the past few years, LV DCER training has received much attention in the lay literature, but relatively few studies have documented the potential benefits of this type of resistance training (13,15,21,28). There is some evidence that LV training increases strength (28). The increase in strength is suspect, however, because velocity specific testing (low velocity group tested at a low velocity, traditional velocity group at a traditional velocity) was used to determine the difference between groups (28). It was suggested that a common test be utilized to assess strength in future studies (28), and it should be noted that this investigation did not utilize a control group to assess a learning effect (28).
There is no evidence as of yet to support an improvement in cardiovascular function (13,15), or body composition (15,21) using LV resistance training. Keeler et al. (15) did show, however, that both a LV and traditional resistance training program were able to increase total exercise time and maximal work rate during a maximal cycle ergometer test, without any difference between the two training programs. This study (15) however, did not compare the performance to a muscular endurance-training program, which would be more likely to improve a low resistance, high repetition exercise such as cycling; as well, it did not compare the training groups to a control group to see if the improvements seen in total exercise time and maximal work rate were due to a learning effect. Also, although body composition did not change in the previous studies (15,21), other studies have found a change in body composition following short-term training programs (6 weeks) in women (26), however, this study also did not use a control group. Due to these conflicting results, further research is needed to clarify the early phase responses of body composition to a variety of resistance-training techniques, such as the LV training and more traditional methods, and also to assess the response as compared to a control group.
One recent investigation concerning LV training has examined muscular power (21). Neils et al. (21) found no improvement for a LV training protocol for muscular power. In this study, a traditional strength training group was compared to a LV training group and no control group was utilized.
The purpose of our study was to investigate the early-phase adaptations of a LV resistance training program on various performance measures as compared to a traditional resistance training program (TS), a traditional muscular endurance-training program (TE) and a control group (C). The performance variables analyzed included muscular strength, muscular endurance, muscular power, cardiovascular endurance, and body composition. This investigation complements previous published data by comparing LV training using the two extremes of the strength-endurance training continuum. Unlike previous investigations, this study also utilized a control group.
Experimental Approach to the Problem
This study determined the effects of TS, TE, and LV training on strength, muscular endurance, maximal oxygen consumption (including time to exhaustion and maximal power output), muscular power (as assessed by a vertical jump), and body composition over a 6-week period. The 3 training groups performed 3 sets each of the following exercises: leg press (LP), knee extension (KE), and Smith-rack back squats (SQ). The TS group trained using a 6-10 RM with a 1-2 second concentric/1-2 second eccentric muscle action, the TE group trained using a 20-30 RM with a 1-2 second concentric/1-2 second eccentric muscle action, and the LV group trained using a 6-10 RM with a 10 second concentric/4 second eccentric muscle action. This contraction speed is similar to those used in past investigations that either used 10 second concentric/4 second eccentric (28) or 10 second concentric/5 second eccentric muscle actions (13,15,21). Initial training loads were set at a given percentage of the 1 RM and then adjusted to meet the prescribed repetitions. All participants were closely supervised during each training session. A minimum of 16 of the 17 training sessions must have been completed for the subject to be included in this investigation. The time frame of this study was chosen due to both logistical reasons and because it has been shown that skeletal muscle adaptations occur in untrained women in this short training period (25,26), including skeletal muscle hypertrophy (26).
Table 1 depicts basic subject characteristics. Thirty-four healthy adult females (21.1 ± 2.7 y) volunteered to participate in this study. The subjects were not trained regarding resistance exercise, and all were instructed to maintain a consistent level of physical activity throughout the training period. This was confirmed by physical activity questionnaires completed both before and after the study. The subjects were randomly divided into 4 groups: control (C), traditional strength (TS), traditional endurance (TE), and LV. All subjects completed an institutional review board-approved informed consent and medical exam prior to involvement with the study.
