During the past 30 years, the body of literature on the topic of resistance exercise has reached enormous proportions. The prescription of resistance exercise involves several variables, such as muscle action, loading, volume, exercise selection, exercise order, rest intervals among sets, velocity of muscle action, and frequency of sessions. How these variables are structured over time determines specific muscular adaptations that are associated with measurable characteristics, such as power, absolute strength, hypertrophy, and localized muscular endurance (2,5).
A less commonly studied phenomenon that may occur during a resistance exercise set is reaching failure at the end of a set of repetitions. Failure typically occurs initially during the concentric phase of a repetition when the muscles cannot produce sufficient torque to lift a given load beyond a critical joint angle or sticking region (13,23,26). At this time, a spotter may provide the lifter with sufficient assistance to progress through the sticking region so that the repetition can be completed; this is known as a partner-assisted repetition (Figures 1, 2), (1,7). However, reaching failure during the concentric phase does not indicate that the muscles are maximally fatigued. Lifters can typically generate sufficient torque to extend a set with additional partner-assisted repetitions and the descending sets technique (10) (Table 1 and Figure 3).
Intentionally reaching failure during resistance exercise sets is a common practice in recreational and sports conditioning settings. However, sometimes failure may occur unintentionally because of accumulated fatigue. This circumstance commonly occurs during the last set of an exercise when there is an attempt to maintain a prescribed number of repetitions. Conversely, during strength testing scenarios, intentionally reaching failure occurs when the objective is to perform a repetition maximum (RM) (e.g., 6 or 10RM) with a submaximal load.
Training to failure has been studied less frequently versus other well-established prescriptive variables (e.g., intensity and volume-number of sets, repetition ranges). Anecdotally, the benefits of training to failure are strongly supported among bodybuilders (24) and could be most applicable to hypertrophy-oriented programs. The 2009 American College of Sports Medicine position stand did not include specific discussion or recommendations on the application of training to failure (2). The decision to prescribe resistance exercise sets with the specific intent of reaching failure may depend on factors such as training status and goals, and the point in a yearly training cycle. Baechle et al. (5) recommended that athletes perform full RM sets one day per week and exclusive nonfailure sets the other days of the week.
Therefore, training to failure can and should be periodized, just like other well-established prescriptive variables (e.g., intensity and volume-number of sets, repetition ranges). Coaches should consider the training objective, and then strictly control the number of sets that are performed to failure. The purpose of this review will be to discuss the applications of existing research on failure versus nonfailure approaches within the context of different training objectives like power, absolute strength, hypertrophy, and localized muscular endurance. Furthermore, the use of extended set techniques like partner-assisted repetitions and descending sets will be discussed with applications based on the scientific literature.
RESEARCH: FAILURE VERSUS NONFAILURE TRAINING APPROACHES
One of the greatest challenges in comparing the efficacy of failure versus nonfailure approaches is the issue of equating training volume. If training volume is defined as the load lifted per set, multiplied by the sets performed per exercise, multiplied by the repetitions completed per set (i.e., load × sets × repetitions), then performing three sets to failure would result in a higher volume versus performing 3 sets with submaximal repetitions if the load and the number of sets are equal. The strength increases might be greater with the former approach because of the higher training volume, rather than reaching failure per se.
Peterson et al. (19) performed a meta-analysis comparing the effectiveness of failure versus nonfailure training approaches. Using a subset of studies from previously conducted meta-analyses (18,20), they concluded that the nonfailure approach was superior for maximal strength increases. However, a close inspection of the reference lists from both of the previous meta-analyses (18,20) indicated that none of the studies directly compared failure versus nonfailure training approaches. Studies were reportedly classified as failure or nonfailure based on the presence or absence of the phrase training to failure in the methodology. When interpreting this study, it should be considered that none of the studies (18,20) directly compared failure versus non-failure training approaches.
Therefore, training to failure is an issue that should receive additional examination to determine if the current dose-response recommendations should be amended. Research has demonstrated that when multiple sets of the bench press and back squat were performed to failure, there were significant reductions in the repetitions performed over consecutive sets with an absolute load (27-29). This was true even when using 3- to 5-minute rest intervals between sets (27,29). Willardson and Burkett (28) suggested that to maintain performance over multiple RM sets, the load must be progressively reduced, even for highly trained lifters. However, progressively reducing the load reduces the absolute training intensity, which is not ideal when training for maximal strength.
