Pete McCall by Pete McCall

There is a major paradox for a number of the recreational fitness enthusiasts who make up our clientele and participate in our group fitness classes: While some barely have enough motivation to get off the couch to make it to the gym, others are overly enthusiastic and rarely, if ever, miss a workout. If you're a personal trainer, group fitness instructor or simply a die-hard gym junkie, you likely work with or know a number of people who fall into the latter category. While working out or being physically active is good for us, there is such a thing as too much exercise. 

Throughout this series on the variables of exercise program design there has been one consistent theme:

Exercise is physical stress applied to the body.

All of the variables of program design—exercise selection, intensity, repetitions, tempo, sets, frequency and volume—dictate how to impose the physical demands of that stress. While proper application of all the variables is important for helping clients achieve results, the neuromuscular adaptations responsible for physiological change occur primarily after the exercise stimulus has been applied. In applying this understanding it can be argued that the final two variables of program design—rest and recovery—are the most important.

The secret of many of the top strength and performance coaches in the world isn't the exercises used in an athlete's workout, it's how the overall program is structured to allow time for optimal recovery between training sessions. Even though few of us are training professional or even extremely competitive amateur athletes, we should follow the lead of the top coaches. After all, if it works for someone making seven figures throwing or kicking a ball or swinging a club or a bat, it will probably work for our clients who simply want to "tone up and lose weight."

When designing exercise programs, there are two types of rest and recovery to consider: the short-term rest interval between sets in a workout and the long-term recovery period between separate training sessions. 

Exercise is a catabolic (breaking down) process that causes both metabolic fatigue and mechanical stress. Mechanical stress refers to the damage caused to the protein structures of muscle, while metabolic fatigue refers to depleted energy stores. If the rest interval between sets is too short, a few things could happen: muscles might not have enough time to remove metabolic waste like hydrogen ions, or replenish the fuel for the next set, and the nervous system responsible for initiating muscle contractions could fatigue. Any one of these could be a potential mechanism of injury. For some clients with specific goals, training to metabolic fatigue or exercising with short rest intervals to induce an energy-depleted state may be necessary. For many clients, however, training without adequate rest time could compromise their ability to achieve their goals.

Adequate recovery between sets and training sessions is important for a number of reasons. In the short-term, the rest interval provides time for the involved muscles to restore the glycogen and adenosine triphosphate (ATP) used to fuel muscle contractions, as well as to recover from the neural fatigue caused by motor unit activation. Similar to intensity and repetitions, intensity and rest have an inverse relationship. Generally speaking training for strength or power requires higher intensities with heavier loads, which necessitates longer recovery periods between sets. Conversely, using lighter loads to develop strength-endurance or increasing muscle volume (hypertrophy) requires shorter rest intervals.

Rest Intervals and Recovery Time as Determined by Intensity

Training Goal

Rest Interval Length

Recovery Between Workouts*

Muscular Endurance
< 70% 1RM
12-15+ reps

≤ 30 seconds

24 hours

70-85 % 1RM
6-12 reps

30-90 seconds

24-72 hours

>85% 1RM
1-5 reps

2-5 minutes

48-72 hours

>85% 1RM
1-5 reps

2-5 minutes

48-72 hours

Source:  NSCA Essentials of Strength Training and Conditioning (3rd ed.) 2008.
*Before training the same muscle groups.

Without adequate rest between sets, the quality of future efforts becomes compromised while greatly increasing the risk of developing delayed onset muscle soreness (DOMS). For an individual new to exercise, DOMS creates the perception that exercise is painful, which could provide an excuse for failing to show up for the next class or training session. Just because you may feel that muscle soreness is an indicator of a good workout doesn't mean that a client who finds making it to the gym a challenge will agree with you. Gradually increasing intensity while shortening the rest interval and adding an extra set or two is an extremely effective way of increasing the level of difficulty of a program without changing any of the exercises. 

The longer recovery period between workouts allows time for repairing damaged muscle fibers and rest for the nervous system responsible for initiating muscles contractions. It also gives muscles a chance to remove metabolic waste and fully replenish all fuel stores. Again, a client could have a specific goal requiring shorter recovery periods between workouts to help that individual adapt to exercising in a slightly fatigued state, but overall the optimal recovery time between strength-endurance workouts is approximately 24 to 36 hours. The recommended recovery time between high-intensity strength and power workouts is anywhere from 48 to 72 hours. This is why most bodybuilders and competitive weightlifters follow workout programs that call for training specific body parts or movements on separate days. A bodybuilder can do a high volume of chest training on a Monday, back training on a Tuesday and leg training on a Wednesday. When Thursday comes it's time to train chest again, because these muscle have had a full 72-hour recovery period.

One thing I try to drill into my clients’ heads is that the preparation for tomorrow's workout starts at the end of today's class or training session. Hydration, proper fueling (nutrition) and adequate sleep all play a critical role during the post-workout recovery process. As a fitness professional you should be able to recommend specific recovery strategies for what to do after the workout to ensure that the exercise stimulus has the desired effect. Designing a program with too many high-intensity workouts too close together will not allow time for your clients’ bodies to rest, replace lost energy stores or rebuild new muscle tissue. The right rest intervals during a workout and recovery strategies between training sessions can greatly reduce the risk of injury while promoting the optimal response to the exercise program.

Change does not occur without a preceding stimulus. The body is a very complex and adaptable organism that can adjust to almost any physical stimulus applied. If our job is to help clients make changes, then we need to challenge them to be uncomfortable. This does not mean that we hurt them or cause them physical harm, but it does mean that we need to ask them to work harder than they may be accustomed to. After all, that is why they're hiring us or coming to our group workouts in the first place. Hopefully, this series on the variables of exercise program design has given you some ideas about how you can challenge your clients to work a little differently on the way to their goals.

Part 1: How to Select the Right Exercises for Your Clients

Part 2: How to Select the Right Intensity and Repetions for Your Clients

Part 3: How to Select the Right Sets and Tempo for Your Clients

Part 4: How to Select the Right Volume and Frequency for Your Clients

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