Figure 3 illustrates the comparison of HR between SS and TM. Elbow flexion elicited a significantly greater HR during TM vs. SS at PHR1 (SS = 131 ± 18, TM = 144 ± 19). KE elicited a significantly greater HR during TM vs. SS at PHR1 (SS = 126 ± 23, TM = 139 ± 17) and PHR2 (SS = 133 ± 24, TM = 145 ± 17). Observed power for HR was 1.00 while performing both EF and KE.
Ratings of Perceived Exertion
Figure 4 shows the differences between SS and TM for RPE. The TM RPE was significantly greater than the SS RPE during EF at T2 (SS = 12.6 ± 2.5, TM = 16.0 ± 2.0) and T3 (SS = 16.9 ± 1.8, TM = 18.7 ± 1.8) for set 1, T1 (SS = 11.8 ± 2.0, TM = 13.9 ± 2.5) and T2 (SS = 15.1 ± 2.1, TM = 17.0 ± 2.0) for set 2, and T3 (SS = 18.1 ± 1.5, TM = 19.5 ± 1) for set 3. The TM RPE was significantly greater than the SS RPE during KE at T2 (SS=13.8 ± 1.8, TM=16.2 ± 1.9) for set 1. Observed power was 0.80 for EF and 1.00 for KE.
Total Volume Load
Figure 5 illustrates the differences between SS and TM for TV. For TM, TV was significantly greater than for SS for all sets and for both exercises. Observed power was 1.00 for TV during EF and KE (SS vs. TM).
Total Time Under Load
Figure 6 shows the differences between TT for SS and TM. For SS, TT was significantly greater than for TM for all sets and for both exercises.
Table 2 shows the amounts of repetitions accomplished by each subject for SS and TM. Subjects were able to perform a significantly greater amount of repetitions during TM as compared with SS.
Ratios of Heart Rate per Total Volume of Work
Ratios of HR per TV (HR/TV) were significantly higher for SS vs. TM for both exercises. This higher ratio during SS could suggest a higher cardiovascular strain while performing SS. However, care must be taken in the interpretation of HR/TV because HR and TV are not congruent. The ratios for SS could be artificially inflated, considering that HR has a lower and upper limit whereas TV can change immensely. Therefore, the remainder of this article will focus on more practical methods of determining cardiovascular strain.
The results show no significant differences in SBP or DBP between SS and TM. Therefore, neither regimen seems to present a greater danger than the other on the basis of BP readings taken immediately postexercise. However, the ratio between BP and TV would actually be higher during TM because of the greater amount of TV accomplished during TM.
It could be assumed that the Valsalva maneuver would be more likely to occur during SS. If the Valsalva maneuver did occur to a greater degree during SS, it could be expected that the BP response would be elevated during SS. However, the BP response was similar between SS and TM. This is consistent with a study by Heffernan et al. (6), which found that changes in BP were consistent between resistance exercise bouts and an experimental condition consisting of repeated Valsalva maneuvers. Therefore, a couple of speculations can be made from the current study and the study by Heffernan et al. (6). First, it could be speculated that the Valsalva maneuver does not contribute to an exaggerated increase in BP as might be expected. However, the more likely theory is that the Valsalva maneuver did contribute to an increase in BP in some subjects. Therefore, the Valsalva maneuver could have contributed equally among SS and TM.
Total volume load was much higher during TM vs. SS for both exercises. This higher TV during TM could lead one to assume that the subjects' BP responses would follow this increase. However, as mentioned before, there were no differences in BP between protocols. Pichon et al. (13) examined the differences in the BP response between circuit training and traditional weight training. In the study by Pichon et al. (13), the circuit training protocol had a greater total work load, which led to a higher metabolic cost. However, even though metabolic cost was higher, no differences were found in the BP responses of the subjects among the two weight training protocols. Therefore, it seems that a greater amount of work performed may not be a significant contributing factor in elevating BP. However, care should be taken when comparing the current study with the study by Pichon et al. (13) because of the difference in the calculations used for the determination of TV (weight × reps) in the current study vs. the determination of work by Pichon et al. (13) ([weight of body segment × distance moved against gravity] + [weight of the bar and plates × distance moved against gravity]).