The alternative would be an exclusive nonfailure approach, which might allow for absolute training intensity to be maintained with greater consistency in repetitions over multiple sets. However, the appropriate time to end a set short of reaching failure has never been established. For example, if approximately 6 repetitions can be performed when lifting a load of 85% of 1RM for a given exercise, then should the set be ended after 3, 4, or 5 repetitions for maximal strength gains? Rhea et al. (20) and Peterson et al. (18,19) appeared to ignore this issue in their dose-response recommendations.
To determine the most appropriate application of failure versus nonfailure training approaches, the volume (and ideally the total work) should be equalized between groups. In reviewing the literature, relatively few studies have directly examined failure versus nonfailure training approaches on muscular adaptations, while equating for all other variables (6,7,12,30). The following sections will provide an overview of the relevant studies within the context of different training objectives.
This objective is typically the most sought after during late preseason and in-season training cycles when athletes are striving to achieve their peak physical condition. The ability to produce muscular power is associated with factors such as high levels of absolute strength and movement velocity. For athletes who already have a high level of absolute strength, maintaining power output and movement velocity during resistance exercise sets are key factors that may allow for further power development. When training for muscular power, a nonfailure training approach should be practiced for the majority of sets. Research has demonstrated that performing sets to failure may hinder development of muscular power because of reduced acute power output and movement velocity.
Lawton et al. (16) demonstrated that a traditional full-RM set was detrimental to acute repetition power output. In this study, acute repetition power output was examined during 4 bench press sessions that consisted of the following: (a) continuous: full 6RM set to failure, (b) singles: 6 repetitions with the 6RM load and 20-second rest between single repetitions, (c) doubles: 3 sets of 2 repetitions with 50-second rest between clusters, and (d) triples: 2 sets of 3 repetitions with 100-second rest between clusters. The results demonstrated significantly greater power output for each repetition of the singles, doubles, and triples conditions versus the continuous condition; this was especially evident for the last 3 repetitions.
These results suggest that performing full RM sets might not be the most effective approach for power training (16). Additionally, because several anaerobically based sports (i.e., American football, baseball, and tennis) require short explosive efforts, the transfer to performance might be greater by dividing a traditional RM set into clusters (i.e., singles to triples) with short rest intervals (i.e., 20-100 seconds) between clusters.
The maintenance of a high repetition velocity is another key variable that determines increases in muscular power. Izquierdo et al. (11) determined that maintenance of a high repetition velocity is best accomplished by ending a set well ahead of reaching failure. Bench press and back squat repetition velocity were examined throughout full RM sets performed at 60, 65, 70, and 75% of 1RM. The results demonstrated that the rate of decline in repetition velocity was not significantly different between all percentages of 1RM examined. However, significant reductions in repetition velocity occurred at 34% of the total repetitions for the bench press and 48% of the total repetitions for the back squat, irrespective of the intensity.
These results suggest that if the objective is to maintain a high repetition velocity (with the intent of increasing muscular power), the intention should be to end a set well ahead of reaching failure (11). For example, when performing explosive bench press and back squat sets with 75% of 1RM (or approximately a 10RM), the sets should be ended after approximately 3-5 repetitions. How these results relate to other commonly prescribed exercises (e.g., hang clean, overhead press, and deadlift) requires further research, but the same relationship probably exists. A coach should specifically determine how many repetitions are possible for a given exercise and at a given percentage of 1RM, then adjust the number of repetitions per set accordingly. Athletes might be capable of maintaining higher velocities for more repetitions per set for exercises that emphasize the lower-body musculature (e.g., back squat) versus the upper-body musculature (e.g., bench press).
