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Understanding the various methods of resistance training

This is an excerpt from Scientific Foundations and Practical Applications of Periodization With HKPropel Access by G. Gregory Haff.

The various methods of resistance training affect maximal strength, the RFD, power output, and the ability to repetitively produce force. When considering the classification of strength, a hierarchy ranging from ballistic to supramaximal resistance-training methods can be conceptualized (table 13.2) (498).

Ballistic Methods

Training methods that require acceleration throughout the entire concentric movement are often referred to as ballistic exercises (82, 485). The most employed ballistic exercises include plyometrics, jump squats, bench throws, and medicine ball throws (478, 480, 485, 498). Ballistic exercises have been shown to produce greater forces, velocities of movement, power outputs, and muscle activation when compared to the same exercise performed quickly (286, 345). These types of exercises may lead to a lowering of the motor unit recruitment threshold (103, 519) and a more rapid activation of the entire motor neuron pool (116). Ultimately, due to these alterations to motor unit recruitment, ballistic exercises exert a significant influence on the RFD, which can directly translate to an enhanced power output (485). When compared to traditional resistance-training exercises, such as the back squat, bench press, and deadlift, ballistic exercises have a greater ability to enhance the RFD, especially in stronger individuals (80-82).

Although ballistic exercise can be incorporated throughout the annual training plan, the goal of the training phase will affect which ballistic exercise is used (485). For example, during a general preparation phase that targets hypertrophy, loaded jump squats would be avoided due to the phase’s focus on increasing work capacity and muscle CSA (485). It would be far better to incorporate this exercise into a strength–speed or speed–strength phase of training because the goals of the exercise and the phase would better align. Although it is often recommended that all athletes can benefit from ballistic exercises (485), the athlete must establish an appropriate strength base prior to incorporating these exercises (80, 81).

Speed–Strength Methods

The primary goals of speed–strength (i.e., explosiveness) training methods are to enhance the RFD and increase power development (479, 548). Verkhoshansky and Siff (522) suggest that when targeting speed–strength, the development of speed against resistance is vital and overall strength development is less important. The development of speed–strength is accomplished with loaded sport movements (498), lifting movements with loads 40% to 60% of 1RM (339), or depth jumps (548). Exercises such as loaded bench throws and jumps performed with relatively low loads (≤50% of 1RM) are commonly used to develop speed–strength. Kettlebells (485) and medicine balls can also be used to target speed–strength development (548).

Some authors suggest that performing weightlifting movements and their derivatives with relatively light loads is useful for the development of speed–strength (254, 479). For example, Suchomel and colleagues (479) suggest the jump shrug (482) and the hang high pull (481) are useful training exercises for enhancing speed–strength. Ideally, if maximizing speed–strength is the primary focus of the training phase, strength or power training should be performed twice per week (209).

Strength–Speed Methods

Although both speed–strength and strength–speed resistance-training methods develop the RFD and increase power development (479), strength–speed methods also target the continued development of maximal strength (479). DeWeese and colleagues (104) suggest that the primary goal of strength–speed resistance-training methods is moving relatively heavy loads quickly to enhance the RFD and continue to develop strength. Weightlifting (e.g., snatch, clean, jerk) and the weightlifting derivatives (e.g., clean and snatch pull, push jerk) are ideally suited for the development of strength–speed (104). Based on figure 13.6, various weightlifting derivatives can be selected to target specific aspects of the force–velocity curve. For example, the high-force end of the curve can be targeted with the use of the snatch/clean deadlift, midthigh pull (107, 480), pull from the knee (109), and pull from the floor (108, 480). Alternatively, the jump shrug (482), the hang high pull (477), power snatch/clean from the knee (76, 483), and power snatch/clean from the thigh (74, 75) can be used to target the higher-velocity end of the force–velocity curve.

