There are a number of issues with a multi-split (MS) routine that causes them to be both hazardous for long term health and functioning, and inefficient for long-term sustained growth and hypertrophy.
The human body is designed to work in totality, not in isolation. And while one can analyze specific movement patterns and term them 'isolated' movements, in general, we move through and manipulate the space and environment around us through multi-planer, mutli-joint coordinated movements. The development of 'large' muscles and 'small' muscles and their placement on the body is not done by chance: we are constructed through evolution to have a complete system of skeletal muscles that allow us to perform multiple tasks efficiently and purposefully. It is not designed to isolate individual muscles for specific tasks, but to use as many muscles as are available to perform the given function.
When you attempt to artificially isolate a muscle/muscle group, you are breaking this design, which has implications on joint health, connective tissue stability, neuromuscular coordination, bone densities, and the development of speed, strength, power, and function. The use of a large selection of single joint isolation exercises is a significant failing of MS routine design, which is due to the specific methodology of attempted muscular isolation for localized hypertrophy of individual muscles apart from their natural inclusion in a total kinesthetic chain. Multi-joint movements are also difficult to place into a MS routine because of the complexity of the gross muscular innervation of these exercises and an innability to classify the primary mover while ignoring the innervation of other 'unwanted' muscles/muscle groups. By artificially isolating the anatomical heads of the deltoid, for instance, in an attempt to produce maximum hypertrophy of each, the potential to develop an imbalance (where there previously would not have been) between the forces acting on the glenohumeral joint is significantly increased. This can lead to serious shoulder injuries, damage, or pathologies (1). Muscles are designed to work as systems, and to develop and gain strength as a total system, not in an artificial isolation.
Most isolation movements, such as the dumbbell fly, are particularly inefficient in providing proper loading to produce useable adaptations throughout the ROM as well (2). Not only will this develop substantial strain on the agonist at the weakest point within the ROM, it will cause additional stress on the joint and ligamentous structure that protects the joint in an unnatural manner in comparison to real-world functional movement, which does not prepare the individual for sport-specific or life-needs strength and joint stability (3). Ultimately, this methodology will lead to a greater occurrence of musculotendinous trauma, joint instability, and loss of function.
For the implicit desire of localized muscular hypertrophy, isolation exercise may potentially be able to produce a greater localized serum endocrine response over that of compound movements; however, it is the nature of MS routines that ultimately makes this an inferior choice for total hormonal response. The specific loading coupled with volume for optimal endocrine response is found with the manipulation of the greatest number of muscle fibers recruited for an exercise, large muscle group movements, at >85% 1RM for multiple sets (4,5). By the nature of human muscle force and physiology, intensity is inversely related to volume, and as volume increases, intensity must decrease (4,5,6). A MS routine, while utilizing a large volume, must suffer from a decreased intensity of force production, seeking less than maximal/near maximal fiber recruitment and neuromuscular activity for the sake of exercise volume. This is not, therefore, optimal in producing the largest amount of the widest variety of hormones responsible for human muscle tissue hypertrophy, such as testosterone, GH, IGF-1, and thyroid hormones. This is also not optimal for producing maximal increased muscular adaptations of Type II muscle fibers because significant loading is not achieved. Further, it is this continued stimulation of large motor units that will allow for continued growth, with adaptations occurring at the neural level after genetic potential reaches its zenith.(7) It is postulated that hypertrophy will be most prevalent in strength athletes or weightlifters that utilize training protocols of 90-100% of 1RM voluntary contractile force (8), which is not possible in a high volume routine. Additionally, it appears that intensity/load chosen has a far greater effect on muscle size and strength than does volume within a workout design and exercise program (9).
The advantage of increased frequency and total microcycle volume of full-body (FB) workouts or simple splits (SS) when compared to multi-split program designs must also be acknowledged: The frequency of stimulus plays a critical role in increasing muscle strength and size through adaptive gene expression (5,10,11), and this clearly favors FB and SS over MS routine designs.
The natural, drug-free athlete cannot contend with the significant volume of work on the skeletal muscle system in a typical bodybuilder MS routine, nor does such a routine allow for optimal rest periods of limited but sufficient time for physiological adaptation to occur, and produces incomplete rest periods coupled with rest periods that are too long in duration(5), by the nature of the haphazard pairing of muscles. MS routines also have a serious affect on CNS recovery, which is thought to be responsible for increased incident of Overreaching and Overtraining syndrome, leading to more time off and more time spent away from the field of play or the gym (4). Proper rest intervals that allow for CNS recovery will allow the athlete to continue in competition or in resistance training with continued adaptation and growth. Most importantly, the contention that significant damage and subsequent increased rest periods are superior in producing hypertrophy in skeletal muscle tissue is not supported by the literature (5,12).
1. J Biomech. 1990;23(5):405-15. Glenohumeral muscle force and moment mechanics in a position of shoulder instability. Bassett RW, Browne AO, Morrey BF, An KN.
2. J Strength Cond Res. 2005 May;19(2):449-52. Electromyographic activity of the pectoralis major and anterior deltoid muscles during three upper-body lifts. Welsch EA, Bird M, Mayhew JL.
3. American Journal of Sports Medicine, Vol 24, Issue 4 518-527. A comparison of tibiofemoral joint forces and electromyographic activity during open and closed kinetic chain exercises. KE Wilk, RF Escamilla, GS Fleisig, SW Barrentine, JR Andrews and ML Boyd
4. Essentials of Strength Training and Conditioning/National Strength and Conditioning Association; Thomas Baechle, Roger Earle, editors, 2nd Ed. 2000.
5. Journal of Strength & Conditioning Research. Manipulating resistance training program variables to optimize maximum strength in men: a review. B Tan. 1999
6. Strength & Conditioning Journal, Volume 21, Number 2. Periodization: Effects of manipulating volume and intensity—Part 1. MH Stone, HS O'Bryant, et al.
7. The Journal of Strength and Conditioning Research: Vol. 16, No. 1, pp. 25–32. The Effects of Accentuated Eccentric Loading on Strength, Muscle Hypertrophy, and Neural Adaptations in Trained Individuals
JASON P. BRANDENBURG, and DAVID DOCHERTY
8. Hypertrophy and Hyperplasia: Adaptations of Muscular Tissue to Various Resistance Training Protocols. Anton Luis Sevilla. 2003.
9. Effect of resistance training volume on strength and muscle thickness.
Medicine & Science in Sports & Exercise. 28(10):1311-1320, October 1996.
STARKEY, DAVID B.; POLLOCK, MICHAEL L., et. al.
10. Effect of training frequency and specificity on isometric lumbar extension strength. Spine, Vol. 15, No. 6. 1990. JE Graves, ML Pollock, et. al.
11. Med Sci Sports Exerc. 1997 Dec;29(12):1646-52. Muscular adaptation and strength during the early phase of eccentric training: influence of the training frequency. Sorichter S, Mair J, Koller A, et. al.
12. Acute adaptation to low volume eccentric exercise. Medicine & Science in Sports & Exercise. 33(7):1213-1219, July 2001. PADDON-JONES, DOUGLAS; ABERNETHY, PETER J.
