Relative validity of clinical techniques for measuring the body composition of persons with amyotrophic lateral sclerosis.

Tracking body composition is necessary to understand how amyotrophic lateral sclerosis (ALS) is affecting a patient's morphology and to provide a basis for appropriate nutritional advice throughout disease progression. Dual X-ray absorptiometry (DEXA) has been shown to reliably detect body composition changes in persons with ALS. However, this procedure is expensive and available primarily for research. The purpose of this study was to determine the relative validity of two common clinical techniques, anthropometry and bioelectrical impedance analysis (BIA), for measuring the body composition of persons with ALS. Twenty-three persons with ALS volunteered for the study; seven with primarily bulbar symptoms, five with primarily arm weakness, five with primarily leg weakness, and six with significant weakness in all extremities. On a single day subjects underwent body composition analysis by the three techniques, with DEXA serving as the criterion method. Anthropometry and BIA results were converted to lean and fat mass using eight prediction equations commonly cited in the literature. Anthropometry measures were also converted to estimates of muscle mass using two additional equations. Both BIA and anthropometry tended to overestimate lean mass and underestimate fat mass compared to DEXA. However, the BIA prediction equations had smaller mean differences, larger correlations, and smaller standard errors of estimate than the anthropometry equations. The Lukaski et al. BIA equation (Lukaski, H.C., Bolonchuk, W.W., Hall, C.B., Siders, W.A., 1986. Validation of tetrapolar bioelectrical impedance method to assess human body composition. J. Appl. Physiol. 60, 1327-1332) most closely matched the values derived by DEXA and is probably the best method for measuring the lean and fat mass of persons with ALS, as long as they maintain adequate hydration levels. The Heymsfield et al. equation (Heymsfield, S.B., McManus, C., Smith, J., Stevens, V., Nixon, D.W., 1982. Anthropometric measurement of muscle mass: revised equations for calculating bone-free arm muscle area. Am. J. Clin. Nutr. 36, 680-690) for estimating muscle mass may also be a useful clinical tool for this population. Further longitudinal studies are needed to determine whether the equations that correlated best with DEXA at a single point in time are also sensitive enough to detect changes in body composition over a period of time.

Individuals with amyotrophic lateral sclerosis are in caloric balance despite losses in mass.

The purpose of this study was to quantify body composition changes during amyotrophic lateral sclerosis (ALS) progression and to determine whether these subjects were losing or maintaining the energy stored in their bodies. The body composition of 12 males in the early stages of ALS and 6 age-matched controls was measured twice over a 6-month period using dual X-ray absorptiometry. During the study period the control group did not change. The ALS group lost an average of 2 kg of lean mass while gaining 0.55 kg of fat mass, resulting in a 1.45 kg loss in total body mass. When the changes in mass were converted to their energy equivalents, the ALS subjects lost an average of 1800 kcal of energy stored in lean mass but gained 4900 kcal in fat mass, resulting in a net increase of 3100 kcal stored. In conclusion, a small increase in fat mass can successfully compensate for the energy lost in lean mass from disease progression. Therefore, it is possible to preserve the amount of energy stored in the body of ALS patients, even when there are significant losses in lean and overall body mass. Consequently, a moderate loss of body mass should be expected and even encouraged among this patient population.

Physiological responses to nine different exercise:rest protocols.

This study determined the metabolic responses to different exercise:rest protocols during circuit exercise using hydraulic resistance. In experiment 1, nine subjects underwent nine different 27 min exercise circuits. There were three variations of three exercise:rest protocols (2:1, 1:1, 1:2). The VO2 for the nine circuits averaged (mean +/- SEM) 1.94 +/- 0.03 l.min-1 (43% of treadmill VO2max), with the largest difference between the protocols being 13%. Heart rate averaged 152.2 +/- 3.1 beats.min-1, with the largest difference between the protocols being 8%. Increasing the exercise duration per minute or the number of exercise bouts per minute had minimal effects on the mean VO2 and heart rate response to hydraulic resistive exercise. In experiment 2, nine subjects underwent three different 9 min exercise circuits using exercise:rest protocols of 2:1, 1:1, and 1:2 while work and VO2 were simultaneously measured. Surprisingly, increases in work were not necessarily accompanied by corresponding increases in VO2.

