Suppose you’re following a push pull legs workout routine and train on Monday, Wednesday, and Friday. You don’t sleep well on Thursday night and you’re dragging anchor on Friday—leg day. Should you dig in and get it done anyway or push the workout back to Saturday?

Or suppose you wake up on Wednesday—pull day—and your upper body is bushed from your push workout on Monday. Should you do all you can or swap it for the leg workout you normally do on Friday?

Many people sniff at the idea of programming their workouts according to how they feel on any given day, but there’s evidence this approach can be more effective than hewing rigidly to the same routine week in, week out. 

A notable example of this is a study conducted by scientists at St. Francis College, which divided 16 beginner weightlifters into two groups: 

  1. A rigid programming group, which performed all of their workouts in the same order and on the same days each week.
  2. A flexible programming group, which was allowed to choose what workout they did each day of the week based on how they felt.

Both groups did the same number and type of workouts, and after twelve weeks, the flexible programming group gained significantly more strength than the rigid programming group.

Flexible programming can also help you better stick to your program. In a nine-week study conducted by scientists at South Florida University, powerlifters using flexible programming missed four workouts, whereas those using rigid programming missed eight workouts. 

Yet another benefit of flexible programming is it can reduce the risk of injury. While I’m not aware of any research on this point, most experienced weightlifters can tell you of at least a couple of injuries they’ve sustained along the way in workouts they knew they should’ve skipped because of how they felt going into them.

Flexibility is easy to effectively integrate into your routine, too. Here are a few tips:

  • Instead of rigidly assigning specific workouts to specific days, create a list of workouts you aim to complete each week (two upper-body workouts and one lower-body workout, for instance) as well as a minimum number of weekly workouts to stay on track (one upper-body and lower-body workout).
  • Pay attention to your levels of fatigue, soreness, and motivation, and when any of these factors are significant enough to noticeably impair your performance in the gym, choose a less challenging workout from your “menu.”
  • Don’t view flexibility as a free pass to skip training. Remember that compromising always beats surrendering. Great workouts aren’t always the ones you asked for.