The effect of age and sex on peak oxygen uptake during upper and lower body exercise: A systematic review

BACKGROUND

Large scale population norms for peak oxygen uptake (VO2peak) during cycle ergometry (CE) have been published for men and women across a wide range of ages. Although upper body functional capacity has an important role in activities of daily living far less is known regarding the effect of age and sex on upper body functional capacity (i.e. arm crank ergometry; ACE). The aim of this review was to determine the effect of age and sex on VO2peak obtained during ACE and CE in the same participants.

METHOD

The review was pre-registered with PROSEPERO (Ref: CRD42022349566). A database search using Academic Search Complete including CINAHL complete, CINHAL Ultimate, Medline, PubMed, SPORTDiscus was undertaken.

RESULTS

The initial search yielded 460 articles which was reduced to 243 articles following removal of duplicates. Twenty-five articles were subsequently excluded based on title resulting in 218 articles considered for retrieval. Following review of the abstracts, 78 further articles were excluded leaving 140 to be assessed for eligibility. Eighty-five articles were subsequently excluded, resulting in 55 articles being included. The decrease in VO2peak with age during CE was consistent with previous studies. Decreases in VO2peak during ACE with age, although paralleling those of CE, appeared to be of greater functional importance. When changes in VO2peak were considered below the age of 50 years little change was observed for absolute VO2peak during ACE and CE. In contrast, relative VO2peak demonstrated decreases in VO2peak for both ACE and CE likely reflecting increases in body mass and body fat percentage with age. After 50 years of age absolute and relative VO2peak demonstrated more similar and subtle responses. Heterogeneity across studies for both absolute and relative VO2peak between ACE and CE was large. Although strict inclusion criteria were applied, the inter-individual variation in sample populations was likely the main source of heterogeneity. There was a considerable lack data sets available for ages above 40 years of age.

CONCLUSIONS

These responses suggest that upper body VO2peak decreases in line with that of the lower body but, due to the lower peak values achieved during ACE, decreases in VO2peak may have more profound functional impact compared to that for the lower body. Using absolute and relative measures of VO2peak results in different age-related profiles when considered below 50 years of age. To further our understanding of whole body ageing more data is required for participants in mid and later life. The association between VO2peak and underlying physiological factors with age needs to be studied further, particularly in conjunction with activities of daily living and independent living.

Arm cycle ergometry in critically ill patients: A systematic review

BACKGROUND

Intensive care unit (ICU) survivors face functional limitations due to ICU-acquired weakness. Arm cycle ergometry (ACE) introduced in the ICU may improve physical function. To our knowledge, there is limited evidence on the effectiveness of ACE and physical function outcomes in critically ill patients.

OBJECTIVE

The objective of this systematic review was to examine the impact of ICU-based ACE on physical function, safety, and other clinical outcomes.

REVIEW METHOD USED

Systematic Review.

DATA SOURCES

A search of seven databases was conducted from the inception to January 1, 2023: Medline Ahead of Print, Ovid MEDLINE(R), Allied and Complementary Medicine Database (AMED), Embase, Cochrane Central, Physiotherapy Evidence Database, and Cumulative Index to Nursing and Allied Health Literature (CINAHL).

REVIEW METHODS

We included two arm studies of critically ill adults admitted to the ICU who received ACE and any comparator for our primary outcome, physical function. Our secondary outcomes included severe events. We included safety studies with or without a comparator group. Screening, data abstraction, and risk-of-bias assessments were completed independently, in duplicate. We used the Grading of Recommendations, Assessment, Development, and Evaluation approach to assess the overall certainty of evidence.

RESULTS

We screened 651 citations and included eight studies that enrolled 183 patients. Due to heterogeneity, meta-analysis was not performed. For our primary outcome, one randomised controlled trial found significant improvements in physical function, measured by the Barthel Index with ACE, whereas a nonrandomised study showed no difference. Out of the six studies reporting safety, none reported any severe safety events. The overall certainty of evidence was very low.

CONCLUSION

ACE initiated in the ICU is a likely safe intervention. Based on the limited ACE studies and heterogeneity between studies, further research with more rigorous studies evaluating important outcomes for patients is needed.