Furthermore, according to the results of this experiment, while performing EF, SBP decreased significantly from the resting value during SS and TM. However, while performing KE, SBP increased significantly above the resting value. A possible explanation for the decrease in SBP during EF could be that the subject experienced a vasodilation immediately after cessation of the exercise. Blood pressure was not measured during the contraction phases of the exercise, but a large increase in SBP would be expected. However, on completion of the exercise and relaxation of the active musculature, SBP may decrease, possibly because of vasodilation. As expected, there were no significant differences observed during SS and TM in DBP.
It is also plausible that menstrual phase variations of the female subjects may have skewed the SBP and DBP responses. However, according to Esformes et al. (3), there seems to be little difference in SBP and DBP across the menstrual cycle. According to Esformes et al. (3), there were no significant differences shown between the phases of the menstrual cycle for SBP. However, there was shown to be a significant main effect for DBP during the early follicular phase, which showed that DBP was consistently lower during this early follicular phase than during other phases of the menstrual cycle. Still, there were not any significant differences found at any individual time points of BP responses between the various phases of the menstrual cycle. Furthermore, actual data should be considered to determine the practical differences in BP among the phases of the menstrual cycle. Mean DBP during the early follicular phase was 69 ± 4 mm Hg, 74 ± 3 mm Hg during the late follicular phase, and 72 ± 5 mm Hg during the midluteal phase. Therefore, the lack of a significant difference at individual time points and the lack of a practical difference in mean DBP values (as seen above) support the idea that menstrual phase variations do not play a major role in skewing BP responses in women.
The results of this study show that TM brought about a significantly greater response in HR when compared with SS for both exercises. This response could have been attributable to greater resistance used during TM. It was thought that by increasing the resistance and the speed of TM, the overall difficulty would equal the decreased resistance and speed of SS. However, the greater resistance must have played a role in the greater HR response by TM. Also, the increased number of repetitions per set could have played a role in the greater HR brought about by TM (reps for SS and TM [Table 2]). However, on average, subjects could not perform the same amount of repetitions as were performed by subjects in a study by Hoeger et al. (7). Even though similar percentages of 1RM were used in the current study as in the study of Hoeger et al. (7), the resulting lower numbers of repetitions accomplished were expected because of the slower speed of movement used. Furthermore, from Figure 5 it can be seen that TV is greater during TM than SS. This provides more evidence as to why HR was higher during TM vs. SS. This holds true despite the fact that TT was significantly greater during SS compared with TM (Figure 6). Therefore, this leads one to believe that the greater resistance must have played a significant role in the increased HR during TM. Although this outcome may have been anticipated, from a practical standpoint the resistances selected were similar to what might be used when employing the specific lifting techniques (SS and TM). Consequently, the ecological validity in the current design was magnified by applying such resistances. Had similar loads been applied for TM and SS, it is conceivable that the results may have been altered. However, the emphasis in the current study was to attempt to mimic, as closely as possible, the loads that might be selected for the different techniques, to determine what results might occur in typical SS and TM lifting paradigms.
It is also reasonable to consider the effect of menstrual cycle variations of the female subjects on HR. According to Esformes et al. (3), there were no differences in central hemodynamic variables (including HR) among menstrual cycle phases. Therefore, it is evident that menstrual cycles of the female subjects would not have a significant effect on HR.
Subjects perceived TM as more difficult than SS at each time point (Figure 4). It is plausible to hypothesize that SS would elicit a greater pain response attributable to a potentially greater ischemic response, which could possibly produce an elevated RPE. However, the results contradicted this hypothesis. Traditional machine training brought about a greater RPE or pain response than did SS (Figure 4). Pain causes an increase in adrenaline release. The increase in adrenaline will then cause an increase in the cardiovascular response (HR). However, it must be noted that adrenaline was not measured in this study. Because TM brought about a greater RPE, it can be speculated that the pain response was higher. Therefore, the greater response in HR for TM could be partially attributable to its greater RPE or greater pain response.
