Cardiorespiratory fitness among adults with fibromyalgia.

This review presents and addresses the conflicting results on cardiorespiratory fitness among adults with fibromyalgia. The heterogeneity in study designs, symptom severity and the assessment protocols might partly explain these conflicting results. It also presents the possible relationship between cardiorespiratory fitness and exercise prescription, attrition from exercise/rehabilitation programmes and independence with activities of daily living. Cardiorespiratory fitness might impact aerobic exercise and independence in daily activities of patients with fibromyalgia, which is often concomitantly diagnosed in patients with sleep disordered breathing, including patients with obstructive sleep apnoea. Therefore, cardiorespiratory fitness evaluation should be considered by general and respiratory physicians as well as physiotherapists who treat patients diagnosed with fibromyalgia for more accurate diagnosis, exercise prescription and monitoring of patients' status. KEY POINTS: Adults with fibromyalgia often present with reduced cardiorespiratory fitness.Reduced cardiorespiratory fitness might have an important impact on functional capacity and quality of life.Adults with fibromyalgia who have a secondary condition affecting their ventilatory anaerobic threshold and/or V'O2peak, for example chronic obstructive pulmonary disease, might present with a greater reduction of their cardiorespiratory fitness which may not be entirely related to their lung disease. EDUCATIONAL AIMS: To better understand the cardiorespiratory fitness results among adults with fibromyalgia in general, and when taking into account differences in assessment protocol (maximal versus submaximal testing protocol; cycle ergometer versus treadmill testing protocol) and symptom severity (fibromyalgia severity level).To better understand how cardiorespiratory fitness among adults with fibromyalgia could: 1) assist in exercise prescription; 2) minimise dropout rates from exercise/rehabilitation programmes; and 3) promote independence with activities of daily living.To learn why fibromyalgia might be important to consider in adults who have concurrent fibromyalgia and lung disease.

Introduction

Fibromyalgia (FM) is characterised by widespread pain, fatigue and non-restorative sleep. In the USA, the prevalence of FM is roughly 2% of the adult population, with a ratio of approximately seven women to three men [1, 2]. Although chronic widespread pain is seen as the defining feature of FM, poor sleep and respiratory problems have also been reported and have even surpassed pain as the most prominent complaints. Decreased thoracoabdominal mobility, impaired respiratory muscle mechanics, dyspnoea and reduced cardiorespiratory fitness (CRF) have been observed for these patients [3, 4]. General practitioners and respiratory physicians and physiotherapists should be aware of these problems to propose optimal management for these patients. Unfortunately, CRF remains overlooked. Decreased CRF can cause dyspnoea on exertion and impact the patient’s functional capacities and these problems need to be addressed in rehabilitation. Guidelines for FM management recommend a multidisciplinary approach involving physicians, physiotherapists and occupational therapists, where prescription of aerobic exercises represents a significant part of the rehabilitation [5-7].

However, the results on CRF seem to be controversial and this might explain the differences observed between clinical practice guidelines (e.g. Canadian Guidelines for the Diagnosis and Management of Fibromyalgia Syndrome and American College of Sports Medicine) regarding aerobic exercise prescription [5, 6]. These conflicting results could be explained by heterogeneity in protocols used to assess CRF (e.g. maximal versus submaximal testing protocol; cycle ergometer versus treadmill testing protocol). For clinicians involved in the management of FM patients, it is important to have a clear synthesis of the evidence on CRF results and on the evaluation protocols used to produce this knowledge. Although aerobic exercise training can help in the management of symptoms and may improve CRF and functional capacities, it can also cause an increase in symptoms such as pain and dyspnoea, potentially contributing to attrition from exercise programmes [8, 9]. Furthermore, an increase in symptoms might negatively affect self-management of the condition and subsequently have a negative impact on the level of participation in physical activities including exercise. This might cause deconditioning and lead to a decline in functional capacities. Furthermore, attrition from an exercise or rehabilitation programme would prevent progression toward maintenance or a return to work, which, in turn, might affect direct and indirect costs, particularly work-related costs.

The aim of this review is to synthesise the scientific evidence on CRF among women with FM to shed light on the controversies in clinical practice guidelines and provide some recommendations on the evaluation of CRF.

Cardiorespiratory fitness level

Studies showing a significantly lower CRF in participants with FM

12 studies showed a lower CRF in women with FM [10-21] compared with a control group or normative values. These studies were published between 1994 and 2015, and used a maximal exercise test protocol on either a cycle ergometer (n=7) or treadmill (n=5).