Exercise capacity in children with bronchopulmonary dysplasia at school age

OBJECTIVE

To assess the exercise capacity, exercise habits, and lung function of preterm born children with bronchopulmonary dysplasia (BPD) compared to term born controls at school age.

METHODS

Cardiopulmonary exercise test (CPET) by cycle ergometer and pulmonary function test were performed in children with BPD (n = 42) and compared with a term born control group (n = 42). Daily activity, participation in sports and respiratory symptoms were assessed by questionnaire.

RESULTS

Children with BPD versus controls had significantly lower values for oxygen consumption (V̇O₂ [mL/min] 1442 ± 417 vs. 1766 ± 541), minute ventilation (VE [L/min] 48 ± 14.92 vs. 60 ± 18.33), and workload (W [watt] 96.1 ± 16.7 vs. 110.6 ± 17.2) at peak exercise and a lower anaerobic threshold (VO₂ AT [mL/min] 1183 ± 345 vs. 1382 ± 398). When corrected for weight, only for the workload (2.7 ± 0.5 vs. 3.1 ± 0.5, p = 0.0013) did significant differences persist. The forced expiratory volume in 1 s and forced expiratory flow between 25 and 75% of expired forced vital capacity were significantly reduced in the BPD group (p < 0.0001). Children with BPD have a higher risk of reporting difficulties in physical activity (OR 2.5) and of suffering from wheezing or shortness of breath while exercising (OR 2.5).

CONCLUSION

Compared to term born controls, children with BPD at school age show airflow obstruction, a lower workload in CPET, and more respiratory symptoms related to physical activity. The comparable oxygen consumption based on weight suggests a functionally normal alveolar compartment.

The effect of test modality on dynamic exercise biomarkers in children, adolescents, and young adults

Cardiopulmonary exercise testing (CPET) modalities, treadmill (TM), and cycle ergometer (CE), influence maximal gas exchange and heart rate (HR) responses. Little is known regarding CPET modality effect on submaximal biomarkers during childhood and adolescence. Ninety‐four healthy participants (7–34 y.o., 53% female) performed TM and CE CPET to address two major gaps: (1) the effect of modality on submaximal CPET biomarkers, and (2) estimation of work rate in TM CPET. Breath‐by‐breath gas exchange enabled calculation of linear regression slopes such as V˙O₂/ΔHR and ΔV˙E/ΔV˙CO₂. Lean body mass (LBM) was measured with dual X‐ray absorptiometry. We tested a novel TM CPET estimate of work rate based on TM velocity², incline, and body mass (VIM). Like the linear relationship between V˙O₂ and work rate in CE CPET, V˙O₂ increased linearly with TM VIM. TM ΔV˙O₂/ΔHR was highly correlated with CE (r = 0.92), and each increased substantially with LBM (P < 0.0001 for TM and CE). ΔV˙O₂/ΔHR was to a small (~8.7%) but significant extent larger in TM (1.6 mL/min/beat, P = 0.04). In contrast, TM and CE ΔV˙E/ΔV˙CO₂ decreased significantly with LBM, supporting earlier observations from CE CPET. For both CE and TM, males had significantly higher ΔV˙O₂/ΔHR but lower ΔV˙E/ΔV˙CO₂ than females. Novel TM CPET biomarkers such as ΔVIM/ΔHR and ∆V˙O₂/ΔVIM paralleled effects of LBM observed in CE CPET. TM and CE CPET submaximal biomarkers are not interchangeable, but similarly reflect maturation during critical periods. CPET analysis that utilizes data actually measured (rather than estimated) may improve the clinical value of TM and CE CPET.

Effect of in-bed cycling on acute muscle wasting in critically ill adults: A randomised clinical trial

PURPOSE

To examine whether in-bed cycling assists critically ill adults to reduce acute muscle wasting, improve function and improve quality of life following a period of critical illness.

