Twelve human subjects were studied to determine the effect of three different floor surfaces on the medial shin musculature during stationary running. Electromyographic equipment, gated by an accelerometer affixed to the subject's shin, was used to separate the impact (eccentric) phase from the propulsive (concentric) phase of each running step. Excessive eccentric muscle activity has been associated with increased muscle damage, and recent investigations have linked medial tibial shin pain with actual structural damage to the muscle-fascial attachments to the posteromedial aspect of the tibia. Therefore, this study tends to verify the previous assumption that running on hard, noncompliant sport surfaces would predispose running and dancing athletes to shin muscle damage and resultant pain.

The purpose of this study was to investigate potential improvements in the methodology associated with the Physical Working Capacity at the Fatigue Threshold (PWCFT) test including: (1) the use of a continuous test protocol; (2) the use of a treadmill; (3) the use of a bipolar EMG lead system for noisy electronic environments; and (4) the potential for residual fatigue from tests repeated 24 hours apart. The results of the continuous test protocol (mean +/- S.D. = 210 +/- 73 watts) correlated well (r = 0.856) with the original discontinuous technique (222 +/- 83 watts) and there was no significant (p greater than 0.05) difference between the mean values (t = 1.146). Treadmill testing required a bipolar lead system to counteract the electrical noise generated by the treadmill motor. The heart rate values which corresponded to PWCFT on the treadmill (mean +/- s.d. = 164 +/- b.p.m.) and bicycle ergometer (153 +/- 18 b.p.m.) were highly correlated (r = 0.833) and there was no significant (p greater than 0.05) difference between the mean values (t = 2.22). The use of a bipolar lead EMG system on the bicycle ergometer resulted in significantly (p less than 0.05) smaller voltage for any given power output, and the PWCFT exhibited a low to moderate correlation (r = 0.60) with PWCFT derived from a unipolar arrangement. The test-retest results of discontinuous PWCFT measurements performed 24 hours apart on the bicycle ergometer were correlated at r = 0.812 with no significant (p greater than 0.05) difference (t = 0.52) between the mean values (test = 198 +/- 60; retest = 191 +/- 63 watts).(ABSTRACT TRUNCATED AT 250 WORDS)

The test for estimating physical working capacity at the fatigue threshold (PWCft), previously validated for young men, was evaluated for use with elderly men and women. A sample of 27 volunteer subjects (67.6 +/- 5.6 years, 11 male, 16 female) was divided into three matched groups: (1) controls (n = 10), (2) low intensity (70% PWCft) training group (n = 10) and (3) high intensity (85% PWCft) training group (n = 7). The subjects were tested for PWCft before and after 10 weeks of exercise training on cycle ergometers (30 min/day, 3 days/week). Controls did not exercise but met once a week for a health lecture. No significant pre-test to post-test change was noted in the mean PWCft of the control group (78.8-78.5 W); low intensity training resulted in 29.8% improvement in PWCft (81.0 to 105.0 W); and the high intensity group realized an improvement of 38.4% (83.6-115.7 W). One-way ANOVA indicated that the gains made by each of the groups were significantly different (p less than 0.01). Post hoc analysis revealed that the gains made by each exercise training group were significantly greater than controls (p less than 0.05) with no significant difference between high and low intensity groups. Reproducibility of the PWCft was excellent (R = 0.976). Since RPE averaged 14.2 at PWCft and 64% of subjects provided useful data, this test appears to be useful for evaluating the fitness of the elderly.

Presently available tests of physical working capacity (PWC) such as [Vdot]O2max and critical power may not be appropriate for unfit subjects because they require maximal or supramaximal workloads. Therefore, the purpose of this study was to evaluate a submaximal discontinuous incremental bicycle ergometer test (PWCFT) with an end point (fatigue threshold) determined by recording electromyographic (EMG) fatigue curves in the quadriceps muscle. The fatigue threshold was defined as the lowest workload producing a slope of the EMG voltage-time relation that was significantly different from zero slope at p<0.05 (single tail). The test-re-test reproducibility of PWCFT (n=17 subjects) was found to be r = 0.947, with no significant difference between trials. Thirty-two healthy male subjects aged 18-29 (mean 23-4 ± 31 years) whose fitness levels ranged from highly trained to untrained sedentary level were tested for PWCFT, lactate threshold (OBLA), percentage heart rate range at PWCFT (%HRR), and heart rate-workload relation (HR-WL). Stepwise multiple regression resulted in R = 0.833 with %HRR accounting for 40.7%, OBLA for 22.8% and HR-WL for 5.9% of the total variance. In addition, 12 subjects performed critical power (CP) testing. PWCFT and CP were correlated at r=0.670 with no significant difference p<005) between the means for the two methods. The results of this study indicated that the PWCFT test was objective, valid and highly reproducible and particularly useful for evaluating the PWCFT of unfit subjects.

