Partial range of motion training elicits favorable improvements in muscular adaptations when carried out at long muscle lengths

Abstract

The study compared changes in strength and regional muscle hypertrophy between different ranges of motion (ROM) in the knee extension exercise. Forty-five untrained women were randomized to either a control group or to perform the exercise in one of the following 4 groups (0°=extended knee): Full ROM (FULL ROM : 100°−30°of knee flexion); Initial Partial ROM (INITIAL ROM : 100°−65°); Final Partial ROM (FINAL ROM : 65°−30°); Varied ROM (VAR ROM : daily alternation between the ROM of INITIAL ROM and FINAL ROM ). Pre-and post-training assessments included one repetition maximum ( 1RM) testing in the ROM corresponding to the initial, final and full ROM, and measurement of cross-sectional areas of the rectus femoris and vastus lateralis muscles at 40%, 50%, 60% and 70% of femur length in regard to regional muscle hypertrophy. Results showed that the INITIAL ROM group presented a greater relative increase than all groups at 70%, and at 50% and 60% the increases were greater than FINAL ROM , FULL ROM , and non-training control (CON) groups. Moreover, FINAL ROM group presented similar changes compared to the CON group at 60% and 70%. In regard to 1RM, FINAL ROM and INITIAL ROM groups presented greater relative increases at the ROM trained, and no group showed greater increases than VAR ROM or INITIAL ROM , regardless the ROM tested. In conclusion, partial ROM training in the initial phase of the knee extension exercise promoted greater relative hypertrophy in certain muscle regions than training in other ROM configurations, and no group promoted a greater 1RM increase than VAR ROM group, which showed similar 1RM increases in the different ROMs tested.

Partial range of motion and muscle hypertrophy: not all ROMs lead to Rome

“…In summary, while investigations often report greater hypertrophy of fROM training when compared to pROM at short muscle lengths, 2,4,5,7,13 this superiority disappears when the comparison is made between pROM at longer muscle lengths versus fROM; in some cases, the pROM training at longer muscle lengths is actually more effective than the fROM, at least in certain muscles of the lower limbs. 7 Therefore, it is necessary to consider the joint angle in which the pROM is performed-that is, at a shorter or longer muscle length-when comparing changes in muscle size. Importantly, the hypertrophic effects of training throughout various ROM configurations may vary based on the given exercise, muscle, and site of hypertrophy assessment; these considerations warrant further investigation.…”

“…In the four studies included for meta-analysis, [2][3][4][5] muscles were trained at shortened length during the pROM condition. However, a study included in the systematic review, 6 but not in the meta-analysis, as well as a more recently published study, 7 indicates that pROM elicits similar or superior hypertrophy to fROM when the pROM was performed at longer muscle lengths. The distinction between pROM at short vs. long muscle lengths was not discussed by the authors, and we feel it warrants deeper discussion to provide a nuanced understanding of the topic.…”

“…8 Several studies published subsequent to that paper have shown greater hypertrophy at longer versus shorter muscle lengths in dynamic training of the hamstrings 9 and biceps brachii. 10 Most recently, Pedrosa et al 7 found that pROM knee extension training at a long muscle length was at least as effective, and in some cases superior, in eliciting increases in quadriceps CSA compared to fROM training.…”

Partial range of motion and muscle hypertrophy: Not all ROMs lead to Rome—Response

“…Finally, we believe it is important to stress that our review 1 included scientific articles from the earliest record up to and including March 2021. Therefore, although some of the experimental studies used by Kassiano et al to support their letter certainly contribute a great deal of knowledge around the topic, the date on which they were published (Pedrosa et al 4 = May 2021; Maeo et al 7 = April 2021; Sato et al 8 = September 2021), impeded the inclusion in our meta-analysis. Hence, these recently published investigations should be discussed and analyzed together in a future synthesis study rather than being used to judge the results of an already published review.…”

“…Moreover, since muscle hypertrophy has been proved to be non-homogeneous throughout the same muscle due to factors like the exercise trained or the type of contraction performed, measuring the MT in a single point has been found to lack the sensitivity to accurately detect muscle hypertrophy induced by resistance training. 3 Indeed, the study conducted by Pedrosa et al 4 (used by Kassiano et al to support some of their statements) used the MT as a control measure for the randomization process, but then evaluated the muscle hypertrophy by measuring the CSA at different thigh regions. Hence, we believe that the inclusion of Werkhausen et al 2 in the muscle architecture analysis, instead of in the muscle hypertrophy one, is adequately justified in both our review and this response.…”