Multiple-set higher-load resistance exercise regimes have been recommended for improving strength and power in trained athletes (1). Conversely, lower-load slower cadence regimes, known colloquially as high-intensity training (HIT), have been suggested to evoke greater metabolic stress (18). The HIT model became popular with the Nautilus equipment in the 1970s and was characterized by slow exercise cadences to volitional fatigue (17). Others, however, have advocated that greater metabolic stress is generated by using additional assisted repetitions (2) and slower repetitions (14,20).
Combative sports such as wrestling and judo require muscle force efforts in situations where muscular pH is low. For these sports, fatiguing isometric repetitions, or repetitive isotonic contractions with lower loads, are suitable metabolic stressors that lead to improved combative performance (15). Fatiguing and forced repetitions also have been reported to evoke greater muscular activation, as measured by surface electromyography (2), and that aspect may explain the putative benefits of isometric or slow resistance exercise. Therefore, an HIT bout in comparison to a traditional resistance training (RT) bout using a greater load would potentially exhaust the body's anaerobic capacity to a greater degree.
Resistance training evokes muscular hypertrophy, increases muscular strength and endurance, and improves work capacity (8). The final component, work capacity, is measured commonly using cycle ergometry. Advances in the last decade have led to a more rapid assessment of an athlete's critical power (CP) and work capacity above CP, denoted as W' (N.B., pronounced W-prime) (12). The CP parameter represents the maximal rate for sustaining exercise for an extended period of time (12). Conversely, the W' parameter represents a finite anaerobic energy reservoir, which is both load and time dependent. Specifically, the higher the intensity an exercise bout is relative to CP the more rapid the catabolism of glycogen and high-energy phosphates will occur, along with the accumulation of metabolites known to impede muscular contractions (13). As such, the CP model represents a novel method for exploring the effects of resistance exercise on anaerobic capacity. To our knowledge, no investigators have used the CP model to explore acute responses to resistance exercise.
We used the CP model in the present study to compare the metabolic effects of an HIT bout using a lower-load HIT bout vs. a traditional RT bout using a higher load. Our primary hypothesis was that the HIT bout is a superior metabolic workout and would cause a greater decline in total power and W' in comparison to the traditional RT bout. Our secondary hypothesis was that neither exercise bout would alter the CP because the CP metric represents an aerobic parameter (5).
Experimental Approach to the Problem
We used a counterbalanced order repeated-measures design to investigate the acute effect of 2 resistance exercise regimes on anaerobic work capacity. The subjects visited the laboratory on 4 or 5 occasions, with at least 48 hours between visits. The first visit was for the purpose of conducting a baseline 3-minute all-out exercise test (3 MT) (5,19) on a bicycle ergometer (Lode Excalibur Sport Cycle Ergometer, Groningen, The Netherlands). If the subjects encountered difficulties (e.g., too high of a load to complete the 3 MT), a second visit to repeat the 3 MT was conducted (N.B., retesting for baseline 3 MTs was necessary for 2 subjects). A subsequent visit consisted of 10 repetition maximum (10RM) testing, characterized by 4-second eccentric and 2-second concentric repetitions (i.e., 4:2 cadence) (20), was conducted along with familiarization training for exercise on the leg press (Nautilus Nitro Leg Press; Nautilus, Med-Fit Systems, Inc., Independence, VA, USA) and leg extension (Nautilus Nitro Leg Extension; Med-Fit Systems, Inc.) machines. The 2 remaining visits consisted of the HIT bout and the traditional RT bout after a post-intervention 3 MT. The HIT and traditional bouts were counterbalanced to avoid an order effect (i.e., half of the subjects did the HIT bout first, the other half did the HIT bout second). A period of approximately 3 minutes was needed after each bout and the initiation of the 3 MT.
Eight recreationally trained men (mean ± SD: age 21.9 ± 1.9 years, body mass 84.7 ± 14.2 kg, and height 182.6 ± 9.1 cm) volunteered for this study and agreed to follow their standard diets and to refrain from using alcohol and tobacco as well as performing any strenuous physical activity 24 hours before testing. Subjects were deemed healthy for participation by reviewing a completed health questionnaire, and the study's procedures were preapproved by the sponsoring university's institutional review board for human subjects. Informed consent was obtained for each subject before data collection.