MATERIALS AND METHODS

A single-centre, two-group, randomised controlled trial with blinded assessment of the primary outcome was conducted in a tertiary ICU. Critically ill patients expected to be mechanically ventilated for at least 48 h were randomised to 30 min daily in-bed cycling in addition to usual-care physiotherapy (n = 37) or usual-care physiotherapy (n = 37). The primary outcome was muscle atrophy of rectus femoris cross-sectional area (RF_CSA) measured by ultrasound at Day 10 following study enrolment. Secondary outcomes included manual muscle strength, handgrip strength, ICU mobility score, six-minute walk test distance and health-related quality of life up to six-months following hospital admission.

RESULTS

Analysis included the 72 participants (mean age, 56-years; male, 68%) who completed the study. There were no significant between-group differences in muscle atrophy of RF_CSA at Day 10 (mean difference 3.4, 95% CI -6.9% to 13.6%; p = .52), or for secondary outcomes (p-values ranged p = .11 to p = .95).

CONCLUSIONS AND RELEVANCE

In-bed cycling did not reduce muscle wasting in critically ill adults, but this study provides useful effect estimates for large-scale clinical trials.

TRIAL REGISTRATION

anzctr.org.au Identifier: ACTRN12616000948493.

Acceptability, safety, and feasibility of in-bed cycling with critically ill patients

BACKGROUND

In-bed cycling is a promising intervention that may assist critically ill patients to maintain muscle mass and improve their trajectory of recovery. The acceptability of in-bed cycling from the different perspectives of patients, clinicians, and families are unknown. In addition, the safety and feasibility of in-bed cycling in an Australian tertiary intensive care unit (ICU) is relatively unknown.

OBJECTIVES

The objective of this study was to examine the acceptability, safety, and feasibility of in-bed cycling in an Australian tertiary, adult, mixed medical, surgical, trauma ICU.

METHODS

An observational process evaluation was embedded in one arm of a two-arm parallel phase II randomised controlled trial that was conducted in an Australian tertiary ICU. The process evaluation was of the acceptability, safety, and feasibility of passive and active in-bed cycling for participants allocated to the trial intervention group. In-bed cycling acceptability questionnaires were designed through a three-step Delphi process. Questionnaire responses from patients, family members, and clinicians who participated in or observed the intervention during the Critical Care Cycling Study (CYCLIST) were evaluated to determine the acceptability of in-bed cycling. The congruence of responses between respondents was also compared. Safety and feasibility of the in-bed cycling intervention were assessed against predetermined criteria.

RESULTS

Acceptability questionnaire responses demonstrated that in-bed cycling was an acceptable intervention from the perspectives of patients, family members, and clinicians. Questionnaire responses were congruent across the respondent groups. Safety was demonstrated with two minor transient adverse events occurring during 276 in-bed cycling sessions (adverse event rate: 0.7%). In-bed cycling sessions were feasible with 276 of 304 (90%) planned sessions conducted.

CONCLUSIONS

Acceptability questionnaire responses found that in-bed cycling was regarded as an acceptable intervention to patients, family members, and clinicians. The implementation of in-bed cycling was safe and feasible to complete with critically ill patients during the early stages of their critical illness in an Australian tertiary ICU setting.

Extended steep ramp test normative values for 19-24-year-old healthy active young adults

Purpose

To extend currently available sex and age-specific normative values in children and adolescents for the peak work rate (WR_peak) attained at the steep ramp test (SRT) to healthy active young adults.

Methods

Healthy male and female participants aged between 19 and 24 years were recruited. After screening and anthropometric measurements, participants performed a SRT on a cycle ergometer (increments of 25 W/10 s), monitoring and recording SRT-WR_peak, heart rate (HR), and blood pressure (BP) at rest and directly after peak exercise.

Results

Fifty-seven participants (31 males and 26 females; median age of 21.3 years) volunteered and were tested. Anthropometrics, resting BP and lung function were all within normal ranges. Ninety-three percent of the participants attained a peak HR (HR_peak) > 80% of predicted (mean HR_peak 87 ± 5% of predicted). No differences were found in resting and peak exercise variables between females and males, except for absolute SRT-WR_peak (350 W [Q1: 306; Q3: 371] and 487 W [Q1: 450; Q3: 517], respectively) and SRT-WR_peak normalized for body mass (relative SRT-WR_peak; 5.4 ± 0.5 and 6.2 ± 0.6 W/kg, respectively). Low-to-moderate correlations (ρ [0.02–0.71]) were observed between SRT-WR_peak and anthropometric variables for females and males separately. Extended reference curves (8–24-year-old subjects) for SRT performance show different trends between male and female subjects when modelled against age, body height, and body mass.