The previous studies (11,16) examined acute responses, which limits the ability to make inferences regarding long-term gains. Izquierdo et al. (12) conducted one of the few studies to date that examined failure (RF) versus nonfailure (NRF) training approaches on muscular power (ballistic bench press and back squat with 60% of 1RM) after 11 weeks in physically active men; absolute strength (bench press and back squat of 1RM) and localized muscular endurance (total repetitions bench press and back squat with 75% of 1RM) were also examined. After the initial 11 weeks, an additional 5-week peaking period was included during which both groups performed the same ballistic style nonfailure training program designed to maximize power. Muscular testing and blood draws were conducted to determine basal hormone concentrations before the initiation of training and at regular intervals throughout the study period.
After the initial 11 weeks, increases in power were higher in the NRF group for the bench press (20% RF, 23% NRF) and back squat (26% RF; 29% NRF). The RF and NRF groups demonstrated similar percentage increases in 1-RM bench press (20% increase both groups) and 1-RM back squat (19% RF; 20% NRF), but localized muscular endurance was higher in the RF group for the bench press (85% RF; 69% NRF). A key finding was that RF group experienced a reduction in resting insulin-like growth factor-1 concentration, whereas, the NRF group experienced a reduction in resting cortisol concentration and an elevation in resting serum total testosterone concentration. During the final 5-week peaking period, the NRF group continued to increase muscular power, despite both groups performing the same ballistic style nonfailure training program. This may indicate that the RF group was in an overtrained state, as evidenced by the reduction in resting insulin-like growth factor-1 concentration (12).
The results of this study suggest that consistently performing sets to failure may inhibit gains in power, despite absolute strength results being equivocal and localized muscular endurance results being greater by reaching failure (these objectives are discussed in later sections) (12). The greater fatigue following sessions that involve sets to failure may interfere with other important components of conditioning like sports specific skill practice and related movement training. Furthermore, failure training performed too frequently may promote psychological burnout and the overtraining syndrome (9), which could be especially detrimental to performance during late preseason and in-season cycles.
The aforementioned study by Izquierdo et al. (12) demonstrated similar gains in maximal bench press and back squat strength with consistent failure or nonfailure training approaches after 11 weeks. However, from a practical standpoint, the consistent use of either of these approaches involves considerably shorter periods and a combination of approaches is more often used (Table 2). Two studies have examined failure versus nonfailure approaches over 6-week training cycles on strength gains (6,7).
Drinkwater et al. (6) examined the efficacy of training leading to repetition failure on 6-RM bench press strength and 40-kg bench throw power output in elite junior athletes. After the pretests, participants were matched based on their initial strength level and assigned to 1 of 2 bench press training groups that performed either 4 sets of 6 repetitions to failure (RF group) or 8 sets of 3 repetitions not to failure (NF group). Both groups were equated for volume (24 total repetitions each workout) and relative intensity (85-105% 6RM), training 3 times per week for 6 weeks. During each workout, the RF group needed assistance on at least 1 repetition, whereas the NF group was able to complete all repetitions without assistance.
Greater increases in 6-RM strength were demonstrated by the RF group (7.3 kg) versus the NF group (3.6 kg). Additionally, greater increases in bench throw power were demonstrated by the RF group (40.8 W) versus the NF group (25 W). A second experiment established that the RF protocol induced greater fatigue, as indicated by less power for the bench throw immediately before and after lifting (6).
The results from this study suggest that for trained lifters, reaching failure might be prescribed only on the last set of a given exercise or series of exercises that address similar muscle groups or movement patterns. This strategy is nothing new to resistance exercise prescription, in that reaching failure only on the last set has been practiced for decades. However, by limiting the number of sets to failure, the risk for overtraining is reduced and coaches might be able to effectively address other training objectives concomitantly during the same workout. For example, begin a workout by alternating high-intensity nonfailure sets with plyometric drills for power development and then end a workout with limited full RM sets for absolute strength or hypertrophy development.
Partner-assisted repetition is a common technique that allows for additional repetitions beyond initially reaching concentric failure. Anecdotally, this is a very popular technique (Figures 1, 2); whenever an individual has a spotter present, they will likely perform at least one partner-assisted repetition to progress through the sticking region. However, research has indicated that performing a greater number of partner-assisted repetitions are not necessarily better to increase strength (7).
