Vastus lateralis oxygenation during prolonged cycling in healthy males

This study examined the relationship between acute cardiorespiratory and muscle oxygenation and blood volume changes during prolonged exercise. Eight healthy male volunteers (mean maximum oxygen uptake ([Formula: see text]O2max) = 41.6 ± 2.4 mL/kg/min) performed 60 min submaximal cycling at 50% [Formula: see text]O2max. Oxygen uptake ([Formula: see text]O2) was measured by indirect spirometry, cardiac output (CO) was estimated using a PortapresTM, and right vastus lateralis oxyhemoglobin/ myoglobin (oxyHb/Mb), deoxyhemoglobin/myoglobin (deoxyHb/Mb), and total hemoglobin/myoglobin (total Hb/Mb) were recorded using near-infrared spectroscopy (NIRS). After 40 min of exercise, there was a significant increase in [Formula: see text]O2 due to a significantly higher arteriovenous oxygen difference ((a - v)O2diff). After 30 min of exercise CO remained unchanged, but there was a significant decrease in stroke volume and a proportionate increase in heart rate, thus indicating the occurrence of cardiovascular drift. During the first few minutes of exercise, there was a decline in oxyHb/Mb and total Hb/Mb, whereas deoxyHb/Mb remained unchanged. Thereafter, oxyHb/Mb and total Hb/Mb increased systematically until the termination of exercise while deoxyHb/Mb declined. After 40 min of exercise, these changes were significantly different from the baseline values. There were no significant correlations between the changes in the NIRS variables and systemic [Formula: see text]O2 or mixed (a - v)O2diff during exercise. These results suggest that factors other than localized changes in muscle oxygenation and blood volume account for the increased [Formula: see text]O2 during prolonged submaximal exercise. Key words: near infrared spectroscopy, cardiovascular drift, systemic oxygen consumption.

Reliability of near-infrared spectroscopy measures of cerebral oxygenation and blood volume during handgrip exercise in nondisabled and traumatic brain-injured subjects

We compared the test-retest reliability of near-infrared spectroscopy (NIRS) measures of cerebral oxygenation and blood volume during a rhythmic handgrip exercise in 13 nondisabled subjects and 25 subjects with moderate to severe traumatic brain injury (TBI). Subjects with TBI (average Glasgow Coma Scale score = 4.2, average time since injury = 21 mo) had completed an acute brain injury rehabilitation program. After 2 min of rest, each subject performed 60 s of maximal rhythmic handgrip contractions with the right hand in two trials 24 to 48 h apart. We used NIRS to measure cerebral oxygenation and blood volume responses from the left prefrontal lobe. Both groups' cerebral oxygenation and blood volume increased during handgrip contractions. The change in cerebral oxygenation was significantly lower in subjects with TBI compared with nondisabled subjects. Intraclass correlations between the two trials for cerebral oxygenation and blood volume were 0.83 and 0.80, respectively, in nondisabled subjects and 0.70 and 0.64, respectively, in subjects with TBI. The findings indicate that NIRS is a reliable noninvasive technique for evaluating cerebral oxygenation and blood volume changes during motor function. NIRS can be useful in monitoring recovery of cerebral oxygenation during rehabilitation of patients with TBI.

Relationship between erector spinae static endurance and muscle oxygenation-blood volume changes in healthy and low back pain subjects

The purposes of this study were to: (1) compare the muscle blood volume (Mbv) and oxygenation (Mox) responses on the right and left side erector spinae during the Biering-Sorensen muscle endurance (BSME) test between healthy, low back pain active (LBP-A) and LBP-sedentary (LBP-S) subjects using near infrared spectroscopy (NIRS), and (2) determine the relationships between the BSME time and Mbv and Mox. Informed consent was obtained from 30 healthy and 30 chronic LBP subjects. The latter group was subdivided into an active (LBP-A; n = 18) and sedentary (LBP-S; n = 12) subgroups based on physical activity patterns. The groups were age and sex matched. The NIRS probes were placed bilaterally on the erector spinae muscle at the level of the third lumbar vertebrae. The testing protocol was: 2-min resting baseline, BSME to voluntary fatigue, and 4-min recovery. During the BSME Mbv immediately increased for approximately 30-60 s, then showed an asymptote, and a steady decline towards the baseline at termination. Mox demonstrated either an initial increase followed by a systematic decrease until the termination of the BSME, or a systematic decrease throughout the BSME until termination. The LBP-S subjects showed a reduced Mox-range and slower Mox (1/2) recovery time on the left side suggesting a reduced aerobic capacity of the erector spinae muscle in this group. Significant correlations were noted between BSME time and the pooled values of Mox-delta and-range only in the LBP-A group. These observations suggest that factors other than erector spinae aerobic capacity can influence BSME performance.

