Terje Gjøvaag

Energy Expenditure of Transfemoral Amputees Walking on a Horizontal and Tilted Treadmill Simulating Different Outdoor Walking Conditions

Transfemoral amputees often report that walking on tilted pavements or on terrain with the prosthesis on the side of higher elevation is quite strenuous. This study investigates the energy expenditure of transfemoral amputees (n = 8) on a motorized treadmill, simulating different strenuous outdoor walking conditions. Oxygen uptake at self-selected speed of gait was measured during walking at three different treadmill positions: (i) Horizontal treadmill, (ii) 3% tilt in the sagittal plane and (iii) 3% tilt in both the sagittal and frontal plane of the treadmill. The difference in median values of oxygen uptake between position (i) and (ii) was 4.3%, and 16.4% between position (ii) and (iii) (p ≤ 0.05, for both comparisons). The subjects utilized about 50% of their VO2max when walking in position (i) and (ii), with an increase to about 60% of their VO2max when walking in position (iii). Transfemoral amputees use significantly more energy when walking on a moderately tilted surface in the frontal plane compared to walking with a tilt in the sagittal plane. This is probably because the prosthetic leg becomes functionally too long when the walking surface is tilted sideways, and the transfemoral amputees adopt a more energy consuming gait pattern.

Effect of training with different mechanical loadings on MyHC and GLUT4 changes

PURPOSE There is an inverse relationship between insulin sensitivity and percentage of myosin heavy chain IIx (MyHC IIx) isoform in sedentary, obese, and type 2 diabetic humans. How different exercise conditions may reduce the proportion of MyHC IIx and in parallel elevate glucose transporter 4 (GLUT4) content is interesting in a therapeutic setting. This study investigates the nature of exercise signals regulating MyHC gene switching and whether it is accompanied by GLUT4 changes. METHODS Thirty-two subjects performed high loading (60% of 1 repetition maximum [RM]) or low loading (30% of 1 RM) elbow extensions in a training apparatus and exercised three times per week for either 5 wk (low volume) or 8 wk (high volume). MyHC and GLUT4 contents in the musculus triceps brachii were measured by Western blotting pre- and posttraining and after 8 wk of detraining. RESULTS All training regimes resulted in MyHC IIx changes of similar magnitude, and differences in training volume had no effect on the outcome. The reduction in MyHC IIx content after high loading, high volume was similar to low loading, matching volume of training. Thus, there was no effect of training load on MyHC changes. GLUT4 increased more after high than low loading (P < 0.0.1). In addition, the larger increases in the GLUT4 were associated with the larger reductions in MyHC IIx content (r = -0.56, P < 0.01). Detraining returned GLUT4 to baseline, but MyHC IIx content was still higher than baseline (P < 0.01). CONCLUSION Magnitude of loading is not important for suppression of MyHC IIx but for increases in GLUT4 content. The GLUT4 content responded, however, more rapidly to detraining than the MyHC IIx and IIa isoforms.

A Review of the Role of the Partial Pressure of Carbon Dioxide in Mechanically Loaded Tissues: The Canary in the Cage Singing in Tune with the Pressure Ulcer Mantra

Pressure ulcers (PUs) can occur in any situations where people are subjected to non-uniform distribution of pressure over a prolonged period. They can have devastating effects on the patients’ well-being and in extreme conditions can prove fatal. In addition to traditional wisdom implicating mechanically induced ischaemia, there is strong evidence that other mechanisms play a role in the cascade of events which can initiate the PU damage process at the cellular level. Some of these refer to a metabolic imbalance with compromised delivery of nutrients and accumulation of waste products in the local environment of the cells. The approach of much research has focused on the measure of oxygen in compressed tissues as a means of predicting early damage. However, the present review adopting a hierarchical approach, using length scales ranging from cells through to human models, has revealed compelling evidence which highlights the importance of carbon dioxide levels and associated concentration of other metabolites, such as lactate and purines. The temporal profiles of these metabolites have been monitored in the various models subjected to periods of mechanical-induced loading where the localized cells have converted to anaerobic metabolism. They reveal threshold levels of carbon dioxide which might be indicative of early tissue damage during both mechanical-induced ischaemia and subsequent reperfusion and an appropriate sensor could be used in a similar manner to the long-standing “canary in a cage” method to detect toxic gasses in enclosed mines.

Hemodynamic Responses to Resistance Exercise in Patients with Coronary Artery Disease.