A submaximal all-extremity exercise test to predict maximal oxygen consumption.

PURPOSE: Submaximal aerobic exercise testing is utilized with a variety of populations to assess fitness level and predict maximal oxygen uptake (VO2peak) when a maximal test is not possible or preferable. Many submaximal tests have been developed on traditional exercise equipment, such as the treadmill and the cycle ergometer, but are not available for newer equipment such as an all-extremity ergometer. The purpose of this study was to develop and validate a submaximal exercise test using the Pro II Power Trainer, an all-extremity ergometer, in women ages 30-60 without disability and with varying fitness levels. A secondary purpose was to compare VO2peak values achieved during the all-extremity maximal test and the treadmill test. METHODS AND RESULTS: A linear regression equation was developed to predict VO2peak from submaximal data using heart rates and power output at the sixth and ninth minutes of the submaximal test. The linear regression derived for the submaximal all-extremity test was VO2peak L.min-1 = -0.01 (age in years) - 0.0029 (HR 1) - 0.0099 (HR2) - 0.0029 (PO1) + 0.0151(PO2) + 3.010. Predicted residual sum of squares of the linear equation revealed an R2 value of 0.722 and standard error of estimate of 0.216 L.min-1. Treadmill VO2 speak values correlated strongly with all-extremity VO2 speak values (r = 0.918) and were not significantly different (P, 0.05). CONCLUSION: A similar submaximal test needs to be developed for field estimates of VO2peak for subpopulations of individuals with physical disabilities such as rheumatoid arthritis, head or spinal cord injury, cerebral vascular accident, multiple sclerosis, amputation, and cerebral palsy.

A 1-day maximal lactate steady-state assessment protocol for trained runners.

PURPOSE: Identification of the maximal lactate steady state (MLSS) involves multiple days of testing. Heart rate (HR), rating of perceived exertion (RPE), breathing frequency (bf), and race pace may be useful in estimating the MLSS, thus allowing for testing to occur in a single day. The purpose of this investigation was to design a single-session protocol for determining MLSS using HR, RPE, bf, and race pace as predictors. METHODS: Twelve endurance athletes (mean +/- SD, VO2max 64.6 +/- 7.8 mL x kg(-1) x min(-1)) performed the MLSS protocol run and two 27-min validation runs on a treadmill. Running velocity at 87% HRmax RPE of 12, bf of 32 breaths x min(-1), and race pace were used as a starting point for testing. Blood was collected every 3 min of each 9-min stage of the protocol run and analyzed for lactate (La) concentration. The velocity associated with the MLSS was determined as the average of the stage of La steady state and the stage of La accumulation. Validation runs were performed at a velocity 7.5 m x min(-1) below and 7.5 m x min(-1) above the protocol-determined MLSS. If the slower run exhibited a La steady state and the faster run an accumulation of La, then the protocol-determined MLSS value was considered valid. RESULTS: The protocol run was successful in predicting the MLSS in 9 out of 12 subjects (P < or = 0.05). CONCLUSIONS: The proposed protocol employing HR, RPE, bf, and race pace as a starting point for testing can be used to identify the MLSS in one testing session.

Acute L-glutamine ingestion does not improve maximal effort exercise.

BACKGROUND: L-glutamine (GLN) may have an ergogenic effect during exercise considering its base generating potential. We attempted to determine whether GLN ingestion influences acid-base balance and improves high intensity exercise performance. METHOD: Ten trained males performed five exercise bouts on a cycle ergometer at 100% of VO2 peak. The first four bouts were 60 sec in duration, while the fifth bout was continued to fatigue. Each bout was separated by 60 sec of recovery. The exercise bouts were initiated 90 min after ingesting 0.03 g.kg body mass-1 of either GLN or placebo (PLC). Venous blood samples were collected pre-ingestion (PRE-IN), pre-exercise (PRE-EX), and following bouts four (B4) and five (B5) and analyzed for pH, bicarbonate concentration (HCO3), and lactate concentration (La-). Time to fatigue for B5 was used as a performance measure. RESULTS: pH, [HCO3], and [La-] were not significantly different (p > 0.05) between conditions for PRE-IN, PRE-EX, B4, and B5. Time to fatigue was not significantly different between conditions and averaged 263.4 +/- 24.5 sec and 263.2 +/- 19.4 sec for the GLN and PLC trials, respectively. CONCLUSIONS: These data indicate that acute ingestion of L-glutamine does not enhance either buffering potential or high intensity exercise performance in trained males.

