Peak Power Measurement Research Articles

Effects of a competitive wrestling season on body composition, endocrine markers, and anaerobic exercise performance in NCAA collegiate wrestlers

Few data exist examining the body composition, endocrine, and anaerobic exercise performance changes over a competitive wrestling season. Eighteen NCAA wrestlers were tested for endocrine markers, body composition, hydration, grip strength, and power on four occasions: prior to pre-season training (T1); after pre-season training 3 days prior to the first seasonal meet (T2); mid-season one day prior to a meet (T3); and at the end of the season 2-3 days following the last meet (T4). Body mass, percent body fat (BF %), and fat mass were significantly lower (P ≤ 0.05) at T2 and T3 compared to T1 but were not different between T1 and T4. Lean body mass was significantly reduced at T2 only. Urine specific gravity was significantly elevated at T3 compared to T1, T2, and T4. Resting cortisol concentrations did not change but resting testosterone concentrations were significantly reduced at T2, T3, and T4. Maximal grip strength was significantly reduced at T2. Vertical jump peak power was significantly reduced at T2, T3, and T4. Wingate peak power was significantly reduced at T2 and T3. However, Wingate average power and total work did not significantly change. Fatigue rate during the Wingate test was significantly improved at T2, T3, and T4 compared to T1. In conclusion, body mass, BF %, and measures of peak force and power were reduced for most of the competitive wrestling season. Competitive wrestling reduces resting total testosterone concentrations throughout the entire season.

The Effects of Ionized and Nonionized Compression Garments on Sprint and Endurance Cycling

The aim of this study was to examine the effects of ionized and nonionized compression tights on sprint and endurance cycling performance. Using a randomized, blind, crossover design, 10 well-trained male athletes (age: 34.6 ± 6.8 years, height: 1.80 ± 0.05 m, body mass: 82.2 ± 10.4 kg, VO2max: 50.86 ± 6.81 ml·kg(-1)·min(-1)) performed 3 sprint trials (30-second sprint at 150% of the power output required to elicit VO2max [pVO2max] + 3 minutes recovery at 40% pVO2max + 30-second Wingate test + 3 minutes recovery at 40% pVO2max) and 3 endurance trials (30 minutes at 60% pVO2max + 5 minutes stationary recovery + 10-km time trial) wearing nonionized compression tights, ionized compression tights, or standard running tights (control). There was no significant effect of garment type on key Wingate measures of peak power (grand mean: 1,164 ± 219 W, p = 0.812), mean power (grand mean: 716 ± 68 W, p = 0.800), or fatigue (grand mean: 66.5 ± 6.9%, p = 0.106). There was an effect of garment type on blood lactate in the sprint and the endurance trials (p < 0.05), although post hoc tests only detected a significant difference between the control and the nonionized conditions in the endurance trial (mean difference: 0.55 mmol·L(-1), 95% likely range: 0.1-1.1 mmol·L(-1)). Relative to control, oxygen uptake (p = 0.703), heart rate (p = 0.774), and time trial performance (grand mean: 14.77 ± 0.74 minutes, p = 0.790) were unaffected by either type of compression garment during endurance cycling. Despite widespread use in sport, neither ionized nor nonionized compression tights had any significant effect on sprint or endurance cycling performance.

Smith Machine Counterbalance System Affects Measures of Maximal Bench Press Throw Performance