Maximal Strength Methods

Numerous resistance-training strategies can target the development of maximal strength. Generally, optimal strength gains occur in response to training within what is referred to as the strength zone (422). This zone requires the performance of one to six repetitions per set, with loads of 80% to 100% of 1RM (365, 443, 479, 492, 498). It is generally believed that training within this zone enhances neuromuscular adaptations that facilitate force production (246, 422). In fact, Jenkins and colleagues (246) reported greater increases in percentage of voluntary activation and electromyographic amplitude after 6 weeks of training with loads that correspond to 80% of 1RM compared to training with 30% of 1RM.

Generally, we see a dose–response relationship between load lifted and the amount of strength gained (422). For example, significantly greater strength gains occur when training in the strength zone compared to training within the hypertrophy zone (i.e., 8-12 repetitions per set) (63, 302, 419, 426). Although it is clear that training with heavier loads is essential for maximizing muscular strength, consistently training to muscular failure is not necessary (92, 127, 171, 501) and may be detrimental to long-term strength gains (65, 66). For example, Carroll and colleagues (66) reported that consistently training to failure (i.e., RM loads) results in an increased training strain, monotony, and overall injury risk, whereas training based on percentages of RM, with heavy and light days, results in superior maximal strength gains and improvements in RFD and vertical jump performance. Additionally, training with percentages of RM results in greater increases in type II muscle fiber CSA, type I muscle fiber CSA, and anatomical CSA when compared to training to failure (65).

It is likely that frequently training to failure creates a fatigue-management problem that impedes the athlete’s ability to recover (331) and adapt to the training stimulus, which can negatively affect the ability to increase maximal strength. Morán-Navarro and colleagues (331) reported that the time necessary to recover from training to failure is significantly longer than not training to failure. The effect of training to failure and the associated slower rate of recovery may be magnified when resistance training is integrated into the preparation of athletes who use multiple and more frequent training activities (359, 360).

Based on the overwhelming evidence presented in the scientific literature, frequently training to failure in an attempt to maximize strength gains is unnecessary (66, 92, 127) and should be used sparingly (92). Ideally, when the main goal of a resistance-training program is maximal strength, training not performed to failure is recommended (92, 127, 171, 501).

An additional consideration when constructing resistance-training programs that target maximal strength is the duration of the inter-set rest interval. It is well-documented that inter-set rest intervals of at least 2 to 3 minutes are required to maximize strength gains (12, 62, 172). It is likely that longer rest intervals are most important when using multijoint resistance-training exercises. It is generally recommended that multijoint resistance-training exercises make up the majority of a resistance-training program due to their more efficient stimulation of maximal strength (361), so it is important to ensure adequate inter-set rest to maintain training intensity.

Supramaximal Strength Methods

Generally, an individual can lower a heavier load than they can lift. Therefore, when employing traditional strength-training methods where the load is limited by concentric maximal strength, the load prescribed will not provide an overload for the eccentric portion of the lift (204). To address this issue, supramaximal resistance-training methods can be integrated into a resistance-training program. With this training method, loads that are in excess of concentric maximums are applied during targeted eccentric training (439) or with accentuated eccentric loading strategies (discussed in more detail later in the chapter) (529, 530, 532).

Generally, the use of supramaximal training methods (i.e., eccentric training) may stimulate fiber-type shifts toward faster MHC isoforms (135, 136), which are commonly associated with increases in force and power production (1, 135). Furthermore, the unique loading parameters associated with supramaximal training can also increase fascicle lengths (130, 131, 157), which may lead to faster maximal shortening velocities and translate into increased potential for power development (292, 341). Therefore, supramaximal training methods may be useful for maximizing the adaptive responses to the resistance-training program.

Supramaximal training methods use eccentric loads that range between 105% and 140% of concentric 1RM depending on the targeted outcome. It is important to note that this type of training is very intense and can create significant muscle damage if not programmed correctly (205, 387, 532). Although Thibaudeau (498) suggests that these methods should be used only during shock microcycles and for no more than two microcycles (i.e., short mesocycle), research shows that these methods can be very effective when employed for a 4-week mesocycle (205) or two successive 5-week mesocycles (532).