Conclusions

The present study provides sex-, age-, body height-, and body mass-related normative values (presented as reference centiles) for absolute and relative SRT performance throughout childhood and early adulthood.

Electronic supplementary material

The online version of this article (10.1007/s00421-019-04255-x) contains supplementary material, which is available to authorized users.

Prediction of peak V˙ O2 in Children and Adolescents With HIV From an Incremental Cycle Ergometer Test

PURPOSE

To examine the capacity of physiological variables and performance to predict peak oxygen consumption (peak V˙ O₂) in children and adolescents living with HIV.

METHOD

Sixty-five children and adolescents living with HIV (30 boys) aged 8-15 years, participated in the study. Peak V˙ O₂ was measured by breath-by-breath respiratory exchange during an incremental cycle ergometer until volitional exhaustion. Information on the time to exhaustion, maximal power output (Pmax), and peak heart rate (peak HR) were also recorded.

RESULTS

Predictive models were developed and all equations showed the ability of performance variables to predict peak V˙ O₂. However, Model 1 was based only on Pmax by following equation: Y = 338.8302 + (Pmax [W] * 11.16435), R² = 0.90 and standard error of estimation (SEE) = 180 ml ⋅ min^-1.

CONCLUSION

The V˙ O₂ peak can be predicted simply by the Pmax obtained from the incremental cycle ergometer test. This protocol is a valid and useful tool for monitoring the aerobic fitness of children and adolescents living with HIV, especially in resource-limited settings.

Carbohydrate consumption and variable-intensity exercise responses in boys and men

PURPOSE

The effect of carbohydrate (CHO) supplementation on physiological and perceptual responses to steady-state exercise has been studied in children. However, little is known about these responses to variable-intensity exercise (VIE) and how these responses might differ from adults. This study examined the physiological and perceptual effects of CHO on VIE in boys and men.

METHODS

Eight boys (11.1 ± 0.9 years) and 11 men (23.8 ± 2.1 years) consumed CHO or a placebo (PL) beverage before and throughout VIE (three 12-min cycling bouts with intensity varying every 20-30 s between 25, 50, 75, and 125% peak work rate). Pulmonary gas exchange was assessed during the second 12-min bout. RPE was assessed twice per bout.

RESULTS

In CHO, blood glucose increased and then decreased more from pre-exercise to 12 min and was higher in this trial at the end of exercise in men versus boys. In boys, blood glucose in CHO was higher at 24 and 36 min of exercise than in PL. RER during the CHO trial was higher in both groups; the other physiological responses were unaffected by CHO. All RPE measures (whole body, legs and chest) increased over time, but were not different between groups or trials.

CONCLUSION

Blood glucose patterns during VIE were differentially affected by CHO in boys and men, but most physiological and perceptual responses to VIE were unaffected by CHO in either group. Knowledge of the underlying mechanisms of glucose regulation and effects on physical performance during this type of exercise in children is warranted.

Effects of Single-Dose Dietary Nitrate on Oxygen Consumption During and After Maximal and Submaximal Exercise in Healthy Humans: A Pilot Study