3-Minute All-Out Exercise Testing
A minimum of 2 separate 3 MTs (5,19) were performed to determine pretesting along with posttesting values subsequent to the HIT and RT bouts, respectively. The loads for the 3 MTs for pretesting and posttesting were the same and were set at 2, 2.5, or 3% body mass, based on the subject's level of physical activity (3,6). The 3 MT included a brief warm up (50 W) followed by a 5-minute rest period. A build up of cadence 5 seconds before the start of the 3 MT was programmed to avoid pedaling against the prescribed fixed-load from a dead start. Subjects then pedaled all-out, as fast and as hard as possible, for the entire test. Verbal encouragement was provided, but the subjects were neither informed of the time elapsed nor the time remaining in an effort to avoid pacing.
Raw power-time data for each 3 MT were exported at 6 Hz to a Microsoft Excel (Microsoft Corporation, Redmond, WA, USA) spreadsheet and Butterworth filtered (11). Two subjects were retested for their baseline 3 MT because of excessive noise in the raw power-time data. We attribute the noise in the power data was the result of the subject's inability to complete the 3 MT at their preferred cadence. Overall power for the first 150 seconds (P 150 s), CP, and W' were determined from the 3 MT. Figure 1 illustrates a representative subject from our study.
High-Intensity Training Bout
The HIT bout consisted of a single set of 8–12 repetitions per leg press and leg extension exercises, with no more than 30 seconds of rest between exercises. Each repetition on the leg press machine included a 4-second eccentric phase and a 2-second concentric phase (4:2 second cadence), whereas the leg extension exercises included a 1-second pause between the 4:2 second cadence (17). The principal investigator instructed the subjects on the repetition cadence with the aid of a hand-held stopwatch. Each set was performed to concentric failure, characterized by the subjects' inability to move the resistance through the entire concentric phase of the movement. After concentric failure, additional forced repetitions were completed. These were characterized by two 10-second eccentric repetitions with assistance. Resistance levels were determined based on 10RM testing using a 4:2 second cadence (14,20).
Traditional Resistance Training Bout
The traditional RT bout consisted of 3 sets of 10 repetitions on the leg press and leg extension machines, with 1 minute of rest between sets and 3 minutes between exercises. The subjects typically used a 1:1 second cadence; however, no instruction on cadence was provided. Moreover, this regime did not include additional forced repetitions. Resistance levels were determined based on 10RM using a 1:1 second cadence. The differences in loads between the bouts were approximately 20% (i.e., loads used for the HIT-bout was approximately 80% of the loads used for the traditional RT bout).
Reliability analyses were calculated on P 150 s, CP, and W' using intraclass correlation coefficient, typical error, and coefficient of variation (10). The parameters of P 150 s, CP, and W' were evaluated with a series of 1-way analyses of variance with repeated measures to compare across baseline, post-HIT bout, and post-traditional RT bout. Effect size differences are reported for the 2-trial (Cohen's d) and 3-trial comparisons (partial eta squared;
). The null hypothesis was rejected if p < 0.05. All summary statistics are reported as mean ± SD.
The mean 3 MT performances for baseline, the post-HIT bout, and the post-traditional RT bout are shown in Figure 2. The dependent variables of P 150 s, CP, and W' are reported in Table 1. Effect size differences from baseline W' measures were greater for the HIT bout (d = 0.25) vs. traditional RT bout (d = 0.01). No significant differences in P 150 s (F = 2.37, p = 0.17,
= 0.44), CP (F = 0.09, p = 0.91,
= 0.03), and W' (F = 1.53, p = 0.29,
= 0.33) were observed from the baseline measurements.
Table 2 lists the consistency of dependent variables between baseline and each lifting intervention. The measures of P 150 s and CP were very consistent. Conversely, the measure of W' was considerably more variable.