Drinkwater et al. (7) divided trained lifters into 3 bench press groups that included (a) 4 sets of 6 repetitions (4 × 6), (b) 8 sets of 3 repetitions (8 × 3), and (c) 12 sets of 3 repetitions (12 × 3). Each group performed their respective protocols 3 times per week for 6 weeks. The intensity of each set varied from 90 to 100% of a predetermined 6-RM load. Each protocol was designed to elicit a different number of forced repetitions per training session ([4 × 6] and [12 × 3] > [8 × 3]), and the volume of work was monitored using optical encoders. Bench press strength (3 and 6RM) and bench throw power output (mean and peak) were assessed before and after intervention.
Significant increases in bench press strength and bench throw power were demonstrated by all groups with no significant differences between groups (7). The 4 × 6 and the 12 × 3 groups averaged a significantly greater number of forced repetitions (4.1 ± 2.6 and 3.1 ± 3.5) per training session versus the 8 × 3 group (1.2 ± 1.8). The 12 × 3 group accomplished a significantly greater average training volume (26,591 ± 3,020 J) per session versus the 4 × 6 and 8 × 3 groups (15,871 ± 1,985 and 16,655 ± 2,502 J). The results of this study suggest that neither increasing the number of forced repetitions nor increasing the training volume is more effective for increasing strength. Therefore, coaches should not overprescribe forced repetitions and also closely monitor athletes so that the number of forced repetitions does not become excessive.
Numerous mechanisms (e.g., hypoxic factors and free radicals) have been implicated in promoting exercise-induced hypertrophy (3,4,8,25). However, within the context of failure versus nonfailure training approaches, one mechanism that has been specifically compared is the acute secretion of growth hormone. This hormonal response is positively correlated with greater levels of blood lactate, indicative of the emphasis on anaerobic glycolysis for adenosine triphosphate (ATP) production (1,10,14,15,17,21). These physiological responses are especially pronounced when moderate repetition sets (e.g., 8-12RM) are performed in conjunction with shorter rest intervals between sets (e.g., 30 seconds to 2 minutes).
Performing sets to failure with a moderate intensity load (e.g., 8-12RM) induces different physiological responses versus performing sets to failure with a higher intensity load (e.g., 4-6RM). When considering performance of multiple sets, anaerobic glycolysis is the primary avenue for ATP production with the moderate intensity load, and the ATP-PCr system is the primary avenue for ATP production with the higher intensity load (21). The greater repetitions per set and metabolic stress associated with moderate intensity sets performed to failure might be key factors that stimulate greater acute secretion of growth hormone and thus contribute to hypertrophy.
Linnamo et al. (17) demonstrated the importance of RM sets in stimulating greater acute secretion of growth hormone. Five consecutive sets of the sit-up, bench press, and leg press were performed with 2-minute rest intervals between sets. This exercise sequence was repeated under the following 3 loading schemes: (a) heavy: 10RM each set (i.e., failure), (b) explosive: 10 repetitions each set with 70% of 10RM (i.e., nonfailure, load lifted explosively), and (c) submaximal: 10 repetitions each set with 70% of 10RM (i.e., nonfailure, load lifted at a constant speed). The results indicated significantly greater elevations in growth hormone and blood lactate immediately after the heavy session versus the explosive and submaximal sessions. The results of this study suggest that the combination of a heavy load (i.e., 10 RM) and reaching failure may provide a superior stimulus for growth hormone secretion versus a submaximal load (i.e., <10 RM) and not reaching failure.
With regard to hypertrophy, a potential advantage associated with training to failure might be greater recruitment of lower threshold motor units, commensurate with greater repetitions per set (22). During a typical heavy (e.g., >60% 1RM) resistance exercise set, a certain number of higher threshold motor units (i.e., fast twitch type IIa and type IIx) are initially recruited to meet the requisite force requirements to lift a given load. As the higher threshold motor units become fatigued, lower threshold motor units (slow twitch type I) are asynchronously recruited to maintain the requisite force requirements for continued repetitions. Eventually, fatigue of motor units increases to the extent that force production is not sufficient to lift a given load beyond a critical joint angle or sticking region; this is typically considered the point at which failure has been initially reached.
