We were often asked how Vmaxpro builds up a velocity profile, how the 1 rep maximum (1RM) is deterÂmined and how exactly the whole thing actuÂally comes about at the end. To be honest, even me as the develÂoper cannot predict or explain the exact paths to the result. NowaÂdays, many algoÂrithms work in parallel, e.g. to deterÂmine the 1RM, the results of which are calcuÂlated on the basis of different confiÂdence interÂvals. All algoÂrithms are also continÂuÂously optiÂmized on the founÂdaÂtion of millions of executed repeÂtiÂtions with Vmaxpro.

However, one quesÂtion can be definÂiÂtively answered â€” the results can be extremely accuÂrate if a few boundary condiÂtions are met during usage. We are constantly working on making our algoÂrithms as stable as possible. But even the most stable calcuÂlaÂtion cannot give good results with bad input values. With this short article I would like to shed some light on the three quesÂtions and demysÂtify the magic behind Vmaxproâ€™s algoÂrithms.

### The velocity profile

The basis for velocity-based strength training is the quasi-linear relaÂtionÂship between the concenÂtric execuÂtion velocity and the load used. In simple terms â€” 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 moveÂment would be slower and the athlete would no longer be able to master the concenÂtric phase. The MVT is the velocity at maximum load. It is imporÂtant that this relaÂtionÂship is different for each athlete and each exerÂcise. The profile must thereÂfore be built up for each athlete in each exerÂcise. Luckily Vmaxpro does this completely autoÂmatÂiÂcally in the backÂground on the base of all data.

### The 1 rep maximum

As already mentioned, the underÂlying relaÂtionÂship is linear. At least it is in the area of interest we have. With this knowlÂedge, the slope of the straight line can be deterÂmined by executing submaxÂimal loads at maximal velocity. It is recomÂmended to use a load of more than 55 % 1RM, because the maximal velocity with light loads is diffiÂcult to achieve for inexÂpeÂriÂenced athletes and this is simply not possible in some exerÂcises. Although two loads would be mathÂeÂmatÂiÂcally suffiÂcient, several loads lead to a more reliÂable result. Vmaxpro uses the best repeÂtiÂtions of all repeÂtiÂtions 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 adapÂtaÂtion time. Within 42 days the relaÂtionÂship is quite stable.

Vmaxpro takes a close look at all repeÂtiÂtions in order to elimÂiÂnate possible incorÂrect measureÂments or recordÂings of partial moveÂments. For example, in squats, repeÂtiÂtions with missing depth are not considÂered in comparÂison to all other repeÂtiÂtions because they are not repreÂsenÂtaÂtive.

In addiÂtion to the slope of the straight line, the MVT for the accuÂrate deterÂmiÂnaÂtion of the 1RM is now missing. The MVT can be deterÂmined by pushing an athlete to his 1RM or by moving a submaxÂimal load to techÂnical failure. Here, the higher the load, the more reliÂable the result. Anything over 80 % usually leads to a very good result. The literÂaÂture recomÂmends caution when doing deadÂlifts. Besides very high correÂlaÂtions in all other exerÂcises, the approach of the submaxÂimal failure theorem does not always seem to be correct for deadÂlifting.

InterÂnally Vmaxpro autoÂmatÂiÂcally uses the slowest, valid, last repeÂtiÂtion of a set with a load above 70 % 1RM within the last 6 months. The MVT is adjusted in each training if necesÂsary. The MVT is very stable over time and can thereÂfore be considÂered over 6 months.

Besides the pure velocity based approach Vmaxpro also calcuÂlates the 1RM over submaxÂimal sets until failure. Depending on the exerÂcise and the scope, various algoÂrithms are used. With the execuÂtion of a single set to failure, a reliÂable profile is created.

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

### The accuracy

In order to clarify how accuÂrate the whole thing can actuÂally be, the meaning of the calcuÂlated 1RM must first be discussed. The calcuÂlated 1RM is always a theoÂretÂical 1RM under optimal condiÂtions. EspeÂcially with less advanced athletes, with loads close to 1RM, techÂnique or local failÂures can occur. Such factors cannot be calcuÂlated, but they are signifÂiÂcantly reduced with increased training expeÂriÂence.

When an athleteâ€™s profile is set, the 1RM can be reliÂably predicted in the range of Â±2.5%. However, it is particÂuÂlarly imporÂtant that this error is not random but systemÂatic. This means that the 1RM, for example, is always underÂesÂtiÂmated by 1%. This does not negaÂtively influÂence the use in daily training to deterÂmine the training load used.

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