Altogether, the 12 studies showed that participants with FM have a significantly lower peak oxygen uptake (V′Opeak) compared with a control group, or were at or below the 35th percentile compared with normative values. Two studies compared their results to normative values instead of a control group without FM [18, 19]. The study by Sañudo and Galiano [19] evaluated two groups of participants with FM: a severely affected group (n=16) and a moderately affected group (n=16), on two separate occasions, approximately 1 week apart. The Fibromyalgia Impact Questionnaire (FIQ) was used to classify the participants (moderately affected and severely affected participants), using a cut-off point of 54 on the total FIQ score (<54 versus ≥54). The study found that the average V′Opeak of the severely affected participants was significantly lower than the moderately affected participants for both tests. When compared to American College of Sports Medicine (ACSM) normative values, the average V′Opeak of the moderately affected participants were at the 35th percentile, whereas the severely affected participants were under the 10th percentile [19]. For its part, the study by Soriano-Maldonado et al. [18] reported an average V′Opeak below the 10th percentile for an American population of the same sex and age.

Figure 1 shows percentage differences in V′Opeak between control and FM groups [8–15, 18, 19]. This difference ranges from −11.4% to −34.3%, with lower V′Opeak results in all the FM groups with a mean of −24.1%.

Figure 1

Percentage difference in V′Opeak between the FM and control groups in studies showing a significant difference between study groups. The dotted line represents the mean percentage difference.

Four of the studies [11, 13, 15, 21] identified oxygen uptake at the ventilatory anaerobic threshold (V′OVAT) between the FM and control group, and one study [19] compared V′OVAT between severely and moderately affected participants with FM. The four studies showed a significantly lower V′OVAT in the FM group compared with the control group [11, 13, 15, 21] and the other study showed a significant difference in V′OVAT between severely and moderately affected participants during the second trial only [19]. Figure 2 shows the percentage difference in V′OVAT between the FM and control groups across the four studies [11, 13, 15, 21]. The percentage difference ranges from −12.8% to −37.0%, with a mean difference of −22.9%.

Figure 2

Percentage difference in V′OVAT between the FM and control groups in studies ­showing a significantly lower CRF in participants with FM. The dotted line represents the mean percentage difference.

More specifically, seven studies [10-16] used a maximal exercise protocol on a cycle ergometer. Bachasson et al. [10] showed a significantly lower V′Opeak (p<0.01) in the FM group (n=11) compared with the healthy sedentary age-, sex- and body mass index (BMI)-matched control group (n=11) (FM: 23.7±2.7 mL O2⋅min−1⋅kg−1; control: 36.1±6.3 mL O2⋅min−1⋅kg−1). No data on V′OVAT were reported. Bardal et al. [11] compared the FM group (n=12; except for V′Opeak values, n=11) to a healthy sex- and age-matched control group (n=12). V′Opeak and V′OVAT were significantly lower in the FM group than in the control group (V′Opeak: 1.7±0.3 versus 2.2±0.5 L O2⋅min−1, p=0.007; V′OVAT: 1.3±0.3 versus 1.7±0.4 L O2⋅min−1, p=0.011). da Cunha Ribeiro et al. [12] also reported significantly lower V′Opeak in FM participants compared with sex-, age- and BMI-matched healthy controls (FM: 22±1 mL O2⋅min−1⋅kg−1 versus control: 32±2 mL O2⋅min−1⋅kg−1; p<0.01). Hsieh et al. [13] recruited 31 Chinese women with FM, as well as 31 gender-, body weight-, daily activity level- and exercise habit-matched healthy women for the control group. The V′Opeak and V′OVAT values for the FM group were 18.6±3.7 and 10.7±2.3 mL O2⋅min−1⋅kg−1, and for the control group were 21.0±3.2 and 13.1±2.9 mL O2⋅min−1⋅kg−1, presenting a significant difference between both groups (V′Opeak: p=0.009; V′OVAT: p=0.001). The authors mention that eight women with FM and 25 women from the control group met the maximal oxygen uptake (V′Omax) criterion. The research study by McIver et al. [14] selected eight women with FM and eight healthy controls matched for age and exercise training status. There was no significant difference in BMI between the groups. Criteria for achievement of V′Omax were listed and all the participants met at least two of the four criteria. V′Omax was 16.9±1.32 mL O2⋅min−1⋅kg−1 for the FM group and 21.5±1.44 mL O2⋅min−1⋅kg−1 for the control group, with a significant difference between both groups (p=0.035). Lund et al. [15] recruited nine women for the FM group and nine matched women for the control group, with similar age, height and weight, and did not include any trained athletes. The median (range) V′Opeak was 24 (21–39) mL O2⋅min−1⋅kg−1 for the FM group and 36 (28–46) mL O2⋅min−1⋅kg−1 for the control group with a significant difference between both groups (p<0.01). The ventilatory anaerobic threshold was reached at a lower absolute and relative work level in the FM group compared with the control group, with a median (range) V′Opeak of 17 (11–24) mL O2⋅min−1⋅kg−1 for the FM group and 27 (20–34) mL O2⋅min−1⋅kg−1 for the control group with a p-value of <0.001 between both groups. Nørregaard et al. [16] also used a maximal exercise protocol on a cycle ergometer, but without measuring gas exchange. Therefore, V′Omax was estimated using the following formula: V′Omax (mL O2⋅min−1⋅kg−1)=3.5+(maximal performance (W)×13/weight (kg)). Using the median maximal workload obtained, the equivalent oxygen uptake was 22 mL O2⋅min−1⋅kg−1 (range: 20–27) for the FM group and 30 mL O2⋅min−1⋅kg−1 (range: 25–31) for the control group (p=0.012).

