Thursday, November 6, 2014

Partial Reps, Full Strength? For Squats, Combining Both via Block Periodization Yields Greater Strength Gains During the Early Phase of the Movement in Trained Gymrats

Not full or partial, but full and partial squats will yield maximal performance increases in trained athletes.
In a recent study from the East Tennessee State and the California Lutheran University researchers were able to show the common wisdom that only full reps would guarantee full development is true, but not the be-all and end-all of strength training wisdom.

When it comes to strength gains on squats, incorporating partial lifts - something that is common practice among strength trainers, anyway (Harris. 2000; Stone. 2000; Clark. 2008 & 2011), is in fact an effective training method for improving maximal strength and early force-time curve characteristics in men with previous strength training experience.
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Speaking of men with previous strength training experience, the subjects of the study that was conducted by Caleb Bazyler, Kimitake Sato, Craig Wassinger, Hugh Lamont, and Michael Stone, were 18 recreationally trained college aged males with at least 1 year of resistance training experience on the squat (>=1.3 body mass).
"Throughout the study, subjects were instructed to cease any supplementation use, refrain from lower-body resistance training outside of the study, and they were instructed not to participate in physical activity 24 hours before testing or training sessions. Subjects also completed a dietary log 24 hours before both preintervention testing sessions and were instructed to replicate the log for postintervention testing." (Bazyler. 2014)
The subjects trained according to a classic block-periodized model to control for volume and intensity manipulation (28,33). In that, the scientists included heavy and light days with weights that differed by 10-15% "to manage fatigue and avoid training to failure" (Bazyler. 2014). The load for the squat and partial squat was calculated using percentage of preintervention 1RM.
Table 1: Overview of the strength training program. *RM = repetition maximum. †F (full ROM) performed 6 3 5 on squats; FP (full plus partial ROM) performed 3 3 5 on squats and partial squats. zF performed 6–7 3 3 on squats; FP performed 3 3 3 on squats and partial squats (Bazyler. 2014).
Each training session began with a dynamic warm-up followed by warm-up sets on squat. The F group performed full squats only, whereas the FP group performed full squats followed by partial squats (from 100° knee angle to lockout position).
  • All training sessions were supervised to ensure correct technique and safety. 
  • Each training session began with a dynamic warm-up followed by warm-up sets on squat. 
  • The F group performed full squats only. 
  • The FP group performed full squats followed by partial squats (from 100° knee angle to lockout position). 
To assess the effects of the training manipulation, the researchers assessed anthropometrics, 1RM squat, 1RM partial squat, dynamic and isometric strength at the beginning of weeks 4 and 12 dynamic testing sessions.
Figure 1: Changes in 1RM squat and 1RM partial squat (left) and changes in isometric squat peak force (IPFa) at 90 and 120° of knee flexion. 180° is full extension (Bazyler. 2014).
As you can see in Figure 1 the researchers did measure significant differences with respect to the increase in 1RM on both the full squat (FP), only, and the full + partial squat group - albeit without significant inter-group differences. Inter-group differences were obvious, however, for the  allometrically scaled isometric squat peak performance, where the specificity of the exercise is reflected in the difference between the peak performance at different positions, with
  • Tip: Partials work with back exercises, as well! Doing partials in the contracted position at the end of almost every back / pulling movement is going to increase the activation of the target muscle | learn more in the SuppVersityEMG Series.
    the full squat increasing the peak performance at a knee-angle of 90° (lower portion of the squat) to a significantly greater extend, and
  • the full + partial squat increasing the peak performance at a knee-angle of 120° (upper portion of the squat) to a significantly greater extend,
an observation that would not exactly warrant the scientists conclusion that "[p]ractically, partial squats may be beneficial for strength and power athletes during a strength-speed mesocycle while peaking for competition" (Bazyler. 2014).
Figure 2: Changes in impulse scaled at 90° and 120° knee-angle (Bazyler. 2014).
Against that background it is actually quite surprising that the changes in the scaled impulse at 90° and 120° was significantly larger in the full + partial squat (FP) group for both angles. In physics the impulse is the integral of a force with respect to time, which implies that the overall force the trainees in the FP group were able to apply to the bar over a certain time period was larger at both 90° and 120°, in spite of the fact that the isometric peak force was lower at 90°.
"That's not 90°, yet. Go deeper, if you want to see results!"
Bear in mind: We are not comparing full ROM to partial ROM training. This comparison has been done by McMahon et al. one year ago and as you, as a loyal SuppVersity reader know, the results of their realistic 8 weeks leg training + 4 weeks detraining program shows that "Full ROM = More Growth, More Strength, More Structural Changes & More Sustainable Gains & Fat Loss" | learn more.
A very similar result that is even more closely relate to the study at hand was presented in another study I wrote about. A study by Blomquist et al. in their 2012 study which clearly proves that full squats are better strength builders than partial squats (only!).
Practically speaking this is a significant advantage, because the guys in the FP group would be less likely to "die" at the dead point of the squat exercise at 90° - it's after all not the isometric peak force, but a "constant" force that is applied for an extended period of time that's required to move the bar up (the peak force would matter for exercises like jump squats).

