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Kenneth L Knight, Christopher D Ingersoll, and John Bartholomew
Problem:
Isokinetic contractions are thought to be superior to isotonic contractions for developing strength because resistance during them is greater. Because isokinetic resistance is accommodating, however, it decreases with fatigue. It is constant during multiple repetitions, so an aggressive isotonic procedure should produce more force as the muscle fatigues, which would be an advantage in strength development.
Purpose:
To compare force production in isokinetic and isotonic muscle contractions at the beginning and end of a set of fatiguing repetitions.
Methods:
Subjects performed 25 maximal-effort isokinetic knee extensions at 60°/s. After 25–72 hours, they performed maximal repetitions isotonically using 70% of the isokinetic peak torque with speed set at a maximum of 300°/s.
Results:
Peak force during the first 3 repetitions was greater isokinetically, but average force was similar. During the last 3 repetitions, isotonic force was higher than isokinetic force.
Conclusion:
Muscle is more active as it nears fatigue during an isotonic contraction. These data support the hypothesis that isotonic contractions recruit extra motor units at the point of fatigue.
Lisa S. Jutte, Kenneth L. Knight, and Blaine C. Long
Objective:
Examine thermocouple model uncertainty (reliability + validity).
Design:
First, a 3 × 3 repeated measures design with independent variables electrothermometers and thermocouple model. Second, a 1 × 3 repeated measures design with independent variable subprobe.
Intervention:
Three electrothermometers, 3 thermocouple models, a multi-sensor probe and a mercury thermometer measured a stable water bath.
Main Outcome Measures:
Temperature and absolute temperature differences between thermocouples and a mercury thermometer.
Results:
Thermocouple uncertainty was greater than manufactures’ claims. For all thermocouple models, validity and reliability were better in the Iso-Themex than the Datalogger, but there were no practical differences between models within an electrothermometers. Validity of multi-sensor probes and thermocouples within a probe were not different but were greater than manufacturers’ claims. Reliability of multiprobes and thermocouples within a probe were within manufacturers claims.
Conclusion:
Thermocouple models vary in reliability and validity. Scientists should test and report the uncertainty of their equipment rather than depending on manufactures’ claims.
Kenneth L. Knight and David O. Draper
Column-editor : David O. Draper
Mack D Rubley, Jody B Brucker, Kenneth L Knight, Mark D Ricard, and David O Draper
Objective:
To determine the retention of flexibility 25 days after 5 days of three 30-second stretches.
Design:
A 2 × 4 repeated-measures factorial. Treatment and time were independent variables. The dependent variable was flexibility as measured by a sit-and-reach box.
Measurements:
33 college students were tested before and after stretching for 5 consecutive days and without stretching on days 8 and 30. Control subjects were prone for 15 minutes; stretch subjects received 15 min of diathermy or sham diathermy and then performed three 30-second standing right-hamstring stretches.
Results:
Flexibility was greater on days 5, 8, and 30 than day 1, but days 5, 8, and 30 were not different from each other.
Conclusion:
Gains in flexibility are retained for at least 3 weeks after a stretching program. It also appears that 2 sets of 3 repetitions of a sit-and-reach test is sufficient stimulus to induce long-term flexibility gains.
Kevin C. Miller, Kenneth L. Knight, Steven R. Wilding, and Marcus B. Stone
Context:
Electrically induced muscle cramps (EIMC) do not last long enough to study many cramp treatments. Increasing stimulation frequency lengthens cramp duration; it is unknown which frequency elicits the longest EIMC.
Objective:
To determine which stimulation frequency elicits the longest EIMC and whether cramp duration and stimulation frequency are correlated.
Design:
Randomized, crossover.
Setting:
Laboratory.
Participants:
20 participants (12 male, 8 female; age 20.7 ± 0.6 y; height 174.9 ± 1.9 cm; mass 76.6 ± 2.2 kg) with a self-reported history of muscle cramps in their lower extremities within the 6 mo before the study.
Interventions:
The dominant leg’s tibial nerve was percutaneously stimulated with 2-s-duration electrical stimuli trains starting at a frequency of 4 Hz. After 1 min of rest, stimulation frequency increased in 2-Hz increments until a cramp occurred in the flexor hallucis brevis. The stimulation frequency at which a cramp occurred was termed cramp threshold frequency (TF). Cramp duration was determined using strict clinical criteria (loss of hallux rigidity and return of hallux neutral). On the next 4 consecutive days, participants were stimulated at 5, 10, 15, or 20 Hz above TF, and cramp duration was reassessed.
Main Outcome Measures:
Cramp TF and duration.
Results:
Cramp TF was 16.9 ± 5.1 Hz. Cramp duration was longer at 15 and 20 Hz above TF (77.9 ± 37.6 s and 69.5 ± 36.9 s, respectively) than at TF (40.8 ± 34.0 s; P < .05). Cramp duration and TF were highly correlated (r = .90). Conclusions: Stimulating at 15 and 20 Hz above cramp TF produces the longest-lasting EIMC.