The remaining five studies [17-21] used a maximal exercise test on a treadmill instead of a cycle ergometer. The first study [17] included 28 women with FM and 22 age-matched women without FM as the control group. There was no significant difference between the groups for height but there was a significant difference for BMI (FM: 28.6±6.5 kg⋅m−2 versus control: 23.5±28.6 kg⋅m−2; p=0.001). V′Opeak was significantly lower in the FM group than in the control group (FM: 21.4±4.9 mL O2⋅min−1⋅kg−1 versus control: 28.8±5.4 mL O2⋅min−1⋅kg−1; p<0.001). In the second study [18], 31 women with FM were included in cardiorespiratory data analysis. There was no control group. V′Opeak was 19.5±3.4 mL O2⋅min−1⋅kg−1. Compared to normative values, the findings indicated that CRF was severely impaired with an average V′Opeak below the 10th percentile compared with American women of the same age [22]. As mentioned previously, the study by Sañudo and Galiano [19] compared two groups of women with FM: a moderately affected group and a severely affected group. Each group included 16 women between the ages of 42 and 63 years. The authors compared physiological parameters such as V′Opeak and V′OVAT between the moderately and severely affected participants during a first trial (T1) and a second trial (T2) approximately 1 week apart. V′Opeak and V′OVAT at T1 were 26.17±​3.62 mL O2⋅​min−1⋅​kg−1 and 20.28±2.70 mL O2⋅min−1⋅​kg−1 for the moderately affected participants and 22.13±​2.50 mL O2⋅min−1⋅kg−1 and 19.21±​2.22 mL O2⋅min−1⋅kg−1 for the severely affected participants, with a respective p-value of <0.001 for V′Opeak and 0.163 for V′OVAT. Therefore, there was no significant difference in V′OVAT between both groups at T1. At T2, V′Opeak and V′OVAT were 23.59±2.83 mL O2⋅min−1⋅kg−1 and 20.29±3.04 mL O2⋅min−1⋅kg−1 for the moderately affected group and 20.89±1.62 mL O2⋅min−1⋅kg−1 and 18.55±1.67 mL O2⋅min−1⋅kg−1 for the severely affected group, with a significant difference in V′Opeak (p=<0.001) and V′OVAT (p=0.019) between both groups. Therefore, there was a significant difference in V′OVAT between both groups at T2 but not at T1. Furthermore, 63% of participants in the moderately affected group and 40% in the severely affected group achieved the V′Omax criterion. The fourth study [20], using a maximal exercise protocol on a treadmill, showed a lower V′Opeak by an average of 21.2% in the FM group (n=18; V′Opeak=22.66±3.18 mL O2⋅min−1⋅kg−1) compared with the control group (n=15; 27.46±4.68 mL O2⋅min−1⋅kg−1; p=0.001). The last study by Valim et al. [21] compared 50 women with FM to 50 healthy sedentary women matched for age, weight and BMI. The results showed a significantly lower V′Opeak and V′OVAT in the FM group (V′Opeak: 25.64±5.21 mL O2⋅min−1⋅kg−1; V′OVAT: 16.35±​2.94 mL O2⋅min−1⋅kg−1) compared with the control group (V′Opeak: 30.77±5.56 mL O2⋅​min−1⋅kg−1; V′OVAT: 18.74±3.86 mL O2⋅min−1⋅kg−1) (V′Opeak p=0.000001; V′OVAT p=0.001).

