We were often asked how Vmaxpro builds up a velocity profile, how the 1 rep maximum (1RM) is determined and how exactly the whole thing actually comes about at the end. To be honest, even me as the developer cannot predict or explain the exact paths to the result. Nowadays, many algorithms work in parallel, e.g. to determine the 1RM, the results of which are calculated on the basis of different confidence intervals. All algorithms are also continuously optimized on the foundation of millions of executed repetitions with Vmaxpro.

However, one question can be definitively answered — the results can be extremely accurate if a few boundary conditions are met during usage. We are constantly working on making our algorithms as stable as possible. But even the most stable calculation cannot give good results with bad input values. With this short article I would like to shed some light on the three questions and demystify the magic behind Vmaxpro’s algorithms.

### The velocity profile

The basis for velocity-based strength training is the quasi-linear relationship between the concentric execution velocity and the load used. In simple terms — the higher the load, the slower it can be moved. If the load is maximal, it is moved at the minimum velocity threshold (MVT). If the load would be increased further, the movement would be slower and the athlete would no longer be able to master the concentric phase. The MVT is the velocity at maximum load. It is important that this relationship is different for each athlete and each exercise. The profile must therefore be built up for each athlete in each exercise. Luckily Vmaxpro does this completely automatically in the background on the base of all data.

### The 1 rep maximum

As already mentioned, the underlying relationship is linear. At least it is in the area of interest we have. With this knowledge, the slope of the straight line can be determined by executing submaximal loads at maximal velocity. It is recommended to use a load of more than 55 % 1RM, because the maximal velocity with light loads is difficult to achieve for inexperienced athletes and this is simply not possible in some exercises. Although two loads would be mathematically sufficient, several loads lead to a more reliable result. Vmaxpro uses the best repetitions of all repetitions of the last 6 weeks with loads above 60% of the maximum load used. Why 6 weeks? It takes some time to change the velocity profile through training. One speaks here of about 42 days adaptation time. Within 42 days the relationship is quite stable.

Vmaxpro takes a close look at all repetitions in order to eliminate possible incorrect measurements or recordings of partial movements. For example, in squats, repetitions with missing depth are not considered in comparison to all other repetitions because they are not representative.

In addition to the slope of the straight line, the MVT for the accurate determination of the 1RM is now missing. The MVT can be determined by pushing an athlete to his 1RM or by moving a submaximal load to technical failure. Here, the higher the load, the more reliable the result. Anything over 80 % usually leads to a very good result. The literature recommends caution when doing deadlifts. Besides very high correlations in all other exercises, the approach of the submaximal failure theorem does not always seem to be correct for deadlifting.

Internally Vmaxpro automatically uses the slowest, valid, last repetition of a set with a load above 70 % 1RM within the last 6 months. The MVT is adjusted in each training if necessary. The MVT is very stable over time and can therefore be considered over 6 months.

Besides the pure velocity based approach Vmaxpro also calculates the 1RM over submaximal sets until failure. Depending on the exercise and the scope, various algorithms are used. With the execution of a single set to failure, a reliable profile is created.

As an example: 10 repetitions of pull-ups with a body weight of 75 kg and a maximal execution velocity of 0.7 m/s, in one of the first repetitions, results in a 1RM of about 95 kg. With the slowest velocity in this set of 0.35 m/s, two loads with two velocities and an MVT of 0.35 m/s result.

### The accuracy

In order to clarify how accurate the whole thing can actually be, the meaning of the calculated 1RM must first be discussed. The calculated 1RM is always a theoretical 1RM under optimal conditions. Especially with less advanced athletes, with loads close to 1RM, technique or local failures can occur. Such factors cannot be calculated, but they are significantly reduced with increased training experience.

When an athlete’s profile is set, the 1RM can be reliably predicted in the range of ±2.5%. However, it is particularly important that this error is not random but systematic. This means that the 1RM, for example, is always underestimated by 1%. This does not negatively influence the use in daily training to determine the training load used.