However, when failure is initially reached during the concentric phase, the muscles are still not maximally fatigued. Lifters can typically maintain sufficient force to perform additional repetitions through the use of partner-assisted repetitions and descending sets. There are limited studies that have examined acute responses when using partner-assisted repetitions and descending sets, despite the popularity in hypertrophy-oriented training programs (24). For the purpose of this discussion, partner-assisted repetitions and forced repetitions will be considered synonymous.
Ahtiainen et al. (1) examined acute growth hormone secretion and muscle activity after a maximal repetitions protocol (MR) versus a force repetitions protocol (FR) with equated work. Each protocol involved 4 sets of 12 repetitions for the leg press and 2 sets of 12 repetitions for the squat and leg extension with 2-minute rest between sets and 4-minute rest between exercises. The work was equated between protocols becasue the FR protocol used a 15% greater load, which necessitated the use of forced repetitions to complete the required 12 repetitions on all sets. The exact assistance given was measured with force plates and dynamometers.
Significantly greater growth hormone levels were evident for the FR protocol immediately after and at 15 and 30 minutes after the session (1). However, the muscle activity, assessed with maximal isometric muscle actions, was significantly lower at 24 hours after the session for the FR protocol and remained depressed for 72 hours. The results of this study suggest that when using force repetitions, a lower frequency of training might be required to allow for sufficient recovery between sessions for the same exercises or muscle groups.
Descending sets is another common technique used to stimulate hypertrophy. This technique is commonly used after a set with a heavy load (e.g., 90% 1RM); on reaching failure, the heavy load is immediately reduced (i.e., <30-second rest interval) and additional repetitions are then performed with a lighter load to failure (Figure 3 and Table 1). Goto et al. (10) compared acute growth hormone secretion after different load reductions using the descending sets technique. A typical heavy load session consisting of 5 sets at 90% of 1RM, with 3-minute rest intervals between sets, was followed by an additional set (approximately 30-second rest interval) performed at 90, 70, or 50 of 1RM.
The results demonstrated that acute growth hormone secretion was significantly greater when the load was reduced to 50% of 1RM versus the 70%, or kept constant at 90% of 1RM. However, a limitation of this study was that session volume (load × sets × repetitions) was not equated between groups. Therefore, the question remains as to whether the results were because of the utilization of the descending sets technique or the greater volume completed (10). Further research should address this question.
The results of these studies (1,10) indicate some positive scientific support for the anecdotally supported practice of partner-assisted repetitions and descending sets. These techniques appear to augment acute secretion of growth hormone and may result in greater gains in hypertrophy. However, further longitudinal research is necessary to validate the link between acute secretions of anabolic hormones and hypertrophy. Furthermore, the overprescription of failure sets may result in decreased resting levels of testosterone and increased resting levels of cortisol, which are counterproductive to hypertrophy (9,12).
LOCALIZED MUSCULAR ENDURANCE
Localized muscular endurance is an important objective for sports that require long repetitive efforts (e.g., distance running, cycling, and cross-country skiing) (2,5). Because of the definition of localized muscular endurance (i.e., the ability to sustain repeated submaximal muscle actions), the assumption might be that repetition failure sets would be an ideal training approach for this objective. Indeed, the aforementioned study by Izquierdo et al. (12) demonstrated that a repetition failure approach resulted in greater gains in localized muscular endurance (i.e., maximal bench press repetitions with 75% of 1RM) after 11 weeks. However, Willardson et al. (30) demonstrated contradictory results in comparing failure (F) versus nonfailure (NF) training approaches with equated intensity and volume on lower-body muscular endurance in trained men.
Each participant performed one lower-body workout per week for 6 weeks that involved the squat, leg curl, and leg extension exercises (30). Participants in the F group performed 3 sets of 13-15 repetitions to failure, whereas participants in the NF group performed 4 sets of 10-12 repetitions, and did not reach failure on any set. The additional set performed for each exercise by the NF group allowed for the volume to be equated between groups. Both groups performed a pre- and postintervention muscular endurance test, during which concentric work was assessed over 3 sets of the back squat, leg curl, and leg extension exercises. Concentric work was assessed using the 15-RM load for each exercise (measured preintervention), multiplied by the distance the load (plus body mass) was lifted per repetition, multiplied by the maximal repetitions over 3 sets for each exercise.
