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Cited by 37Muscle metabolism and nutritionNutrition and Health in AgingMuscle Physiology and Disorders

Effect of resistance training and fish protein intake on motor unit firing pattern and motor function of elderly

Open access
Watanabe, Kohei, Holobar, Aleš, Mita, Yukiko, Kouzaki, Motoki, Ogawa, Madoka, Akima, Hiroshi, Moritani, Toshio·2018·Frontiers in Physiology
DOI 10.3389/fphys.2018.01733PMC PMC6288440
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Abstract

We investigated the effect of resistance training and fish protein intake on the motor unit firing pattern and motor function in elderly. Fifty healthy elderly males and females (69.2 ± 4.7 years) underwent 6 weeks of intervention. We applied the leg-press exercise as resistance training and fish protein including Alaska pollack protein (APP) as nutritional supplementation. Subjects were divided into four groups: fish protein intake without resistance training (APP-CN, n=13), placebo intake without resistance training (PLA-CN, n=12), fish protein intake with resistance training (APP-RT, n=12), and placebo intake with resistance training (PLA-RT, n=13). Motor unit firing rates were calculated from multi-channel surface electromyography by the Convolution Kernel. A greater improvement in the motor function, i.e., chair-stand test, was observed in APP-RT compared with PLA-RT at 6W (p 0.05). Time courses of changes in the results of the chair-stand test and motor unit firing rate were different between APP-RT and PLA-RT. These findings suggest that, in the elderly, the effect of resistance training on the motor unit firing rate is observed in motor units with a low-recruitment threshold, and additional fish protein intake modifies these changes in motor unit firing patterns and the motor function following resistance training.

AI snapshot

Written from the paper’s full text.

TL;DR

In 50 healthy elderly adults, 6 weeks of leg-press resistance training increased chair-stand performance and altered motor unit firing rates mainly in low-recruitment-threshold motor units, while fish protein (Alaska pollack protein) plus training changed the time course and broader recruitment-threshold firing patterns. Fish protein alone did not change motor unit firing rates, and no intervention significantly changed muscle mass, MVC, or gait time.

Key findings

  • Chair-stand performance improved at 6 weeks versus 0 week in all groups; APP-RT improved significantly from 0 to 3 weeks and 0 to 6 weeks (18.2 ± 1.9 at 0 week to 19.8 ± 2.2 at 3 weeks and 21.2 ± 1.9 at 6 weeks).
  • Motor unit firing-rate changes were mainly noted in low-recruitment-threshold motor units in APP-RT and PLA-RT at 3 and 6 weeks; at 50% MVC, APP-RT changed from 12.3 pps at 0 week to 13.6 pps at 3 weeks and 12.1 pps at 6 weeks, while PLA-RT changed from 12.9 pps to 13.9 pps and 14.1 pps, but not in APP-CN or PLA-CN.
  • APP-RT also showed significant firing-rate changes in middle- and high-recruitment-threshold motor units at 80% MVC, including decreases at 3 and/or 6 weeks, and the time course differed from PLA-RT.
  • No significant intervention effects were found for body mass, body fat, muscle mass, muscle or subcutaneous tissue thickness, MVC, or gait time in any group; the hypothesis that fish protein intake increases muscle volume was not supported.

Methods

  • Randomized, double-blind, placebo-controlled 6-week intervention in 50 healthy elderly males and females (69.2 ± 4.7 years), divided into APP-CN (n = 13), PLA-CN (n = 12), APP-RT (n = 12), and PLA-RT (n = 13); fish protein groups received 5 g/meal Alaska pollack protein, and resistance-training groups performed bilateral horizontal leg press twice weekly, 3 sets of 10 repetitions at 70% 1RM.
  • Motor unit firing rates were calculated from multi-channel surface EMG of the vastus lateralis using 64 electrodes and Convolution Kernel Compensation decomposition, with only motor units with pulse-to-noise ratio >30 dB retained; subjects performed ramp contractions from 0 to 90% MVC, and motor units were grouped by recruitment threshold (<20%, 20–40%, 40–60% MVC).
  • A total of 1,204 motor units were detected from 50 subjects at three periods; non-parametric tests were used (Kruskal–Wallis, Friedman, Dunn/Bonferroni–Dunn), with significance set at p < 0.05.