Testing and Training Schedule
The subjects were tested (2 weeks each of pre- and posttesting) and trained (6 weeks, or 16-17 training sessions) according to the following schedule:
Pretesting (2 weeks)
- Body Composition, VO2max, and Muscular Power (first week)
- Muscular Strength and Endurance (second week)
Training (6 weeks)
- One week training 2 days/week (total of 2 training sessions)
- Five weeks training 3 days/week (total of 15 training sessions)
Posttesting (2 weeks)
- Body Composition, VO2max, and Muscular Power (first week)
- Muscular Strength and Endurance (second week)
Familiarization sessions for the resistance training exercises to be performed were conducted prior to the actual testing and training sessions for all groups, including the control group. During the familiarization sessions, the subjects were instructed on proper form and speed of each exercise, and ranges of motion were noted for each exercise. For the LP, the subjects were instructed not to allow their knees to flex beyond 90 degrees during the eccentric portion of the exercise. This position was marked by taped numbers on the side of the machine and recorded for each subject. During testing and training, the supervisor of the exercise would inform the subject when this position was attained, at which point the subject performed the concentric portion of the lift. For the SQ, each subject was instructed to perform the eccentric portion of the exercise until their thighs were parallel to the floor. This position was determined when the end of the bar touched an elastic band stretched horizontally between supports of the Smith rack at the height corresponding to the thighs parallel to the floor position, which was marked by a specific number. This procedure ensured a consistent inferior position to gauge lowering the bar during testing and training. For the KE, subjects were seated in a position in which the center of the knee joint was in line with the axis of rotation of the machine, and the pad of the machine was placed at ankle-level.
Tests of muscular strength were conducted pre- and posttraining. All subjects performed a 5-min general warmup on a cycle ergometer prior to testing. The procedures utilized for each subject and exercise, were identical. A specific warmup was performed for each exercise by the subject, who performed 8-10 repetitions (40-60% of 1RM) prior to the testing. After 3-5 min of rest, the subject then performed a set of 2-3 repetitions (75% of estimated 1RM), and a set of 1 repetition (90% of estimated 1RM). After each of these sets, the subject was allowed 3-5 minutes of rest. The subject then made the first attempt at 1RM. If the lift was successful or unsuccessful, 3-5 minutes of rest were given while the weight was increased or decreased, respectively, and a second 1RM was attempted. This procedure was repeated if necessary with the 1RM ultimately being determined within 5 attempts. Strength was expressed in both absolute and relative terms. Only those lifts completed within the prescribed range of motion for each subject and exercise were judged successful. Evaluation of a lift was the responsibility of an experienced evaluator.
Muscular Endurance Tests
Tests of muscular endurance were conducted pre- and posttraining in an identical manner. These tests were conducted at the same time as the 1 RM tests. After the 1RM was determined for a given exercise, the subject was given 10 minutes of rest. The resistance was then set at 60% of the subject's 1 RM and the subject performed as many repetitions as possible until fatigue. The number of repetitions performed served as the measure for muscular endurance.
Muscular Power Tests
In order to assess muscular power, a vertical jump test was performed by each subject both pre- and posttraining. Using a Vertec device (Sports Imports, Columbus, OH) and the procedures set forth by Baechle and Earle (1), the subject was allowed 3 attempts to obtain their maximal jump height. The best of 3 trials was recorded to the nearest 1.27 cm. Muscular power was calculated by the following formula (24), using the maximal jump height (difference between the standing vertical reach and the highest point of the jump recorded) as well as body mass:
Watts = [60.7 * (jump height in cm)] + [45.3 * (body mass in kg)] - 2055.
Maximal Oxygen Consumption Tests
A continuous, ramp protocol performed to exhaustion was completed by each subject on a calibrated Monark 874E cycle ergometer (Monark Exercise AB, Vansbro, Sweden) both pre- and posttraining. The subject pedaled the cycle ergometer at 60 rpm throughout the entire test and a metronome was utilized to assure consistency of the cadence. The workload started at 30 W and was increased by 18 W every minute until the test's conclusion. VO2max was achieved when 2 of the following criteria were met: a plateau or decrease in oxygen consumption despite an increase in power output, a respiratory exchange ratio ≥1.10, attainment of predicted maximal heart rate, or volitional fatigue (12).
The subjects were fitted with headgear and a mouthpiece in order to collect expired gases using semi-computerized open-circuit spirometry (Vacumed, Ventura, CA). The subject's oxygen consumption (VO2), ventilation (VE), expired carbon dioxide volume (VCO2), and respiratory exchange rate (RER) were measured. VO2max was expressed both in absolute and relative terms. Heart rate was monitored using a Polar Heart rate monitor A1 (Lake Success, NY) and recorded manually.