Dietary nitrate (NO₃^-) has been shown to reduce oxygen consumption (VO₂) during moderate to high-intensity (e.g. time to fatigue, time trials) exercise and often in trained athletes. However, less is known regarding prolonged exercise and the potential impact of NO₃^- on post-exercise excess oxygen consumption (EPOC), particularly in untrained individuals, who may have different metabolic goals during exercise than trained individuals. We tested the hypothesis that acute nitrate supplementation in the form of beet root juice will significantly decrease both VO₂ during maximal exercise and EPOC in both maximal and submaximal exercise trials. Eight young, moderately active, healthy males (age: 24.8±1.4 years, body mass index: 23.7±0.4 kg/m²; VO²max: 34.2±3.9 ml/kg/min) performed step-wise maximal cycle exercise (n=4) and prolonged submaximal cycle exercise (n=6) (45 min; 38±2% of max work rate) in control (anti-bacterial mouthwash) and acute NO₃^- supplemented conditions [70ml concentrated beet root juice (0.4g NO₃^-), 2 hrs prior to exercise] on separate occasions. Measurements of VO₂ (indirect calorimetry), arterial blood pressure (MAP; sphygmomanometry), and heart rate (HR; ECG) were made before, during, and following exercise bouts. NO₃^- reduced MAP at rest ~1-3mmHg. However, NO₃^- had no impact on VO₂ during maximal (VO₂max, Ctrl: 34.2±3.9 ml/kg/min vs NO₃^-: 31.7±4.4 ml/kg/min), submaximal exercise (average of min 25-45, Ctrl: 24.6±2.4 ml/kg/min vs NO₃^-: 26.8±3.3 ml/kg/min) or EPOC (area under the curve, Ctrl: 0.57±0.24 L vs NO₃^-: 0.66±0.16 L). Thus, while NO₃^- supplementation may have performance benefits in elite athletes exercising at high intensities, in recreationally active males, there appears to be little impact on changes in VO₂ due to maximal or submaximal prolonged exercise.

Effects of ambient particulate matter on aerobic exercise performance

Background/Objective

Wintertime thermal inversions in narrow mountain valleys create a ceiling effect, increasing concentration of small particulate matter (PM_2.5). Despite potential health risks, many people continue to exercise outdoors in thermal inversions. This study measured the effects of ambient PM_2.5 exposure associated with a typical thermal inversion on exercise performance, pulmonary function, and biological markers of inflammation.

Methods

Healthy, active adults (5 males, 11 females) performed two cycle ergometer time trials outdoors in a counterbalanced design: 1) low ambient PM_2.5 concentrations (<12 μg/m³), and 2) an air quality index (AQI) ranking of “yellow.” Variables of interest were exercise performance, exhaled nitric oxide (eNO), c-reactive protein (CRP), forced vital capacity (FVC), and forced expiratory volume in 1 s (FEV₁).

Results

Despite a significant difference in mean PM_2.5 concentration of 9.3 ± 3.0 μg/m³ between trials (p < .001), there was no significant difference (p = .424) in the distance covered during low PM_2.5 conditions (9.9 ± 1.7 km) compared to high PM_2.5 conditions (10.1 ± 1.5 km). There were no clinically significant differences across time or between trials for eNO, CRP, FVC, or FEV₁. Additionally, there were no dose-response relationships (p > .05) for PM_2.5 concentration and the measured variables.

Conclusion

An acute bout of vigorous exercise during an AQI of “yellow” did not diminish exercise performance in healthy adults, nor did it have a negative effect on pulmonary function or biological health markers. These variables might not be sensitive to small changes from acute, mild PM_2.5 exposure.

Chronic eccentric arm cycling improves maximum upper-body strength and power

INTRODUCTION

Eccentric leg cycling (cycle ergometry adapted to impose muscle lengthening contractions) offers an effective exercise for restoring lower-body muscular function, maintaining health, and improving performance in clinical and athletic populations.

PURPOSE

We extended this model to the upper body and evaluated the effectiveness of a 7-week eccentric arm cycling (ECC_arm) intervention to improve upper-body muscular function. We also explored whether ECC_arm would alter arterial function.

METHODS

Participants performed ECC_arm (n = 9) or concentric arm cycling (CON_arm; n = 8) 3×/week while training intensity increased (5-20 min, 60-70% upper-body peak heart rate). Maximum elbow extensor strength, upper-body concentric power, and peripheral and central arterial stiffness were assessed before and after training.

