by Mike Boykin
Ernst Heinrich Weber was a professor of physiology at the University of Leipzig in the 1830s and is considered to be the founder of experimental psychology. One of his many claim-to-fames was as the pioneer of the “just noticeable differences” (JNDs) principle, also known as the difference limen or the differential threshold. Some of Dr. Weber’s experiments, watered down, involved handing a blindfolded individual a weight, followed shortly by a second weight. The subject was then asked if the second weight was lighter, heavier, or the same as the first.
After numerous experiments, Dr. Weber noted that the smallest discernable difference between two stimuli was not an objective, quantitative value. Instead, it was subjective and varied with the magnitude of the stimulus. The equation thus derived was delta*I/I= k, where delta*I is the JND, I is representative of the original intensity, and k is termed the “Weber constant” that (although later proved wrong) denoted the ratio between the two previous values. While Weber’s original belief- that a constant ratio was representative of the entire breadth of magnitudes a stimulus could impose on a sensory system- was wrong, the message can still pertain qualitatively to a periodization model. Due in part to the limited nature of this post, I will not attempt to quantitatively find the JND of forces applied in the weight-room. Instead, understand that there are certain loads that will feel different to your athletes, and certain loads that only appear significant on paper. So how can we apply the concept of noticeable differences to the weight room in a percentage-based model?
The central nervous system’s perception that a weight is heavier or lighter is often more important than the fact itself. Arbitrarily throwing numbers on a card for your athletes to follow adds stress to the wrong microcycles. There are times in the year when you want athletes to feel trashed, times when they need to feel refreshed, and times when you’re on cruise, but still want to subtly increase intensity, volume, or work capacity. During a deload week for example, the intensity and volume may appear to drop off, yet if this qualitative value does not reach the threshold of the JND, you’re wasting your time. On the other end of the spectrum, as coaches, we need to find, and ultimately cross, the noticeable fine line when we want to push and impart stress onto our athletes. Yet significantly exceeding this value may lead to maladaptation. In addition, noticeable differences are not the same value for everyone- they’re dependant on the individual’s existing strength. Just because your stud athlete can add fifty pounds to the bar with each consecutive set, doesn’t mean he should; and it certainly doesn’t mean the redshirt freshman next to him needs to either. Dictating certain numerical values through relative percents allows for group modifications and ensures that the team is peaking together. Due to the subjectivity of the JND, it appears that a percentage-based model that accounts for differences in how weights are perceived relative to a certain benchmark, may allow for individualized programming that collectively impacts the team.
Information and help was provided by Dr. Dane Cook, Ph.D., an Exercise Psychologist at the University of Wisconsin- Madison.