Strength Training Does Not Affect the Accuracy of Force Gradation in an Isometric Force Task in Young Men

Abstract

The aim of this study is to investigate potential differences in fine motor control between strength trained (ST) and non-strength trained (NT) individuals. By use of an isometric force production task, two groups, 20 ST (mean age 25.6, SD 4.9) and 19 NT (mean age 24.1, SD 2.9) male individuals, were measured on the ability to control forces with the muscles of their index finger. The maximum voluntary contraction (MVC) was higher in ST than in NT group. Error and SD of the signal increased with increasing force levels in both groups. Despite higher absolute force levels of the ST group, SD and Error were the same in both groups for a given MVC percentage. Signal to noise ratio values showed inverted U-shapes for both groups, with no significant differences between groups on various force levels. The power spectral density analysis disclosed significant differences between groups, with more power in the lowest frequency band (1 - 6 Hz) for the ST group. It is concluded that strength training of arm muscles has no negative effect on the stability of sustained contractions of finger muscles. No evidence was found to support the notion of a loss in accuracy as a result of strength training.

Key words

coordination - fine motor control - isometric force production - force fluctuations

References

• 1 Aagaard P, Simonsen E B, Andersen J L, Magnusson P, Dyhre-Poulsen P. Neural adaptation to resistance training: changes in evoked V-wave and H-reflex responses.  J Appl Physiol. 2002;  92 2309-2318
• 2 Carolan B, Cafarelli E. Adaptations in co-activation after isometric resistance training.  J Appl Physiol. 1992;  73 911-917
• 3 Carroll T J, Barry B, Riek S, Carson R G. Resistance training enhances the stability of sensorimotor coordination.  Proc R Soc Lond B Biol Sci. 2001;  268 221-227
• 4 Carroll T J, Riek S, Carson R G. The sites of neural adaptation induced by resistance training in humans.  J Physiol. 2002;  544 641-652
• 5 Deutsch K M, Newell K M. Age differences in noise and variability of isometric force production.  J Exp Child Psychol. 2001;  80 392-408
• 6 Duchateau J, Semmler J G, Enoka R M. Training adapations in the behaviour of human motor units.  J Appl Physiol. 2006;  101 1766-1775
• 7 Enoka R M, Fuglevand A J. Motor unit physiology: some unresolved issues.  Muscle Nerve. 2001;  24 4-17
• 8 Franklin D W, Osu R, Burdet E, Kawato M, Milner T E. Functional significance of stiffness in adaptation of multijoint arm movements to stable and unstable environments.  Exp Brain Res. 2003;  151 145-157
• 9 Henneman E. The size-principle: a deterministic output emerges from a set of probabilistic connections.  J Exp Biol. 1985;  115 105-112
• 10 Hortobagyi T, Tunnel D, Moody J, Beam S, DeVita P. Low- or high-intensity strength training partially restores impaired quadriceps force accuracy and steadiness in aged adults.  J Gerontol A Biol Sci Med Sci. 2001;  56 B38-B47
• 11 Jensen J L, Marstrand P C, Nielsen J B. Motor skill training and strength training are associated with different plastic changes in the central nervous system.  J Appl Physiol. 2005;  99 1558-1568
• 12 Jones K, Hamilton A, Wolpert D M. The sources of signal dependent noise during isometric force production.  J Neurophysiol. 2002;  88 1533-1544
• 13 Keen D A, Yue G H, Enoka R M. Training-related enhancement in the control of motor output in elderly humans.  J Appl Physiol. 1994;  77 2648-2658
• 14 Kornatz K W, Christou E A, Enoka R M. Practice reduces motor unit discharge variability in a hand muscle and improves manual dexterity in old adults.  J Appl Physiol. 2005;  98 2072-2080
