Limits...
The single-bout forearm critical force test: a new method to establish forearm aerobic metabolic exercise intensity and capacity.

Kellawan JM, Tschakovsky ME - PLoS ONE (2014)

Bottom Line: There was no systematic difference between test 1 and 2 for fCF(peak) force (p = 0.11) or fCF(impulse) (p = 0.76).TTE predicted by W' showed good agreement with actual TTE during the TTE tests (r = 0.97, ICC = 0.97, P<0.01; typical error 0.98 min, 12%; regression fit slope = 0.99 and y intercept not different from 0, p = 0.31).MVC did not predict fCF(peak force) (p = 0.37), fCF(impulse) (p = 0.49) or W' (p = 0.15).

View Article: PubMed Central - PubMed

Affiliation: School of Kinesiology and Health Studies, Queen's University, Kingston, Ontario, Canada.

ABSTRACT
No non-invasive test exists for forearm exercise that allows identification of power-time relationship parameters (W', critical power) and thereby identification of the heavy-severe exercise intensity boundary and scaling of aerobic metabolic exercise intensity. The aim of this study was to develop a maximal effort handgrip exercise test to estimate forearm critical force (fCF; force analog of power) and establish its repeatability and validity. Ten healthy males (20-43 years) completed two maximal effort rhythmic handgrip exercise tests (repeated maximal voluntary contractions (MVC); 1 s contraction-2 s relaxation for 600 s) on separate days. Exercise intensity was quantified via peak contraction force and contraction impulse. There was no systematic difference between test 1 and 2 for fCF(peak) force (p = 0.11) or fCF(impulse) (p = 0.76). Typical error was small for both fCF(peak force) (15.3 N, 5.5%) and fCF(impulse) (15.7 N ⋅ s, 6.8%), and test re-test correlations were strong (fCF(peak force), r = 0.91, ICC = 0.94, p<0.01; fCF(impulse), r = 0.92, ICC = 0.95, p<0.01). Seven of ten subjects also completed time-to-exhaustion tests (TTE) at target contraction force equal to 10%fCF(peak force). TTE predicted by W' showed good agreement with actual TTE during the TTE tests (r = 0.97, ICC = 0.97, P<0.01; typical error 0.98 min, 12%; regression fit slope = 0.99 and y intercept not different from 0, p = 0.31). MVC did not predict fCF(peak force) (p = 0.37), fCF(impulse) (p = 0.49) or W' (p = 0.15). In conclusion, the poor relationship between MVC and fCF or W' illustrates the serious limitation of MVC in identifying metabolism-based exercise intensity zones. The maximal effort handgrip exercise test provides repeatable and valid estimates of fCF and should be used to normalize forearm aerobic metabolic exercise intensity instead of MVC.

Show MeSH

Related in: MedlinePlus

Force output during a 10 min maximal effort handgrip exercise test in a representative subject.Panel A: Raw force trace output Panel B: Impulse force of contraction plotted for all contractions during the test. Panel C: Impulse force averaged into 30 s time bins. Error bars indicate the contraction-to-contraction variability within each 30 s time bin.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3974771&req=5

pone-0093481-g001: Force output during a 10 min maximal effort handgrip exercise test in a representative subject.Panel A: Raw force trace output Panel B: Impulse force of contraction plotted for all contractions during the test. Panel C: Impulse force averaged into 30 s time bins. Error bars indicate the contraction-to-contraction variability within each 30 s time bin.

Mentions: Upon arrival at the laboratory, subjects lay supine with the experimental arm (left) extended 90o at heart level as previously described [14]. After a period of acclimatization (∼5–10 min) subjects performed 3 maximal voluntary contraction (MVC) efforts separated by 1 minute. The highest of these was identified as the target contraction force for the maximal effort test. Data collection began with an initial 2 min period of quiet rest, followed by 10 min of rhythmic handgrip maximal voluntary contractions (1 s contraction to 2 s relaxation duty cycle). The 10 min duration of the maximal effort test was established during prior pilot work using a 10 min duration test in which it was observed that, while tests consistently resulted in subjects reaching a plateau by the last of the 10 min, some subjects did not reach a plateau prior to this time. Therefore 10 min was used for this duty cycle. It should be noted that the duration of the test would be expected to decrease with a higher contraction/relaxation duty cycle as the total work performed per unit time would be increased. Likewise it would be expected to increase with a lower contraction/relaxation duty cycle. Subjects observed their force output continuously displayed on a computer screen (Powerlab, ADInstruments, Sydney, Australia) (Fig. 1A) and attempted to reach their maximum force on every contraction. Subjects received constant verbal encouragement and coaching by a research assistant to achieve a “square wave” during each maximal voluntary contraction and to engage only the muscles of the forearm.