Equipment with counterbalance weight systems is commonly used for the assessment of performance in explosive resistance exercise movements, but it is not known if such systems affect performance measures. The purpose of this study was to determine the effect of using a counterbalance weight system on measures of smith machine bench press throw performance. Ten men and 14 women (mean ± SD: age, 25 ± 4 years; height, 173 ± 10 cm; weight, 77.7 ± 18.3 kg) completed maximal smith machine bench press throws under 4 different conditions (2 × 2; counterbalance × load): with or without a counterbalance weight system and using 'light' or 'moderate' net barbell loads. Performance variables (peak force, peak velocity, and peak power) were measured using a linear accelerometer attached to the barbell. The counterbalance weight system resulted in significant (p < 0.001) reductions in measures of peak force (mean difference ± standard error: light: -112 ± 20 N; moderate: -140 ± 23 N), peak velocity (light: -0.49 ± 0.10 m·s; moderate: -0.33 ± 0.07 m·s), and peak power (light: -220 ± 43 W; moderate: -143 ± 28 W) compared with no counterbalance system for both load conditions. Load condition did not affect absolute or percentage reductions from the counterbalance weight system for any variable. In conclusion, the use of a counterbalance weight system reduces accelerometer-based performance measures for the bench press throw exercise at light and moderate loads. This reduction in measures is likely because of an increase in the external resistance during the movement, which results in a discrepancy between the manually input and the actual value for external load. A counterbalance weight system should not be used when measuring performance in explosive resistance exercises with an accelerometer.

Physiological Responses of Ionised and Non-ionised Compression Garments to Sprint and Endurance Cycling

PURPOSE: The aim of this study was to examine the effects of ionised and non-ionised compression tights on physiological and performance variables during short-duration sprint and endurance cycling. METHODS: Using a randomised, blind, crossover design, 10 well-trained athletes (triathletes and cyclists) (means ± standard deviation for age and VO2max of the subjects were: 34.6 ± 6.8 years, 50.86 ± 6.81 ml.kg-1.min-1, respectively) performed three power trials (30 s controlled sprint @ 150% pVO2max + 3 min recovery @ 40% pVO2max + 30 s Wingate test) and three endurance trials (30 min at 60% pVO2max + 5 min stationary recovery + 10 km time trial) wearing one of three types of compression tights (ionised, non-ionised, control). Power trials were performed on an electromagnetically-braked cycle ergometer and the endurance trials were completed on a combination of the cycle ergometer and an electromagnetically-braked cycle trainer. Peak power, mean power, rate of fatigue and blood lactate were measured during the power trials and oxygen uptake, heart rate, blood lactate and time trial performance were measured during the endurance trials. RESULTS: There was no significant effect of garment type on key Wingate measures of peak power (grand mean: 1164.44 ± 218.56 W, P = 0.998), mean power (grand mean: 716.45 ± 67.74 W, P = 0.800) or rate of fatigue (grand mean: 66.52 ± 6.88 %, P = 0.106). There was an effect of garment type on blood lactate in the power trials (grand mean: 5.97 ± 3.20 mmol.l-1, P = 0.018). However, post hoc tests were unable to identify where those differences lay. Relative to control, oxygen uptake (grand mean: 34.98 ± 4.66 ml.kg-1.min-1, P = 0.998), heart rate (grand mean: 134 ± 10 b.min-1, P = 0.997), blood lactate (grand mean: 2.11 ± 0.56 mmol.l-1, P = 0.806) and time trial performance (grand mean: 14.77 ± 0.74 min, P = 0.790) were unaffected by either type of compression during endurance cycling. CONCLUSION: Despite widespread use in sport, neither ionised nor non-ionised compression tights have any significant effect on power or endurance cycling.

Procedure to carry out quality checks in photovoltaic grid-connected systems: Six cases of study

Assessing the correct operation of PV grid-connected systems (PVGCS) is paramount not only for mere energy and profitability concerns but also for safety reasons. Intended to this purpose, the IEC 62446 standard is open to some tests to be required in some circumstances, in addition to those stated in this document. Our work proposes a procedure to carry out quality checks in PVGCS complying with this standard and dealing with some tests not mentioned in it – namely, PV generator peak power measurement, inverter response and earth electrode measurement – so that the verification of the system gets more comprehensive. This procedure was carried out in six PV plants sited in different locations with a Mediterranean climate in Spain. The most remarkable results of this experimental campaign may be summarized as follows: an excellent on-site behavior of the inverters, in general very good figures for the isolation and earth electrode resistance and a scarcely relevant existence of hot spots. On the down side, some figures for the peak power of the tested PV generators well below their nominal value were found. The procedure described in this paper has proved to be a useful tool to assist in the verification of a PVGCS after installation and for subsequent re-inspection or maintenance.