Limitations

  • The paper states that there was no supporting evidence that action potentials from the same motor units were recorded or that the same motor units were detected by decomposition across the three periods, and that changes in motor unit recruitment thresholds could have caused the same motor units to be categorized differently among periods.
  • The paper states that detected motor unit numbers differed by recruitment threshold and that not all subjects contributed motor units to every period/group, which may have affected statistical power; it also states that only the right leg was investigated, dominant leg was not identified, and bilateral leg press may have produced leg-dependent training effects.
  • Evident from the text: the intervention was short (6 weeks) and training frequency was low (twice weekly), muscle measurements were limited to one component of the trained muscle group, and the chair-stand test may have shown a learning effect that improved performance in all groups.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.3389/fphys.2018.01733

Cites

61 of 61 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

0 of 43 cited sources checked · 0 supported · 0 flagged

  • Findingown data

    In APP-RT, the chair-stand test significantly increased from 18.2 ± 1.9 at 0 week to 19.8 ± 2.2 at 3 weeks and 21.2 ± 1.9 at 6 weeks.

    “significant increases from 0 to 3 weeks and 6 weeks were observed in APP-RT (18.2 ± 1.9 at 0 week to 19.8 ± 2.2 at 3 weeks and 21.2 ± 1.9 at 6 weeks) (p < 0.05).”
    Quote in the paperSubstantial claim
  • Findingown data

    Time courses of changes in the results of the chair-stand test and motor unit firing rate were different between APP-RT and PLA-RT.

    “Time courses of changes in the results of the chair-stand test and motor unit firing rate were different between APP-RT and PLA-RT.”
    Quote in the paperSubstantial claim
  • Findingown data

    Total energy, protein, and total energy normalized by body weight at 3-6 weeks were significantly greater than at PRE in all groups.

    “Total energy, protein, and total energy normalized by body weight at 3–6 weeks were significantly greater than those at PRE in all groups (p < 0.05) (Table 2).”
    Quote in the paperNot a substantial claim
  • Findingown data

    For the chair-stand test, significant increases were observed at 6 weeks compared with 0 week in all groups.

    “For the chair-stand test, significant increases were observed at 6 weeks compared with 0 week in all groups (p < 0.05) (Table 3).”
    Quote in the paperNot a substantial claim
  • Findingown data

    In APP-RT, firing rates of motor units recruited at 40-60% of MVC at 0 week were significantly higher than at 3 weeks at 80% of MVC.

    “Firing rates of motor units recruited at 40–60 of MVC at 0 week were significantly higher than those at 3 weeks (p = 0.001) at 80% of MVC in APP-RT (Figure 3).”
    Quote in the paperNot a substantial claim
  • Classified as probably not a substantial claim. 28
  • May combine two claims. 32

  • Probably not a substantial claim: may not pass S1 (asserted), S3 (load-bearing), S4 (based).

    Findingown data

    In PLA-CN, none of the firing rates of any motor unit groups significantly changed during intervention.

    “In PLA-CL, none of the firing rates of any motor unit groups significantly changed during intervention (p > 0.05) (Figure 2).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    Increase and/or decrease in motor unit firing rate were mainly noted within motor units with a low-recruitment threshold in APP-RT and PLA-RT at 3 and 6 weeks, but not in APP-CN or PLA-CN.

    “Increase and/or decrease in the motor unit firing rate were mainly noted within motor units with a low-recruitment threshold in APP-RT and PLA-RT at 3 and 6 weeks (12.3 pps at 0 week to 13.6 pps at 3 weeks and 12.1 pps at 6 weeks for APP-RT and 12.9 pps at 0 week to 13.9 pps at 3 weeks and 14.1 pps at 6 weeks for PLA-RT at 50% of MVC) (p < 0.05), but not in APP-CN or PLA-CN (p > 0.05).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    In PLA-RT, firing rates of motor units recruited at <20% of MVC at 3 weeks at 40% of MVC and at 6 weeks at 50% of MVC were significantly higher than at 0 week.

    “Firing rates of motor units recruited at <20% of MVC at 3 weeks at 40% of MVC (p = 0.044) and at 6 weeks at 50% of MVC were significantly higher than that at 0 week in PLA-RT (p = 0.031) (Figure 3).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Protein normalized by body weight significantly increased from PRE to 3-6 weeks for APP-CN, PLA-CN, and PLA-RT, but not for APP-RT.