Figure 3: changes in force-time curve with training (Bazyler. 2014)
I guess this advantage will become even more obvious if you take a look at the changes in force-time curve with training in Figure 3, where the orange curve represents the full squat, only, and the orange curves the full + partial (FP) squat groups.

As you can see the overall increase in force development over the 250s periods the researchers assessed increased to a slightly greater extent in the FP vs. F group.

An advantage that should pay off during any event in terms of increased maximal loads, at the latest, when it comes to doing squats for reps.
No changes in body comp - at least none that were different between groups. As Bazyler et al. point out, "[t]here was no statistical difference between groups during pre- and posttesting for any of the anthropometric variables. A time effect was found for body fat percentage (p <= 0.05). Body fat percentage decreased statistically by 10.3 ± 12.4%, d = 0.27 (p = 0.027) in the F group; however, the decrease did not reach statistical significance in the FP group, 5.3 ± 11.1%, d = 0.12 (p = 0.102)" (Bazyler. 2014)
Whether or to which extend the previously discussed advantages of the full + partial squat regimen were related to the overall increase in intensity and volume (see Figure 4) is difficult to tell - the significant correlation Bazyler et al. found between the overall relative training intensity and the pre- to post 1RM squat change (r = 0.64, p = 0.003) would certainly suggest that there is a close relationship between training intensity and strength gains.
Figure 4: Microcycle volume load (left) and relative training intensity (Bazyler. 2014)
Similarly, the researchers observed strong correlations between 1RM squat and IPFa at a knee-angle of 90° (r = 0.72, p < 0.001), and moderate correlation at the higher position of 120° (r = 0.45, p = 0.005), as well as a moderate correlation between the change in IPFa 90° pre- to postintervention and full ROM squat and the total work load (r = 0.42, p = 0.048).
Suggested read: "You Want Maximal Performance & Size Gains + Complete Thigh Development? Then Full Squats are For You!" | learn more.
Bottom Line: Overall the results of the study at hand do suggest that the addition, not the replacement of full with partial squats may offer significant benefits to previously strength trained individuals, if their goal is not solely to increase their 1-RM, where the difference of 1.6% did not reach statistical significance in the course of the 7-week resistance training intervention.

As the authors point out, though, "the larger relative training intensities accomplished by the FP group during the final 3 weeks of training suggests superior adaptations" (Bazyler. 2014). In conjunction with the previously discussed advantages with respect to the overall rate of force development, the findings do thus "support previous claims that partial plus full ROM training is an effective strategy for improving maximal strength in subjects with previous strength training experience" (Bazyler. 2014) | Comment on FB.
  • Bazyler, Caleb D., et al. "The Efficacy of Incorporating Partial Squats in Maximal Strength Training." Journal of strength and conditioning research/National Strength & Conditioning Association (2014). 
  • Clark, Ross A., Adam L. Bryant, and Brendan Humphries. "An examination of strength and concentric work ratios during variable range of motion training." The Journal of Strength & Conditioning Research 22.5 (2008): 1716-1719. 
  • Clark, Ross A., et al. "The influence of variable range of motion training on neuromuscular performance and control of external loads." The Journal of Strength & Conditioning Research 25.3 (2011): 704-711.
  • Harris, Glenn R., et al. "Short-term performance effects of high power, high force, or combined weight-training methods." The Journal of Strength & Conditioning Research 14.1 (2000): 14-20.
  • Stone, Michael H., et al. "Comparison of the effects of three different weight-training programs on the one repetition maximum squat." The Journal of Strength & Conditioning Research 14.3 (2000): 332-337.