Body structure versus body function in haemophilia: the case of haemophilic ankle arthropathy

Imaging and clinical scores are the main tools used to evaluate the progression of haemophilic arthropathy (HA). Based on haemophilic ankle arthropathy, this study aimed to explore the concordances between structural and clinical alterations, determined by standard radiological and clinical scores, and functional alterations assessed by three-dimensional gait analysis (3DGA). In total, 21 adult haemophilia patients underwent extensive ankle evaluation using the physical examination part of the World Federation of Haemophilia joint score, the Arnold-Hilgartner and the Pettersson radiological scores, and self-reported ankle function assessment using the revised Foot Function Index. Significant associations were found between self-reported ankle function assessment and the three 3DGA variables representative of joint function (range of motion, peak plantar flexion moment, and peak power generated at the push-off phase). Radiological and clinical scores were compared with ankle muscle peak power measurement, the most reliable 3DGA gait variable for ankle function. No significant associations were found between both clinical and functional scores and the 3DGA functional assessment. This discordance may be explained by the lack of a direct relationship between functional alterations detected by 3DGA and the structural changes assessed using X-ray or clinical scoring. Another explanation may be the limitation of clinical and radiological scoring systems in properly determining the severity of HA. Functional assessments such as 3DGA should be used more frequently when monitoring the progression of ankle arthropathy or the effects of therapeutic interventions in adult haemophilia patients.

Target Motion Analysis Based on Peak Power Measurements using Networked Sensors

Target motion analysis (TMA) using a network of wireless sensors/receivers which measure the power from a mobile RF emitter is considered. Due to limited communication capability of each sensor node, only peak power measurements from sensor nodes are transmitted to the fusion center. We present two main results that yield the optimum sensors' configuration such that the asymptotically achievable error variance of the target trajectory's estimate is minimized, and we derive efficient numerical algorithms for computing the optimum estimates of the trajectory of the moving target, thus achieving the goal of TMA.

Effect of Additional Load on Power Output during Drop Jump Training

Effect of Additional Load on Power Output during Drop Jump Training Plyometrics can be an effective way of improving power performance in many sports. The purpose of this study was to examine the effects of additional loading on power during drop jump training. Forty-two untrained physical education students with plyometric training background participated in a six-week training 3 times a week. Subjects were randomized to one of three training groups: without (FREE) and with a weight vest (VEST; 5% body weight), and a control group (CON). Pretraining and post-training measures of concentric peak power (PP), force (Fpp) and velocity (υPP) at peak power and, in addition, time between eccentric and concentric peak power (tPPEC) were analyzed in a countermovement jump (CMJ) and a drop jump (DJ) from a height of 0.3 m. The FREE and VEST groups considerably improved PP in CMJ (p &lt; 0.05), but υPP significantly increased (p &lt; 0.05) and tPPEC significantly decreased (p &lt; 0.05) only in the FREE group. The enhancement of PP and υPP was only demonstrated by the FREE group in DJ. The FREE group significantly decreased (p &lt; 0.05) and the VEST group significantly increased (p &lt; 0.05) tPPEC in DJ. It can be concluded that using additional load during drop jump training does not produce superior gains in power output when compared to a traditional drop jump training program.

