July 2011 Issue

How Much Exercise Do People Really Need? — A Review of the Basic Guidelines
By Joe Cannon, MS, CSCS, NSCA-CPT
Today’s Dietitian
Vol. 13 No. 7 P. 66

A common question people ask fitness trainers is, “How much exercise do I really need?” In case you are ever faced with this ambiguous yet weighty question, let me review the basic guidelines for aerobic exercise, strength training, and flexibility and offer tips gleaned from my own experiences.

Aerobic Exercise
Current American College of Sports Medicine (ACSM) guidelines recommend that people aim to get between 20 and 60 minutes of activity three to five days per week. Another guideline that has appeared in previous versions of ACSM publications is exercising “most days of the week.” In my opinion, while not as concrete as “three to five days per week,” this language may reduce the chance that novice exercisers will overwhelm themselves too quickly with too much activity. Guided by the most-days-of-the-week language, they have the freedom to work at their own pace.

In terms of intensity, the ACSM recommends exercising at about 65 to 95 maximum heart rate (or about 40% to 85% Karvonen heart rate). I prefer to use the rating of perceived exertion (RPE) scale to express intensity and instruct exercisers to aim for an RPE of 3 to 6 (moderate to difficult) when using the 0-to-10 scale.

Strength Training
The ACSM recommends exercisers engage in strength training two to three days per week.

I have noticed that when they are working with beginners, some trainers focus too much on one or two muscle groups. This practice not only leads to greater degrees of delayed-onset muscle soreness (DOMS), but it also flies in the face of ACSM guidelines that state a resistance training program should work all major muscle groups. To achieve this, exercisers need to perform at least seven different exercises; ACSM guidelines call for eight to 10 exercises.

Personal trainers often debate the number of sets of each exercise that people should perform. ACSM guidelines call for only one set per exercise. But according to the National Strength and Conditioning Association (NSCA), people desiring greater levels of strength must perform multiple-set programs (two to four sets). However, it is important to note that according to the ACSM, for beginners, performing one set of an exercise will improve strength almost as much as performing three sets for the first two months of a strength training program.

In addition, exercisers often query about the number of repetitions they should perform. The ACSM recommends performing three to 20 repetitions, but this guideline is very broad and takes into consideration recommendations for those with various health issues. According to the NSCA, for healthy people who want to improve muscle strength and endurance, a more precise guideline is determining the most weight someone can lift for only 10 repetitions. This method is known as the “10 RM.” After determining the weight amount, calculate 67% to 85% of this number. For example, if someone can lift 100 lbs on the chest press for 10 repetitions, the weight they should lift is 67 to 85 lbs. Exercisers should then aim for six to 12 repetitions using this weight.

Another common question is, “Does stretching reduce injuries?” So far research has not shown that stretching reduces the risk of injuries or DOMS.1 The ACSM says people ideally should perform flexibility exercises five to seven days per week. But this recommendation has a caveat, depending on individuals’ goals. If their goal is to improve strength and power, then people should perform flexibility exercises after strength training in light of research showing that stretching just prior to weight lifting decreases muscle power.2

— Joe Cannon, MS, CSCS, NSCA-CPT, is a personal trainer, exercise physiologist, and health educator in the Philadelphia suburbs.


1. Thacker SB, Gilchrist J, Stroup DF, Kimsey CD Jr. The impact of stretching on sports injury risk: A systematic review of the literature. Med Sci Sports Exerc. 2004;36(3):371-378.

2. Bacurau RF, Monteiro GA, Ugrinowitsch C, Tricoli V, Cabral LF, Aoki MS. Acute effect of a ballistic and a static stretching bout on flexibility and maximal strength. J Strength Cond Res. 2009;23(1):304-308.