Targeting inflammation to influence cognitive function following spinal cord injury: a randomized clinical trial

STUDY DESIGN

This study was a randomized, parallel-group, controlled clinical trial.

OBJECTIVES

The purpose of this study was to examine the efficacy of targeting inflammation as a means of improving cognitive function in individuals with spinal cord injury.

SETTING

Participants were recruited from the Niagara region of Ontario Canada and all testing occurred on-site at Brock University.

METHODS

Indices of memory and verbal learning were assessed by means of the California Verbal Learning Test (CVLT). Inflammation and concentrations of neuroactive compounds related to the kynurenine pathway were assessed via a number of pro- and anti-inflammatory cytokines, as well as tryptophan, kynurenine and several large neutral amino acids. All assessments were performed at baseline as well as at 1 month and 3 months during a 3-month intervention by means of an anti-inflammatory diet.

RESULTS

Despite a reduction in inflammation, all measures of the CVLT, including list A, trial 1 (P=0.48), learning slope (P=0.46), long delay free recall (P=0.83), intrusions (P=0.61) and repetitions (P=0.07), showed no significant group × time interaction.

CONCLUSION

It may be possible that the reduction in inflammation achieved in the current study was insufficient to induce substantial changes in indices of verbal learning and memory. Alternatively, as these participants likely underwent years of previous chronic inflammation, the underlying hippocampal damage may have negated potential improvements induced by acute reductions in inflammation.

Immune dysfunction and chronic inflammation following spinal cord injury

STUDY DESIGN

Review article.

OBJECTIVES

The objective of this study is to provide an overview of the many factors that contribute to the chronic inflammatory state typically observed following spinal cord injury (SCI).

METHODS

Literature review.

RESULTS

Not applicable.

CONCLUSION

SCI is typically characterized by a low-grade inflammatory state due to a number of factors. As bidirectional communication exists between the nervous, endocrine and immune systems, damage to the spinal cord may translate into both endocrinal and immune impairment. Damage to the autonomic nervous system may induce immune dysfunction directly, through the loss of neural innervation of lymphoid organs, or indirectly by inducing endocrinal impairment. In addition, damage to the somatic nervous system and the corresponding loss of motor and sensory function increases the likelihood of developing a number of secondary health complications and metabolic disorders associated with a state of inflammation. Lastly, numerous related disorders associated with a state of chronic inflammation have been found to be at a substantially higher prevalence following SCI. Together, such factors help explain the chronic inflammatory state and immune impairment typically observed following SCI. An understanding of the interactions between systems, both in health and disease, and the many causes of chronic inflammation may aid in the effective future treatment of immune dysfunction and related disorders following SCI.

The effects of body-weight supported treadmill training on cardiovascular regulation in individuals with motor-complete SCI

STUDY DESIGN

Four-month longitudinal within-subject exercise training study.

OBJECTIVE

Although body-weight supported treadmill training (BWSTT) has not shown promise as a means of improving ambulation in individuals with motor-complete spinal cord injury (SCI), it may still improve cardiovascular health and function in this population. The purpose of this study was to (i) investigate the effects of BWSTT on peripheral muscular and elastic artery dimension and function and measures of heart rate variability (HRV) and blood pressure variability (BPV) in individuals with motor-complete SCI, and (ii) to make a preliminary examination of what factors may predict favourable cardiovascular outcomes following BWSTT in this population.

SETTING

Centre for Health Promotion and Rehabilitation, McMaster University, Hamilton, Ontario, Canada.

METHODS

Six individuals (four male, two female; age 37.7+/-15.4 years) with chronic SCI (C4-T12; ASIA A-B; 7.6+/-9.4 years post-injury) were included in the present investigation. Doppler ultrasound was used to determine femoral (exercising; muscular), carotid (elastic) and brachial (non-exercising control; muscular) artery dimension and function before and after 4 months of BWSTT. Continuous heart rate and blood pressure were also recorded before and after 4-months of BWSTT to determine frequency domain measures of HRV and BPV; clinically valuable indices of neurocardiac and neurovascular control, respectively.

RESULTS

Two-way ANOVA (vessel x time) revealed no exercise-induced change in femoral or carotid artery cross-sectional area, blood flow or resistance and no change in carotid artery compliance following the 4 months of BWSTT compared to the non-exercising control brachial artery. However, there was a significant exercise-induced increase in femoral artery compliance. There were no exercise-induced changes in HRV or BPV when all participants were considered together. However, the results suggest that the subgroup of individuals who had a substantial heart rate response to BWSTT (n=3), experienced exercise-training induced changes in HRV reflective of a relative shift toward cardiac vagal predominance and reductions in BPV.