PURPOSE Investigate hemodynamic responses of resistance exercise (RE) with moderate load (i.e., international guidelines for RE of patients) versus RE with high load in patients with coronary artery disease (CAD). METHODS Medically stable male (n = 11) and female patients (n = 4) treated with PCI or percutaneous coronary intervention, or coronary artery bypass surgery a minimum of 6 months before this study, performed three sets of 15RM and 4RM RE in a randomized order on separate days. Beat-to-beat systolic (SBP), diastolic (DBP) blood pressure, heart rate (HR), stroke volume (SV), cardiac output (CO), and systemic vascular resistance (SVR) were monitored at preexercise, and continuously during RE. RESULTS Compared with preexercise, SBP and DBP (mean of three sets) increased by 12% to 13% (both; P < 0.001) and 35% to 40% after 15RM RE (both; P < 0.001). 15RM SBP and DBP were higher than 4RM SBP and DBP (both; P < 0.001). The SBP of the fourth repetition of 15 RM RE was similar to the SBP of the fourth repetition of 4RM RE. Compared with preexercise, SV increased moderately after 4RM and 15 RM RE, respectively (both, P < 0.001). HR increased more after 15RM compared with 4RM RE (P < 0.05); thus, higher CO after 15RM (compared with 4RM RE; P < 0.05) was mainly caused by higher HR. SVR decreased by 15% (P < 0.001) and 50% (P < 0.01) after 4RM and 15RM RE. CONCLUSIONS SBP and DBP increased significantly more during moderate load RE; thus, the magnitude of the external load is not the prime determinant of the pressure response during RE. If management of blood pressure is of concern, high load/low rep RE is preferable to medium load/high rep RE.

Assessment of aerobic capacity and walking economy of unilateral transfemoral amputees

Background: Studies of the maximal oxygen uptake (VO2max) of transfemoral amputees have mostly used protocols that activate a relatively small muscle mass. Consequently, transfemoral amputee VO2max may be systematically underestimated, and the validity of these test protocols is questionable. Objectives: (1) Investigate validity and reliability of a VO2max walking protocol and (2) compare the VO2max of a transfemoral amputee group with a group of matching controls. Study design: (1) Randomized crossover study: walking versus running VO2max for the control group and (2) case-control study: transfemoral amputees versus control group VO2max. Methods: Twelve transfemoral amputees and control participants performed a walking VO2max test with increasing treadmill inclinations to voluntary exhaustion. The control group also completed a running (“gold-standard”) VO2max test. Results: Mean (standard deviation) control group VO2max following walking and running was similar, that is, 2.99 (0.6) L min−1 and 3.09 (0.7) L min−1, respectively. Mean (standard deviation) transfemoral amputee walking VO2max was 2.14 (0.8) L min−1 (compared to CON; p < 0.01). Mean intraclass correlation coefficient of repeated VO2 measurements was 0.97, and within-subjects standard deviation was 60 mL min−1. Conclusions: The walk protocol is valid. Walking VO2max of transfemoral amputees was 40% lower compared to control group. Reliability of the walking protocol is comparable to other walking protocols. Clinical relevance The design, alignment, and materials of prostheses are important for effective ambulation. Cardio-respiratory fitness is, however, also important in this regard, and a low fitness may compromise health and independent living. Hence, transfemoral amputees with low physical fitness should engage in regular physical activity to improve health, gait capacity, and independency.

Energy expenditure of transfemoral amputees during floor and treadmill walking with different speeds

Background: Walking energy expenditure, calculated as the percent utilization of the maximal aerobic capacity, is little investigated in transfemoral amputees. Objectives: Compare the energy expenditure of healthy participants (control participants) and transfemoral amputees walking with their respective preferred walking speeds on the treadmill (TPWS) and floor (FPWS). Study design: Randomized cross-over study. Methods: Oxygen uptake (VO2) was measured when walking with the FPWS and TPWS. VO2max was measured by an incremental treadmill test. Results: Mean ± standard deviation VO2max of the transfemoral amputees and control participants were 30.6 ± 8.7 and 49.0 ± 14.4 mL kg−1 min−1, respectively (p < 0.05). TPWS for the transfemoral amputees and control participants was 0.89 ± 0.2 and 1.33 ± 0.3 m s−1, respectively (p < 0.01). FPWS for the transfemoral amputees and control participants was 1.22 ± 0.2 and 1.52 ± 0.1 m s−1, respectively (p < 0.01). Walking on floor with the FPWS, the energy expenditure of the transfemoral amputees and control participants was 54% and 31% of VO2max, respectively (p < 0.01). Walking on the treadmill with the TPWS, the energy expenditure of the transfemoral amputees and control participants was 42% and 29% of the VO2max, respectively (p < 0.05). Conclusion: Energy expenditure is higher for the transfemoral amputees than the control participants, regardless of walking surface. There are minimal differences in energy expenditure between treadmill and floor walking for the control participants but large differences for the transfemoral amputees. Clinical relevance During walking, the transfemoral amputees expend a larger percentage of their maximal aerobic capacity than healthy participants. With a low VO2max, ordinary activities, such as walking, become physically more challenging for the transfemoral amputees than the control participants, and this may, in turn, have a negative effect on the walking range of the transfemoral amputees.

Near-Infrared Spectra in Buccal Tissue as a Marker for Detection of Hypoxia.