    “Protein normalized by body weight significantly increased from PRE to 3–6 weeks for APP-CN (p = 0.004), PLA-CN (p = 0.021), and PLA-RT (p = 0.023), but not for APP-RT (p = 0.062) (Table 2).”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingown data

    Carbohydrate normalized by body weight significantly increased from PRE to 3-6 weeks for APP-CN and PLA-CN.

    “Carbohydrate normalized by body weight significantly increased from PRE to 3–6 weeks for APP-CN (p = 0.007) and PLA-CN (p = 0.021) (Table 2).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    No significant effects of intervention were noted on body mass, body fat, muscle mass, muscle and subcutaneous tissue thicknesses, MVC, or gait time in any group.

    “No significant effects of intervention were noted on the body mass, body fat and muscle mass estimated by InBody, muscle and subcutaneous tissue thicknesses, MVC, or gait time in any of the groups (p < 0.05) (Table 3).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    Changes in motor unit firing rate were noted only in motor units with a low-recruitment threshold for PLA-RT, while significant changes were noted in motor units with both low- and high-recruitment thresholds for APP-RT.

    “While changes in the motor unit firing rate were noted only in motor units with a low-recruitment threshold for PLA-RT, significant changes were noted in motor units with both low- and high- recruitment thresholds for APP-RT (Figure 3).”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: The detected motor unit populations within the motor unit groups did not critically vary during the different periods in this study.

  • May combine two claims.

    Findingown data

    In APP-RT, firing rates of motor units with low-recruitment thresholds significantly increased at 3 weeks but not at 6 weeks.

    “In APP-RT, significant increase in firing rates of motor units with low-recruitment thresholds were noted at 3 weeks (p < 0.05), but not at 6 weeks (p > 0.05) (Figure 3)”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: The detected motor unit populations within the motor unit groups did not critically vary during the different periods in this study.

  • May combine two claims.

    Findingown data

    Increases in firing rate during resistance training were mainly noted in motor units recruited at <20% MVC for APP-RT and PLA-RT, at low to moderate force levels 30-50% MVC, but not at higher force levels.

    “Increases in the firing rate during resistance training were mainly noted in motor units recruited at <20% of MVC for APP-RT and PLA-RT, and these increases were noted at low to moderate force levels, i.e., 30–50% of MVC, but not at higher force levels (Figure 3).”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: The detected motor unit populations within the motor unit groups did not critically vary during the different periods in this study.

  • May combine two claims.

    Findingown data

    Chair-stand test results were significantly improved following 6 weeks of intervention in APP-CN, PLA-CN, and PLA-RT, and at 3 and 6 weeks in APP-RT.

    “the chair-stand test results were significantly improved following 6 weeks of intervention in APP-CN, PLA-CN, and PLA-RT (p < 0.05) and at 3 and 6 weeks of intervention in APP-RT (p < 0.05) (Table 2).”
    • Also stated in: § Effect of Exercise and Nutritional Interventions on Motor Functions · plain
      “The chair-stand test results were improved during 6 weeks of intervention in all groups, including those with no exercise intervention, i.e., APP-CN and PLA-CN (Table 2).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    In the present study, motor unit firing rate reduction was observed in APP-RT, but not in PLA-RT.

    “In the present study, motor unit firing rate reduction was observed in APP-RT, but not in PLA-RT.”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: The detected motor unit populations within the motor unit groups did not critically vary during the different periods in this study.

  • May combine two claims.

    Findingown data

    Increases in motor unit firing rate were noted in APP-RT, but not in APP-CN or PLA-CN.

    “Increases in the motor unit firing rate were also noted in APP-RT, but not in APP-CN or PLA-CN (Figure 2).”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: The detected motor unit populations within the motor unit groups did not critically vary during the different periods in this study.

  • May combine two claims.

    Findingown data

    Numbers of detected motor units were different depending on recruitment thresholds, and those for 40-60% MVC were smaller than those for <20% and 20-40% MVC.

    “However, numbers of detected motor units were different depending on recruitment thresholds and those for 40–60% MVC of recruitment threshold were smaller than those for <20% and 20–40% MVC of recruitment threshold (Table 4).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    While previous studies showed an increase in MVC following training, our study revealed an improvement in 1RM on leg-press exercise, but not in MVC.