Effects of circuit training on body composition and peak cardiorespiratory responses in patients with moderate to severe traumatic brain injury

OBJECTIVE

To examine the time course of the changes in body composition and peak cardiorespiratory fitness resulting from routine brain injury rehabilitation program (BIRP) activities and circuit training in patients with moderate to severe traumatic brain injury (TBI).

DESIGN

Time-series design spanning 18 weeks. Trials T1 and T2 were completed in weeks 1 and 2, respectively, to establish reliability of the measurements, followed by trial 3 (T3) 4 weeks later to evaluate changes resulting from the BIRP.

SETTING

A BIRP in a community rehabilitation hospital.

PARTICIPANTS

Fourteen inpatients with moderate to severe acquired TBI (Glasgow Coma Scale score, 4.6+/-1.4; time since injury, 17.2+/-17 mo).

INTERVENTIONS

Twelve-week circuit-training program designed to enhance muscular strength and endurance and aerobic fitness. Subjects were tested midway (T4) through the program and at the end (T5) of 12 weeks. The patients completed an average of 32 supervised sessions, each lasting 1 hour.

MAIN OUTCOME MEASURES

Changes in body composition and peak cardiorespiratory responses.

RESULTS

No significant changes were observed in the body mass or percentage body fat during the study. The peak values of power output, oxygen uptake, and ventilation rate increased significantly as a result of training, with no concomitant increases in peak heart rate or blood lactate (T5>T3, T2, T1; P <.05). No significant changes were evident midway through training.

CONCLUSIONS

In a heterogeneous sample of patients with moderate to severe TBI, (1) body composition and peak cardiorespiratory responses remained fairly stable during 6 weeks of BIRP activities, (2) improvements in peak cardiorespiratory fitness required more than 6 weeks of circuit training, and (3) a 12-week course of circuit training without controlling caloric intake was not effective in reducing body weight or percentage body fat.

Reliability of erector spinae oxygenation and blood volume responses using near-infrared spectroscopy in healthy males

The purpose of this investigation was to (1). describe the trends in oxygenation (OXY) and blood volume (BV) of the right and left paraspinal muscles during the Biering-Sorensen muscle endurance (BSME) test using near infrared spectroscopy (NIRS), and (2). assess the test-retest reliability of OXY and BV changes during the BSME in healthy males. Seventeen healthy males [age=28.4 (9.8) years, height=1.75 (0.05) m, body mass=82.7 (9.1) kg; mean (SD)] completed two BSME trials within 1 week. NIRS probes were placed bilaterally at lumbar 3. The test was performed with the subject in the prone position using the following protocol: 2 min baseline, BSME, and 4 min recovery. The delta and range values of OXY and BV were used for analysis. Acceptable intra-class correlations were observed for endurance time and all the NIRS variables at the point of fatigue and at each 10% segment of the BSME during the two trials. Bland-Altman plots confirmed the reproducibility of the bilateral NIRS responses of the paravertebral muscles. The BV responses were more reliable than the OXY responses during the two trials. The OXY and BV responses of the paravertebral muscles during static contractions can be measured reliably using NIRS. Future studies should focus primarily on BV for analysis.

Reliability of peak cardiorespiratory responses in patients with moderate to severe traumatic brain injury

OBJECTIVE

To examine the test-retest reliability of acute physiologic responses in patients with traumatic brain injury (TBI).

DESIGN

Repeated measures within 1 week.

SETTING

Brain injury rehabilitation program and community rehabilitation hospital.

PARTICIPANTS

Thirty-six inpatients or their legal guardians.

INTERVENTIONS

Each patient performed a symptom-limited incremental cycle ergometer test to voluntary fatigue on 2 separate occasions within 1 week.

MAIN OUTCOME MEASURES

Peak values of power output and cardiorespiratory responses measured with a metabolic cart interfaced with an electrocardiogram.