• 15 Kukulka C G, Clamann H P. Comparison of the recruitment and discharge properties of motor units in human brachial biceps and adductor pollicis during isometric contractions.  Brain Res. 1981;  219 45-55
• 16 Laidlaw D H, Kornatz K W, Keen D A, Suzuki S, Enoka R M. Strength training improves the steadiness of slow lengthening contractions performed by old adults.  J Appl Physiol. 1999;  87 1786-1795
• 17 Martin S, Neale G, Elia M. Factors affecting maximal momentary grip strength.  Hum Nutr Clin Nutr. 1985;  39 137-147
• 18 Milner-Brown H S, Stein R B, Lee R G. Synchronization of human motor units: possible roles of exercise and supraspinal reflexes.  Electroencephalogr Clin Neurophysiol. 1975;  38 245-254
• 19 Muller K, Homberg V. Development of speed of repetitive movements in children is determined by structural changes in corticospinal efferents.  Neurosci Lett. 1992;  144 57-60
• 20 Nijhuis-Van der Sanden M W, Van Asseldonk E H, Eling P A, Van Galen G P. Slow motor performance in girls with Turner Syndrome is not related to increased neuromotor noise.  Motor Control. 2003;  7 111-133
• 21 Osu R, Burdet E, Franklin D W, Milner T E, Kawato M. Different mechanisms involved in adaptation to stable and unstable dynamics.  J Neurophysiol. 2003;  90 3255-3269
• 22 Patten C, Kamen G, Rowland D M. Adaptations in maximal motor unit discharge rate to strength training in young and older adults.  Muscle Nerve. 2001;  24 542-550
• 23 Peolsson A, Hedlund R, Oberg B. Intra- and inter-tester reliability and reference values for hand strength.  J Rehabil Med. 2001;  33 36-41
• 24 Petajan J H. AAEM minimonograph #3: motor unit recruitment.  Muscle Nerve. 1991;  14 489-502
• 25 Slifkin A B, Newell K M. Noise, information transmission, and force variability.  J Exp Psychol Hum Percept Perform. 1999;  25 837-851
• 26 Smits-Engelsman B CM, Westenberg Y, Duysens J. Development of isometric force and force control in children.  Cogn Brain Res. 2003;  17 68-74
• 27 Smits-Engelsman B CM, Van Galen G P, Duysens J. Force levels in uni-and bimanual isometric tasks affect variability measures differently throughout lifespan.  Motor Control. 2004;  8 437-449
• 28 Smits-Engelsman B CM, Rameckers E AA, Duysens J. Late developmental deficits in fine motor control in children with hemiplegia.  Neuroreport. 2004;  15 1931-1935
• 29 Staron R S, Johnson P. Myosin polymorphism and differential expression in adult human skeletal muscle.  Comp Biochem Physiol B. 1993;  106 463-475
• 30 Tesch P A. Acute and long-term metabolic changes consequent to heavy-resistance exercise.  Med Sport Sci. 1987;  26 67-89
• 31 Tracy B L, Byrnes W C, Enoka R M. Strength training reduces force fluctuations during anisometric contractions ofthe quadriceps femoris muscles in old adults.  J Appl Physiol. 2004;  96 1530-1540
• 32 Van Galen G P, De Jong W P. Fitts' law as the outcome of a dynamic noise filtering model of motor control.  Hum Move Sci. 1995;  14 539-572
• 33 Van Marken Lichtenbelt W D, Hartgens F, Vollaard N B, Ebbing S, Kuipers H. Body composition changes in bodybuilders: a method comparison.  Med Sci Sports Exerc. 2004;  36 490-497
• 34 Weinberg J M, Hunt D. The interrelationship between anxiety, motor performance, and electromyography.  J Motor Behavior. 1976;  8 219-224
• 35 Yao W, Fuglevand R J, Enoka R M. Motor-unit synchronization increases EMG amplitude and decreases force steadiness of simulated contractions.  J Neurophysiol. 2000;  83 441-452
• 36 Zehr E P. Training-induced adaptive plasticity in human somatosensory reflex pathways.  J Appl Physiol. 2006;  101 1783-1794