INTRODUCTION Hypoxia caused by high altitude exposure can impair cerebral and mental functions. Blood flow and oxygenation of the buccal tissue can be reliable markers to detect hypoxia. In this study, near infrared spectroscopy was used in combination with a novel optical probe to evaluate the applicability of the novel probe in measuring hypoxia markers in buccal tissue under a hypoxic condition. METHODS Six healthy participants were tested at altitudes from 2000 to 16,000 ft inside a hypobaric chamber. The buccal reference measurements of blood flow and oxygen saturation were synchronized with the spectral measurements of the novel near infrared probe and the relationship between the reference measurements and spectral data were evaluated by multivariate partial least square method. In addition, finger oxygen saturation was measured during the experiment and the recordings were compared with buccal oxygen saturation. RESULTS The spectral analysis illustrated that the spectral data from the near infrared probe correlated strongly with the absorption features of both buccal flow and oxygenation measured by the reflectance sensors (average R(2) = 0.89). The results showed probably overestimated values for buccal oxygen saturation recorded by the reference pulse oximeter in comparison with finger oxygen saturation, with the mean difference increasing from 1.8% at 2000 ft to 11.4% at 16,000 ft. CONCLUSION The novel near infrared probe showed promising results for simultaneous measurement of blood flow and oxygen saturation in the buccal tissue. The suggested method can be used as a new technique for early indication of hypoxia in future clinical applications.

Novel Design of an Optical Probe for Detecting Perfusion Changes in Buccal Tissue

Measuring the blood perfusion and microcirculation at a specific depth in human tissue is an important method to monitor oxygenation in critically ill patients. The optical probes, that are currently available in the market, are not capable of monitoring the blood perfusion from a given tissue layer and at a specific depth. We have designed a novel optical probe which is able to focus the light at a specific depth of ~670×μm in buccal tissue. The new probe consists of two light guides for sending and detecting the reflected light from the sampling area (tissue), and a lens to focus the light into the desired depth of the tissue and collect it back from the same area. The new optical probe has been compared to a commercial laser Doppler probe by collecting data from the same sampling area. The result from our probe showed 15% higher accuracy in detecting changes in blood perfusion compared with an existing commercial probe.

Carbohydrate and fat oxidation in persons with lower limb amputation during walking with different speeds

Background: Studies suggest that the energy expenditure of healthy persons (control) during walking with the preferred walking speed in steady-state conditions is dominated by fat oxidation. Conversely, carbohydrate and fat oxidation during walking is little investigated in transfemoral amputees. Objectives: To investigate carbohydrate and fat oxidation, energy cost of walking, and percent utilization of maximal aerobic capacity ( % V · O 2 max ) during walking. Study design: Eight transfemoral amputees and controls walked with their preferred walking speed and speeds 12.5% and 25% slower and faster than their preferred walking speed. Methods: Energy expenditure and fuel utilization were measured using a portable metabolic analyzer. Metabolic values are means ± standard deviation. Results: For transfemoral amputees (37.0 ± 10.9 years) and controls (39.0 ± 12.3 years), fat utilization at the preferred walking speed was 44.8% ± 7.2% and 45.0% ± 7.2% of the total energy expenditure, respectively. The preferred walking speed of the transfemoral amputees and controls was close to a metabolic cross-over speed, which is the speed where carbohydrate utilization increases steeply and fat utilization decreases. When walking fast, at 90 m min−1 (preferred walking speed plus 25%), transfemoral amputees utilized 70.7% ± 5.6% of their V · O 2 max , while the controls utilized 30.9% ± 4.5% (p < 0.001) at the matching speed (control preferred walking speed). At 90 m min−1, carbohydrate utilization was 78% ± 4.7% and 55.2% ± 7.2% of the total energy expenditure for the transfemoral amputees and controls, respectively (p < 0.01). Compared to the control, energy cost of walking was higher for the transfemoral amputees at all speeds (all comparisons; p < 0.001). Conclusion: At the preferred walking speed, carbohydrate, not fat, dominates energy expenditure of both transfemoral amputees and controls. For the transfemoral amputees, consequences of fast walking are very high V · O 2 max utilization and rate of carbohydrate oxidation. Clinical relevance Research on the relationships between physical effort and fuel partitioning during ambulation could provide important insights for exercise-rehabilitation programs for lower limb amputees (LLA). Regular endurance exercise will improve maximal aerobic capacity and enable LLA to walk faster and at the same time expend less energy and improve fat utilization.

Strength and Functional Capacity of a 70-Year-Old Patient Diagnosed with Parkinson Disease Following 1 Year of Combined Supervised Progressive Resistance Training and Home-Based Training: A Case Report

The value of resistance training (RT) for people with Parkinson disease (PD) is disputed, but recent research shows promising results regarding effects of intensive RT. The main aim of this case report was to develop a combined model consisting of home-based training (HT) and supervised RT as a 1-year follow-up to evaluate changes in functional capacities of a patient with PD. The intervention consisted of 8 weeks of supervised progressive RT, followed by 12 weeks of individual HT. This sequence was then repeated, for a total follow-up of 12 months. Functional capacities were assessed between all training periods with a battery of clinical measures. During the second HT period, functional outcomes and muscle strength were better preserved compared with the first HT period. These results are important regarding how to design and implement efficient exercise regimens for patients with PD and show that progressive RT twice a week for 2 months combined with home training in periods is effective in improving muscular strength and functional capacities.