Aberrant peak lactate response in MS

Blood lactate concentrations during rest and exercise in people with Multiple Sclerosis: A systematic review and meta-analysis

BACKGROUND

Multiple Sclerosis (MS) is a chronic disorder which irreversibly damages axons within brain matter. Blood lactate concentration could be a biomarker of MS onset and progression, but no systematic review has yet sought to confirm or dispute the elevation and biomarker potential of blood lactate in people with MS (PwMS) or to consolidate understanding of lactate production during exercise in PwMS.

OBJECTIVE

To perform a systematic review and meta-analysis on blood lactate in PwMS during rest and exertion compared to Healthy Controls (HC) and following chronic exercise intervention.

METHODS

A systematic search of six electronic databases (PubMed, CINAHL, Science Direct, Cochrane Library, SPORTDiscus and PEDro) was performed on 10th April 2020. Mean, standard deviation and sample size for lactate measures at rest and during exercise were pooled to determine overall effect size using a random effects model.  The 20-point Appraisal tool for Cross-Sectional Studies was utilised to assess study quality and inherent risk of bias. To qualify for inclusion, studies had to include human adults (>18 years) with a confirmed clinical diagnosis of MS, be published in English, have undergone peer review, report absolute blood lactate values for data extraction, and if involving testing during/after exercise, to do so during bilateral exercise methods.

RESULTS

18 studies were qualitatively analysed and 15 studies quantitatively analysed. Outcome data was available for 1986 participants (n_MS = 1129). A total of 7 papers tested blood lactate during rest (Lactate_REST), 7 papers tested during sub-maximal intensity exercise (Lactate_SUB-MAX), and 8 papers tested during maximal intensity exercise (Lactate_MAX). Meta analyses showed elevated Lactate_REST and reduced Lactate_MAX in PwMS compared to HC, higher Lactate_MAX in lower EDSS-scoring PwMS compared to higher EDSS-scoring PwMS, and that Lactate_SUB-MAX decreases and Lactate_MAX increases in PwMS following a chronic exercise intervention. Qualitative analysis reported Lactate_REST to be reduced in PwMS following a chronic exercise intervention.

CONCLUSIONS

Lactate_REST is elevated in PwMS compared to HC. Lactate_MAX is lower in PwMS compared to HC and lower still in higher compared to lower EDSS-scoring groups of PwMS. Chronic exercise interventions have the potential to reduce Lacatate_SUB-MAX for a given power output and increase Lactate_MAX in PwMS compared to baseline values. Lactate_REST may be reduced in PwMS following a chronic exercise intervention but more research is required for confirmation. The results of this review were limited by small sample sizes and number of studies available for each testing condition, limited data available for potentially confounding/correlating factors (eg. VO₂ and power output) as well as heterogeneity of methodology adopted across studies, often due to lactate testing being a secondary outcome measure. PLS: Lactate levels in the blood are different during rest and at intense exercise levels in people with Multiple Sclerosis (MS) compared to healthy counterparts, with people with MS showing a smaller jump in lactate during intense exercise from a higher resting level. After exercising for at least 3 months, blood lactate levels during exercise may become more similar to the levels seen in people without Multiple Sclerosis, but more research is required to give a clearer picture of this. We can hopefully use blood lactate in future to measure the progression of MS in an individual as well as the effectiveness of their exercise programme.

A cross-sectional study on the relationship between cardiorespiratory fitness, disease severity and walking speed in persons with Multiple Sclerosis

BACKGROUND

In persons with Multiple Sclerosis (PwMS) cardiorespiratory fitness has been associated with disease severity, walking capacity and comorbidities. However, current evidence is of moderate quality and a large-scale single-center study is needed to further elucidate these relationships OBJECTIVE: The purpose of the study was 1) to examine the relationship between cardiorespiratory fitness and disease severity in PwMS; 2) to investigate the relationship between cardiorespiratory fitness and walking speed and comorbidities; and 3) to examine the potential impact of Multiple Sclerosis (MS) disease type on these relationships METHODS: Data was collected from a database consisting of data from 700 inpatients at Valens Rehabilitation Center, Switzerland. VO₂peak (cardiorespiratory fitness), information on disease course and MS type, walking performance, comorbidities and anthropometric was eligible from 242 PwMS.

RESULTS

Cardiorespiratory fitness and Expanded Disability Status Scale (EDSS) was inversely related (r = -0.465, p < .01). A multiple linear regression analysis showed that an increase of 1 point on the EDSS score was associated with a decrease of 1.88 mL kg^-1 min^-1 and explained 36% of the variance, when adjusted for time since diagnosis, gender, age, and MS type. Walking speed and cardiorespiratory fitness was significantly correlated (r = 0.584, p < .01) and the relapse remitting MS (RRMS) group (1.12 ± 0.42 m/s) walked significantly faster than the secondary progressive MS (SPMS) group (0.91 ± 0.37 m/s) p < .05, but the difference was non-significant when adjusted for age, p = .429.

CONCLUSION

The present study shows that 1) an increase of 1 EDSS point is associated with a decrease of 1.88 mL kg^-1 min^-1 when adjusted for time since diagnosis, gender, age and MS type, 2) cardiorespiratory fitness and walking speed was significantly related but only minimally affected by MS type, and 3) hypertension is associated with a lower cardiorespiratory fitness level.