RESULTS

Intraclass correlations between the 2 trials were as follows: power output,.96; absolute oxygen uptake,.98; relative oxygen uptake,.97; heart rate,.82; ventilation rate,.96; and respiratory exchange ratio,.81. Bland-Altman plots showed that all data points were within the 95% confidence limits of the mean value of the 2 trials for each variable.

CONCLUSIONS

The reliability of the peak cardiorespiratory responses during non-weight-bearing exercise was high in patients with TBI in a controlled laboratory setting. Therefore, aerobic exercise programs can be accurately prescribed, and changes resulting from such interventions can be confidently evaluated in this population.

Cardiorespiratory and hemodynamic responses during repetitive incremental lifting and lowering in healthy males and females

The purposes of this study were twofold. First, to evaluate the cardiorespiratory and muscle oxygenation (OXY)/blood volume (BV) responses during repetitive incremental lifting and lowering (RILL) in healthy males and females. Second, to develop a predictive equation for predicting peak aerobic power (VO(2peak)) during RILL from the cardiorespiratory, OXY/BV and body composition variables. Fourteen males and 18 females [mean (SD) for age, height and body mass were: 29.6 (8.2) years; 1.75 (0.07) m; 78.9 (10.4) kg and 23.9 (2.1) years; 1.63 (0.06) m; 62.3 (6.3) kg, respectively] completed a RILL from floor to table height at 10 lifts/min to voluntary fatigue. Cardiorespiratory responses were measured using open circuit spirometry and hemodynamic trends were monitored bilaterally at the third lumbar vertebra via near infrared spectroscopy. Significant sex differences ( p<0.05) were observed for the peak values of oxygen uptake (VO(2peak)), ventilation rate (V(E)), oxygen pulse, BV-max and BV-delta. Erector spinae OXY decreased systematically until VO(2peak )was attained, while BV decreased until approximately 50% of VO(2peak) and then leveled off. Stepwise regression analysis indicated that approximately 75% of the variance in VO(2peak )was predicted from cardiorespiratory, hemodynamic and body composition variables, with the most important predictors for absolute and relative VO(2peak )being V(E) ( r=0.75) and fat mass ( r=-0.63) respectively. Inclusion of left side OXY/BV responses increased the predictability of the common variance in VO(2peak )from 40% to 74%, implying that muscle hemodynamics play an important role in determining VO(2peak )during RILL.

The effects of exercise and education, individually or combined, in women with fibromyalgia

OBJECTIVE

To examine the effectiveness of a supervised aerobic exercise program, a self-management education program, and the combination of exercise and education for women with fibromyalgia (FM).

METHODS

One hundred fifty-two women were randomized into one of 4 groups: exercise-only, education-only, exercise and education, or control. The duration of the study was 12 weeks. All subjects were analyzed at 3 times: before study, immediately upon completion, and 3 months after completion of the intervention program on measures of disability, self-efficacy, fitness, tender point count, and tender point tenderness. Of the 152 women, complete data were available for 95 and 69 who complied with the protocol. In order to determine the group time interaction, a 2 way analysis of variance with repeated measures was used for each measure.

RESULTS

The only significant group time interaction was reported with the compliance analysis for the Self-Efficacy Coping with Other Symptoms subscale and the Six Minute Walk. If the program was followed, the combination of a supervised exercise program and group education provided persons with FM with a better sense of control over their symptoms. Fitness improved in the 2 groups undergoing supervised aerobic exercise programs. However, the improvement in fitness was maintained at followup in the exercise-only group and not the combined group. Conclusion. Subjects receiving the combination of exercise and education and who complied with the treatment protocol improved their perceived ability to cope with other symptoms. In addition, a supervised exercise program increased walking distance at post-test, an increase that was maintained at followup in the exercise-only group. Results demonstrate the challenges with conducting exercise and education studies in persons with FM.

Functional electric stimulation-assisted rowing: Increasing cardiovascular fitness through functional electric stimulation rowing training in persons with spinal cord injury

OBJECTIVES

To assess changes in peak functional aerobic power after a 36-session, progressive functional electric stimulation (FES) rowing hybrid training program for persons with spinal cord injury (SCI) and to examine the safety and acceptability of the ROWSTIM II device as well as the integrity of technical modifications to it.

