|Training to Failure
Len Kravitz, Ph.D.
Willardson, J.M. (2007). The application of training to failure in periodized multiple-set resistance exercise programs. Journal of Strength and Conditioning Research. 21(2), 628-631.
In designing resistance training programs, the issue of training to failure or momentary muscular fatigue is regularly discussed between the personal trainer and client. Many trainers adhere to very strict policies, such that if muscular failure during a set is not achieved, the set will be counted as an additional warm-up set. However, as relevant as this training concept is to resistance exercise, there is surprisingly little research to confirm or deny this premise. In this recent article by Willardson (2007), a research review and analysis was completed to better understand the known pros and cons of training to fatigue in multiple-set workout plans.
What is Muscular Failure?
Muscular failure in resistance exercise is the point during exercise performance when the neuromuscular system can no longer produce adequate force to overcome a specific workload. The exercise set must be ended and a brief (1-3 minute) period of recovery begins where more immediate energy (i.e., ATP) is given time to be re-synthesized. During this recovery time some metabolic byproducts (e.g., hydrogen ions, lactate, inorganic phosphates, creatine, potassium) inside and outside of muscle fiber tissues are removed or restored. It is important to note that the challenged muscle fibers arent entirely fatigued at this point, they just cant produce enough force to overcome the specific load. The personal trainer could lighten the resistance and the muscles would be able to overcome this lighter load.
What is the Theoretical Basis for Training to Failure?
The theory for training to failure is based on motor unit (the nerve and muscle fibers innervated by that nerve) recruitment. It is very well known and understood in neuromuscular physiology that the recruitment pattern of motor units is primarily based on the force needs placed on the muscle. Classically, with low threshold challenges, the Type I (also known as oxidative) muscle fibers are primarily recruited (see Table 1 for more characteristics on muscle fiber types). As the force becomes greater the Type IIa (also referred to as glycolytic) are recruited. The greatest force producing fibers in the human body are the Type IIb or Type IIx fibers (the x noting there are several variations of this fiber type). Therefore, if muscular strength is the primary objective, it is felt that the degree of activation of motor units is directly related to the magnitude of the strength training response.
What is the Research on Training to Failure?
It is remarkable that the concept of training to failure, which is so rooted in the foundation of resistance training is based upon so little research. In fact, Willardson (2007) notes in his review that some research is quite misleading on this topic as the study authors state that the subjects trained to a certain % of repetition maximum, and yet the investigators did not designate if failure was attained (intentionally or randomly).
A classic study investigating the training to fatigue issue was completed by Rooney, Herbert and Balnave (1994). In this investigation, strength increases produced by a training protocol in which subjects rested between contractions were compared with those produced when subjects did not rest betweens repetitions (as exercises are commonly performed). Forty-two male subjects were randomly assigned to either a no-rest group, a rest group, or a control group (who did no training). Subjects in the two training groups trained their elbow flexor muscles by lifting a 6RM weight 6-10 times on 3 days per week for 6 weeks. Subjects in the no-rest group performed repeated lifts without resting, whereas subjects in the rest group rested for 30 seconds between each repetition. Intensity and volume of training was matched. Subjects who trained without rests experienced significantly greater mean increases in dynamic strength (+56.3%) than subjects who trained with rests (+41.2%). Thus the best short-term strength increases were achieved when subjects lifted weights as is commonly performed in normal workouts of resistance exercise.
To illustrate a study at odds to the previous study, Drinkwater and colleagues (2005) completed an investigation with 26 elite junior male basketball players and soccer players, all who had been doing resistance exercise for the previous 6 months. The subjects completed bench press training 3 sessions per week for 6 weeks, using equal volume programs (24 repetitions x 80-105% 6RM). Subjects were assigned to one of two experimental groups designed either to 1) elicit repetition failure with 4 sets of 6 repetitions (RFGroup), or 2) complete 8 sets of 3 repetitions not to failure (NFGroup). The RFGroup demonstrated substantial increases in strength (+9.5%) and power (+10.6%) over the NFGroup in strength (+5.0%) and power (+6.8%).
The mixed findings from these two studies indicates the fact that physiological and metabolic processes associated with fatigue, other than just training to failure, contribute to the strength training response. More research is needed in this area to expound upon this physiological phenomenon.
What are the Precautions and Practical Applications for Training to Failure?
From Willardsons (2007) review of the research on this topic, he encourages not always training to failure as this may be a contributing cause to overtraining and overuse injuries. He also cites three studies that show there may be a decrease in growth-promoting hormones if training to failure is done continually. Depending on the client, he suggests to alternate going to failure in sets on sequential workouts, or even alternate weeks. Willardson expands that training to failure should be varied, just as all acute variables of resistance training (e.g., numbers of reps, number of sets, rest between sets, order of exercises, choice of exercises, etc.) are varied in periodization programs. More importantly, Willardson suggests that the athlete or client should stop the set when the exercise performance technique is being compromised (e.g., poor posture, body shifting, accessory movements, etc.) to lift the weight. In addition, for older populations, special populations, those with arthritis and/or osteoporosis, and many recreational exercises, the purpose of training may be much more valuable when the workout purpose is for attaining function and stabilization goals (which do not require training to failure). Competitive athletes and those persons trying to maximize strength and hypertrophy goals may have greater needs to train more frequently to failure in order to reach their performance goals.
Studies clearly show that subjects can positively gain strength and power without always going to the strict discomfort and acute physical effort associated with failure contractions. As personal trainers and fitness professionals working with clients on a daily basis it is also important to always add variety and stimulus change to client workouts. Whether for safety or for variation, the research reviewed suggests that training to failure and not training to failure are acute variables of resistance training to regularly manipulate in program designs.
Table 1. Characteristics of Muscle Fiber Types
Name Fiber Type Characteristics
Type 1 Slow Twitch High oxidative (a lot of mitochondria; organelle in cell that synthesizes ATP via cell respiration) capacity, low glycolytic (energy synthesized from glucose and glycogen) capacity, slow contraction speed, high fatigue resistance, low motor unit strength
Type IIa Fast Twitch Moderately high oxidative capacity, high glycolytic capacity, fast contractile speed, moderate fatigue resistance, high motor unit strength
Type IIb or Type IIx Fast Twitch Low oxidative capacity, very high glycolytic capacity, very fast contractile speed, low fatigue resistance, highest motor unit strength
Adapted from: Wilmore, J.H., and Costill, D.L. (2004). Physiology of Sport and Exercise (Third Edition), Human Kinetics.
Drinkwater, E.J., Lawton, T.W., Lindsell, R.P., Pyne, D.B., Hunt, P.H., and McKenna, M.J. (2005). Training leading to repetition failure enhances bench press strength gains in elite junior athletes. Journal of Strength and Conditioning Research, 19(2):382-388.
Rooney, K.J., Herbert, R.D., and Balnave, R.J. (1994). Fatigue contributes to the strength training stimulus. Medicine & Science in Sports & Exercise, 26(9):1160-1164.