La2Mo2O9-Based Electrolyte: Ion Conductivity and Anode-Supported Cell under Single Chamber Conditions

We demonstrate the applicability of LAMOX as an electrolyte for solid oxide fuel cells (SOFC) by preparing two anode-supported cells based on La0.9Dy0.1Mo2O9 and La0.9Dy0.1Mo1W1O9, and operating at 625°–700°C under single chamber conditions. The two cells, supported by a composite of NiO and Gd-doped ceria (GDC), are initialized with a porous Ni+GDC disk to catalyze the partial oxidation reaction of methane. The partially oxidized methane reduces NiO to Ni catalyst and activates the cell at 650°C. A typical membrane electrode assembly of the single chamber SOFC cell consists of a 60-μm-thick La0.9Dy0.1Mo2O9 electrolyte, an anode of Ni+GDC, and a cathode of lanthanum strontium cobalt ferrite. Its peak power measures 220 mW/cm2 at 700°C in a tubular chamber of 15 mm in diameter, with the total methane/air flow rate of 350 mL/min and CH4:O2=2:1.

DIURNAL VARIATION IN WINGATE TEST PERFORMANCES: INFLUENCE OF ACTIVE WARM-UP

The purpose of the present study was to examine the effects of active warm-up duration on the diurnal fluctuations in anaerobic performances. Twelve physical education students performed a medical stress test (progressive test up to exhaustion) and four Wingate tests (measurement of peak power [Ppeak], mean power [Pmean], and fatigue index during an all-out 30 s cycling exercise). The tests were performed in separate sessions (minimum interval = 36 h) in a balanced and randomized design at 08:00 and 18:00 h, either after a 5 min (5-AWU) or a 15 min active warm-up (15-AWU). AWU consisted of pedaling at 50% of the power output at the last stage of the stress exhausting test. Rectal temperature was collected throughout the sessions. A two-way ANOVA (warm-up × time of day) revealed a significant interaction for Ppeak (F(1.11) = 6.48, p < 0.05) and Pmean (F(1.11) = 5.84, p < 0.05): the time-of-day effect was significant (p < 0.001) in contrast with the effect of warm-up duration (p > 0.05). Ppeak and Pmean improved significantly from morning to afternoon after both 5-AWU and 15-AWU, but the effect of warm-up duration was significant in the morning only. Indeed, the values of Ppeak or Pmean were the same after both warm-up protocols in the afternoon. For rectal temperature, there was no interaction between time-of-day and warm-up duration. Rectal temperature before and after both the warm-up protocols was higher in the afternoon, and the effect of warm-up duration on temperature was similar at 08:00 and 18:00 h. In conclusion, the interpretation of the results of the anaerobic performance tests should take into account time-of-day and warm-up procedures. Longer warm-up protocols are recommended in the morning to minimize the diurnal fluctuations of anaerobic performances. (Author correspondence: n_souissi@yahoo.fr)

Development of a Modified Margaria-Kalamen Anaerobic Power Test for American Football Athletes

This study examined a modification of the Margaria-Kalamen test for football players. The football stair climb test (FST) protocol used in this study increased the vertical displacement (20 steps, 3.12 m) so that the mean best time for the test was 2.048 +/- 0.267 seconds. Fifty-eight Division I-A football players volunteered to participate (mean +/- SD age = 20.2 +/- 1.8 yr, height = 184.1 +/- 7.7 cm, weight = 102.5 +/- 19.4 kg). Subjects performed 25 trials with 30 to 40 seconds of rest between trials. Test-retest reliability was determined using 34 subjects by way of intraclass correlation coefficients with a value of 0.73 for peak power and SEM of 105.4 W, indicating an acceptable level of reliability. Subjects were divided into 3 groups by position: linemen (Line), skill, and linebackers (LB). Alpha level was p < 0.05. Peak power was 1674.5 +/- 300.8, 1712.6 +/- 251.5, and 1388.6 +/- 210.4 W for the LB, Line, and Skill groups, respectively. Groups were significantly different (p < 0.0001), with the LB and Line found to be more powerful than the Skill group. Peak power continued to increase throughout the 25 trials in the Skill and LB group but plateaued after approximately 17 trials in the Line group. It was concluded that the FST was a reliable test for measuring peak anaerobic power in collegiate football players, which, theoretically, should provide more accurate measures of peak power caused by increased vertical displacement and longer duration, resulting in a decreased influence of cheating strategies during test administration. To achieve maximal power in stair climbing tasks, coaches may need to incorporate a greater number of trials or a more intense warm-up than has been previously reported.