The primary aim of the current study was to compare the metabolic stress of a HIT bout vs. a traditional RT bout using the CP model. We specifically evaluated the effect of these 2 bouts on P 150 s, W', and CP. Neither the HIT bout nor the traditional RT bout evoked a significant depreciation in P 150 s and W' (Table 1). Thus, we reject the hypothesis that the HIT bout evoked a greater metabolic stress than the traditional RT bout. We also observed that despite subjects engaging in 2 different resistance exercise regimes, CP measures remained similar (Table 2). Thus, RT does not affect the maximal aerobic steady state, as estimated with CP.
The measure of CP is highly reliable and considered a surrogate measure of the maximal lactate or aerobic steady state (5). The reliability analysis by Johnson et al. (11) indicated that CP had a typical error of 15.3 W, a coefficient of variation of 6.7%, and an intraclass correlation coefficient of 0.93. These statistics are remarkably consistent with the statistics observed between the baseline 3 MTs and those conducted after either resistance exercise regime we used (Table 2). Thus, any perceivable difference in power above CP should have been notable.
We acknowledge that the variability of W', in cycle ergometry, is much greater than that reported for CP (9,11). In the present study, we observed test-retest variability values of W' (approximately 34–36%, Table 2) exceeding those observed for the normal test-retest variability of approximately 21% (11). Such a difference in variability would indicate that each resistance exercise regime altered W'. The effect size difference from baseline was greater for the HIT bout in comparison to the traditional RT bout. Based on the effect size of 0.25, however, we would have required a much greater sample based on power analysis (16) (approximately 75 subjects) to have observed a significant decline in W' with the single 4:2 second cadence regime.
With the observed small effect size decline in W' subsequent to the HIT bout, it seems a different regime is necessary to evoke a substantive metabolic stress on the body. We do acknowledge the time-delay limitation of our study between the intervention and post-intervention 3 MT. The approximately 3-minute time delay may have sufficiently recuperated a large portion of W', particularly given that the reconstitution of W' relative to time is exponential (7). Key delimitations also of our HIT regime include the use of a single set, as opposed to multiple sets, along with the use of a 4:2 second cadence. Both of these delimitations are time dependent. With multiple sets of the 4:2 second cadence regime, a likelihood of greater metabolic stress exists. Likewise, slower repetitions (e.g., 10:5 second cadence) (14,20) may have extended the duration of the bout sufficiently enough to depreciate W'.
Empirical work on the fatigue of isolated muscles comes from that of Burnley (4). He evaluated a series of 3-second isometric contractions of the quadriceps femoris with 2-second recoveries. The 3- to 2-second duty cycle was superimposed with electric stimulation and extended for a 5-minute period (i.e., a total of 60 maximal isometric contractions were performed). His results indicated that 4.5 minutes were necessary to exhaust W' within the quadriceps femoris, with the achievement of critical torque being reached between 4.5 and 5 minutes. His results, taken into context with the results of the present study, suggests that a time period longer than 1 minute is necessary to evoke a substantive depletion of W' using isotonic contractions. Moreover, a regime with multiple sets with a higher %1RM was insufficient (Table 1). A regime with multiples sets of 4:2 second cadence or a regime of more than 4:2 second cadence × 10 repetitions, with a lower %1RM load, is necessary for substantive depletion of W'.
Combative sports such as wresting and judo can benefit from resistance exercise regimes that evoke significant metabolic stress (15). Success in such sports is often predicated on an athlete's ability to contract when energy stores are partially available and when the biochemistry of the muscle is less than favorable (e.g., low pH). Indeed, strength and conditioning professionals often use resistance exercise for the purpose of expanding an athlete's anaerobic work capacity and exercise tolerance (i.e., improved muscular endurance) (8). To our knowledge, this is the first study to use the CP model to investigate voluntary isotonic contractions. We evaluated a HIT bout in comparison to a traditional RT bout, and our reliability data indicated that CP was unaffected by either regime. Thus, future researchers should investigate exercise regimes that include longer cadences for single-set exercise bouts or regimes that include more sets.
The authors report that no external funds were used for the production of this work and that no conflicts of interest exist for this research with respect to the authors. The results of the present study do not constitute an endorsement by the authors or the National Strength and Conditioning Association.