Body Composition Tests
The subjects were pre- and posttested for body composition, assessed by air displacement plethysmography using a calibrated BOD POD® (Life Measurement, Inc., Concord, Calif.). The BOD POD® measures body volume by using air displacement plethysmography as previously described (4). All subjects were tested wearing a lycra swim suit and cap (4). A correction was made on all subjects for the average volume of air contained in the lungs and thorax during normal respiration, which is measured by the BOD POD® using standard plethysmographic technique (4). The same thoracic gas volume was used for posttesting. Density of the body was calculated by dividing body mass by body volume. Percent body fat was then determined using a population specific equation (9). The following 2 equations were utilized:
All analyses were performed using SPSS 12.0 for Windows (SPSS Inc., Chicago, IL). Values are expressed as mean ± SD. Repeated measures, mixed model ANOVAs (2 × 4) were used to assess differences within (pre-post) and between groups for each variable. If a significant interaction was detected, the simple effects were analyzed. If no interaction was detected, main effects were analyzed, and if significant main effect differences were detected between groups, a 1-way ANOVA was performed for both the pre- and posttest data with a Tukey's HSD post hoc. Percent change in relative strength was assessed by using a 1-way ANOVA with a Tukey's HSD post-hoc if significant differences were found. All analyses utilized an alpha of 0.05.
The results from the percent change in both relative and absolute strength for each exercise are shown in Table 2. A one-way ANOVA revealed a significant difference between groups for all 3 exercises (LP (p < 0.001, relative and absolute), SQ (p = 0.004 relative, p = 0.003 absolute), KE (p < 0.001, relative and absolute)). Post hoc analysis for LP showed TS was significantly greater than all other groups (p < 0.001, relative and absolute), and LV was significantly greater than C (p = 0.038 relative, p = 0.024 absolute). Post hoc analysis for SQ showed only that TS was significantly greater than C (p = 0.002, relative and absolute). Post hoc analysis for KE showed TS was significantly greater than all other groups (LV p = 0.025 relative, p = 0.023 absolute; TE p = 0.001 relative and absolute; C p < 0.001 relative and absolute), and LV was significantly greater than C (p = 0.019 relative and absolute).
Table 3 demonstrates the results of the muscular endurance tests. A 2 × 4 repeated measures mixed factor ANOVA for the LP revealed a significant interaction (p = 0.041). Repeated measures ANOVAs for each group revealed a significant increase for both LV (37.3 ± 10.45 pretest; 46.6 ± 9.55 posttest; p = 0.047) and TE (35.1 ± 15.46 pretest; 49.57 ± 11.12 posttest; p = 0.018). One-way ANOVAs revealed a significant difference posttest (p = 0.003) between groups and the post-hoc analysis showed that LV and TE were significantly greater than C (p = 0.007 and 0.004, respectively). For the SQ, a 2 × 4 repeated measures mixed factor ANOVA revealed no significant interaction, but a significant training effect was found (p < 0.001) and a between groups difference was found (p = 0.022). A Tukey's HSD post hoc on the between-groups main effects revealed that LV and TE were both significantly greater than C. For the KE, a 2 × 4 repeated measures mixed factor ANOVA revealed a significant interaction (p < 0.001). Repeated measures ANOVAs for each group revealed a significant increase for TS (12.7 ± 2.29 pretest; 18.3 ± 3.28 posttest; p < 0.001), LV (12.3 ± 2.06 pretest; 14.2 ± 2.39 posttest; p = 0.018), and TE (11.1 ± 2.41 pretest; 17.57 ± 5.68 posttest, p = 0.010). One-way ANOVAs revealed a significant difference posttest (p = 0.004) between groups and the post-hoc analysis showed that TS and TE were significantly greater than C (p = 0.031 and 0.040, respectively).
Table 4 shows the results of the vertical jump tests. A 2 × 4 repeated measures mixed factor ANOVAs showed no significant differences (p > 0.05) for either jump height or muscular power.