    “Also, we should note that while these previous studies showed an increase in MVC following training, our study revealed an improvement in the 1RM on leg-press exercise, but not in MVC.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingown data

    The present study detected a large number of motor units in total (1,204).

    “The present study detected large number of motor units in total (1,204).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    Improvement of motor function and changes in motor unit firing pattern were observed in the groups with resistance training, but not in the groups without resistance training.

    “Improvement of motor function and changes in motor unit firing pattern were observed in the groups with the resistance training, but not in the groups without the resistance training.”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: The detected motor unit populations within the motor unit groups did not critically vary during the different periods in this study.

  • May combine two claims.

    Findingown data

    The group with the combination of fish protein intake and resistance training showed a greater improvement in motor function, a different time course of alterations in firing rates of motor units with a low-recruitment threshold, and decreases in firing patterns of motor units with a high-recruitment threshold.

    “The group with the combination of fish protein intake and resistance training showed a greater improvement in the motor function, a different time course of alterations in firing rates of motor units with a low-recruitment threshold, and decreases in firing patterns of motor units with a high-recruitment threshold.”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: The detected motor unit populations within the motor unit groups did not critically vary during the different periods in this study.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingnone given

    Motor unit firing rates from all subjects were not included in the calculated motor unit firing rates at each period and motor unit group.

    “Also, motor unit firing rates from all subjects were not included in the calculated motor unit firing rates at each period and motor unit group.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Study design and conductown data

    At 0 week, there were no significant differences among the four groups in number of males, age, height, body mass, body fat, muscle mass, muscle and subcutaneous tissue thicknesses, MVC, chair-stand test result, or gait time.

    “At the beginning of intervention (0 week), there were no significant differences among the groups in the number of males (p = 0.995), age (p = 0.643), height (p = 0.023), body mass (p = 0.442), body fat (p = 0.431) and muscle mass estimated by InBody (p = 0.673), muscle (p = 0.512) and subcutaneous tissue thicknesses (p = 0.490), MVC (p = 0.966), result of the chair-stand test (p = 0.455), or gait”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductown data

    There was no significant effect of group on test meal ingestion timing.

    “No significant effect of group on test meal ingestion timing (p < 0.05) (Table 2).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Study design and conductown data

    ICCs between the pre-test and test at 0 week were 0.992 and 0.999 for muscle mass and body fat, 0.696 and 0.936 for muscle and subcutaneous tissue thickness, 0.983 for MVC, 0.942 for the chair-stand test, and 0.900 for gait speed.

    “ICCs between the pre-test and test at 0 week were 0.992 and 0.999 for the muscle mass and body fat measured by the body impedance method, respectively, 0.696 and 0.936 for muscle and subcutaneous tissue thickness by ultrasonography, respectively, 0.983 for MVC, 0.942 for the chair-stand test, and 0.900 for gait speed.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationcitation

    Motor unit firing rate following resistance training could be increased in the early phase and be maintained or decreased after this phase.

    “From the results of previous studies (Patten et al., 2001; Kamen and Knight, 2004; Vila-Cha et al., 2010), the motor unit firing rate following resistance training could be increased in the early phase and be maintained or decreased after this phase.”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites Patten et al., 2001 source

      Not checked in the free run.

    • cites Kamen and Knight, 2004 source

      Not checked in the free run.

    • cites Vila-Cha et al., 2010 source

      Not checked in the free run.

  • May combine two claims.

    Interpretationreasoning

    Results in APP-RT regarding motor performance and motor unit firing patterns would be specific to APP, and not to protein intake volume.

    “We thus consider that the results in APP-RT regarding motor performance and motor unit firing patterns would be specific to APP, and not to the protein intake volume.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Study design and conductnone given

    A randomized, double-blind, placebo-controlled treatment was conducted for test meals.

    “A randomized, double-blind, placebo-controlled treatment was conducted for test meals.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Premisecitation

    The effect of exercise on muscle strength and volume in aged individuals can be enhanced by nutritional supplementation.

    “Some evidences that the effect of exercise on the muscle strength and volume in aged individuals can be enhanced by nutritional supplementation has been reported.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    Reduction in motor unit firing rate at the same absolute force level after resistance training reveals that lower motor unit firing rate can generate the same absolute force following resistance training.

    “Also, reduction in the motor unit firing rate at the same absolute force level after resistance training reveals that the lower motor unit firing rate can generate the same absolute force following resistance training.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim. May combine two claims.