Studies not showing a significant reduction in CRF in participants with FM

Six studies did not demonstrate a lower CRF in women with FM when compared with matched control participants [23-28]. These studies were published between 1994 and 2016, and all used a cycle ergometer to evaluate CRF. Three studies used a submaximal exercise test protocol [24-26] and three studies used a maximal exercise test protocol [23, 27, 28]. None of the studies evaluated V′OVAT. Therefore, the fact that these studies did not demonstrate a significantly lower CRF is based solely on V′Opeak.

The study by Vincent et al. [23] recruited 30 women with FM (age: 47.0±10.4 years; BMI: 25.8±4.6 kg⋅m−2) and 30 healthy pain- and fatigue-free women (age: 41.1±8.4 years; BMI: 26.0±4.0 kg⋅m−2). There was no significant difference in BMI between the groups, but there was a significant difference between the groups with regard to age (p=0.019). Therefore, they included age as a covariate in all consecutive analyses [23]. The maximal testing protocol on the cycle ergometer was not explained in detail, only that the workload was increased in increments until participants achieved V′Omax or exhaustion. There was no significant difference between the V′Opeak of the FM group and the control group (FM: 23.5±5.2 mL O2⋅min−1⋅kg−1; control: 28.3±6.9 mL O2⋅min−1⋅kg−1; adjusted for age, p=0.07). However, they mention that more participants with FM than participants from the control group were excluded from the test because of comorbidities. It is not clear how many participants from each group completed the maximal exercise test. Finally, the average revised FIQ total score was 43, which is considered a moderate level of FM severity.

One of the purposes of the study by Sener et al. [24] was to investigate the maximal aerobic capacity of women with FM (n=39). The results were compared with a control group of 40 BMI-matched healthy women. There was no significant difference in age between the groups. Participants’ V′Omax was estimated using a submaximal exercise protocol (Astrand) on a computerised cycle ergometer (Monark; Sverige, Sweden). The results did not show a significant difference in V′Omax between the FM group (40.2±10.3 mL O2⋅min−1⋅kg−1) and the control group (37.3±8.4 mL O2⋅min−1⋅kg−1), with a p-value above 0.05 (p=0.627).

The study by Nielens et al. [25] also used a submaximal cycle ergometer test. This study compared the CRF of 30 women with FM to a control group of 67 age-matched healthy women. They used a graded multistage test, starting at 25 Watts (W) with increments of 25 W every three or four 2-min stage. The test was stopped when the participant’s heart rate reached 65% of the heart rate reserve using the Karvonen formula. Based on the calculation, their results showed no significant difference (p=0.08) between the FM group (1.52±0.42 physical working capacity index of 65% (PWC65%) per kg) and the control group (1.67±0.39 PWC65% per kg).

The third study to use a submaximal testing protocol on a cycle ergometer employed Astrand’s method of indirect measurement to estimate the maximum oxygen uptake [26]. The FM group included 37 women (median (range) age: 34 (21–42) years) and the control group included 20 heathy sedentary women (age: 31 (22–44) years). The results showed no significant difference in estimated V′Omax between the FM group (28 (25–33) mL O2⋅min−1⋅kg−1) and the control group (31 (24–33) mL O2⋅min−1⋅kg−1) (p=0.8).

The remaining two studies, one by Nørregaard et al. [27] and the other by Simms et al. [28], used a maximal exercise test on a cycle ergometer. Nørregaard et al. [27] included a control group as part of the overall study, but the control group was not part of the CRF evaluation. 126 women with FM participated in this CRF testing. The median age of the FM group was slightly lower than 47 years, ranging from 39 to 54 years. The testing protocol did not include gas exchange. The results were estimated using a formula. Therefore, the corresponding maximal performance was 21 (16–25) mL O2⋅kg−1⋅min−1. However, the median maximal heart rate was only 63% (44–90%) of the predicted maximal heart rate (220 − age). Considering the expected maximal heart rate, the estimated aerobic capacity (V′Omax) would have been 30 (24–39) mL O2⋅kg−1⋅min−1. This estimated V′Omax corresponds to the normative values for “normal” physically inactive individuals of the same age [27]. The other study by Simms et al. [28] included 13 women with FM and 13 “normal” physically inactive women. There was no significant difference in terms of age, height and weight between the groups. Continuous monitoring of gas analysis was included as part of the measurements. The V′Opeak between the FM group (29.7±8.1 mL O2⋅min−1⋅kg−1) and the control group (32.1±7.2 mL O2⋅min−1⋅kg−1) did not show a significant difference (p=0.43).

