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Neural adaptations following cross-education strength training: A pilot study
Abstracts / Journal of Science and Medicine in Sport 12 (2010) e1–e232
and movement patterns) that is specific to running and not adversely influenced by the preceding bike-leg. However, a previous study has shown that running muscle recruitment is influenced by cycling in 36% of highly-trained triathletes, despite their years of training. This altered muscle recruitment is due to a direct influence of cycling on neuromuscular control during running and is independent of fatigue. However, it is not known if cycling has the same direct influence on neuromuscular control during running in lesser-trained triathletes. Purpose: To investigate the direct influence of cycling on running muscle activity and movement patterns in lessertrained triathletes. Methods: 15 lesser-trained triathletes participated. 3-D kinematics of the pelvis and lower limbs and recruitment of 11 leg and thigh muscles were compared between a control run (no prior exercise) and a 30 min run that was preceded by a 15 min cycle (transition run). Results: Neuromuscular control was not different between control and transition runs, or differences were only transient, in most triathletes. Changes in joint position (mean difference of 3◦ ) were evident in 5 triathletes, but these changes persisted beyond 5 min of running in only 1 triathlete. One triathlete displayed altered recruitment of the biceps femoris muscle (7.4% decrease in average amplitude over the running stride), which was not associated with a change in kinematics, and persisted for 20 min of the transition run. Discussion: Short periods of cycling have no direct influence on running muscle activity in most lesser-trained triathletes. Muscle recruitment during running was influenced by cycling in only 1 of 15 lesser-trained triathletes (<7%), compared to 36% of highly-trained triathletes, and the magnitude of this change was less than previously reported in highly-trained triathletes (7.4% vs. 10–20%). Cycling did cause some transient changes to running kinematics in 30% of lesser-trained triathletes. Conclusion: Our findings suggest that optimal neuromuscular control for running is preserved after cycling in lesser-trained triathletes. The differing influence of cycling on neuromuscular control during subsequent running in lessertrained and highly-trained triathletes is likely related to training history.
e51
doi:10.1016/j.jsams.2009.10.106
of the contralateral homologous muscle. This increase in strength is thought to be due to changes in motor cortex (M1) excitability, suggesting unilateral ST may affect synaptic connectivity within the M1, leading to an increased ability to produce force, however, this hypothesis has never been tested. The aim of this project was to use transcranial magnetic stimulation (TMS) to investigate the effect of unilateral ST on M1 excitability. Method: 16 subjects (29.5 ± 7.0 years) participated in the study and were randomly allocated into either ST or control group (C). ST subjects (n = 7) completed 12 supervised ST sessions over 4 weeks that involved 4 sets of 6 repetitions of a dumbbell biceps curl for the right arm only. Strength testing (1 repetition maximum, 1RM) of the right and left biceps and TMS at 10% above motor threshold (MT) during 10% background muscle activity was obtained prior to and following training. Corticospinal parameters of MT, motor evoked potential amplitude (MEP), and Electromyographic silent period duration (EMG SP) were obtained prior to and following training. Results: There was 26.4% increase in strength of the trained right limb and this resulted in a 16.3% transfer of strength to the left untrained arm (p = .001). No differences in strength between the right and left arms of the control group were noted. There was a 10.6% increase in MEP amplitude of the right M1 following training, although not significant (p = 0.06), there was a large effect size (ES = 1.25). There was no change within the control group. No significant differences in EMG SP durations for the right hemisphere were noted in the trained or control group (p > 0.05). Discussion: The findings suggest that unilateral ST does increase strength of the untrained homologous muscle. Although not statistically significant, the large ES and percentage change in MEP amplitude suggests, that for a given level of background contraction, there was an increase in the size of the descending corticospinal volley, intimating that the change in strength of the untrained arm may be due to improved motor unit activation. Conclusion: Strength training one limb; increased strength of the opposite limb by 16.3%; this improvement maybe due to changes in M1 excitability. Since descending corticospinal volleys terminate onto alpha motoneurons, the change in strength may have been due to improved motor unit activation.