Effect of Progressive Resistance Training on Muscle Performance after Chronic Stroke

This study investigated the effects of high-intensity progressive resistance training (PRT) and high-intensity cycling (cycling) on muscle performance and the time course of strength gains in a chronic stroke population. Forty-eight individuals with chronic stroke sequelae (mean +/- SD; age = 63 +/- 9 yr, time since stroke = 57 +/- 54 months) were randomly allocated to one of four treatment groups: PRT + cycling, PRT + sham cycling, sham PRT + cycling, or sham PRT + sham cycling groups in a fully factorial clinical trial. Thirty exercise sessions were conducted over a 10- to 12-wk period. The main outcomes investigated were measures of unilateral muscle strength, peak power, and muscle endurance. Those undergoing PRT improved their lower limb muscle strength, peak power, and endurance compared with participants receiving sham PRT or cycling only (P < 0.05), and combined exercise was not superior to PRT alone. Strength improvements occurred primarily during the first 6 to 8 wk (98%-100% of total gain) and then reached a plateau during the final 2 to 4 wk. We have shown for the first time in a direct comparison study that high-intensity PRT, but not cycling or sham exercise, can improve muscle strength, peak power, and muscle endurance in both affected and unaffected lower limbs after chronic stroke by a significant and clinically meaningful amount. Although strength gains plateaued earlier than anticipated, adherence to the intended continuous high-intensity progressive overload protocol was largely achieved (average load of 84% +/- 4% of one repetition maximum).

Relating motor cortical oscillations to motor γ-Aminobutyric acid (GABA)

Event Abstract Back to Event Relating motor cortical oscillations to motor γ-Aminobutyric acid (GABA) William Gaetz1*, James C. Edgar1, D-J Wang1 and Timothy P. Roberts1 1 The Children's Hospital of Philadelphia and The University of Pennsylvania, Department of Radiology, United States Animal [1] and non-invasive human studies [2] demonstrate a strong relationship between cortical motor oscillations and the inhibitory neurotransmitter γ-Aminobutyric acid (GABA). A relationship between GABA concentration and cortical gamma oscillations was recently demonstrated in visual cortex [3]. Movement-related gamma (MRG), and post-movement beta rebound (PMBR) observed in humans may also depend on interneuronal GABA inhibitory currents [4]. Direct measures between motor cortex oscillations and motor cortex (MI) GABA, however, have not yet been demonstrated. The present study examined associations between PMBR and MRG and MI GABA. Adult subjects (N=8) made a right finger button response to a visual cue while whole-cortex MEG was obtained. PMBR (1-100 Hz) and PMG (65-90Hz) were estimated by first localizing contralateral MI using a differential SAM beamformer (Beta ERD; 15-30Hz). Time-frequency transforms were then applied to source waveforms from peak ERD locations, yielding frequency and power measures of PMBR and MRG oscillations. In the same subjects, single voxel (30x30x30mm) GABA magnetic response spectroscopy (MRS) was obtained using MEGA-PRESS. The MRS voxel was centered on the “hand-knob” of the left central sulcus. GABA measures were also obtained from a head coil reference phantom (50mM GABA). GABA levels were estimated as the ratio of the MI GABA integral to that of the phantom. PMBR power (% change) showed a marginally significant linear association with motor GABA concentration (r2 = 0.33, p=0.07). MRG frequency was associated with motor GABA concentration (r2 = 0.48, p=0.03). Present results support the hypothesis that motor cortical gamma power and frequency depend on MI GABA concentrations.