Absence of the achilles tendon reflex (T) has been reported to increase with age. Other investigators have reported no age relationship. Age changes in the Hoffmann reflex (H) have been examined in only one recent investigation. It was our purpose to compare the T and H reflexes of healthy, active old (n = 20) against young (n = 20) subjects using methods which provide stimulus-response data for both T and H. We also compared the age differences of H against T to estimate fusimotor involvement in age changes. No significant age difference were found in the response:stimulus ratio for T. Amplitude of H responses were 32.7 percent smaller in the old (P less than 0.04) and M waves were smaller by 24 percent (P less than 0.025). No significant age difference was found between mechanically and electrically elicited reflexes; and, therefore, our data do not support fusimotor involvement in the age changes of monosynaptic reflexes.

deVries, H. A.; Simard, C. P.; Wiswell, R. A.; Heckathorae, E.; Carabetta, V. Author Information

The purpose of this study was to define the relation between 'critical power' (CP) and the onset of fatigue (fatigue threshold or FT) as estimated from electromyographic data taken from representative leg muscles during cycling. The rate of rise in integrated EMG (IEMG) activity as a function of time (IEMG slope) was calculated at each of three or four constant power output ergometer bouts for 11 subjects. The IEMG slopes so obtained were plotted against workload resulting in linear plots (0-88

Monod and Scherrer (1965) showed that there was a linear relation between the maximal work and the maximal time over which the work was performed until the onset of local muscular exhaustion. This linear relation could be expressed by the equation: W lim =a+bT lim, where maximal work (Wlim) was thought to result from the use of an energy reserve (a) and an energy reconstitution whose maximal rate was (b) We have extended this concept to total body work (bicycle ergometer). Eight male and eight female college students underwent exercise tests at 400, 350, 300,275 and 300,250,200,175 W respectively, to the onset of fatigue. The regression analysis revealed that the linearity of individual plots was found to be 0-982

The time course of strength gain with respect to the contributions of neural factors and hypertrophy was studied in five young men and five older men during the course of 8 weeks progressive strength training. Young and old men showed similar and significant percentage increases in strength. However, the neurophysiological adaptations in response to the training were quite different. Increases in maximal muscle activation (neural factors) played a dominant role throughout the training for old subjects, while young subjects showed strength gains due to neural factors only at the initial stage, with hypertrophy becoming the dominant factor after some 4 weeks of training. Our data suggest that the effect of muscle training in the old may entirely rest on the neural factors presumably acting of various levels of the nervous system which could result in increasing the maximal muscle activation level in the absence of significant hypertrophy.

A sedentary life style may contribute as much to functional losses in the elderly as the aging process itself. In a series of studies involving over 200 older men and women over a period of 5 years, carefully prescribed exercise resulted in significant physiologic improvement. Healthy older subjects can be trained in relatively the same way as younger people, but the hazards of endurance training are greater. Medical screening, individual assessment of exercise response, and careful progression in training challenge are essential.

The time course of strength gain with respect to the contributions of neural factors and hypertrophy was studied in seven young males and eight females during the course of an 8 week regimen of isotonic strength training. The results indicated that neural factors accounted for the larger proportion of the initial strength increment and thereafter both neural factors and hypertrophy took part in the further increase in strength, with hypertrophy becoming the dominant factor after the first 3 to 5 weeks. Our data regarding the untrained contralateral arm flexors provide further support for the concept of cross education. It was suggested that the nature of this cross education effect may entirely rest on the neural factors presumably acting at various levels of the nervous system which could result in increasing the maximal level of muscle activation.

The integrated electromyogram (IEMG)--force relationships were studied in 26 physically active young men across the entire domain of forces in the elbow flexor group. All possible error factors (fatigue, muscle length, and co-contraction) were controlled to the greatest extent possible. The experimental conditions were more clearly defined than in previous experiments. The results confirm earlier observations of a linear relationship between IEMG and isometric force, under these experimental conditions and using a unipolar lead system. Highly significant correlations were found. Possible methodological error factors were studied. Bipolar recording produced a curvilinear, relationship which may explain some of the discrepancies of results reported in the literature.

Adams, G. M.; deVries, H. A.; Girandola, R. M.; Blrren, J. S.; Adams, Gene M. Author Information

The effect of saddle height upon oxygen consumption during bicycle ergometer work was measured. Five subjects were tested on a continuous work protocol from 50 watts to 200 watts in 25 watt increments at experimental saddle heights of 100%, 103%, 106%, 109%, and 112% of inside leg length measured from the ischium to the floor. Data were recorded on Vo2, Vco2, VE, and heart rate. It was found that Vo2 progressively increased as saddle height increased; the highest Vo2 occurred at the highest experimental setting of 112%; the most effective saddle positions in the experiment as measured by lowest Vo2 per unit of work were 100% and 103%; and there was no significant difference between the VO2 AT 100% AND 103%. It was concluded that in light of our data and earlier data showing power output to be maximized at 104% (by our measurement method), the saddle height of choice should be approximately 103% to 104% of leg length. A convenient and objective method for setting seat height is presented.

University of Southern California, Los Angeles Herbert A. deVries 32194 Vista de La Luna South Laguna, CA 92667