    Study design and conductnone given

    Identified motor units were manually verified on visual inspection by one investigator, and the results were checked by another investigator.

    “Identified motor units were manually verified on visual inspection by 1 investigator, and the results were checked by another investigator.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Study design and conductown data

    Age, number of male and/or female subjects, motor functions, and food intake were controlled among the four groups using measurement data obtained at 3 weeks before the intervention.

    “The age, number of male and/or female subjects, motor functions, and food intake were controlled among the four groups using the measurement data obtained at 3 weeks before the intervention (Table 1).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationown data

    APP intake enhanced some process of muscle protein synthesis and then accelerated the time course of adaptation in the motor unit firing pattern.

    “We suggest that APP intake enhanced some process of muscle protein synthesis and then accelerated the time course of adaptation in the motor unit firing pattern.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductreasoning

    Inter-discharge intervals <33.3 or >250 ms were excluded from the calculation of the firing rate.

    “Inter-discharge intervals <33.3 or >250 ms were excluded from the calculation of the firing rate, since they lead to an unusually high (>30 Hz) or low (<4 Hz) instantaneous firing rate.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Study design and conductnone given

    There was no supporting evidence that action potentials from the same motor units were recorded or that the same motor units were detected by decomposition analysis.

    “Although we endeavored to place electrodes at the same position each time using bone markers as a reference, there was no supporting evidence that action potentials from the same motor units were recorded or that the same motor units were detected by decomposition analysis.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Interpretationreasoning

    Alterations in contractile properties of different types of muscle fibers could lead to changes in firing patterns in motor units with low- and high-recruitment thresholds.

    “These alterations in the contractile properties of different types of muscle fibers could lead to changes in the firing patterns in motor units with low- and high-recruitment thresholds.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationown data

    Although all or most motor units are recruited during training, adaptations in rate coding were not uniform among recruited motor units.

    “We therefore suggest that although all or most motor units are recruited during training, adaptations in rate coding were not uniform among the recruited motor units (Figure 3).”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: The detected motor unit populations within the motor unit groups did not critically vary during the different periods in this study.

  • Probably not a substantial claim: may not pass S4 (based).

    Interpretationreasoning

    Modification of muscle protein processes by APP intake may play a role in the increase and/or decrease of motor unit firing rates.

    “a modification of muscle protein processes by APP intake may play a role in the increase and/or decrease of the motor unit firing rates.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Study design and conductcitation

    Only motor units with PNR > 30 dB, corresponding to an accuracy of motor unit firing identification > 90%, were used for analysis.

    “Only motor units with PNR > 30 dB (corresponding to an accuracy of motor unit firing identification > 90%) were used for further analysis, and all other motor units were discarded (Holobar et al., 2014).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Holobar et al., 2014 source

      Not checked in the free run.

  • May combine two claims.

    Interpretationown data

    Motor unit firing pattern is not affected by APP intake alone, but could be modified by APP intake in conjunction with resistance training.

    “These findings indicate that the motor unit firing pattern is not affected by only APP intake, but could be modified by APP intake in conjunction with resistance training.”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: The detected motor unit populations within the motor unit groups did not critically vary during the different periods in this study.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Study design and conductcitation

    Firing rates were excluded from further analysis when the coefficient of variation in mean firing rate was greater than 30% or when the number of firings was lower than two.

    “Firing rates were excluded from further analysis when the coefficient of variation in mean firing rate was greater than 30% or when the number of firings was lower than two, i.e., one firing (Fuglevand et al., 1993).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Fuglevand et al., 1993 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    A single operator blinded to information on the subjects and test periods carried out the ultrasonographic image analysis.

    “A single operator blinded to information on the subjects and test periods carried out this analysis.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Omega-3 fatty acids, creatine, and β-hydroxy β-methylbutyrate have been reported to promote muscle functions.

    “Also, the effectiveness of some other nutritional supplements such as omega-3 fatty acids, creatine, and β-hydroxy β-methylbutyrate, to promote muscle functions were reported (Fragala et al., 2015).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Fragala et al., 2015 source

      Not checked in the free run.

  • May combine two claims.

    Interpretationown data

    In the elderly, the effect of resistance training on motor unit firing rate can be observed in motor units with a low-recruitment threshold, and additional fish protein intake alters the adaptations of motor unit firing patterns and motor function following resistance training.