RESULTS

During training, heart rates and perceived exertion did not differ between groups (~68% upper-body peak heart rate, ~12 Borg units, both P > 0.05), whereas power during ECC_arm was ~2× that for CON_arm (122 ± 43 vs. 59 ± 20 W, P < 0.01). Muscle soreness for ECC_arm was greater than CON_arm (P = 0.02), however, soreness was minimal for both groups (<0.50 cm). Following training, ECC_arm exhibited greater changes in elbow extensor strength (16 ± 10 vs. 1 ± 9%, P = 0.01) and upper-body power (6 ± 8 vs. -3 ± 7%, P < 0.01) compared to CON_arm. Peripheral and central arterial stiffness did not change for either group (both P > 0.05).

CONCLUSION

Upper-body eccentric exercise improved dynamic muscular function while training at low exertion levels. Results occurred with minimal soreness and without compromising arterial function. ECC_arm findings parallel eccentric leg cycling findings and indicate that eccentric cycle ergometry offers a robust model for enhancing upper-body muscular function. ECC_arm could have applications in rehabilitation and sport training.

Change in maximal fat oxidation in response to different regimes of periodized high-intensity interval training (HIIT)

PURPOSE

Increased capacity for fat oxidation (FatOx) is demonstrated in response to chronic endurance training as well as high-intensity interval training (HIIT). This study examined changes in maximal fat oxidation (MFO) in response to 20 sessions of periodized HIIT in an attempt to identify if various regimes of HIIT similarly augment capacity for FatOx.

METHODS

Thirty-nine habitually active men and women (mean age and VO₂max = 22.5 ± 4.4 year and 40.0 ± 5.6 mL/kg/min) completed training and 32 men and women with similar physical activity and fitness level served as non-exercising controls (CON). Training consisted of ten sessions of progressive low-volume HIIT on the cycle ergometer after which participants completed an additional ten sessions of sprint interval training (SIT), high-volume HIIT, or periodized HIIT, whose assignment was randomized. Before and throughout training, MFO, FatOx, and carbohydrate oxidation (CHOOx) were assessed during progressive cycling to exhaustion.

RESULTS

Compared to CON, there was no effect of HIIT on MFO (p = 0.11). Small increases (p = 0.03) in FatOx were evident in response to HIIT leading to an additional 4.3 g of fat oxidized, although this value may not be clinically meaningful.

CONCLUSIONS

Our results refute the widely reported increases in capacity for FatOx demonstrated with HIIT, which is likely due to marked day-to-day variability in determinations of MFO and exercise fat oxidation as well as the heterogeneity of our sample.

Physiological responses to interval endurance exercise at different levels of blood flow restriction

PURPOSE

We aimed to identify a blood flow restriction (BFR) endurance exercise protocol that would both maximize cardiopulmonary and metabolic strain, and minimize the perception of effort.

METHODS

Twelve healthy males (23 ± 2 years, 75 ± 7 kg) performed five different exercise protocols in randomized order: HI, high-intensity exercise starting at 105% of the incremental peak power (P _peak); I-BFR30, intermittent BFR at 30% P _peak; C-BFR30, continuous BFR at 30% P _peak; CON30, control exercise without BFR at 30% P _peak; I-BFR0, intermittent BFR during unloaded exercise. Cardiopulmonary, gastrocnemius oxygenation (StO₂), capillary lactate ([La]), and perceived exertion (RPE) were measured.

RESULTS

V̇O₂, ventilation (V̇ _E), heart rate (HR), [La] and RPE were greater in HI than all other protocols. However, muscle StO₂ was not different between HI (set1-57.8 ± 5.8; set2-58.1 ± 7.2%) and I-BRF30 (set1-59.4 ± 4.1; set2-60.5 ± 6.6%, p < 0.05). While physiologic responses were mostly similar between I-BFR30 and C-BFR30, [La] was greater in I-BFR30 (4.2 ± 1.1 vs. 2.6 ± 1.1 mmol L^-1, p = 0.014) and RPE was less (5.6 ± 2.1 and 7.4 ± 2.6; p = 0.014). I-BFR30 showed similar reduced muscle StO₂ compared with HI, and increased blood lactate compared to C-BFR30 exercise.

CONCLUSION

Therefore, this study demonstrate that endurance cycling with intermittent BFR promotes muscle deoxygenation and metabolic strain, which may translate into increased endurance training adaptations while minimizing power output and RPE.