Maximal Oxygen Consumption
Table 4 shows the results of the maximal oxygen consumption tests. A 2 × 4 repeated measures mixed factor ANOVA showed no significant interaction or significant difference between groups, but a significant training effect was found for relative VO2max (p = 0.002). Time to exhaustion during the maximal test was analyzed with a 2 × 4 repeated measures mixed factor ANOVA, and a significant interaction (p = 0.044) was revealed. Repeated measures ANOVAs for each group demonstrated a significant increase for TE (8.9 ± 1.46 min pretest; 9.9 ± 1.77 min posttest; p = 0.010), but not for any other group. One-way ANOVAs showed no difference between groups either pretest or posttest. A 2 × 4 repeated measures mixed factor ANOVA for maximal power output achieved during the VO2max test was performed and no significant interaction or significant difference between groups was found, but a significant training effect was detected (p = 0.031). A 2 × 4 repeated measures mixed factor ANOVA revealed no significant differences (p < 0.05) in maximal heart rate.
Table 1 shows the results of the body composition tests. A 2 × 4 repeated measures mixed factor ANOVA was performed for percent fat (%FAT) and no significant interaction was found, but a significant training effect (p = 0.002) and a significant main effect between (p = 0.029) groups was detected. A Tukey's HSD post hoc on the between-groups main effects revealed a difference between the LV and C groups. A 2 × 4 repeated measures mixed factor ANOVA was performed for fat mass (FM) and no significant interaction was found, but a significant training effect (p = 0.008) with no significant main effect between groups was detected. A 2 × 4 repeated measures mixed factor ANOVA for fat free mass (FFM) was performed and no significant interaction was found, but a significant training effect (p = 0.001) with no significant difference main effect between groups was detected.
In the current investigation, the TS group improved strength significantly more than the other groups for the LP and KE, and was the only group significantly different from C in the squat. This finding is in support of the strength-endurance continuum and is similar to other investigations (2,27). The LV group improved above C in the LP and KE, but not the SQ, and was not significantly different from TE for any exercise. This is similar to some findings which have investigated LV training (15,21), however not all (28). Possible reasons that our findings differed from this peer-reviewed study could be the methods utilized in both studies. Wescott et al. (28) compared the training effects of a traditional velocity and low velocity group, but did not use the same test of strength for each group, whereas in the current study a common test was utilized for all subjects to assess the training effects on strength gain.
Another point that could help explain the results from the LV training could be the lower load the LV group utilized compared to the TS group in order to perform the required number of repetitions at such a slow velocity. While all 3 training groups in the current study trained using sets to failure, the average training load for the sets varied. Average load over the 17 training sessions for the LV group was lower (162 kg for LP, 36 kg for SQ, 25 kg for KE) than the TS (227 kg for LP, 55 kg for SQ, 53 kg for KE) and was similar to TE (155 kg for LP, 29 kg for SQ, 22 kg for KE) groups. The fact that the LV group did not show as great an improvement in strength as the TS group indicates that the load utilized in training relates to the magnitude of the effect. Evidence to this fact is indicated in the current study in that no statistically significant differences in strength gain were detected between the TE and LV group, and the loads utilized were similar.
As suggested previously (28), a common test of strength was utilized in the current investigation. However, the speed of the 1 RM could have affected the results. From past literature, it could be assumed that the higher velocity training would increase force at that specific velocity and all those below it (3,18), which means the low velocity group could possibly show an equal level of improvement for a slower velocity test as compared to the other groups. Indeed, in the current study, there was a significant strength gain above the control group in the LV group for 2 of the 3 exercises. Although not as great as the TS group (45.5-61.8% increase), there was still a gain in muscular strength for the LV group (26.6-30.0% increase), even though it was tested at a traditional velocity. However, other studies have not found the same velocity-specific results (19). In the future, it may be necessary to test both a traditional speed 1RM and a low velocity 1RM to determine the specific training effects.
The muscular endurance results of the current study illustrated further support for the strength-endurance continuum of training. The TE and LV groups improved consistently in the number of repetitions performed at 60% of the 1 RM for all 3 exercises. The TS group only improved for 2 of the 3 exercises. The difference between the LV and TE groups was that the LV group did not show a significant difference from the C group in 2 of the 3 exercises, but the TE group did show a significant difference above the C group for 2 of the 3. Since the LV group lifted a similar amount of weight as the TE group, but performed less repetitions during the training sessions, this lends support to the fact that the findings were due to training specificity (the group performing the most repetitions demonstrated the most consistent improvement in muscular endurance). However, it does show that LV training could enhance muscular endurance, just not to the same extent as TE training. The results of this study are similar to the findings of Stone and Coulter (27) and Campos et al. (2) in that a group that performed high repetition, low resistance training improved more in terms of muscular endurance compared to a high resistance, low repetition protocol. However, only the study by Campos et al. (2) determined that this was a statistically significant difference.