CONCLUSIONS

BWSTT may cause an increase in femoral artery compliance in individuals with motor-complete SCI and therefore, should be encouraged as a means of improving cardiovascular health in this population. BWSTT may also cause modest improvements in measures of HRV and BPV in a select subgroup of individuals who respond to ambulation with moderate to large increases in HR. In the present study, factors associated with a substantial HR response to BWSTT were a propensity to orthostatic intolerance and muscular spasticity.

Maintenance of exercise participation in individuals with spinal cord injury: effects on quality of life, stress and pain

STUDY DESIGN

Follow-up study of seven individuals with spinal cord injury (SCI) who completed a 9-month randomized control trial (RCT) of exercise training.

OBJECTIVE

In a 9-month RCT conducted in our lab, individuals with SCI who participated in a twice-weekly supervised exercise training reported greater perceived quality of life (PQOL), and less stress and pain than a nonexercising control cohort. The present follow-up study examined the voluntary continuation of exercise training after the study ended and the persistence of the accrued psychosocial benefits.

SETTING

Centre for Health Promotion and Rehabilitation, McMaster University, Hamilton, Ontario, Canada.

METHODS

Five men and two women (age 42.3+/-3.6 years) with SCI (C5-T12; ASIA A-D 12.7+/-8.2 years postinjury) were invited to continue supervised exercise training twice weekly at the completion of the 9-month RCT. Exercise adherence, PQOL, stress and bodily pain were measured at a 3-month follow-up and were compared to values obtained at baseline, and at 3, 6 and 9 months during the intervention.

RESULTS

There was a significant decrease in adherence at the 3-month follow-up compared to the overall 9-month adherence rate (42.7 versus 80.6%, respectively; P<0.01). There was also a significant decrease in PQOL (P<0.05) and a trend for increased pain (P=0.07) and stress (P=0.12), at follow-up compared to the end of the 9-month trial. Finally, there was a significant negative correlation between pain at the conclusion of the RCT and exercise adherence over the 3-month follow-up period (r=-0.91; P<0.01).

CONCLUSIONS

These findings emphasize the importance of continued exercise adherence to the maintenance of exercise-related increases in psychological well-being among individuals with SCI.

Na+,K+-ATPase concentration and fiber type distribution after spinal cord injury

Complete spinal cord injury (SCI) is characterized, in part, by reduced fatigue-resistance of the paralyzed skeletal muscle during stimulated contractions, but the underlying mechanisms are not fully understood. The effects of complete SCI on skeletal muscle Na(+),K(+)-adenosine triphosphatase (ATPase) concentration, and fiber type distribution were therefore investigated. Six individuals (aged 32.0 +/- 5.3 years) with complete paraplegia (T4-T10; 1-19 years since injury) participated. There was a significantly lower Na(+),K(+)-ATPase concentration in the paralyzed vastus lateralis (VL) when compared to either the subjects' own unaffected deltoid or literature values (from our laboratory, utilizing the same methodology) of VL Na(+),K(+)-ATPase concentration for the healthy able-bodied (141.6 +/- 50.0, 213.4 +/- 23.9, 339 +/- 16 pmol/g wet wt., respectively; P < 0.05). There was also a significant negative correlation between the Na(+),K(+)-ATPase concentration in the paralyzed VL and years since injury (r = -0.75, P < 0.05). These findings are clinically relevant as they suggest that reductions in Na(+),K(+)-ATPase contribute to the fatigability of paralyzed muscle after SCI. Unexpectedly, the VL muscles of our subjects had a higher proportion of their area represented by type I fibers compared to literature values for the VL of the healthy able-bodied (52.6 +/- 25.3% vs. 36 +/- 11.3%, respectively; P < 0.05). As all our subjects had upper motor neuron injuries and, therefore, experienced muscle spasticity, our findings warrant further investigation into the relationship between muscle spasticity and fiber type expression after SCI.

Long-term exercise training in persons with spinal cord injury: effects on strength, arm ergometry performance and psychological well-being

STUDY DESIGN

Randomized controlled trial of exercise training in persons with spinal cord injury.

OBJECTIVE

The purpose of this study was to examine the effects of 9 months of twice-weekly exercise training on strength, arm ergometry performance, and indices of psychological well-being and quality of life.

SETTING

Centre for Health Promotion and Rehabilitation, McMaster University, Hamilton, Ontario, Canada.

METHODS

Thirty-four men and women (aged 19-65 years) with traumatic spinal cord injury (C4-L1; ASIA A-D) of 1-24 years duration volunteered to participate, and were randomized into exercise (EX; n=21) and control (CON; n=13) groups. Twenty-three subjects (11 EX; 12 CON) successfully completed the 9-month study. Subjects were assessed for one repetition maximum (1RM) strength, arm ergometry performance, and several indices of quality of life and psychological well-being at baseline, 3, 6, and 9 months.