1. American College of Sports Medicine Position Stand. Progression models in resistance training for healthy adults. Med Sci Sports Exerc 41: 687–708, 2009.
2. Ahtiainen JP, Häkkinen K. Strength athletes are capable to produce greater muscle activation and neural fatigue during high-intensity resistance exercise than nonathletes. J Strength Cond Res 23: 1129–1134, 2009.
3. Bergstrom HC, Housh TJ, Zuniga JM, Camic CL, Traylor DA, Schmidt RJ, Johnson GO. A new single work bout test to estimate critical power
and anaerobic work capacity
. J Strength Cond Res 26: 656–663, 2012.
4. Burnley M. Estimation of critical torque using intermittent isometric maximal voluntary contractions of the quadriceps in humans. J Appl Physiol 106: 975–983, 2009.
5. Burnley M, Doust JH, Vanhatalo A. A 3-min all-out test to determine peak oxygen uptake and the maximal steady state. Med Sci Sports Exerc 38: 1995–2003, 2006.
6. Clark IE, Murray SR, Pettitt RW. Alternative procedures for the 3-min all-out exercise test. J Strength Cond Res, 2012. doi: 10.1519/JSC.0b013e3182785041.
7. Ferguson C, Rossiter HB, Whipp BJ, Cathcart AJ, Murgatroyd SR, Ward SA. Effect of recovery duration from prior exhaustive exercise on the parameters of the power-duration relationship. J Appl Physiol 108: 866–874, 2010.
8. Fleck SJ, Kraemer WJ. Designing Resistance Training Programs (3rd ed.). Champaign, IL: Human Kinetics, 2004.
9. Gaesser GA, Wilson LA. Effects of continuous and interval training on the parameters of the power-endurance time relationship for high-intensity exercise. Int J Sports Med 9: 417–421, 1988.
10. Hopkins WG. Measures of reliability in sports medicine and science. Sports Med 30: 1–15, 2000.
11. Johnson TM, Sexton PJ, Placek AM, Murray SR, Pettitt RW. Reliability analysis of the 3-min all-out exercise test for cycle ergometry. Med Sci Sports Exerc 43: 2375–2380, 2011.
12. Jones AM, Vanhatalo A, Burnley M, Morton RH, Poole DC. Critical power
: Implications for the determination of VO2 max and exercise tolerance. Med Sci Sports Exerc 42: 1876–1890, 2010.
13. Jones AM, Wilkerson DP, DiMenna F, Fulford J, Poole DC. Muscle metabolic responses to exercise above and below the “critical power
” assessed using 31P-MRS. Am J Physiol Regul Integr Comp Physiol 294: R585–R593, 2008.
14. Keeler LK, Finkelstein LH, Miller W, Fernhall B. Early-phase adaptations of traditional-speed vs. superslow resistance training on strength and aerobic capacity in sedentary individuals. J Strength Cond Res 15: 309–314, 2001.
15. Kraemer WJ, Vescovi JD, Dixon P. The physiological basis of wrestling: Implications for conditioning programs. Strength Cond J 26: 10–15, 2004.
16. Lipsey MW. Design Sensitivity. Newbury Park, CA: Sage Publications, 1990.
17. Smith D, Bruce-Low S. Strength training methods and the work of Arthur Jones. J Exerc Physiol 7: 52–68, 2004.
18. Tanimoto M, Ishii N. Effects of low-intensity resistance exercise with slow movement and tonic force generation on muscular function in young men. J Appl Physiol 100: 1150–1157, 2006.
19. Vanhatalo A, Doust JH, Burnley M. Determination of critical power
using a 3-min all-out cycling test. Med Sci Sports Exerc 39: 548–555, 2007.
20. Westcott WL, Winett RA, Anderson ES, Wojcik JR, Loud RL, Cleggett E, Glover S. Effects of regular and slow speed resistance training on muscle strength. J Sports Med Phys Fitness 41: 154–158, 2001.
Keywords:Copyright © 2013 by the National Strength & Conditioning Association.
anaerobic work capacity; critical power; high-intensity training