A recent advancement in strength training equipment has created a new way to train the muscles of the torso. The new standing Hammer Strength Ground Base Twist machines address the limitations of the traditional seated rotary torso machine.

The torso is comprised of the abdominal and back muscle groups. Collectively they provide stability to the spine as well as create flexion, extension, lateral bending and rotational force during movement. The abdominal and back muscles must work together to move and stabilize the spine while coordinating with the muscles of the pelvis and extremities (Kumar, Narayan and Garand, 2001; Ng, et al., 2001; Hodges and Richardson, 1997). Recognition of this synergistic relationship has shifted current strength training practice away from traditional isolated exercises and toward an integrated approach that trains the muscle groups of the torso and extremities simultaneously.

Integrated training overloads the abdominal and back muscles in stabilization and movement production to promote coordination and movement pattern development. Research shows that the highest risk of low back disorder is associated with complex movement patterns of the trunk (Fathallah, Marras and Parnianpour, 1998). These complex patterns require the proper coordination of the activation of the abdominal and back muscles because incorrect activation can lead to injury (Ng, et al., 2002). The integrated exercise approach trains the muscles and the coordination necessary to maximize function and minimize injury risk.

But muscle groups also should be loaded to facilitate hypertrophy and increases in strength. Ng, et al. (2002) concluded that it was important to train the trunk muscles for coordination as well as strength. The complexity of this approach is in combining the progressive overloads that build muscle while making integrated movements.

The Hammer Strength Ground Base Twist Right, Twist Left and Combo Twist utilize movement patterns that address both overload and coordination training. By having the feet on the ground, the abdominal muscles can be isolated during the torso twist using a square stance and stabilizing the pelvis with the lower extremity muscles while pushing with a single arm. In this position, the activation of the abdominal muscles can be compared to that found during a seated torso twist. In the seated position, the pelvis is passively stabilized by the seat, so the lower extremity muscles are not worked. The seated torso machine locks the upper and lower body together in one unit of motion, which is not typically how the body works in real-life activities. In contrast, the standing twist involves arm movement, so the abdominal muscles are trained in coordination with this movement.

In addition to providing a more traditional isolation-like challenge, motion in the standing position can be advanced by adding a simultaneous pulling motion with the opposite arm and/or by moving the feet into a variety of task-specific positions. This allows various muscle groups to be added and muscle sequencing to be varied, thereby making the exercise mimic the demands of more complex movements. This variety is not available in the seated torso position.

The uniqueness of the Hammer Strength Ground Base Torso Twist machines is in the variety of the positions users can assume and the ease at which overload is combined with movement. Perhaps the greatest benefit of this design is the potential for improving the exerciser's functional capabilities. Traditional isolated training has been heralded as the gold standard for improving muscle size and strength. However, it is recognized that strength alone cannot predict functional outcomes (Salem, et al., 2000; Skelton, et al., 1995). In addition to changes within the muscle, neural changes affect the extent to which exercise will improve function (Rutherford, 1988).

This is consistent with the concept of specificity of training in resistance exercise. Morrissey, Harman and Johnson (1995) conducted a review of the role of various resistance training modes in the enhancement of functional performance. Overall, they concluded that the more specific the resistance exercise was to the type of contraction, speed of movement and joint angles of the functional movement, the greater the functional benefit. Smidt, Blanpied and White (1989) found the mode specificity and transfer of training concepts applied to the torso muscles.

So which mode - seated versus standing torso rotation - can better mimic the demands of activities of work, sport or daily life? In seated torso rotation machines, the fixed movement pattern, unnatural locking of the upper and lower body and the propensity to drive rotation too far (and thereby risk injury) limit the functional transfer.

The design of the Ground Base Torso Twist machines affords the greatest flexibility in type of contraction (e.g., isometric vs. isotonic), speed of movement, and, most importantly, joint angle and range of motion. This specificity, combined with the coordination of the upper and lower extremities during an exercise, creates the best available mode for maximizing the transfer of training. Strength and coordination carry over to improve function outside of the gym.

Finally, what is the difference regarding the magnitude of compression force applied to the lumbar spine during activity in a seated versus a standing torso rotation exercise? In 1981, Nachemson measured the intradiscal pressure of the lumbar spine in various positions. The article reports the pressures of each position as a percent of the load found in an upright standing position. Surprisingly, the seated position increased the load on the intervertebral discs of the lumbar spine by 40%.

So when seated, the discs are compressed 40% more than while standing. This compression, combined with simultaneous rotation, could result in a higher risk of injury to the disc during a seated torso rotation exercise. Considered in conjunction with the lack of integrated activation and minimized functional benefits, the seated torso rotation should be regarded as a limited use tool and not appropriate for all users.

With the evolution of equipment design, the standing Hammer Strength Ground Base Torso Twist machines now offer an alternative to the traditional isolated seated torso rotation exercise. The benefits of the standing position include hypertrophy and increased strength for the torso muscles, integrated training to improve coordination, enhanced functional performance and greater safety.

For more information on Hammer Strength, call 1.800.634.8637 or visit www.hammerstrength.com

References
Fathallah, F.A., W.S. Marras and M. Parnianpour (1998). The role of complex, simultaneous trunk motions in the risk of occupation-related low back disorders. Spine, 23(9): 1035-1042.
Hodges, P.W. and C.A. Richardson (1997). Contraction of the abdominal muscles associated with movement of the lower limb. Phys Ther, 77(2): 132-142.
Kumar, S., Y. Narayan and D. Garand (2001). Isometric axial rotation of the trunk in the neutral posture. Eur J Appl Physiol, 86: 53-61.
Morrissey, M.C., E.A. Harman and M.J. Johnson (1995). Resistance training modes: specificity and effectiveness. Med Sci Sports Exerc, 27(5): 648-660. Nachemson, A.L. (1981). Disc pressure measurements. Spine, 6(1): 93-97.
Ng, J.K-F., M. Parnianpour, C.A. Richardson and V. Kippers (2001). Functional roles of abdominal and back muscles during isometric axial rotation of the trunk. J Orthop Res, 19: 463-471.
Ng, J.K-F., C.A. Richardson and V. Kippers (2002). EMG activity of the trunk muscles and torque output during isometric axial rotation exertion: a comparison between back pain patients and matched controls. J Orthop Res, 20(1): 112-121.
Rutherford, O.M. (1988). Muscular coordination and strength training: implications for injury rehabilitation. Sports Med, 5: 196-202.
Salem, G.J., M-Y. Wang, J.T. Young, M. Marion and G.A. Greendale (2000). Knee strength and lower- and higher-intensity functional performance in older adults. Med Sci Sports
Exerc, 32(10): 1679-1684. Skelton, D.A., A. Young, C.A. Greig and K.E. Malbut (1995). Effects of resistance training on strength, power, and selected functional abilities of women aged 75 and older. J Am Geriatr Soc, 43: 1081-1087.
Smidt, G.L., P.R. Blanpied and R.W. White (1989). Exploration of mechanical and electromyographic responses of trunk muscles to high-intensity resistive exercise. Spine, 14(8): 815-830.

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