Reliability of Performance Measurements Derived From Ground Reaction Force Data During Countermovement Jump and the Influence of Sampling Frequency

Force platforms are used extensively to measure force and power output during countermovement jump (CMJ). The purpose of this study was to examine measurement reliability and validity of commonly used performance measurements derived from ground reaction force (GRF)-time data during CMJ and the influence of sampling at different frequencies. Twenty-four men performed 2 trials of CMJ on a force platform, and GRF-time data were sampled at a rate of 500 Hz. Data obtained at 500 Hz were considered as the reference, and then data were resampled at 400, 250, 200, 100, 50, and 25 Hz, using interpolation. Commonly used power, force, and velocity performance measures were obtained from GRF-time data. Reliability was assessed by intraclass correlation coefficient (ICC) and coefficient of variation (CV) between the 2 trials within the session. Peak power, peak force, and peak velocity were highly reliable across all sampling frequencies (ICC = 0.92-0.98, CV = 1.3-4.1). Percentage differences from 500-Hz reference values ranged from -0.85 to 0.20% at 400 Hz, -1.88 to 0.89% at 250 Hz, -1.80 to 1.31% at 200 Hz, -3.63 to 3.34% at 100 Hz, -11.37 to 6.51% at 50 Hz, and -13.17 to 9.03% at 25 Hz. In conclusion, peak power, force, and velocity measurements derived from GRF to assess leg extensor capabilities are reliable within a test session except for peak rate of force development and time to peak power. With regard to sampling frequency, scientists and practitioners may consider sampling as low as 200 Hz, depending on the purpose of measurement, because the percentage difference is not markedly enlarged until the frequency is 100 Hz or lower.

The Influence Of Music On A Supramaximal Exercise Bout

PURPOSE: To evaluate the influence of music on anaerobic performance using a maximal effort Wingate anaerobic test. METHODS: Physically active male and female participants (N = 25) completed a 30-second Wingate anaerobic test under two different conditions: music and no music. The volume of the music was standardized at 75dB. The musical selection was the same for each participant, and was selected based upon a survey of musical preferences of undergraduate students using the BMRI-2. During the task physiological and psychological data were collected. Monark anaerobic testing software was used to obtain measures of peak power, mean power, and % power drop, while a scale questionnaire was administered immediately after the trial to gauge the subject‘s level of motivation, exertion, and affect. Data analysis was conducted using a series of paired-sample t-tests in SPSS. RESULTS: Peak power and mean power were significantly higher with music than without. In addition, participants reported increased motivation and more positive affect in the music condition as opposed to the non-music condition. CONCLUSIONS: The results of this study suggest that music can have a positive influence over anaerobic performance. This supports previous research that has suggested music can be a valuable tool during physically strenuous activities, and extends these findings to include supramaximal exercise.

Measurement of Parameters of X-Band High-Power Microwave Superradiative Pulses

This paper describes the waveguide antenna, the detector based on the thermionic microwave diode, and the alcohol-filled calorimeter developed at the Institute of High Current Electronics. The techniques were used to measure parameters of X-band microwave pulses with a peak power of approximately 1 GW and a pulse length from 0.7 to 1 ns. The error of the peak power measurement was about 15%.

Sex Differences in Single Muscle Fiber Power in Older Adults

This study was conducted to determine whether differences in power at the single muscle fiber level contribute to sex differences in whole muscle power production in the elderly. A total of 16 sedentary older persons (10 women, 6 men), mean age 72 yr, had percutaneous needle biopsy of musculus vastus lateralis. Chemically skinned single muscle fibers were activated with Ca for maximal isometric force measurement (Po). The slack test was performed to determine maximal unloaded shortening velocity (Vo). Force-velocity and power curves were generated via a series of isotonic contractions, allowing measurement of peak power and specific power. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) was used to determine myosin heavy chain composition of single muscle fibers. Whole muscle strength, velocity, and power were measured for knee extension and double leg press. Men had greater whole muscle strength, power, and velocity compared with women. Studied were 274 type I and 33 type IIa single fibers. No significant sex differences were found for fiber size, Po, specific force, Vo, power, or specific power in type I or IIa fibers. Single muscle fiber quality in older women is equivalent to that in older men and can not explain the differences seen in whole muscle strength, power, or function.