David A. Kaiser, Kenneth L. Knight, Jeremy M. Huff, Lisa S. Jutte, and Preston Carlson
Objective:
To determine the time needed to heat hot packs to water temperature (73–75 °C) in 4- and 8-pack Hydrocollator® units.
Design and Setting:
A 2 × 2 factorial design, with heating unit (4- or 8-pack) and number of packs added (1 or 3/7) as independent variables. Dependent variables were hot-pack and Hydrocollator-water temperatures.
Measurements:
Temperatures were measured with type T thermocouples interfaced with a 16-channel Isothermex™. Hydrocollator temperatures were measured with 2 thermocouples, and hot-pack temperatures, with 6 thermocouples inserted in 6 cells of a hydrated, 10- by 12-in Hydrocollator pack. Temperature was measured every 30 s for 5 min before and 45 min after pack immersion.
Results:
Packs warmed rapidly from ~18 to 65–68 °C by 10 min and to 72.5–75 °C by 20 min. Heating slowed by ~5% when 7 packs were added to the large unit. Water temperatures decreased ~2 °C (from ~75 °C) after 7 packs were immersed and returned to preimmersion temperatures by 20 min.
Conclusions:
Rewarming is quicker than commonly believed (20–150 min) and might be a function of the number of packs being simultaneously warmed.
Blaine C. Long, Kenneth L. Knight, Ty Hopkins, Allen C. Parcell, and J. Brent Feland
Context:
It is suggested that postinjury pain is difficult to examine; thus, investigators have developed experimental pain models. To minimize pain, cryotherapy (cryo) is applied, but reports on its effectiveness are limited.
Objective:
To investigate a pain model for the anterior knee and examine cryo in reducing the pain.
Design:
Controlled laboratory study.
Setting:
Therapeutic modality laboratory.
Participants:
30 physically active healthy male subjects who were free from any lower extremity orthopedic, neurological, cardiovascular, or endocrine pathologies.
Main Outcome Measures:
Perceived pain was measured every minute. Surface temperature was also assessed in the center of the patella and the popliteal fossa.
Results:
There was a significant interaction between group and time (F68,864 = 3.0, P = .0001). At the first minute, there was no difference in pain between the 3 groups (saline/cryo = 4.80 ± 4.87 mm, saline/sham = 2.80 ± 3.55 mm, no saline/cryo = 4.00 ± 3.33 mm). During the first 5 min, pain increased from 4.80 ± 4.87 to 45.90 ± 21.17 mm in the saline/cryo group and from 2.80 ± 3.55 to 31.10 ± 20.25 mm in the saline/sham group. Pain did not change within the no-saline/cryo group, 4.00 ± 3.33 to 1.70 ± 1.70 mm. Pain for the saline/sham group remained constant for 17 min. Cryo decreased pain for 16 min in the saline/cryo group. There was no difference in preapplication surface temperature between or within each group. No change in temperature occurred within the saline/sham. Cooling and rewarming were similar in both cryo groups. Ambient temperature fluctuated less than 1°C during data collection.
Conclusion:
Intermittent infusion of sterile 5% hypertonic saline may be a useful experimental pain model in establishing a constant level of pain in a controlled laboratory setting. Cryotherapy decreased the induced anterior knee pain for 16 min.
David O. Draper and Kenneth L. Knight
Column-editor : David O. Draper
Billy E. Cotts, Kenneth L. Knight, J. William Myrer, and Shane S. Schulthies
Context:
It has been suggested that contrast-bath therapy alters sensation and enables patients to return to exercise more quickly.
Objective:
To determine whether contrast-bath therapy alters sensation of pressure in the ankle.
Design:
A 2 × 4 × 4 factorial design with repeated measures on 2 factors. Independent variables included gender, time (preapplication and 1, 6, and 11 min postapplication), and treatment (control, cold bath, hot bath, and contrast bath).
Setting:
Laboratory.
Participants:
12 men and 12 women, college track athletes actively engaged in preseason workouts 5-6 days/wk.
Interventions:
Sensation of pressure was tested preapplication and 1, 6, and 11 min postapplication. Each treatment lasted 20 min.
Main Outcome Measure:
Sensation of pressure at baseline and 1, 6, and 11 min postapplication over the anterior talofibular ligament of the right ankle.
Results:
There was no difference between genders. Sensation of pressure was greater for the heat condition than the other 3 conditions at 1 and 6 min postapplication. During the heating condition, sensation of pressure was greater at 1 and 6 min postapplication than during preapplication. During the contrast condition, sensation of pressure was less at 6 min postapplication than during preapplication.
Conclusion:
Contrast- and cold-bath therapy (at 13 °C) do not affect numbness.