RESULTS

At baseline, there were no significant differences between groups in age, submaximal arm ergometry performance, muscle strength, or psychological well-being. Following training, the EX group had significant increases in submaximal arm ergometry power output (81%; P<0.05), and significant increases in upper body muscle strength (19-34%; P<0.05); no significant changes occurred in CON. Participants in EX reported significantly less pain, stress and depression after training, and scored higher than CON in indices of satisfaction with physical function, level of perceived health and overall quality of life (P<0.05). Exercise adherence (per cent of prescribed sessions attended) in those subjects who completed the 9 months of training was 82.5%.

CONCLUSIONS

These results demonstrate that long-term twice-weekly exercise training in this population is feasible, and results in significant gains in both physical and psychological well-being.

Sex differences in human skeletal muscle fatigue

Research on muscle fatigue suggests that greater fatigue resistance may be evident in females compared with males. The possible mechanisms for this sex difference include factors related to muscle mass, substrate utilization, muscle morphology, and neuromuscular activation.

The effect of age and gender on the relative fatigability of the human adductor pollicis muscle

The purpose of this study was to examine the relative influence of such factors as age, gender, and absolute force on the fatiguability of the human adductor pollicis muscle. 12 young males (YM, 25.3 ± 2.1 y), 12 young females (YF, 23.5 ± 2.1 y), 12 older males (OM, 71.7 ± 5.6 y) and 12 older females (OF, 69.5 ± 4.6 y) participated. Three minutes of intermittent (5 s contraction, 2 s rest) maximal voluntary contractions (MVC) were used to fatigue the adductor pollicis muscle; the ulnar nerve was also stimulated in each 2 s rest period to evoke a maximal twitch. Males were stronger than females in both voluntary and evoked force (PT) in the young age group (MVC: YM, 10.0 ± 2.7 kg vs. YF, 6.6 ± 1.1 kg, P < 0.05) (PT: YM, 0.99 ± 0.21 kg vs. YF, 0.71 ± 0.12 kg, P < 0.05). In the older adults, however, males were stronger only in the evoked twitch (OM, 0.73 ± 0.24 kg vs. OF, 0.48 ± 0.07 kg, P < 0.05). There was no significant effect of gender or absolute muscle force on relative fatigability; the only variable found to significantly affect fatigability was age. Older adults were significantly less fatigable than young adults as indicated by the voluntary fatigue index (FI) (percentage of force reduction from baseline; FI-young, 40.2 ± 12.6% vs. FI-old, 25.2 ± 12.3%). This age effect, however, was more prominent in males than females (FI-YM, 44.7 ± 10.5% vs. FI-OM, 24.2 ± 10.7%, P < 0.01; FI-YF, 37.8 ± 14.1% vs. FI-OF, 26.3 ± 14.5%, P = 0.13). In conclusion, age was found to be the strongest single predictor of fatigability during short duration, intermittent exercise in human adductor pollicis muscle.Key words: neuromuscular fatigue, gender, age, muscle membrane excitability, absolute force.

The effect of age and gender on the relative fatigability of the human adductor pollicis muscle

The purpose of this study was to examine the relative influence of such factors as age, gender, and absolute force on the fatiguability of the human adductor pollicis muscle. 12 young males (YM, 25.3 +/- 2.1 y), 12 young females (YF. 23.5 +/- 2.1 y), 12 older males (OM, 71.7 +/- 5.6 y) and 12 older females (OF, 69.5 +/- 4.6 y) participated. Three minutes of intermittent (5 s contraction, 2 s rest) maximal voluntary contractions (MVC) were used to fatigue the adductor pollicis muscle; the ulnar nerve was also stimulated in each 2 s rest period to evoke a maximal twitch. Males were stronger than females in both voluntary and evoked force (PT) in the young age group (MVC: YM, 10.0 +/- 2.7 kg vs. YF, 6.6 +/- 1.1 kg, P < 0.05) (PT: YM, 0.99 +/- 0.21 kg vs. YF, 0.71 +/- 0.12 kg, P < 0.05). In the older adults, however, males were stronger only in the evoked twitch (OM, 0.73 +/- 0.24 kg vs. OF, 0.48 +/- 0.07 kg, P < 0.05). There was no significant effect of gender or absolute muscle force on relative fatigability; the only variable found to significantly affect fatigability was age. Older adults were significantly less fatigable than young adults as indicated by the voluntary fatigue index (FI) (percentage of force reduction from baseline; FI-young, 40.2 +/- 12.6% vs. FI-old, 25.2 +/- 12.3%). This age effect, however, was more prominent in males than females (FI-YM, 44.7 +/- 10.5% vs. FI-OM, 24.2 +/- 10.7%, P < 0.01; FI-YF, 37.8 +/- 14.1% vs. FI-OF, 26.3 +/- 14.5%, P = 0.13). In conclusion, age was found to be the strongest single predictor of fatigability during short duration, intermittent exercise in human adductor pollicis muscle.