Effects Of Oxygen Breathing On Wingate Test Parameters

It is well established in the literature that oxygen breathing during intense aerobic exercise improves performance. However, the magnitude of performance enhancement cannot be completely explained by metabolic mechanisms and therefore may involve central and peripheral neural factors. PURPOSE To examine the potential effect of O2-breathing during a predominantly anaerobic test. METHODS Twenty active male and female subjects (18–25yrs), completed a series of 4 Wingate tests using a Monark 894E computerized system. Two tests were completed while breathing 21% O2 and two breathing 100% O2. Each test was preceded by a 10 min breathing period. All tests were randomly assigned, single-blind with a least a day between tests. Measurements of peak power, minimum power, average power and power drop (%) were collected. In addition, VCO2 was collected during the test and for 10min recovery in order to estimate aerobic metabolism. RESULTS Peak power in watts (W) was attained for all tests during the first 5sec. 60% of subjects achieved max. peak power during hyperoxia. Peak power was 2.9% greater for hyperoxia (803 W) than normoxia (780 W) and average power was 2.5% greater for hyperoxia (611 W) than normoxia (596 W). Average power drop was similar between test conditions: during the first 15 sec. (normoxia=11.8%, hyperoxia=11.6%) and for the 30 sec. duration of the test (normoxia=39.8%, hyperoxia=38.7%). Total VCO2 was highest in all but 2 subjects during hyperoxia, suggesting a slight increase in aerobic metabolism. Following test completion subjects' perceived exertion was consistently less in hyperoxia than normoxia. CONCLUSION The data suggest that O2 breathing has minimal effect on work performance parameters measured during a primarily anaerobic test.

Traceable RF Peak Power Measurements for Mobile Communications

A technique to provide traceability for RF pulsed power measurements, predominantly used in 2G and 2.5G mobile communications is described. The method is used to verify the performance of an RF pulsed power signal generator and peak-power meter. The implications and limitations of the method for other data formats are discussed.

Reliability of Knee Extenstion Mechanical Power Across a Load- Spectrum

2387 An inexpensive computer-interfaced dynamometer, incorporating what is essentially a linear position transducer, can be used to calculate instantaneous external power and related variables in situations in which the load is known, constant, and moved linearly. The device is tethered to the load while velocity and displacement are measured directly with a sampling rate of 100 HzFinewtonian physics are used for calculating acceleration, force and power. PURPOSE: To determine the stability reliability of external power data obtained from a single-joint lift using this dynamometer. METHODS: Maximum-acceleration, concentric-only knee extensions through 90° were performed at 40, 65, and 90% 1RM in a random sequence by 24 men who had been engaged in weight training for no less than the previous 3 months. Power was evaluated at 50, 100, 200, and 300 ms intervals as well as for peak and average. At each session, participants completed 2 single-repetition trials at each load interspersed by 3 min rest. The identical test battery was repeated 48 h later to assess reliability (intraclass correlation coefficient or ICC) and precision (standard error of measurement or SEm). RESULTS: ICC's ranged from .54 to .82 for peak power, between .74 and .85 for average power, and between −.03 and .79 for measurements taken between 50 and 300 ms over the load spectrum. Precision was ≤ 13.7 W except at 300 ms for the 40% 1RM load and at 50 ms for the 90% 1RM load (Table 1). CONCLUSIONS: For the dynamometer in question, reliable measures of knee extension peak power appear to be obtainable for young men at loads ranging from 40% to 65% 1RM, and to a lesser extent at 90% 1RM. When expressed as an average, reasonably reliable measures of power would be expected across the load spectrum. Knee extension instantaneous power appears to be a reliable measure up to about 200 ms. However, a transient software problem emerged at 50 ms for the 90% 1RM load that we have been unable to explain. Therefore, precise measures of power would be expected across the load spectrum for peak, average, and most time-dependent expressions.Table