A new paper from a research group Down Undah compared the effects of different exercise prescriptions on fatigue.
The goal of exercise prescription is to apply the correct type and amount of training stress on the individual, which varies based on their current fitness level, goals, and individual responses to training.
There are many ways to prescribe loading in resistance training. % of 1-Rep Max (%1RM) is often used, as it is objective and relatively simple to test an individual’s 1RM. However, an individual’s 1RM changes day-to-day and over time, which may produce inappropriate loading. Rate of Perceived Exertion (RPE) and Reps in Reserve (RIR) are both subjective methods of prescribing how hard a set should feel, thereby dictating load. While subjective rating of exertion seems to be viable in beginners and advanced trainees alike, many people have raised concerns that choosing weights based on subjective “feelings” leaves gainzZz on the table. Finally, Velocity Based Training (VBT) is another way to determine loading, as the speed of movement is a reliable correlate to effort and fatigue. The slower the movement, the harder the effort and higher the fatigue, generally speaking. Drawbacks of VBT include the requirement of specialized equipment and for maximal intent on each set, whereas “mailing it in” on a set may result in spurious results.
Subjects performed 1 training session each week in a randomized manner. To assess for existing fatigue, each session started with an assessment of perceived muscle soreness. Then, the subjects performed 3-reps of counter-movement jumps (CMJ) for max height and 3 reps bench press @ 45% 1RM for maximum velocity. Next, the subjects did a number of sprints to create fatigue prior to lifting, as most athletes are not going to train fatigue-free. Finally, the subjects trained using one of the prescriptive methods above. The training was 5 sets of squats, then 5 sets of bench press.
15 somewhat trained subjects (11 men w/ 1.3x BW bench and 4 women with 0.8x BW bench) trained under 4 separate conditions:
- %1RM (Percent of 1-Repetition Maximum) - Used 70% 1RM for 10 reps or failure
- RPE (Rate of Perceived Exertion) - Lifted 70% 1RM to > RPE 8
- RIR (Reps in Reserve) - adjusted loads to ~ 2 RIR in order to achieve 10 reps per set
- VBT (Velocity Based Training)- adjusted loads to maintain specific velocity that did not drop below velocity of 90% 1RM obtained during testing
After the completion of each set and at 24 hours post workout, soreness, neuromuscular function, and perceived exertion were assessed.
In this study, RIR was not used as the proxy for RPE. Rather, a scale similar to chart below was used:
Results-wise, there were no meaningful differences in soreness or neuromuscular function assessments. I wouldn’t expect much from a relatively short-term exposure, but I also am unclear about the validity of this testing within a session. Anyway, moving on…
With respect to training volume, RPE (using the scale above) did the fewest reps on average, with %1RM being the next lowest, and RIR and VBT having the highest. This was worth ~ 12-20 more reps for RIR and VBT between the squat and bench press combined. The %1RM condition also resulted in the more sets taken to failure than any other condition.
As far as the average velocity for each set, the %1RM condition was the slowest, whereas RIR, RPE, and VBT were all faster and about the same.
Subjects ranked VBT as their favorite prescription tool, with RPE second, RIR third, and %1RM last.
Overall, I think the main takeaway from this study is that people using an autoregulatory approach to exercise prescription are likely to complete more training volume than those using a fixed approach like %1RM. While differences in volume or sets taken to failure in a single session is unlikely to make a difference in outcomes, the volume and fewer sets taken to momentary failure are likely to better for strength development long term. The advantages of auto regulation are likely to be magnified long term.
As an aside, it is interesting to note that the authors do not attempt to define fatigue. I’ve gotten some flack for pointing out that there is no accepted definition of fatigue, but that doesn’t mean it’s not true. Instead, the authors attempt to measure fatigue using performance (CMJ and BP45%) and subjective metrics (soreness). I think these tests are reasonable fatigue proxies. They also highlight the complex nature of fatigue, as it’s not just performance (e.g. CMJ), it’s also how you feel.