Hypertrophy Methods

When training to increase muscular size, it is generally believed that performing 8 to 12 repetitions per set (i.e., the zone of hypertrophy) with loads of 65% to 80% of 1RM provides the most efficient stimulus (184, 422). Although it is often said that training to failure is necessary to stimulate muscle growth, there is an emerging body of evidence that suggests that training to failure is not necessary for maximizing muscle hypertrophy (65, 285, 411, 526). In fact, when training loads of 65% to 80% of 1RM are used, there is convincing evidence that not training to failure is a more effective method for stimulating muscle hypertrophy (285). Conversely, if lower loads (i.e., 30%-50% of 1RM) are used, training to failure appears to be a prerequisite for stimulating muscle hypertrophy (287, 334, 420). However, hypertrophy training performed to failure creates greater fatigue (331, 412), delayed rates of recovery (420), and greater levels of discomfort (412). Based on the available research, if resistance training is performed within the hypertrophy zone, training to failure is not necessary and training not performed to failure is a better training approach.

Although the load employed in resistance-training programs that target muscle hypertrophy is important, it is likely that the volume load (sets × reps × load) of training is a more important factor for enhancing muscle hypertrophy (55, 137, 287, 295). For example, several studies reported that training with more sets per muscle group, which results in an overall increase in volume load, resulted in greater increases in muscle hypertrophy (55, 284, 418). Ultimately, muscle hypertrophy follows a dose–response relationship, with greater gains being achieved with higher volume loads of training (418, 423).

Classically, shorter inter-set rest intervals coupled with higher volumes (i.e., 8-12 repetitions) of resistance training have been recommended to target acute hormonal responses when hypertrophy is the goal of a resistance-training program (280). Although the acute hormonal response is often cited as a rationale for using short rest intervals, research suggests that acute hormonal fluctuations play a minor role in stimulating hypertrophy, and mechanical loading factors (538, 539), such as volume load, likely exert a greater influence. Support for this contention can be found in research that reported that longer inter-set rest intervals allow for greater volume loads of training, which translate into greater hypertrophic gains (425). Ultimately, it appears that employing rest intervals of 2 to 3 minutes during resistance training targeting hypertrophy results in the greatest adaptive responses.

Finally, the type of exercise used also seems to influence the hypertrophy stimulated by the training program. Generally, it is recommended that resistance-training programs should contain combinations of multijoint and single-joint exercises (385). Although some evidence shows that these combinations can result in increased muscle hypertrophy (27, 53), research has questioned the efficacy of this practice (26). Specifically, the addition of single-joint exercises to a resistance-training program that contains multijoint exercises has been reported to offer no additional muscular adaptations in untrained individuals (26, 156) or trained individuals (26, 95). Although there continues to be debate about the need to incorporate single-joint exercises into a resistance-training program (53), research indicates that these exercises do not seem to affect hypertrophy (349). Remember, however, that strength is maximized when multijoint exercises are placed before single-joint exercises.

Strength–Endurance Methods

Strength–endurance can be defined as the ability to resist muscular fatigue when performing resistance training with submaximal loads (391). It is often targeted with resistance-training programs that employ more than 12 repetitions and loads that are less than 65% of 1RM (184, 443). This type of resistance training has been proposed to enhance buffering and oxidative capacity, increase mitochondrial density, enhance metabolic enzymatic activity, and increase capillary density (443). Classically, the inter-set rest interval is recommended to be 30 seconds or less for strength–endurance (184). Short inter-set rest intervals stimulate greater oxygen consumption (i.e., 30 s | 60 s | 120 s | 180 s), which may partially explain the common physiological adaptations associated with this type of training (386). Depending on the structure of the training session and the exercises used, the inter-set rest intervals can be short (less than 1 min) or long (1-2 min). If multijoint exercises are used, longer inter-set rest intervals will be needed to maintain performance. Specifically, if short rest intervals (i.e., 30-60 s) are used, the load lifted may have to be reduced by 5% to 15% across each set performed to maintain training volume (386).

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