The rest interval during the strength training session impacts the extent and nature of involvement of the anaerobic energy sources and the intensity of the training load. There are five main interrelated causes of fatigue, all of which affect recovery from exercise (Pahlkle and Peters 1992, Davis and Bailey 1997, Green 1997):

 

1.) Fatigue/Lactic Acid

2.) Glycogen level depletion

3.) Lowered blood pH

4.) Disturbed movement coordination

5.) Neural drive connections

 

   Generally, if you want to maximize the impact on the nervous system, full recovery is recommended. When maximal strength is a concern, longer rest intervals are more likely to promote strength gains than shorter rest intervals because near-maximal recovery of force generation parallels restoration of energy substrates. The greater voluntary effort and excitation typically associated with brief bursts of maximal exercise recruits the highest-threshold motor units to make use of their greater strength and rate of force development. This is why every repetition must be performed with full concentration and maximal effort; The required high intensity calls for the use of long rest periods. The ability to restore neural drive, active muscle tension and energy substrates is a time-dependent process demonstrating the importance of a non-contractile period of rest after exercise.

 

The length of the rest interval is dictated by the training goal.

The strength coach should determine the training objective before deciding on the length of the rest intervals; then determine if the athlete wants full recovery or incomplete recovery. Rest intervals need to be prescribed based on the training intent (such as strength or relative strength, functional, hypertrophy and endurance).

 

The nervous system takes 5-6 times longer to recover than the muscular system.

The nervous system is connected to the muscles and takes longer to recover. Exercise enthusiasts who forget this often recommend rest intervals that are too short.

 

The length of rest interval dictates the hormonal response to a given workout.

Generally, the shorter the rest interval, the greater the metabolic adaptation. The shorter the rest interval, the greater the growth hormone response. When repetitions are low and the interval is long, there is minimal hormonal response.

 

When training the galactic (maximal) power system, the longest rest intervals are required.

When training with maximal loads (1 RM, 5 RM at 85-100% of maximum), rest periods of 3-4 minutes (Wiess 1991) or even up to 5 minutes (Schmidtbleicher 1986, Zatiorsky 1995), have been suggested to prevent the onset of early fatigue and to allow for repeated efforts at high intensities. Some research has found that both PCr (Phosphagen Creatine) and ATP (Adenosine Triphosphate) stores are almost completely restored after a 4-minute rest interval.

 

The length of rest interval is a function of the magnitude of the range of motion.

The greater the range of motion, the more a longer rest interval is needed. For example, podium trap bar deadlifts performed while standing on a 6-inch platform require longer rest intervals than the same exercise performed from the ground. Also, for a given rep range, heavy dumbbell work is more demanding than barbell work; so for a 3RM set, incline dumbbell presses require more rest than incline barbell presses for 3RM.

 

The length of the rest interval is a function of the amount of muscle mass recruited.

The larger the muscle mass recruited, the greater the length of the rest interval. The back squats recruit the largest muscle mass in the human body, and need a longer rest interval. The glutes and thighs need longer rest intervals than bicep curls, which recruit only the elbow flexors.

 

The length of the rest interval is the function of the size and strength levels of the athlete.

The bigger and stronger the trainee, the longer the rest interval should be. There is a direct relationship between the length of the rest interval and the weight class of the weightlifter. For example, an offensive lineman would rest longer than a running back. That athlete's needs are different than a skill position. THe 2016 NFL APX group was comprised primarily of Offensive lineman. Due to their prescriptive aerobic needs for their postition drills and their Pro Days/ Combines - aerobic capacity work was inplemented. Whereas, upon the start of their seasons, aerobic capacity week is diminished almost entirely as they no longer need or will rely on that particular energy system.

 

The length of the rest interval is a function of the neurological complexity of the exercise.

The more demanding an exercise is on the neurla system, the greater the length of the rest interval. Exercises of a highly coordinative nature, such as split jerks and power snatches, need longer rest intervals than simple isolation exercises such as rotation cuff work.

 

Pair antagonistic muscles for greater motor unit recruitment, shorter rest intervals and greater total volume.

By having the antagonistic pairs contracting alternately (such as flexion followed by extension) instead of using agonist contractions alone (pre-contraction), the ability to achieve full motor unit activation (MUA) in a muscle contraction is often enhanced. This offers the added benefit of allowing double the workload per training unit. A good plan is to alternate exercises working agonist muscles with exercises working antagonistic muscles, while using long rest intervals. For example, after doing a 3RM set of close-grip triceps presses, rest 2-3 minutes and repeat for the desired amount of sets. By training in this way, an athlete can do greater tonnage per training unit, as alternating antagonist pairs have been shown repeatedly to lower drop-off curves more effectively than traditional standard sets even with rest intervals. Paired muscle groups are normally in opposite motor patterns. For example, alternating overhead presses with forms of chin ups, and lying presses alternated with rows. However, you don’t necessarily need to pair large motor patterns with other large motor patterns. Will discuss within your Cert.

 

The length of the rest interval is a function of the prescribed tempo.

Another factor that influences rest interval selection is the cadence at which it is performed. Although there is a scarcity of research in this particular area, you may consider total time under tension of a given set before prescribing the proper rest interval. Given that information, you would prescribe a rest interval that is inversely proportionate to the total time under tension of that set. For example, there would be significant differences in the nature and extent of the energy substrate for sets of single repetitions in the chin-up down at a 5:0:1:0 tempo versus reps done at a 30:0:30:0 tempo.

 

The length of the rest interval is a function of the training age.

Tolerance to short rest intervals with load in the 60-80 percent range (6-20 reps) is a function of years of accumulated training. Short rest periods are linked to greater psychological anxiety and fatigue, and the lactate buildup resulting from this type of training is tolerated by only the well-conditioned athlete. Consequently, shortening the rest intervals when working with 10RM loads should be done progressively as the buffering mechanisms adapt to increased muscle and blood lactate concentrations.

Rest intervals have to be shortened for only the advanced trainee, as lactate buildup will interfere with the maintenance of proper technique in the learning trainee.

 

Short intra-set rest intervals recruit higher-threshold motor units.

The rest interval between repetitions within a series is an extremely important loading parameter. Gym experience and scientific research from the past two decades have clearly shown that taking small intra-set rest intervals in an advantageous angle of execution permits the recruitment of higher-threshold motor units. For a given sub maximal force of contraction, motor unit activation is greater for repeated (intermittent) contractions than for sustained contractions. For the development of maximal strength, the intra-set rest interval should never exceed 15 seconds and that is only for high fast-twitch individuals training only on complex compound exercises.

 

The aerobic base is not a factor in strength development.

The higher an athlete’s aerobic base, the shorter the rest interval an athlete will want to take. However, the more aerobically fit trainee is normally weaker. These athletes often have a hard time grasping the concept of a long rest between heavy sets to bring about neural adaptations. MMA fighters could complain they aren’t sweating enough when doing relative strength training and regard this as a negative to the training process.

    Remember these important factors when approaching your training population's program design needs, evaluations and training goal desires. It is too often that we see these critical points mishandled in today's Cross Fit (High-Aerobic/Anaerobic Linear) and/or Power Lifting-Pyramid Schemed (anaerobic linear) threshold programming in the private industry and within the high school-collegiate-pro athletic training programs. These programs are not an 'Optimal' choice to improve overall athleticisim, prevent injury or improve body mass ratios.