DESIGN

Repeated-measures training study, quasi-experimental design, within-person data comparison.

SETTING

A university-based recreational physical activity facility for persons with physical disabilities.

PARTICIPANTS

Six persons with level C7-T12 SCI (American Spinal Injury Association classes A-C).

INTERVENTION

Progressive rowing training program, 30 minutes per session, 3 times a week for 12 weeks at 70% to 75% of pretest peak functional aerobic power during FES rowing on an open loop control, FES-assisted rowing machine.

MAIN OUTCOME MEASURES

Total rowing distance, peak functional oxygen consumption, and peak oxygen pulse.

RESULTS

Subjects completed between 22 to 36 sessions. After 3 months of training, rowing distance increased by 25% (P<.02), peak oxygen consumption by 11.2% (P<.001), and peak oxygen pulse by 11.4% (P<.01). Heart rate response to hybrid training did not change at the end of training, although peak heart rate with FES lower-extremity exercise increased significantly from pre- to posttraining (P<.01).

CONCLUSIONS

Pre- and posttraining peak aerobic power values for ROWSTIM II training were comparable to previously reported values for hybrid cycle and upper-extremity exercise. We conclude that FES-assisted rowing is an effective, safe, and well-tolerated training system for persons with SCI.

Predictors of success of intervention programs for persons with fibromyalgia

OBJECTIVE

To determine which sociodemographic, psychological, and behavioral characteristics of persons with fibromyalgia (FM) will predict a positive response to treatment; and to determine if subjects classified according to the Multidimensional Pain Inventory (MPI) responded differently to the interventions.

METHODS

One hundred twenty-eight women with FM underwent baseline testing and were randomized into one of 3 intervention groups or a control group. After the 12 week program, the subjects were reexamined on the same pretest measures. Stepwise regression analyses were conducted to determine the variables that could significantly predict the change in the dependent variables. A reliability of change index was calculated to determine the proportion of responders and nonresponders.

RESULTS

The stepwise regression revealed significant predictor variables for change for all dependent variables except the Fibromyalgia Impact Questionnaire; however, the percentage of the variance in the change scores explained by the independent variables ranged from 4 to 15%. Results from the reliability of change index indicated that no MPI subgroup responded more than another group on any measure.

CONCLUSION

Select sociodemographic and psychosocial variables and type of intervention were not strong predictors of improvement in a variety of measures after a treatment program. The low percentage of explained variance may be due to the heterogeneity of FM. Additionally, the low percentage of responders suggests that current forms of treatment are not effective for a large portion of the FM population.

Physiology of wheelchair racing in athletes with spinal cord injury

Wheelchair racing is one of the most popular sporting activities of individuals with spinal cord injury. Athletes with this impairment have unique changes in metabolic, cardiorespiratory, neuromuscular and thermoregulatory systems, which reduce their overall physiological capacity compared with able-bodied individuals or individuals with other types of impairments. This review on spinal cord injury: presents the International Stoke Mandeville Games Federation classification of wheelchair athletes; describes methods commonly used to characterise anaerobic and aerobic fitness; presents the findings of physiological studies that have evaluated wheelchair racing performance; identifies the risks associated with temperature regulation when competing in wheelchair races; and discusses special conditions that can influence wheelchair racing performance. Currently there is limited research that has examined the relationship between sprint or distance wheelchair racing performance and the anaerobic and aerobic components of physical fitness. Although the descriptive evidence indicates that the profiles of these athletes reflect their training and participation in these specific events, the association between their physiological profiles and real or simulated racing performance is unclear. The generally accepted concept that high values of aerobic and anaerobic power are strongly correlated with endurance and sprint racing performance, respectively, are not necessarily true in this population. Athletes with spinal cord injury have an impaired thermoregulatory capacity, because the compromised autonomic and somatic nervous system functions disrupt control of skin blood flow and sweating below the level of the lesion. As a result, they may be more susceptible to hyperthermia during distance wheelchair racing performance. Wheelchair athletes should follow recommendations advocated for able-bodied individuals to minimise their risks of heat stress during competition. Many athletes with quadriplegia voluntarily induce autonomic dysreflexia (commonly known as boosting) during distance racing events to improve performance. Experimental evidence indicates that boosting can improve performance time by 10% in elite wheelchair marathon racers during simulated racing, as a result of increased oxygen utilisation in the boosted state. However, since boosting can be dangerous to health, the International Paralympic Committee has banned athletes from voluntarily inducing it during competition. The use of anti-gravity suits to increase lower-body positive pressure can increase the peak oxygen uptake, cardiac output and stroke volume. However, the use of abdominal binders does not influence these physiological responses. An effect of either of these techniques on wheelchair racing performance has not been demonstrated.