Focusing on the results of the LV group, the current study does not support an improvement in muscular endurance above and beyond the TS and TE training methods. It could be that the improvement in muscular endurance is exercise-specific depending on training method. This is shown by the opposing results for the LP and SQ when comparing the TS and LV groups (Table 3).
Previous investigations have demonstrated inconsistencies concerning improvement of muscular power following resistance-training at varying velocities (21,23,29,30). In the current study, there was no significant improvement seen in muscular power or vertical jump height. The main reason for this finding is most likely that subjects were not training specifically for muscular power. A study by Neils et al. (21) demonstrated an increase in countermovement jump peak power with traditional resistance training, but not with LV training. Our study did not find improvement with TS, TE, or LV methods, so it varies somewhat from the recent findings of Neils et al. (21). Reasons for the variation could be the method of testing. Neils et al. (21) used a force plate to measure power production, but the current study utilized jump height and calculated the power produced. Wilson et al. (29) however, also found that traditional resistance training, while able to improve counter movement jump height, did not do so to the same degree as training for maximal power production. The maximum power training group also improved in 30-m sprint time (nonsignificant) and 6-second cycle ergometer peak power, unlike the traditional resistance-training group, which shows that specificity of training may be more important in determining improvement in a power movement such as the vertical jump performed in the current investigation (29).
The current investigation found a difference in body composition measurements from pre- to posttest, with no significant interaction between repeated measures and groups. According to our results, all groups (even the control group) had a slight but significant decrease in %FAT and fat weight, and increase in lean body mass (Table 1). Some past literature has shown that a decrease in percent fat occurs in untrained individuals when utilizing resistance training protocols (7,11,26), and in some cases trained subjects have not shown these same results (10,25,26). The results from the current study, therefore, may demonstrate that the subjects were in an untrained state. Another explanation for our results could be the time of year when the subjects were training, which was immediately after a 6-week winter break. The subjects may have been returning to a more normal activity level at this time. This could potentially explain why no difference between the training groups and control group was found.
In the current study, significant main effects for training (pre-post) were found for VO2max, and maximal power output on a cycle ergometer for all groups, including the control group. For time to exhaustion during the VO2max tests, the only significant difference was an increase found in the TE group (Table 4). Our findings are in agreement with the other investigation regarding LV training which also found no improvement in cardiorespiratory fitness as measured by VO2max (15). Many studies have not found significant changes in VO2max following traditional velocity resistance training protocols (11,14,16). Most studies reporting an increase in cardiovascular fitness postresistance training examined responses in older, sedentary subjects (5,7,8,17). Therefore, the VO2max results of the current study are not surprising, especially considering that the subjects were younger, and many subjects were active, but simply had not trained using resistance exercises.
Keeler et al. (15) found an increase in time to exhaustion and maximal work rate during a maximal cycle ergometer test for both a LV and traditional resistance training group. Campos et al. (2) also found that a high repetition training group improved time to exhaustion and maximal power output without changes in VO2max. Therefore, like previous investigations (2,11,15,16) we agree that resistance training, specifically TE training, has the potential to improve short-term endurance without improving aerobic capacity. This may be related to increases in muscular strength or anaerobic potential of the subjects, the latter of which we could not detect with our testing method.
Although all groups improved in strength and muscular endurance, this study demonstrated that to optimize one or the other, specific training methods show greater early phase improvement as compared to LV training. For example, to show the greatest early phase improvements in muscular strength or muscular endurance, a high load, low repetition or low load, high repetition program, respectively, would be more ideal than a LV training program, which showed a response in-between the two traditional training methods. It was also concluded that none of the training programs in the current study demonstrated benefit in terms of cardiovascular fitness, power, or body composition, with the exception of an improvement in short-term endurance, again demonstrating that training specificity is important for early phase adaptations to occur.
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