The initial goal before starting this study was to equate overall difficulty by adjusting the resistance and repetitions of SS and TM, respectively. However, it seems that the greater resistance during TM had an effect on the subjects' overall perceptions of effort. The subjects' RPE values were very likely driven by the pain experienced during the exercises. However, a pain scale was not incorporated, so no definite conclusions can be made in regard to pain.
As with HR, TV (Figure 5) seems to have played a role in the greater RPE experienced during TM vs. SS. Again, this holds true despite the fact that TT was significantly greater during SS as compared with TM (Figure 6). Therefore, the resistance during TM must have been a principal factor contributing to the greater RPE during TM. This increased perception of effort and the possible increase in adrenaline release could have ultimately contributed to an increase in HR. All of these variables combined may have had an effect on the greater RPE experienced during TM. Because multiple factors influence perceptual responses, it is difficult to discern the precise reason for greater RPE during TM. One might consider menstruation of the female subjects to be a confounding variable that could have skewed perceptual responses. However, according to Stephenson et al. (15), changes in ovarian/uterine function during the menstrual cycle do not affect RPE at any exercise level.
The current results suggest that greater resistance has a more significant effect on RPE than does TT. The current findings are consistent with past research in that a higher percentage of 1RM elicited a higher RPE (2,5,12,16). However, it must be noted that in this previous research (2,5,12,16), subjects were only required to perform a certain amount of repetitions per percentage of 1RM, and not necessarily to failure. This is in contrast to the current study, in which subjects performed repetitions until volitional fatigue. Still, similar results were found in the current study regardless of the amount of repetitions accomplished or the speed at which the repetitions were performed. Further work is needed on perceptual responses during resistance training, particularly with different training techniques.
Rate pressure product can be determined by multiplying HR by SBP. Rate pressure product is indicative of the metabolic demand of the heart during exercise (8). Thus, factors that increase HR and SBP can increase the metabolic demand of the heart. In this experiment, EF elicited a lower SBP than the resting value, and KE brought about a higher SBP than the resting value during both protocols (SS and TM). Because TM elicited a significantly greater HR than SS, RPP could be greater while performing KE during TM, causing a greater metabolic demand on the heart. Conversely, because SBP was significantly lower during EF as compared with KE, RPP would be lower, resulting in a lower myocardial oxygen requirement. Super Slow resistance training did not produce an HR as great as that of TM. Therefore, RPP would probably be lower during SS. Finally, RPP should be given consideration when prescribing exercise to hypertensive populations. As regards this study, the greatest concern with RPP would be while performing KE during TM. As HR and SBP go down in SS while performing EF, RPP becomes less of a problem. However, it should be kept in mind that this variable was not measured because of the mismatched time points at which HR and BP were measured. Thus, no definite conclusions regarding exact demands placed on the heart during the different protocols can be made.
In conclusion, even though SBP was greater than resting SBP within SS and TM, there were no significant differences found between the two training regimens. In future studies, BP should be measured during resistance training exercises incorporating SS. With HR, TM showed a greater response. Ratings of perceived exertion coincided with this rise in HR and with greater resistance. It seems that the greater resistance in TM elicited a higher subjective assessment of effort (RPE) or pain. This, along with the greater TV, could have contributed heavily to a greater HR. On the other hand, it is also a possibility that the increase in HR contributed more to the greater RPE experienced during TM. It must be noted that differing results could be seen if a complete training regimen (i.e., more exercises and more muscle groups used) were used. Furthermore, the results of this study should be interpreted in consideration of the small muscle group exercises (EF and KE) used. In other words, this study should not be used to generalize to exercises that employ multiple muscle groups (i.e., leg press). Therefore, future research warrants testing the variables used in the current study while using a complete training regimen. Also, more research should be done in this area incorporating weight training exercises that recruit numerous muscle groups.
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Keywords:© 2009 National Strength and Conditioning Association
weight training; slow resistance training; cardiovascular