The single-bout forearm critical force test: a new method to establish forearm aerobic metabolic exercise intensity and capacity.

Kellawan JM, Tschakovsky ME - PLoS ONE (2014)

Force output during a 10 min maximal effort handgrip exercise test in a representative subject.Panel A: Raw force trace output Panel B: Impulse force of contraction plotted for all contractions during the test. Panel C: Impulse force averaged into 30 s time bins. Error bars indicate the contraction-to-contraction variability within each 30 s time bin.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3974771&req=5

pone-0093481-g001: Force output during a 10 min maximal effort handgrip exercise test in a representative subject.Panel A: Raw force trace output Panel B: Impulse force of contraction plotted for all contractions during the test. Panel C: Impulse force averaged into 30 s time bins. Error bars indicate the contraction-to-contraction variability within each 30 s time bin.
Mentions: Upon arrival at the laboratory, subjects lay supine with the experimental arm (left) extended 90o at heart level as previously described [14]. After a period of acclimatization (∼5–10 min) subjects performed 3 maximal voluntary contraction (MVC) efforts separated by 1 minute. The highest of these was identified as the target contraction force for the maximal effort test. Data collection began with an initial 2 min period of quiet rest, followed by 10 min of rhythmic handgrip maximal voluntary contractions (1 s contraction to 2 s relaxation duty cycle). The 10 min duration of the maximal effort test was established during prior pilot work using a 10 min duration test in which it was observed that, while tests consistently resulted in subjects reaching a plateau by the last of the 10 min, some subjects did not reach a plateau prior to this time. Therefore 10 min was used for this duty cycle. It should be noted that the duration of the test would be expected to decrease with a higher contraction/relaxation duty cycle as the total work performed per unit time would be increased. Likewise it would be expected to increase with a lower contraction/relaxation duty cycle. Subjects observed their force output continuously displayed on a computer screen (Powerlab, ADInstruments, Sydney, Australia) (Fig. 1A) and attempted to reach their maximum force on every contraction. Subjects received constant verbal encouragement and coaching by a research assistant to achieve a “square wave” during each maximal voluntary contraction and to engage only the muscles of the forearm.

Bottom Line: There was no systematic difference between test 1 and 2 for fCF(peak) force (p = 0.11) or fCF(impulse) (p = 0.76).TTE predicted by W' showed good agreement with actual TTE during the TTE tests (r = 0.97, ICC = 0.97, P<0.01; typical error 0.98 min, 12%; regression fit slope = 0.99 and y intercept not different from 0, p = 0.31).MVC did not predict fCF(peak force) (p = 0.37), fCF(impulse) (p = 0.49) or W' (p = 0.15).

View Article: PubMed Central - PubMed

Affiliation: School of Kinesiology and Health Studies, Queen's University, Kingston, Ontario, Canada.

ABSTRACT
No non-invasive test exists for forearm exercise that allows identification of power-time relationship parameters (W', critical power) and thereby identification of the heavy-severe exercise intensity boundary and scaling of aerobic metabolic exercise intensity. The aim of this study was to develop a maximal effort handgrip exercise test to estimate forearm critical force (fCF; force analog of power) and establish its repeatability and validity. Ten healthy males (20-43 years) completed two maximal effort rhythmic handgrip exercise tests (repeated maximal voluntary contractions (MVC); 1 s contraction-2 s relaxation for 600 s) on separate days. Exercise intensity was quantified via peak contraction force and contraction impulse. There was no systematic difference between test 1 and 2 for fCF(peak) force (p = 0.11) or fCF(impulse) (p = 0.76). Typical error was small for both fCF(peak force) (15.3 N, 5.5%) and fCF(impulse) (15.7 N ⋅ s, 6.8%), and test re-test correlations were strong (fCF(peak force), r = 0.91, ICC = 0.94, p<0.01; fCF(impulse), r = 0.92, ICC = 0.95, p<0.01). Seven of ten subjects also completed time-to-exhaustion tests (TTE) at target contraction force equal to 10%fCF(peak force). TTE predicted by W' showed good agreement with actual TTE during the TTE tests (r = 0.97, ICC = 0.97, P<0.01; typical error 0.98 min, 12%; regression fit slope = 0.99 and y intercept not different from 0, p = 0.31). MVC did not predict fCF(peak force) (p = 0.37), fCF(impulse) (p = 0.49) or W' (p = 0.15). In conclusion, the poor relationship between MVC and fCF or W' illustrates the serious limitation of MVC in identifying metabolism-based exercise intensity zones. The maximal effort handgrip exercise test provides repeatable and valid estimates of fCF and should be used to normalize forearm aerobic metabolic exercise intensity instead of MVC.

Show MeSH
Related in: MedlinePlus