Using the force-velocity imbalance to individualise training

A research review from the Performance Digest

Background & Objective

For each individual, an optimal force-velocity (F-V) relationship exists that maximises lower-limb ballistic performance (e.g. vertical jump) and represents the optimal balance between force and velocity qualities. Thus, F-V profiling may provide a more accurate representation of an athlete’s maximal force production capabilities. At this point in time, only one study has investigated the effects of an optimised training program based on individual F-V profiles (see HERE). However, the duration of this study was reasonably short (9 weeks), which may have resulted in only some subjects reaching an optimal F-V profile.

Therefore, the aims of this study were to:
1) Analyse the individual adaptation in the F-V profile until every subject reached their optimal profile;
2) Study the individual F-V profile in response to a three-week detraining period.

What They Did

Pre-Intervention
All sixty subjects (age = 23.7 ± 3.7 years) were trained professional futsal or semi-professional soccer and rugby players. The squat jump (SJ) was used to determine each subject’s F-V profile in a Smith machine. Five to eight progressive loads were used after body weight ranging from 15- 90kg.

Intervention
Subjects were assigned to one of four groups based on their F-V profile in relation to their optimal profile (F-V imbalance). 100 % was considered perfectly balanced and the exercise prescription of each group included:

• High force deficit (HFD) < 60% of optimal profile; performed mainly very high load training.
• Low force deficit (LFD) 60 – 90 % of optimal profile; strength-power emphasis.
• Low-velocity deficit (LVD) 110-140 % of optimal profile; power-speed emphasis.
• High-velocity deficit (HVD) > 140 % of optimal profile; performed mainly very high-velocity training.

Once the subjects’ F-V imbalance reached the next group’s range, they changed training group. As each got closer to their optimal profiles, F-V profiling was monitored every two weeks then eventually every week. Once a well-balanced profile was reached (defined as 90-110 %), targeted training stopped.

What They Found

HFD and LFD groups:

• Extremely large increases in theoretical maximum force (F0) (HFD = 44.1 ± 11.7%; LFD = 16.5 ± 5.1%).
• Extremely large reductions in F-V imbalance.
• Large increases in jump height (HFD = 17.1 ± 8.1%; LFD = 7.8 ± 2.8%).

HVD and LVD groups:

• Extremely large increases in V0 (HVD = 20.2 ± 2.4%; LVD = 12.6 ± 3.9%)
• Extremely large reductions in F-V imbalance.
• Moderate increases in jump height (HVD = 11.6 ±2.8%; LVD = 9.1 ± 2.2%)

De-training period:

• All variables maintained their post-training values with minimal
  differences.

SJ height was significantly correlated with differences in both F-V imbalance (explained variance of 48.2%) and maximal power (explained variance of 37.7%)

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Practical Takeaways

Based on the results from this study, it seems the larger the initial deficit, the longer the training intervention needs to be to reach an optimal profile. Furthermore, F-V imbalance change had a greater effect on jump performance than maximal power change. It is important to note that an improvement in maximal power may not incur an increase in jump height, which provides practical significance to coaches looking to maximise jump height with their athletes. This highlights that focusing on reducing the F-V imbalance may provide greater performance improvements when compared to traditional programming.

Rather than a “one-size-fits-all” approach, F-V profiling can provide individual information not only on training content but also on training duration. Given the ease of measurement, it could be recommended to monitor F-V profiles regularly to adjust athletes in different groups throughout a training period (e.g. every three weeks). The image below shows the training guidelines for each group. The My Jump 2 app is the easiest, low-cost way of monitoring F-V profiles. SJs performed over 4 progressive loads can be performed at the end of the warm-up and will only take approximately 10 min for a small group of athletes. These are the loading guidelines I have used successfully:
Males – 0, 20, 40, 60kg.

Females – 0, 15, 30, 45kg.

Reviewer’s Comments

To touch on the de-training period in the present study, only one other study has looked at changes in F-V profiles during a tapering period (see HERE). This previous study showed a “performance rebound” (improvement in performance after a de-training period) while the present study did not, which indicates changes in F-V profiles during de-training or tapering may be influenced by prior training. Furthermore, in Issue #32 of the Performance Digest, I reviewed a paper that showed a lot of strength can be retained after a 20-week detraining period. The present study showed all variables can be retained after three weeks of de-training potentially allowing resistance training to be left during small periods of training/competition depending on the sporting culture.

There is one pertinent question that must be asked before embarking on balancing everyone’s F-V profile: Will a well-balanced profile for sports that have positions that require high force or velocity outputs hurt or enhance their sports performance? For example, a prop in rugby union requires the ability to produce large amounts of force during scrummaging. An initial F-V profile will reflect this likely showing a high-velocity deficit. Neglecting high-load exercise for the sake of balancing the F-V profile and improving jump performance may leave the athlete lacking in the specific area they need to play their sport well.”

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The full study can be read here.