    “These findings suggest that, in the elderly, the effect of resistance training on the motor unit firing rate can be observed in motor units with a low-recruitment threshold and additional fish protein intake alters the adaptations of motor unit firing patterns and the motor function following resistance training.”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: The detected motor unit populations within the motor unit groups did not critically vary during the different periods in this study.

  • Classified as probably not a substantial claim. May combine two claims.

    Premisenone given

    While the effect of chronic and/or acute resistance training on motor unit firing rate has been investigated in several studies, the recruitment threshold of individual motor units has not been considered.

    “While the effect of chronic and/or acute resistance training on the motor unit firing rate has been investigated in several studies, the recruitment threshold of individual motor units has not been considered.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Other studies demonstrated no significant changes in motor unit firing rate during submaximal contraction in the vastus lateralis muscles.

    “Other studies demonstrated no significant changes in the motor unit firing rate during submaximal contraction in the vastus lateralis muscles (Rich and Cafarelli, 2000; Kamen and Knight, 2004).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Rich and Cafarelli, 2000

      Not checked in the free run.

    • cites Kamen and Knight, 2004 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    They also noted a significant increase of myosin heavy chain gene expression in Myh4, which is related to fast-twitch muscle fibers in the APP intake group.

    “They also noted a significant increase of myosin heavy chain gene expression in Myh4, which is related to fast-twitch muscle fibers in the APP intake group.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Kawabata et al., 2015 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    It is well-known that resistance training improves muscle strength and stimulates muscle protein synthesis even in the elderly.

    “It is well-known that resistance training improves the muscle strength and stimulates muscle protein synthesis even in the elderly (Dickinson et al., 2013)”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Dickinson et al., 2013 source

      Not checked in the free run.

  • Classified as probably not a substantial claim. May combine two claims.

    Study design and conductreasoning

    Since the present study did not track the same motor units among the three periods, the same motor units may have been categorized as different motor unit groups among the periods.

    “Since the present study didn’t track same motor units among three periods during the intervention, same motor units may be categorized as different motor unit group among the periods.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Pucci et al. (2006) reported a decrease in motor unit firing rate at the same absolute force level during 3 weeks of isometric training in the quadriceps femoris muscles.

    “On the other hand, Pucci et al. (2006) reported a decrease in the motor unit firing rate at the same absolute force level during 3 weeks of isometric training in the quadriceps femoris muscles (Pucci et al., 2006).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Pucci et al., 2006 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationreasoning

    Firing rate of motor units with different recruitment thresholds were calculated from different numbers of samples.

    “Therefore, firing rate of motor units with different recruitment thresholds were calculated from different numbers of samples.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Premisecitation

    Relationships between muscle fiber contractile properties and motor unit firing pattern have been reported.

    “Relationships between muscle fiber contractile properties and the motor unit firing pattern have been reported (Herda et al., 2015, 2016; Trevino and Herda, 2016; Trevino et al., 2016).”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites Herda et al., 2015, 2016

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites Trevino and Herda, 2016 source

      Not checked in the free run.

    • cites Trevino et al., 2016 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    In rat muscles, daily spontaneous running such as endurance training induced adaptations of electrophysiological properties in slow motoneurons but not in fast motoneurons.

    “In rat muscles, daily spontaneous running such as endurance training induced adaptations of electrophysiological properties in slow motoneurons but not in fast motoneurons (Beaumont and Gardiner, 2002).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Beaumont and Gardiner, 2002

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Protein intake has a beneficial effect.

    “and that protein intake has a beneficial effect (Houston et al., 2008).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Houston et al., 2008 source

      Not checked in the free run.

  • Classified as probably not a substantial claim. May combine two claims.

    Premisecitation

    Muscle proteins are constantly being broken down and synthesized, and they are controlled predominantly by physical activity and food consumption.

    “Muscle proteins are constantly being broken down and synthesized, and they are controlled predominantly by physical activity and food consumption (Landi et al., 2016; Tipton et al., 2018).”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites Landi et al., 2016 source

      Not checked in the free run.

    • cites Tipton et al., 2018 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Study design and conductnone given

    This study investigated the right leg only for MVC, muscle thickness, and surface EMG, while the dominant leg was not identified for each subject.