Figure 3 shows the percentage difference in V′Opeak between the FM and the control groups in studies not showing a significant difference between the two groups. However, out of the six studies, two studies were not included in figure 3: Nielens et al. [25] used a different unit of measurement (PWC65% per kg) and the study carried out by Nørregaard et al. [27] did not evaluate the V′Opeak of the control group. Of the remaining four studies, one showed V′Opeak results from the FM group were nonsignificantly superior to the V′Opeak results of the control group. The other three studies demonstrated a nonsignificant reduction in V′Opeak in participants from the FM group. The percentage difference between the FM and the control group ranged from 7.8% to −17.0% with a mean difference of −6.6%. The study by Nielens et al. [25] (not included in figure 3) showed a percentage difference of −9% with lower V′Opeak results from the FM group.

Figure 3

Percentage difference in V′Opeak between the FM and control groups in studies not showing a significant ­difference between the two groups. The dotted line represents the mean percentage difference.

Maximal versus submaximal testing protocol

15 studies [10–21, 23, 27, 28] used a maximal exercise test protocol and only three [24-26] used a submaximal testing protocol. None of the studies showing a lower CRF among women with FM used a submaximal exercise test protocol. Therefore, three of the six studies showing no difference in CRF among women with FM when compared to a control group used a submaximal exercise test protocol.

Cycle ergometer versus treadmill testing protocol

13 out of the 18 studies [10–16, 23–28] used a cycle ergometer to evaluate CRF. All the studies showing no difference in CRF among women with FM used a cycle ergometer, and seven out of the 12 studies showing a lower CRF among women with FM used a cycle ergometer [10-16].

FM severity level

Sañudo and Galiano [19] compared the participants’ V′Omax to the ACSM (1998) normative values and reported that participants in the moderately affected group scored in the 35th percentile compared with the severely affected participants who were under the 10th percentile. Therefore, these authors concluded that the CRF of FM participants is different based on FM severity. Furthermore, the study by Valim et al. [21] reported that participants with a CRF level below average (weak and very weak) presented the worst results with the FIQ.

Deconditioning: physiological aspects and its impact on functional capacities

Of the 18 articles identified, 12 studies showed a reduction in V′OVAT and/or V′Opeak in women with FM compared with a control group or normative values [10-21]. The physiological explanation for lower CRF might be due to deconditioning. Individuals with FM often adopt a more sedentary lifestyle, which might include bed rest, in response to their symptoms. This sedentary lifestyle might lead to a reduction of their CRF level and impact their functional capacities. Therefore, individuals with FM might experience more difficulties in completing certain physical activities. Furthermore, it has been suggested that FM patients have lower respiratory muscle endurance, inspiratory muscle strength and thoracic mobility [3], which could also contribute to a lower CRF. Consequently, individuals with FM who have a secondary condition affecting their V′OVAT and/or V′Opeak, for example asthma or chronic obstructive pulmonary disease, might present with a greater reduction in their CRF that may not be entirely related to their lung disease. This can cause more dyspnoea on exertion and have a greater impact on their ability to perform certain physical activities. These observations are relevant for healthcare providers because FM could influence the prognostic outcome of patients living with other comorbidities such as asthma, chronic obstructive pulmonary disease or cardiovascular disease.

Different methods exist to measure the intensity of physical activities. These include oxygen uptake, heart rate and metabolic equivalent of tasks (METs) to name a few. METs is a measure used to describe the intensity and energy expenditure of physical activities. For example, the estimated standard METs to carry groceries up a flight of stairs is 7.5 METs [29], which represents 26.3 mL O2⋅kg−1⋅min−1. The energy expenditure required to complete this task might be above their V′OVAT or even above their V′Opeak. This could result in greater difficulties completing certain daily activities or exercise, since fatigue increases significantly when working above the ventilatory anaerobic threshold and it might be impossible for some individuals with FM to complete activities above their V′Opeak.

Discussion

To our knowledge, this is the first review focusing on CRF in adults with FM and we found conflicting results in the current literature. Although most of the studies (12 out of 18) pointed towards a lower CRF among adults with FM, caution must be taken before drawing such a conclusion.