Both groups demonstrated significant increases in total work during the postintervention test, with no significant differences between the groups (30). These results suggest that when intensity and volume are equated, failure or nonfailure training approaches will result in similar gains in lower-body muscular endurance. It should be noted that in the Izquierdo et al. (12) study, despite significant greater gains in bench press repetitions with the failure approach, back squat repetitions were similar with both the failure and nonfailure approaches, similar to the Willardson et al. (30) study. Therefore, it appears that a repetition failure approach might be superior for upper-body endurance. Conversely, when training for lower-body endurance, the total volume (load × sets × repetitions) might be more important versus whether or not sets are performed to failure.
Intentionally reaching failure during resistance exercise sets is a common practice in recreational and sports conditioning settings, despite relatively few studies that have directly compared failure versus nonfailure training approaches. Anecdotally, the benefits are strongly supported among bodybuilders. The research does indicate that training to failure and beyond with partner-assisted repetitions and descending sets might be most beneficial to hypertrophy-oriented training programs because of greater acute secretions of growth hormone.
However, further longitudinal research is necessary that specifically compares failure versus nonfailure approaches to validate the link between acute elevations in anabolic hormones and hypertrophy. Failure training performed too frequently may result in decreased resting levels of testosterone and increased resting levels of cortisol, which are counterproductive to hypertrophy. Therefore, training to failure can and should be periodized just like other well-established prescriptive variables (e.g., intensity, volume-number of sets, repetition range).
Trained lifters may tolerate sets to failure with greater frequency versus untrained lifters. The current research suggests that performing sets to failure may provide greater gains in absolute strength, hypertrophy, and localized muscular endurance when practiced consistently over 6-week cycles, interspersed with exclusive nonfailure cycles over equal periods. When power production is the objective, training to failure should be discouraged and coaches should consider athletes' training status and goals, and the point in a yearly training cycle to determine whether sets are to be performed to failure or ended short of reaching failure.
1. Ahtiainen JP, Pakarinen A, Kraemer WJ, and Hakkinen H. Acute hormonal and neuromuscular responses and recovery to forced vs. maximum repetitions multiple resistance exercises. Int J Sports Med
24: 410-418, 2003.
2. American College of Sports Medicine. Position stand on progression models in resistance training for healthy adults. Med Sci Sports Exerc
41: 687-708, 2009.
3. Anderson J. A role for nitric oxide in muscle repair: nitric oxide-mediated activation of muscle satellite cells. Mol Biol Cell
11: 1859-1874, 2000.
4. Baar K and Esser K. Phosphorylation of p70 (S6k) correlates with increased skeletal muscle mass following resistance exercise. Am J Physiol Cell Physiol
276: C120-C127, 1999.
5. Baechle TR, Earle RW, and Wathen D. Resistance training. In: Essentials of Strength Training and Conditioning
. Beachle TR and Earle RW, eds. Champaign, IL: Human Kinetics, 2008. pp. 381-412.
6. Drinkwater EJ, Lawton TW, Lindsell RP, Pyne DB, Hunt PH, and McKenna MJ. Training leading to repetition failure enhances bench press strength increases in elite junior athletes. J Strength Cond Res
19: 382-388, 2005.
7. Drinkwater EJ, Lawton TW, McKenna MJ, Lindsell RP, Hunt PH, and Pyne DB. Increased number of forced repetitions does not enhance strength development with resistance training. J Strength Cond Res
21: 841-847, 2007.
8. Febbraio M and Pedersen B. Muscle derived interleukin-6: mechanisms for activation and possible biological roles. FASEB J
16: 1335-1347, 2002.
9. Fry AC and Kraemer WJ. Resistance exercise overtraining and overreaching. Neuroendocrine responses. Sports Med
23: 106-29, 1997.
10. Goto K, Sato K, and Takamatsu K. A single set of low intensity resistance exercise immediately following high intensity resistance exercise stimulates growth hormone secretion in men. J Sports Med Phys Fit
43: 243-249, 2003.