    “This study investigated right leg only for MVC, muscle thickness, and surface EMG, while dominant leg was not identified for each subject.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning

    The bilateral horizontal leg press exercise may lead to leg-dependent training effects because the foot plate was not separated for each leg and it is difficult to estimate balance of force productions by right or left legs.

    “This exercise may lead leg-dependent training effects since the foot plate of our training system was not separated for each leg and it is difficult to estimate balance of force productions by right or left legs.”
    Quote in the paperNot a substantial claim
53 of 53

  • The paper relies on this without support.

    The effect of nutritional supplementation on motor function with neuromuscular control strategies in aged humans has not been investigated.

    “However, the effect of nutritional supplementation on the motor function with neuromuscular control strategies in aged humans has not been investigated.”

  • The authors state this as an assumption.

    The detected motor unit populations within the motor unit groups did not critically vary during the different periods in this study.

    “We thus assumed the detected motor unit populations within the motor unit groups did not critically vary during the different periods in this study.”

  • The paper relies on this without support.

    The leg-press exercise employed for resistance training and standing up from and sitting on a chair are similar lower extremity movements.

    “The leg-press exercise employed for resistance training in the present study and standing up from and sitting on a chair are similar lower extremity movements.”

  • The paper relies on this without support.

    APP is unlikely to act directly on the central nervous system.

    “Since it would be unlikely for APP to act directly on the central nervous system”

  • The paper relies on this without support.

    Under the same training stimulus conditions, types of recruited motor units and muscle fibers should have been similar among subjects in APP-RT and PLA-RT.

    “Under the same training stimulus conditions, types of recruited motor units and muscle fibers should have been similar among subjects in APP-RT and PLA-RT.”

  • The paper relies on this without support.

    Training stimulation in the present study would be sufficient to have an effect on muscle protein metabolism.

    “On the other hand, training stimulation in the present study would be sufficient to have an effect on muscle protein metabolism.”

  • The paper relies on this without support.

    Change in motor unit recruitment threshold could not be greater than 20% of MVC, which was used as force levels to categorize motor unit groups.

    “However, change in motor unit recruitment threshold could not be greater than 20% of MVC which used as force levels to categorize motor unit groups.”
7 of 7

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

  • The motor unit decomposition procedure was previously extensively validated on signals from various skeletal muscles.

    “We followed the decomposition procedure that was previously extensively validated on signals from various skeletal muscles (7,17,21,25–28).”

    From Modulation of Neural and Muscular Adaptation Processes During Resistance Training by Fish Protein Ingestions in Older Adults (2020) · cites this paper as [17]

    The Materials and Methods section says the study used the CKC decomposition procedure, cites earlier accounts of it, and applied an accuracy threshold for identified motor units. It reports recordings from the vastus lateralis, but does not establish that the procedure was extensively validated on signals from various skeletal muscles. Page numbers are not available in our copy. (LLM, conf=0.85)

    Experimental — accuracy not yet measured

  • Similar trend of results was reported in our previous study (17).

    “Similar trend of results was reported in our previous study (17).”

    From Modulation of Neural and Muscular Adaptation Processes During Resistance Training by Fish Protein Ingestions in Older Adults (2020) · cites this paper as [17]

    The Results and Discussion report changes in chair-stand performance and motor-unit firing rates, so the cited paper does report results that could constitute a trend. The citing sentence does not identify which results are being compared, however, so our copy cannot establish that the trends are similar. (LLM, conf=0.68)

    Experimental — accuracy not yet measured

  • The procedures for calculating motor unit firing rates had been previously used in our studies.

    “These procedures for calculating motor unit firing rates had been previously used in our studies (7,17,20).”

    From Modulation of Neural and Muscular Adaptation Processes During Resistance Training by Fish Protein Ingestions in Older Adults (2020) · cites this paper as [17]

  • During 6 weeks of resistance training in leg-press exercise, improvements in chair stand test were found at 3 weeks after intervention in older adults who ingested APP, whereas they were found at 6 weeks after intervention in older adults who ingested placebo food (17).

    “During 6 weeks of resistance training in leg-press exercise, improvements in chair stand test were found at 3 weeks after intervention in the older adults who ingested APP, whereas they were found at 6 weeks after intervention in the older adults who ingested placebo food (17).”

    From Modulation of Neural and Muscular Adaptation Processes During Resistance Training by Fish Protein Ingestions in Older Adults (2020) · cites this paper as [17]

  • Resistance training intervention induces an increase in firing rate in low-recruitment threshold motor units and changes relationship in firing rate among motor unit groups with different recruitment thresholds in older adults.

