For an avid gym enthusiast, it is essential that every moment spent dedicated to their craft is one of productivity. However, what is truly the best way to achieve the greatest muscle growth in the most optimal way? There are many different programs for working out using different techniques including, burnouts, drop sets, iso-holds, cheat reps, and rest-pause to name a few. Each style of lifting implores a different desired result, so how should a person that is looking to achieve pure muscle growth structure their workouts for greatest muscle hypertrophy? The answer is long-length partials, in addition to standard full range of motion (ROM) repetitions (Oranchuk et al., 2019).
Long-length partials involve performing a certain movement of weights only at the point where the muscle will be at its greatest strain. In a full ROM, the repetition of weight or movement is typically done by extending the muscle group and subsequently contracting the muscle group to its maximum range of motion (Pedrosa et al., 2022). In the case of a common exercise known as a biceps curl this involves using a dumbbell and curling the weight by bending your elbow, keeping it close to your body and curling it towards your chin, then slowly lowering the weight in the same path back to its starting position (Rogers, 2023) see figure. 1 below.
Figure: 1 an image depicting a person doing a biceps curl with full (ROM), beginning with the weight at its lowest position and curling it upward towards the chin (Oliveira A, 2008).
Different muscle groups have different ranges at which the force is greatest (Oliveira and Gonçalves, 2008) and in the case of a bicep curl the point at which the most force is being exerted on the elbow joint is at the uppermost point during the long-length partial when then forearm is perpendicular to the ground. Thus, it is crucial to go slightly past this point during the long-length partial to ensure the maximum amount of force being used (Rogers, 2023). At mid-point you are at equilibrium which splits the short partial from the long partial. At this point the torque from the bicep muscle is being balanced from the torque displaced by the weight of the dumbbell. Figure. 2 below shows the mechanics for when a bicep is at equilibrium.
Figure: 2 depicts the bicep at equilibrium when some object with a mass is causing a downward, force along with a downward force from the weight of the forearm, and an upward force from the bicep muscle (Moebs, 2016)
In a long-length partial repetition, the ROM is decreased however the time spent in the most anabolic which is where the greatest amount of protein synthesis occurs is increased (Pedrosa et al., 2022). A study that compared muscle growth between long-length partials and full ROM found that when the joint angle is > 70° (long length partials) a 1.16% muscle growth per week was shown. Compared to a .47% when the joint angle is < 70° (full ROM and short length partials) (Oranchuk et al., 2019). This growth can be viewed as a ratio: Hypothetically if you were to spend 45 seconds doing a set of dumbbell curls you are training the most anabolic part for roughly only half of the time (half is during long length partials and the other is short length partials), thus by spending a full 45 seconds doing full length partials you are maximizing the amount of force on the targeted muscle group, resulting in the greatest hypertrophy. A comparison between short-length and long-length partials can be seen in Figure. 3 below.
Figure: 3 is a comparison between the ROM of short length partials (depicted in red) and the ROM of long-length partials (depicted in green) (Nippard J, 2023).
The amount of torque on a bicep tendon can be calculated using the equation for torque at the midpoint, this is where the most force is being expelled and subsequently where the long-length partial is most effective (Calculation 1).
Calculation: 1 is the force on the bicep when a 40.0 lbs weight is being curled by an arm that is .35m in length, the weight of the forearm is 3.00 lbs, the distance from the weight to the center of the forearm is 0.175m and the distance between the perpendicular line from the center point to the elbow is 0.04m.
Thus, by performing long-length partials we can spend more time at the point where the maximum force is being expelled. When coupling long length partials with full ROM repetitions you can maximize the efficiency of a workout and gain the greatest hypertrophy. Although this is the most efficient way to structure a workout, as long as you are setting achievable goals and putting in effort you will see results!
References
Oliveira, A.S. and Gonçalves, M., 2008. Neuromuscular recovery of the biceps brachii muscle after resistance exercise. Research in Sports Medicine (Print), 16(4), pp.244–256. https://doi.org/10.1080/15438620802310800.
Oranchuk, D.J., Storey, A.G., Nelson, A.R. and Cronin, J.B., 2019. Isometric training and long-term adaptations: Effects of muscle length, intensity, and intent: A systematic review. [e-journal] Scandinavian Journal of Medicine & Science in Sports, 29(4), pp.484–503. https://doi.org/10.1111/sms.13375.
Paul Rogers 2023. Build Your Biceps With Dumbbell Curls. [online] Verywell Fit. Available at: https://www.verywellfit.com/how-to-do-the-biceps-arm-curl-3498604 [Accessed 19 November 2023].
Pedrosa, G.F., Lima, F.V., Schoenfeld, B.J., Lacerda, L.T., Simões, M.G., Pereira, M.R., Diniz, R.C.R. and Chagas, M.H., 2022. Partial range of motion training elicits favorable improvements in muscular adaptations when carried out at long muscle lengths. [e-journal] European Journal of Sport Science, 22(8), pp.1250–1260. https://doi.org/10.1080/17461391.2021.1927199.
Schoenfeld, B.J. and Grgic, J., 2020. Effects of range of motion on muscle development during resistance training interventions: A systematic review. [e-journal] SAGE Open Medicine, 8, p.2050312120901559. https://doi.org/10.1177/2050312120901559.