11. Izquierdo M, Gonzalez-Badillo JJ, Hakkinen K, Ibanez J, Kraemer WJ, Altadill A, Eslava J, and Gorostiaga EM. Effect of loading on unintentional lifting velocity declines during single sets of repetitions to failure during upper and lower extremity muscle actions. Int J Sports Med
27: 718-724, 2006.
12. Izquierdo M, Ibanez J, Gonzalez-Badillo JJ, Hakkinen K, Ratamess NA, Kraemer WJ, French DN, Eslava J, Altadill A, Asiain X, and Gorostiaga EM. Differential effects of strength training leading to failure versus not to failure on hormonal responses, strength and muscle power increases. J Appl Physiol
100: 1647-1656, 2006.
13. Jacobson B. Reach failure to gain success. Nat Strength Coaches Assoc J
3: 24-25, 1981.
14. Kraemer WJ, Marchitelli L, Gordon SE, Harman E, Dziados JE, Mello R, Frykman P, McCurry D, and Fleck SJ. Hormonal and growth factor responses to high intensity resistance exercise protocols. J Appl Physiol
69: 1442-1450, 1990.
15. Kraemer WJ, Noble BJ, Clark MJ, and Culver BW. Physiologic responses to high intensity-resistance exercise with very short rest periods. Int J Sports Med
8: 247-252, 1987.
16. Lawton TW, Cronin JB, and Lindsell RP. Effect of interrepetition rest intervals on weight training repetition power output. J Strength Cond Res
20: 172-176, 2006.
17. Linnamo V, Pakarinen A, Komi PV, Kraemer WJ, and Hakkinen K. Acute hormonal responses to submaximal and maximal high intensity resistance and explosive exercise in men and women. J Strength Cond Res
19: 566-571, 2005.
18. Peterson MD, Rhea MR, and Alvar BA. Maximizing strength development in athletes: A meta-analysis to determine the dose-response relationship. J Strength Cond Res
18: 377-382, 2004.
19. Peterson MD, Rhea MR, and Alvar BA. Applications of the dose-response for muscular strength development: A review of meta-analytic efficacy and reliability for designing training prescription. J Strength Cond Res
19: 950-958, 2005.
20. Rhea MR, Alvar BA, Burkett LN, and Ball SD. A meta-analysis to determine the dose response for strength development. Med Sci Sports Exerc
35: 456-464, 2003.
21. Robergs RA, Ghiasvand F, and Parker D. Biochemistry of exercise induced metabolic acidosis. Am J Physiol Regul Integr Comp Physiol
287: R502-R516, 2004.
22. Sale DG. Influence of exercise and training on motor unit activation. Exerc Sport Sci Rev
15: 95-151, 1987.
23. Stone MH, Chandler J, Conley MS, Kramer JB, and Stone ME. Training to muscular failure: Is it necessary? Strength and Cond
18: 44-48, 1996.
24. Schwarzenegger A. The New Encyclopedia of Modern Bodybuilding
. New York, NY: Fireside, 1998. p. 137.
25. Tatsumi R, Hattori A, Ikeuchi Y, Anderson J, and Allen R. Release of hepatocyte growth factor from mechanically stretched skeletal muscle satellite cells and role of pH and nitric oxide. Mol Biol Cell
13: 2909-2918, 2002.
26. Willardson JM. Brief review: The application of training-to-failure in periodized multiple-set resistance exercise programs. J Strength Cond Res
21: 628-631, 2007.
27. Willardson JM and Burkett LN. A comparison of 3 different rest intervals on the exercise volume completed during a workout. J Strength Cond
Res 19: 23-26, 2005.
28. Willardson JM and Burkett LN. The effect of rest interval length on the sustainability of squat and bench press repetitions. J Strength Cond Res
20: 396-399, 2006.
29. Willardson JM and Burkett LN. The effect of rest interval length on bench press performance with heavy versus light loads. J Strength Cond Res
20: 400-403, 2006.
30. Willardson JM, Emmett J, Oliver JA, and Bressel E. Effect of short-term failure versus non-failure training on lower body muscular endurance. Int J Sports Physiol Performance
3: 279-293, 2008.