106
doi:10.1016/j.jsams.2009.10.107
Neural adaptations following cross-education strength training: A pilot study D. Kidgell 1,∗ , A. Pearce 2 1 Deakin
University University
2 Victoria
Introduction: Strength training (ST) studies have demonstrated strengthening one limb produces increased strength
and movement patterns) that is specific to running and not adversely influenced by the preceding bike-leg. However, a previous study has shown that running muscle recruitment is influenced by cycling in 36% of highly-trained triathletes, despite their years of training. This altered muscle recruitment is due to a direct influence of cycling on neuromuscular control during running and is independent of fatigue. However, it is not known if cycling has the same direct influence on neuromuscular control during running in lesser-trained triathletes. Purpose: To investigate the direct influence of cycling on running muscle activity and movement patterns in lessertrained triathletes. Methods: 15 lesser-trained triathletes participated. 3-D kinematics of the pelvis and lower limbs and recruitment of 11 leg and thigh muscles were compared between a control run (no prior exercise) and a 30 min run that was preceded by a 15 min cycle (transition run). Results: Neuromuscular control was not different between control and transition runs, or differences were only transient, in most triathletes. Changes in joint position (mean difference of 3◦ ) were evident in 5 triathletes, but these changes persisted beyond 5 min of running in only 1 triathlete. One triathlete displayed altered recruitment of the biceps femoris muscle (7.4% decrease in average amplitude over the running stride), which was not associated with a change in kinematics, and persisted for 20 min of the transition run. Discussion: Short periods of cycling have no direct influence on running muscle activity in most lesser-trained triathletes. Muscle recruitment during running was influenced by cycling in only 1 of 15 lesser-trained triathletes (<7%), compared to 36% of highly-trained triathletes, and the magnitude of this change was less than previously reported in highly-trained triathletes (7.4% vs. 10–20%). Cycling did cause some transient changes to running kinematics in 30% of lesser-trained triathletes. Conclusion: Our findings suggest that optimal neuromuscular control for running is preserved after cycling in lesser-trained triathletes. The differing influence of cycling on neuromuscular control during subsequent running in lessertrained and highly-trained triathletes is likely related to training history.
e51
doi:10.1016/j.jsams.2009.10.106
of the contralateral homologous muscle. This increase in strength is thought to be due to changes in motor cortex (M1) excitability, suggesting unilateral ST may affect synaptic connectivity within the M1, leading to an increased ability to produce force, however, this hypothesis has never been tested. The aim of this project was to use transcranial magnetic stimulation (TMS) to investigate the effect of unilateral ST on M1 excitability. Method: 16 subjects (29.5 ± 7.0 years) participated in the study and were randomly allocated into either ST or control group (C). ST subjects (n = 7) completed 12 supervised ST sessions over 4 weeks that involved 4 sets of 6 repetitions of a dumbbell biceps curl for the right arm only. Strength testing (1 repetition maximum, 1RM) of the right and left biceps and TMS at 10% above motor threshold (MT) during 10% background muscle activity was obtained prior to and following training. Corticospinal parameters of MT, motor evoked potential amplitude (MEP), and Electromyographic silent period duration (EMG SP) were obtained prior to and following training. Results: There was 26.4% increase in strength of the trained right limb and this resulted in a 16.3% transfer of strength to the left untrained arm (p = .001). No differences in strength between the right and left arms of the control group were noted. There was a 10.6% increase in MEP amplitude of the right M1 following training, although not significant (p = 0.06), there was a large effect size (ES = 1.25). There was no change within the control group. No significant differences in EMG SP durations for the right hemisphere were noted in the trained or control group (p > 0.05). Discussion: The findings suggest that unilateral ST does increase strength of the untrained homologous muscle. Although not statistically significant, the large ES and percentage change in MEP amplitude suggests, that for a given level of background contraction, there was an increase in the size of the descending corticospinal volley, intimating that the change in strength of the untrained arm may be due to improved motor unit activation. Conclusion: Strength training one limb; increased strength of the opposite limb by 16.3%; this improvement maybe due to changes in M1 excitability. Since descending corticospinal volleys terminate onto alpha motoneurons, the change in strength may have been due to improved motor unit activation.
106
doi:10.1016/j.jsams.2009.10.107
Neural adaptations following cross-education strength training: A pilot study D. Kidgell 1,∗ , A. Pearce 2 1 Deakin
University University
2 Victoria
Introduction: Strength training (ST) studies have demonstrated strengthening one limb produces increased strength