Most strength and conditioning professionals are familiar with the physical representation of the inverse relationship between both force and velocity, otherwise known as the 'force-velocity curve'. The charted area includes a y-axis representing force measured in newtons (N), as well as an x-axis representing velocity measured in meters per second (m/s). Movements such as a one-repetition max (1RM) back squat are a high force at low velocity, whereas a countermovement jump would is high velocity with relatively low force (1). Somewhere in between these two areas is the sweet spot, otherwise known as peak power, which can vary in percent of 1RM depending on the exercise selected. Additionally, scattered both above and below the peak power zone are strength speed and speed-strength zones, respectively, depicted in the graph below.
Figure 1. Adapted (6)
Coaches can easily decipher where a particular exercise falls on the spectrum of the force-velocity curve, but what's more important is to possess a firm understanding of how each zone varies as well as practical methods with which to train each one.
Absolute Strength: Concomitantly termed 'maximal strength' or 'accelerative strength', one's absolute strength is the zone where maximum muscular contractions occur in order to execute a repetition at or near one's 1RM, regardless of the velocity at which it occurs (1). In order to train this quality, loads between 80-100% 1RM are often used, with those >90% being optimal. Each set typically includes 1-5 reps depending on the load chosen, as well as full recovery between each set. Absolute strength is the framework for nearly all biomotor capabilities in athletics, particularly speed and power sports. Thus it is important that coaches ensure their athletes have an adequate foundation to further develop their necessary sports specific qualities.
Strength Speed: This zone is a step away from absolute strength, employing the use of maximum to moderate muscle contractions with a secondary focus on velocity. While much greater power outputs are seen in this range than absolute strength alone, strength still remains the primary emphasis. Moderate to high loads should be used, roughly 60-80% 1RM (again depending on the exercise selected) with 2-5 reps occurring within a given set and complete rest being achieved after each set (4,5). While this zone is critical for developing athletes, coaches often get tricked into allowing their athletes trained in this zone when they intended for peak power to be trained because too great of the load was chosen for the given movement.
Peak Power: This zone is where the sweet spot between both force and velocity coincides, as displayed by the highest power output one can produce in watts (3). On average, peak power is displayed when using loads ~60% 1RM but also varies depending on the exercise chosen or the athlete executing the movement (4,5). Complete recovery should be sought between sets, with a rep range of 2-6 reps occurring within each set.
Speed Strength: This zone is the inverse of strength speed; in that velocity takes the primary emphasis, and force becomes secondary. Intensities of 40-60% 1RM should be used for any given exercise when aiming to develop this quality, or in simple terms, peak power minus ~10%. As with all of the other previously mentioned qualities, complete rest should be sought between sets, and a target rep range of 3-6 reps per set is optimal. Speed is the primary emphasis in this zone.
Absolute Speed: In this zone, the single most important variable is the velocity or the greatest degree of elastic/reactive speed, one can execute a movement at (2). Very low loads are used to train this method and, in some instances, no load at all. No more than 20-30% 1RM should be used when training absolute speed with ballistic movements being highly beneficial. Anywhere from 5-12 repetitions can be executed within a given set, but it is imperative that coaches discontinue the set when any decrease in velocity occurs because absolute speed is then no longer being trained. It then makes clear sense too that maximum recovery should be given between each set of exercises in order to ensure maximum velocity.
Figure 2. Adapted (6)
Shifting the force-velocity curve to the right, or in other words, increasing the rate of force development, is essential for developing successful strength-power athletes. Athletes are at a major advantage over their opponents when they've developed greater explosiveness and the ability to display high levels of power. Coaches must ensure that they not only understand the force-velocity curve but also how to practically train each zone within it relative to their athlete's needs.