The Effects of Acute Aerobic Exercise on Cerebral Blood Flow and Cognition in Persons with Multiple Sclerosis
Authors: Rosenberg Alexander Jacob , Wee Sang Ouk , Shroeder Elizabeth C. , Grigoriadis Georgios , Sandroff Brian M. , Bunsawat Kanokwan , Hilgenkamp Thessa I. , Griffith Garett J. , Motl Robert , Baynard Tracy 
Published: November 2023

Multiple sclerosis (MS) is a chronic autoimmune disease associated with neurological symptoms leading to muscular weakness, pain, and cognitive decline. Cognitive impairment affects 40–70% of individuals with MS and has been associated with reduced physical independence and overall quality of life. Cerebral blood flow (CBF) decreases with aging and is associated with cognitive decline in healthy aging adults. Individuals with MS have an attenuated response in CBF velocity to a head‐up tilt stimulus, independent of age. Exercise and physical activity improves CBF dynamics and cognitive function in older individuals without disease; however, this relationship has not been demonstrated in an MS population.

Purpose

To investigate the effects of acute moderate intensity aerobic exercise on cognitive function and CBF velocity in persons with MS.

Methods

Fourteen individuals with MS (Age = 42 ± 9 yrs, BMI = 26.3 ± 6.3 kg/m2) had aerobic capacity (VO2peak) assessed via a treadmill test. They were then randomized to either 20 min of treadmill walking at 60% of VO2peak or a control condition (20 min quiet rest). Participants completed both conditions in a counterbalanced order (i.e., within‐subjects design). The modified flanker task (inhibitory control, mental processing speed) was administered at baseline, 1‐minute post‐condition, and 30‐minutes post‐condition. The flanker task involves a set of 5 flanking arrows of congruent (>>>>>) and incongruent (>> < >>) orientation and measures reaction time (RT) and accuracy of indicating the direction of the middle arrow. Continuous beat‐to‐beat CBF velocity (CBFv), end‐tidal CO2, and heart rate (HR) measurements were recorded during the entire visit by transcranial Doppler, and CO2/O2 gas analyzer, and wireless three‐lead ECG. Carotid artery beta‐stiffness index and arterial compliance (AC) were measured by ultrasonography and carotid blood pressure (cSBP, cDBP, cMAP) measurements were obtained using applanation tonometry at the same time points as the flanker task.

Results

See table. Both conditions improved reaction time at 1‐minute post (p<0.05), but only the exercise condition maintained the reduction at 30‐minutes (p<0.05). Mean CBFv did not change following either condition, however, CBFv pulsatility increased following exercise (p<0.05) and returned back to baseline at post 30‐min. HR, cSBP, cDBP, cMAP, Beta‐stiffness, and end‐tidal CO2 increased following exercise, while AC decreased (p<0.05).

Conclusion

These data demonstrate the beneficial effect of acute aerobic exercise on mental processing speed and accuracy, independent of CBF dynamics, carotid artery stiffness and carotid blood pressures in persons with MS. Therefore, acute improvements in reaction time following aerobic exercise seems to be attributed to other factors not assessed. Further investigation is required to fully elucidate the effects of aerobic exercise on cognition in MS, given there is no FDA approved treatment available for cognitive impairment in this population.

Variables

Baseline
1‐minute
30‐minute

Congruent RT (ms) *
Control
583.84 ±69.68a
555.18 ±61.90
561.38 ± 77.36

Exercise
585.36 ± 80.49 ab
558.83 ±68.41
551.53 ±64.44

Incongruent RT (ms) *
Control
624.81 ± 78.98
589.47 ± 76.03
624.72 ± 91.67

Exercise
639.23 ± 81.79 ab
607.62 ± 80.76
606.55 ± 81.97

Congruent RT Accuracy (%)
Control
93 ± 9
96 ± 6
96 ± 4

Exercise
96 ± 6
96 ± 4
97 ± 2

Incongruent RT Accuracy (%)
Control
73 ± 30
76 ± 31
76 ± 31

Exercise
80 ± 24
82 ± 27
81 ± 26

Heart Rate (bpm) *† ‡
Control
64 ± 10
62 ± 10
62 ± 10

Exercise
66 ± 9 ab
82 ± 14 b
69 ± 11

cMAP (mmHg) *‡
Control
85 ± 11b
87 ± 12 b
90 ± 13

Exercise
86 ± 11 a
92 ± 10
88 ± 9

cSBP (mmHg) *‡
Control
107 ± 13
108 ± 15 b
112 ± 16

Exercise
110 ± 13a
117 ± 11
112 ± 10

cDBP (mmHg) *
Control
70 ± 11 b
71 ± 11 b
74 ± 12

Exercise
70 ± 11 a
73 ± 11
72 ± 11

Beta‐Stiffness †‡
Control
6.0 ± 1.7
5.8 ± 1.6
5.6 ± 1.4

Exercise
6.2 ± 0.9 a
7.4 ± 1.6 b
6.5 ± 1.1

AC†‡
Control
1.02 ± 0.28
1.08 ± 0.31
1.06 ± 0.39

Exercise
0.94 ± 0.20 a
0.73 ± 0.21 b
0.87 ± 0.24

Max Diameter (mm) ‡
Control
6.85 ± 0.57 a
6.93 ± 0.63
6.92 ± 0.68

Exercise
6.92± 0.80 a
6.67 ± 0.64 b
6.77 ± 0.70

Min Diameter (mm) ‡
Control
6.37 ± 0.53
6.46 ± 0.60
6.44 ± 0.64

Exercise
6.44 ± 0.75 a
6.26 ± 0.62
6.33 ± 0.69

CBFv Mean (cm/s)
Control
58.8 ± 12.6
58.8 ± 12.5
59.4 ± 12.7

Exercise
56.2 ± 12.9
54.5 ± 14.2
55.7 ± 12.7

CBFv Pulsatility Index *†
Control
0.95 ± 0.11
0.96 ± 0.14
0.93 ± 0.13

Exercise
0.98 ± 0.14
1.06 ± 0.16 b
0.97 ± 0.10

End‐Tidal CO2 *‡
Control
4.81 ± 0.43
4.76 ± 0.48
4.82 ± 0.52

Exercise
4.71 ± 0.49 a
5.09 ± 0.42 b
4.56 ± 0.59

All Data are mean ± SD,

Time effect, p<0.05.

Group effect, p<0.05.

Interaction effect, p<0.05.

significantly different from 1‐minute,

significantly different from 30‐minute, p<0.05.