    “Our previous study demonstrated that resistance training intervention induces an increase in firing rate in low-recruitment threshold motor units and changes relationship in firing rate among motor unit groups with different recruitment thresholds in older adults (17).”

    From Modulation of Neural and Muscular Adaptation Processes During Resistance Training by Fish Protein Ingestions in Older Adults (2020) · cites this paper as [17]

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • Conclusion excludes motor-function improvements in nontraining groups

    Major

    The Conclusion says motor-function improvement was not observed without resistance training. The Results report significant chair-stand improvements at 6 weeks in all groups, including both nontraining groups.

  • Ramp contraction rate does not match its duration

    Minor

    Increasing from 0 to 90% MVC over 45 seconds gives 2% MVC/s, not the reported 5% MVC/s.

    Reported 5 · recomputed 2

  • Abstract denies an APP-CN firing-rate effect reported in Results

    Minor

    The Abstract says no firing-rate effect was noted in APP-CN, but the Results report a significant intervention effect in that group at 80% MVC.

  • Meal timing is called nonsignificant despite p < 0.05

    Minor

    The stated p-value meets the paper's significance criterion, contrary to the claim of no significant group effect.

  • Nonsignificant intervention effects are paired with p < 0.05

    Minor

    The Results describe these intervention effects as nonsignificant while giving a p-value range that the paper defines as significant.

  • Baseline height is called nonsignificant despite p = 0.023

    Minor

    The paper calls the between-group height difference nonsignificant, although its reported p-value is below the stated 0.05 significance threshold.

6 of 6

Cites

Flagged first, then by citations

3 of the 64 references couldn’t be matched to a known paper.

Research works printed but not linked: 2

  1. Abe, 2017, Food science in Japan., Nature, 543
  2. Tomczak, 2014, The need to report effect size estimates revisited. An overview of some recommended measures of effect size., Trends Sport Sci., 1, 19

Cited by

Sorted by citations

Related

Authors
Watanabe, K., Holobar, A., Mita, Y., Kouzaki, M., Ogawa, M., Akima, H., & Moritani, T.
Affiliations
  • Chukyo University (JP)
  • University of Maribor (SI)
  • Sugiyama Jogakuen University (JP)
  • Kyoto University (JP)
  • Research Center of Health, Physical Fitness and Sports, Nagoya University (JP)
  • Kyoto Sangyo University (JP)
Corresponding author
Watanabe, Kohei
ORCID
Venue
Frontiers in Physiology
Publisher
Frontiers Media SA
Published
2018-12-04
Volume
9
Pages
1733-1733
ISSN
1664-042X (ISSN-L)
DOI
10.3389/fphys.2018.01733
PMC
PMC6288440
OpenAlex
W2900992712
Semantic Scholar
845b8b704ba17a2b377c409983b3311ae6ef4c6f
Cited by
37
References
64
Citations by year
2026: 2 · 2025: 3 · 2024: 6 · 2023: 7 · 2022: 11 · 2021: 5 · 2020: 2 · 2019: 1
FWCI
1.11
Type
journal article
Language
en
Open access
Licence
Locations
  • Frontiers in Physiology (publishedVersion, cc-by)
  • Europe PMC (PubMed Central) (publishedVersion, cc-by)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
  • Tokyo Tech Research Repository (Tokyo Institute of Technology) (submittedVersion)
Funders
  • Javna Agencija za Raziskovalno Dejavnost RS (P2-0041, J2-7357, Programme funding P2-0041)
  • Council for Science, Technology and Innovation (14533567)
  • Japan Society for the Promotion of Science (18H03158)
  • Bio-oriented Technology Research Advancement Institution
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Cell Biology › Muscle metabolism and nutrition
  • Health Sciences › Medicine › Physiology › Nutrition and Health in Aging
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Muscle Physiology and Disorders
Keywords
resistance training, fish protein, motor unit firing rate, motor function, older adults, leg press, dietary supplementation, surface electromyography, chair stand test

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

Claims read by deepseek-v4.1-flash under definition version 3 (extract-v3) on 2026-10-09.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-10-09.

Statistics and arithmetic are recomputed, not judged.

Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.

What counts as a claim ›How we measure confidence ›How we check this ›

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