Oxygenation trends in vastus lateralis muscle during incremental and intense anaerobic cycle exercise in young men and women

The purposes of this study were to compare the acute cardiorespiratory responses and muscle oxygenation trends during incremental cycle exercise to exhaustion with those observed during 30 s and 45 s Wingate tests in healthy men and women, and to examine the relationships between selected variables among these tests. Seventeen healthy junior badminton players, nine men [mean age, height, body mass and maximal oxygen uptake (VO2max) were 15.8 (SD 0.8) years, 1.73 (SD 0.08) m, 65.6 (SD 6.3) kg and 50.6 (SD 6.9) ml x kg(-1) x min(-1) respectively] and eight women [mean age, height, body mass and VO2max were 16.6 (SD 1.0) years, 1.65 (SD 0.03) m, 62.7 (SD 4.5) kg and 42.0 (SD 5.0) ml x kg(-1) x min(-1) respectively] completed a stepwise incremental exercise test to voluntary exhaustion and two Wingate tests lasting 30 s and 45 s in three separate sessions in random order. Cardiorespiratory responses were monitored breath-by-breath using a metabolic cart interfaced with an electrocardiogram. Tissue absorbancy trends were continuously recorded from the right vastus lateralis muscle using dual wavelength near infrared spectroscopy. Oxygen uptake and heart rate were significantly higher during the incremental test when compared to the two Wingate tests in the men and women. However, the oxygen pulse (oxygen utilization per heart beat, i.e., the product of stroke volume and arterio-venous oxygen difference) was not significantly different among the three tests in both sexes. The minimal tissue absorbancy, an index of muscle deoxygenation, was also not significantly different among the three tests in both sexes. Significant relationships were observed for the oxygen uptake (r2=0.72) and oxygen pulse (r2=0.60) between the incremental and 45 s Wingate tests in the sample for both sexes combined. The minimal tissue absorbancy, however, was not significantly related between the two tests. It was concluded that the significantly higher oxygen uptake during the incremental test was due to the higher heart rate because: firstly, oxygen pulse was not significantly different among the three tests, and secondly, peripheral factors, as indicated by the changes in muscle oxygenation, were not significantly different among the three test conditions. Although the peak values of the oxygen pulse during the incremental and 45 s Wingate tests were significantly correlated, the common variance of the minimal tissue absorbancy measurements between these two tests was quite low, suggesting considerable variation in the peripheral contribution during these two tests.

Validity of the baltimore therapeutic equipment work simulator in the measurement of lifting endurance in healthy men

OBJECTIVE

To examine the criterion validity of the Baltimore Therapeutic Equipment (BTE) work simulator by comparing endurance time, oxygen uptake (VO2), and heart rate measured during real and simulated lifting tasks and to derive a regression equation for predicting actual lifting endurance from measurements on the work simulator.

METHOD

Twenty healthy male volunteers repetitively lifted and lowered a load of 40 lb using the BTE work simulator and actual weights at a laboratory workstation. Postures, location, and frequency of lifts were kept constant. Endurance (defined as the time taken for the rating of perceived exertion to increase 2 units on the Borg scale) was measured under both conditions. VO2 and heart rate were also recorded, using standard physiological procedures.

RESULTS

The mean values for endurance time, steady-state VO2, and heart rate were significantly different between the real and simulated tasks (p < .05). Correlation of endurance time between the two tasks was significant (r = .71, p < .05). Step wise regression analysis resulted in the following equation for predicting real endurance from simulated time measurements: predicted real time = .34 simulated time + 3.29; r = .71; SE = 1.00 min.

CONCLUSION

The BTE work simulator tends to overestimate real lifting endurance performance in healthy men. The lower physiological stress during the simulated task suggests a significant difference between the real and simulated loads. Occupational therapists should exercise caution when using the results of the BTE work simulator during functional capacity evaluations.