First, attention should be given to the heterogeneity of the methods used to evaluate CRF. The 12 studies [10-21] showing that women with FM have a lower CRF used a maximal exercise test protocol, whereas three [24-26] out of the six studies [23-28] that did not demonstrate a lower CRF in women with FM used a submaximal exercise test protocol. Using a maximal exercise test provides a better estimate of V′Omax [6]. This might partly explain these conflicting results.

Secondly, all six studies [23-28] that did not demonstrate a lower CRF among participants with FM used cycle ergometer protocols, whereas cycle ergometers (n=7) [10-16] and treadmills (n=5) [17-21] were used in the studies that identified a lower CRF. Using a treadmill in a FM population might represent a more natural type of movement, and one that is more representative of daily activities and requires less muscle strength in the lower extremities than using a cycle ergometer [30].

Moreover, certain issues regarding the clinical profile of the participants warrant consideration. The study by Sañudo and Galiano [19] concluded that the aerobic capacity of patients with FM differs depending on the severity of the disease assessed using the FIQ. Severely affected participants showed significant statistical differences in V′Opeak and V′OVAT compared with moderately affected participants. Furthermore, the study by Valim et al. [21] reported that participants with a CRF level below average presented the worst results with the FIQ. This inverse correlation between FM severity level and aerobic capacity may help to establish CRF subgroups based on FM severity level to optimise activity and exercise prescription. Since an association between CRF and FM symptom severity was reported, the heterogeneity of the participants’ clinical profile could be another explanatory factor for these conflicting results.

Looking at the results of the studies, the two lowest mean V′Opeak measurements, in mL O2⋅min−1⋅kg−1, from the FM groups were 16.9±1.32 and 18.6±3.7. These values represent 4.8 and 5.3 METs. It is also important to note that few studies provided data on V′OVAT. However, the lowest mean V′OVAT from the FM groups was 10.7±2.3 mL O2⋅min−1⋅kg−1 (age: 42.4±9.1 years), which is equivalent to 3.1 METs. It takes approximately 4.0 METs to push or pull a stroller with a child, to walk with a child at a speed of 2.5 to 3.1 miles per hour or to climb stairs at a slow pace; 5.0 METs to move or lift light loads; and 6.3 METs to climb a hill while walking [29]. On average, these activities are above the V′OVAT of 3.1 METs, which might be difficult to maintain, since fatigue increases significantly when working above this threshold. Furthermore, it might be impossible for some of the participants to complete activities above their V′Opeak. Furthermore, the standard deviations imply that the V′Opeak and V′OVAT measurements of some participants are even lower. Although pain is an important symptom to consider in the management of FM, CRF is as important since it could have an important impact on functional status.

In light of this review, some recommendations are proposed for future studies or clinical practice to better evaluate and understand CRF among FM participants. To minimise the heterogeneity of the participants, FM severity should be taken into consideration and the use of the revised FIQ should be considered to evaluate the FM severity level. Also, when indicated, consideration should be given to using a maximal exercise test (V′Opeak) on a treadmill, which, in our opinion, better reflects functional activities than a cycle ergometer. Considering it was previously reported that FM patients have decreased thoracoabdominal mobility and impaired respiratory muscles mechanics, which could increase dyspnoea symptoms [3, 4], healthcare providers need to carefully assess FM patients to determine if dyspnoea symptoms are related to a lung disease or FM. Future studies should look at the impact of exercise training in FM patients on CRF and improvement in respiratory mechanics. Finally, none of the studies evaluated capacity to recover following a maximal exercise test. Re-evaluating participants with FM 24 h after an initial cardiorespiratory test could provide further information on their capacity to recover. This could help to optimise physical activity recommendations and minimise dropout rates from exercise and rehabilitation programmes, thus promoting independence with activities of daily living, leisure and work.

Conclusion

Studies on CRF among women with FM reveal conflicting results. The heterogeneity of the study design, participant symptom severity and the assessment protocol used might partly explain these conflicting results. However, most of the studies showed a decrease in CRF in participants with FM compared to a control group or normative values. This lower CRF might have an important impact on participants’ capacity to complete certain activities. Therefore, it is an important aspect to consider in the management of this condition.

Studies on CRF among women with FM reveal:

a) Significantly lower CRF in participants with FM compared with a control group or normative values

b) No significant reduction in CRF in participants with FM when compared to a control group

c) Conflicting results

d) None of the above

The possible inverse association between FM severity level and CRF may help to establish CRF subgroups based on FM severity level to optimise activity and exercise prescription.

a) True

b) False

Low CRF might have an impact on participants’ capacity to complete certain activities of daily living or work-related activities.

a) True

b) False

c.

a.

a.