[Research] Velocity Loss as an Indicator of Neuromuscular Fatigue during Resistance Training

[Research] Velocity Loss as an Indicator of Neuromuscular Fatigue during Resistance Training

Med Sci Sports Exerc. 2011 Sep;43(9) Sánchez-Medina L, González-Badillo JJ. Source Faculty of Sport, Pablo de Olavide University, Seville, Spain. lsmedina@upo.es PURPOSE: This study aimed to analyze the acute mechanical and metabolic response to resistance exercise protocols (REP) differing in the number of repetitions (R) performed in each set (S) with respect to the maximum predicted number (P). METHODS: Over 21 exercise sessions separated by 48-72 h, 18 strength-trained males (10 in bench press (BP) and 8 in squat (SQ)) performed 1) a progressive test for one-repetition maximum (1RM) and load-velocity profile determination, 2) tests of maximal number of repetitions to failure (12RM, 10RM, 8RM, 6RM, and 4RM), and 3) 15 REP (S × R[P]: 3 × 6[12], 3 × 8[12], 3 × 10[12], 3 × 12[12], 3 × 6[10], 3 × 8[10], 3 × 10[10], 3 × 4[8], 3 × 6[8], 3 × 8[8], 3 × 3[6], 3 × 4[6], 3 × 6[6], 3 × 2[4], 3 × 4[4]), with 5-min interset rests. Kinematic data were registered by a linear velocity transducer. Blood lactate and ammonia were measured before and after exercise. RESULTS: Mean repetition velocity loss after three sets, loss of velocity pre-post exercise against the 1-m·s load, and countermovement jump height loss (SQ group) were significant for all REP and were highly correlated to each other (r = 0.91-0.97). Velocity loss was significantly greater for BP compared with SQ and strongly correlated to peak postexercise lactate (r = 0.93-0.97) for both SQ and BP. Unlike lactate, ammonia showed a curvilinear response to loss of velocity, only increasing above resting levels when R was at least two repetitions higher than 50% of P. CONCLUSIONS: Velocity loss and metabolic stress clearly differs when manipulating the number of repetitions actually performed in each training set. The high correlations found between mechanical (velocity and countermovement jump height losses) and metabolic (lactate, ammonia) measures of fatigue support the validity of using velocity loss to objectively quantify neuromuscular fatigue during resistance training.

This is VERY interesting study, especially taking into account my recent interest in velocity-based strength training (LINK, LINK, LINK).

The authors did a bunch of novel things:

Established velocity-load profile Tested for 1-RM, 12-, 10-, 8-, 6- and 4-RM Utilized 3 sets of Bench Press or Squat of different relative intensity over 8 weeks (3 × 6[12], 3 × 8[12], 3 × 10[12], 3 × 12[12], 3 × 6[10], 3 × 8[10], 3 × 10[10], 3 × 4[8], 3 × 6[8], 3 × 8[8], 3 × 3[6], 3 × 4[6], 3 × 6[6], 3 × 2[4], 3 × 4[4]) Performed Vertical Jump for the Squat group and bench/squat at load at estimated 1 m/s before and after 3 set protocols to assess neuromuscular fatigue, along with measuring lactate levels and ammonia.

Neuromuscular fatigue and velocity loss over 3 sets of 12 @ 12RM. Taken from Med Sci Sports Exerc. 2011 Sep;43(9) 

What the authors wanted so see is how different reps combinations (how close to failure – a concept explained by excellent system by Mike Tuchscherer) affect neuromuscular and metabolic fatigue.

Here are some of the findings:

...To the best of our knowledge, this is the first study to analyze the acute response to manipulating the number of repetitions actually performed in each training set with regard to the maximum number of repetitions that can be completed ...Our results indicate that, by monitoring repetition velocity during training, it is possible to  easonably estimate the metabolic stress and neuromuscular fatigue induced by resistance exercise. ...The present study confirms that the magnitude of velocity loss experienced during RT gradually increases as the number of performed repetitions in a set approaches the maximum predicted number. ...A finding worth noting is that greater MPV losses were experienced for BP compared with SQ for all protocols analyzed ... In the present study, very high and significant correlations (r = 0.91–0.97) were found between the three different types of mechanical measures used to assess neuromuscular fatigue (Figs. 2 and 3A, B). These relationships are an important finding for the quantification and monitoring of training load during RT. The fact that there exists such a close relationship between loss of MPV over three sets and loss of MPV with the V1 mIsj1 load in two exercises as different as SQ (Fig. 2A) and BP (Fig. 2B), as well as between both variables and loss of CMJ height in the SQ group (Figs. 3A, B), is a novel finding that emphasizes the validity of using percent loss of repetition velocity within a set as an indicator of neuromuscular fatigue. ... The relationships observed in Figure 2 also mean that, for a given percent loss of velocity within a set, the degree of fatigue incurred during RT is very similar irrespective of the number of repetitions the subject is able to perform (shown in different colors in Fig. 2), at least in a range from 4 (~90% RM) to 12 (~70% RM) repetitions. ... Lactate increased linearly as the number of performed repetitions approached the maximum predicted for each type of REP (Table 1) and showed extremely high correlations (r = 0.93–0.97) with loss of MPV over three sets (Fig. 4A), loss of MPV pre–post exercise with the V1 mIsj1 load (Fig. 4C), and loss of CMJ height (Fig. 3C). ... Lactate increased linearly as the number of performed repetitions approached the maximum predicted for each type of REP (Table 1) and showed extremely high correlations (r = 0.93–0.97) with loss of MPV over three sets (Fig. 4A), loss of MPV pre–post exercise with the V1 mIsj1 load (Fig. 4C), and loss of CMJ height (Fig. 3C). ... Although some studies have reported the point within a set where a significant reduction in velocity (18) or power output (1,26) was observed, the optimal time to terminate a set before reaching failure has never been clearly established.Although the present study does not come up with a definitive answer to that question, it does, however, provide us with some valuable information that may indicate when it could be appropriate to end a set. According to our results (Table 1; Figs. 3 and 4), a maximum MPV loss of ~30% for SQ and ~35% for BP could be established to prevent blood ammonia to significantly rise above resting levels. ... Monitoring repetition velocity during resistance exercise seems important because both the neuromuscular demands and the training effect itself largely depend on the velocity at which loads are lifted. A velocity- or power-based approach to RT is not entirely new, and authors such as Bosco (5) and Tidow (37) already provided some initial guidelines for putting it into practice. However, the role placed by movement velocity has not been sufficiently investigated (28). The findings obtained in the present study strongly support the use of velocity monitoring to control the degree of incurred fatigue. … Furthermore, the immediate velocity feed feedback the athlete receives during each session may increase the potential for adaptation. With this training approach, instead of a certain amount of weight to be lifted, strength and conditioning coaches should prescribe resistance exercise in terms of two variables: 1) first repetition’s mean velocity, which is intrinsically related to loading intensity (15); and 2) a maximum percent velocity loss to be allowed in each set. When this percent loss limit is exceed the set must be terminated. The limit of repetition velocity loss should be set beforehand depending on the primary training goal being pursued, the particular exercise to be performed, as well as the training experience and performance level of the athlete. ... In conclusion, the present data show that the relationship between the number of repetitions actually performed in a set and the maximum predicted number that can be completed is an important aspect to take into account when prescribing resistance exercise because the velocity loss and metabolic stress clearly differ when manipulating these variables. The high correlations found between mechanical (velocity and CMJ height losses) and metabolic (lactate, ammonia) measures of fatigue support the validity of using velocity loss to objectively quantify neuromuscular fatigue during RT. The nonlinear response of blood ammonia to loss of repetition velocity could perhaps be used as a reference to indicate the point within a set where the exercise should be terminated when the main training objective is to improve movement velocity or maximal power production.

This reminds me very much of the Prilepin table

Using these recommendations power/velocity loss during the set won’t be bigger than 30-35% as suggested by this article.

I describe one potential approach of prescribing exact % 1RM to be used, but instead of prescribing exact number of reps one could use reps zone (to allow for day to day variability in readiness), but also, if one is equipped with system like GymAware, use quality threshold (QT) – or a maximum percent velocity loss to be allowed in each set.

This quality threshold is very much in line with Mike Tuchscherer’s RPE system (Fatigue Percents and Critical or proximity of failure – of course taken into account that all reps are done with maximum effort.

There is one study done by using 80% quality threshold on experienced bench pressers with great results compared to the group that done sets to failure and without compensatory acceleration.  Results are so great that they are a little bit ‘fishy’. Anyway very interesting study and training concept indeed.

I think with the help of systems like GymAware we will tend to see coaches devising and utilizing more examples of velocity- or power-based strength training.

I am ‘experimenting’ with this at the moment. Just today I performed Bench press at 85% of 1RM with quality threshold set to 80% of the first rep. My first rep average velocity was 0.37 m/s and I set up the alarm on GymAware to 0.29 m/s. I end up doing 10 sets of 2 reps with 2 min rest. One could stop doing sets when one can’t maintain minimum velocity for the first reps with set rest time, or when one exceeds allotment time per exercises (this idea by Charles Staley although I saw Joe Kenn and Mike Tuchscherer using the same; this way productivity is a lot bigger, along with controlling larger group of athletes in the gym).

There are certainly different methods to do this and this might be just one of them. Anyway, one could create different stress and workout goals by prescribing different intensities and quality thresholds. For example intensive workouts should prescribe a bit heavier %1RM, lower QT (keep the quality) and longer rests. Volume (or extensive) workouts should prescribe a little lower %1RM, bigger QT (allow higher fatigue) and shorter rest. One could play with these variable to create different types of workout depending what is more the goal of it, what load aspect is being stresses (quality, grinding, intensity, intensiveness, volume, etc) or what of cycle is being utilized.

I believe velocity- power-based strength training will gain more popularity especially in power and mixed sports in the time to come.