The Effect of Skinfold on the Assessment of the Mean Power Frequency at the Fatigue Threshold

The purpose of this study was to determine if the amount of subcutaneous tissue over the quadriceps affects the assessment of mean power frequency at the fatigue threshold (MPF_FT). It was hypothesized that greater skinfold values will result in lower power outputs associated to the MPF_FT. Fourteen adults (Mean ± SD age = 20.7 ± 0.99; body weight = 72.8 ± 12.6 kg) performed an incremental cycle ergometry test to exhaustion while surface electromyographic (EMG) signals were measured from the vastus lateralis. The skinfold thickness of each leg was taken prior to the test, and skinfold thicknesses were separated into a larger and a smaller groups. The independent t-test showed a significant difference (p = 0.01) between the power outputs associated to the MPF_FT of groups with high (Mean ± SD 130.4 ± 34.5 W) versus low skinfold (212.5 ± 61.2 W) values. The results suggested that higher subcutaneous fat may have affected the assessment of MPF_FT during cycle ergometry.

Inter-individual variability in the patterns of responses for electromyography and mechanomyography during cycle ergometry using an RPE-clamp model

PURPOSE

To examine inter-individual variability versus composite models for the patterns of responses for electromyography (EMG) and mechanomyography (MMG) versus time relationships during moderate and heavy cycle ergometry using a rating of perceived exertion (RPE) clamp model.

METHODS

EMG amplitude (amplitude root-mean-square, RMS), EMG mean power frequency (MPF), MMG-RMS, and MMG-MPF were collected during two, 60-min rides at a moderate (RPE at the gas exchange threshold; RPEGET) and heavy (RPE at 15 % above the GET; RPEGET+15 %) intensity when RPE was held constant (clamped). Composite (mean) and individual responses for EMG and MMG parameters were compared during each 60-min ride.

RESULTS

There was great inter-individual variability for each EMG and MMG parameters at RPEGET and RPEGET+15 %. Composite models showed decreases in EMG-RMS (r (2) = -0.92 and R (2) = 0.96), increases in EMG-MPF (R (2) = 0.90), increases in MMG-RMS (r (2) = 0.81 and 0.55), and either no change or a decrease (r (2) = 0.34) in MMG-MPF at RPEGET and RPEGET+15 %, respectively.

CONCLUSIONS

The results of the present study indicated that there were differences between composite and individual patterns of responses for EMG and MMG parameters during moderate and heavy cycle ergometry at a constant RPE. Thus, composite models did not represent the unique muscle activation strategies exhibited by individual responses when cycling in the moderate and heavy intensity domains when using an RPE-clamp model.

Feasibility and safety of in-bed cycling for physical rehabilitation in the intensive care unit

PURPOSE

The purpose was to evaluate the feasibility and safety of in-bed cycle ergometry as part of routine intensive care unit (ICU) physical therapist (PT) practice.

MATERIALS AND METHODS

Between July 1, 2010, and December 31, 2011, we prospectively identified all patients admitted to a 16-bed medical ICU receiving cycling by a PT, prospectively collected data on 12 different potential safety events, and retrospectively conducted a chart review to obtain specific details of each cycling session.

RESULTS

Six hundred eighty-eight patients received PT interventions, and 181 (26%) received a total of 541 cycling sessions (median [interquartile range {IQR}] cycling sessions per patient, 2 [1-4]). Patients' mean (SD) age was 57 (17) years, and 103 (57%) were male. The median (IQR) time from medical ICU admission to first PT intervention and first cycling session was 2 (1-4) and 4 (2-6) days, respectively, with a median (IQR) cycling session duration of 25 (18-30) minutes. On cycling days, the proportion of patients receiving mechanical ventilation, vasopressor infusions, and continuous renal replacement therapy was 80%, 8%, and 7%, respectively. A single safety event occurred, yielding a 0.2% event rate (95% upper confidence limit, 1.0%).

CONCLUSIONS

Use of in-bed cycling as part of routine PT interventions in ICU patients is feasible and appears safe. Further study of the potential benefits of early in-bed cycling is needed.