Sodium bicarbonate ingestion does not attenuate the VO2 slow component during constant-load exercise.

We examined the effects of sodium bicarbonate ingestion on the VO2 slow component during constant-load exercise. Twelve physically active males performed two 30-min cycling trials at an intensity above the lactate threshold. Subjects ingested either sodium bicarbonate (BIC) or placebo (PLC) in a randomized, counterbalanced order. Arterialized capillary blood samples were analyzed for pH, bicarbonate concentration ([HCO3-]), and lactate concentration ([La]). Expired gas samples were analyzed for oxygen consumption (VO2). The VO2 slow component was defined as the change in VO2 from Minutes 3 and 4 to Minutes 28 and 29. Values for pH and [HCO3-] were significantly higher for BIC compared to PLC. There was no significant difference in [La] between conditions. For both conditions there was a significant time effect for VO2 during exercise; however, no significant difference was observed between BIC and PLC. While extracellular acid-base measures were altered during the BIC trial, sodium bicarbonate ingestion did not attenuate the VO2 slow component during constant-load exercise.

Glycogen replenishment and repeated maximal effort exercise: effect of liquid carbohydrate.

We investigated the effects of carbohydrate ingestion on glycogen replenishment and subsequent short duration, high intensity exercise performance. During Session 1, aerobic power was determined and each subject (N = 6) was familiarized with the 100-kJ cycling test (100KJ-Test). During the treatment sessions, the subjects performed a 100KJ-Test (Ride-1), then consumed 0.7 g.kg body mass-1 of maltodextrin (CHO) or placebo (PLC), rested 60 min, and then performed a second 100KJ-Test (Ride-2). Muscle tissue was collected before (Pre-1) and after Ride-1 (Post-1), and before (Pre-2) and after Ride-2 (Post-2), and analyzed for glycogen concentration. Both treatments yielded a significant increase in glycogen levels following the 60-min recovery, but there was no difference between treatments. Time to complete the 100KJ-Test increased significantly for PLC, but not for CHO. These data indicate that the decrease in performance during Ride-2 in PLC was not the result of a difference in glycogen concentration.

Motor unit number estimation, isometric strength, and electromyographic measures in amyotrophic lateral sclerosis.

Pathologic progression in amyotrophic lateral sclerosis (ALS) results from motor neuron death, while the clinical expression also reflects the compensatory effects of collateral reinnervation consequent to lower motor neuron loss. In a cross-sectional study of ALS subjects, we made comparisons between motor unit number estimation (MUNE) values and several measures reflecting collateral reinnervation, including isometric strength, compound muscle action potential (CMAP) amplitude, surface motor unit action potential (S-MUAP) amplitude, fiber density (FD), macro-EMG potential amplitude, turns-to-amplitude (T/A) ratio, and amplitude and recruitment pattern of low threshold voluntary motor units in elbow flexor muscles. Before comparisons were made, test-retest reproducibility of these measures was assessed in ALS subjects, and is highest for isometric strength, and lower but similar for EMG measures. When the effects of multiple comparisons are considered, borderline significant correlations are found between MUNE values and isometric strength. Neither MUNE values nor isometric strength are significantly correlated with macro-EMG amplitude, FD, T/A ratio, or amplitude and recruitment rate of low threshold voluntary motor units. There are significant correlations of CMAP and S-MUAP with MUNE values, but these are statistical artifacts with no independent interpretation. We conclude that collateral reinnervation prevents isometric strength and EMG measures from accurately reflecting lower motor neuron death in ALS. MUNE measurements are better suited to provide insight into the true natural history of the disease process and may be clinically useful to follow progression and response in drug trials.