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The interaction of force and repetition on musculoskeletal and neural tissue responses and sensorimotor behavior in a rat model of work-related musculoskeletal disorders.

Barbe MF, Gallagher S, Massicotte VS, Tytell M, Popoff SN, Barr-Gillespie AE - BMC Musculoskelet Disord (2013)

Bottom Line: In most cases, performance of the HRHF task induced the greatest tissue degenerative changes, while performance of moderate level tasks induced bone adaptation and a suggestion of muscle adaptation.Both high force tasks induced median nerve macrophage infiltration, spinal cord sensitization (increased substance P), grip strength declines and forepaw mechanical allodynia by task week 12.Prolonged performance of HRHF tasks exhibited significantly increased risk for musculoskeletal disorders, while performance of moderate level tasks exhibited adaptation to task demands.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Anatomy and Cell Biology, Temple University School of Medicine, 3500 North Broad St, Philadelphia 19140, PA, USA. mary.barbe@temple.edu.

ABSTRACT

Background: We examined the relationship of musculoskeletal risk factors underlying force and repetition on tissue responses in an operant rat model of repetitive reaching and pulling, and if force x repetition interactions were present, indicative of a fatigue failure process. We examined exposure-dependent changes in biochemical, morphological and sensorimotor responses occurring with repeated performance of a handle-pulling task for 12 weeks at one of four repetition and force levels: 1) low repetition with low force, 2) high repetition with low force, 3) low repetition with high force, and 4) high repetition with high force (HRHF).

Methods: Rats underwent initial training for 4-6 weeks, and then performed one of the tasks for 12 weeks, 2 hours/day, 3 days/week. Reflexive grip strength and sensitivity to touch were assayed as functional outcomes. Flexor digitorum muscles and tendons, forelimb bones, and serum were assayed using ELISA for indicators of inflammation, tissue stress and repair, and bone turnover. Histomorphometry was used to assay macrophage infiltration of tissues, spinal cord substance P changes, and tissue adaptative or degradative changes. MicroCT was used to assay bones for changes in bone quality.

Results: Several force x repetition interactions were observed for: muscle IL-1alpha and bone IL-1beta; serum TNFalpha, IL-1alpha, and IL-1beta; muscle HSP72, a tissue stress and repair protein; histomorphological evidence of tendon and cartilage degradation; serum biomarkers of bone degradation (CTXI) and bone formation (osteocalcin); and morphological evidence of bone adaptation versus resorption. In most cases, performance of the HRHF task induced the greatest tissue degenerative changes, while performance of moderate level tasks induced bone adaptation and a suggestion of muscle adaptation. Both high force tasks induced median nerve macrophage infiltration, spinal cord sensitization (increased substance P), grip strength declines and forepaw mechanical allodynia by task week 12.

Conclusions: Although not consistent in all tissues, we found several significant interactions between the critical musculoskeletal risk factors of force and repetition, consistent with a fatigue failure process in musculoskeletal tissues. Prolonged performance of HRHF tasks exhibited significantly increased risk for musculoskeletal disorders, while performance of moderate level tasks exhibited adaptation to task demands.

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Inflammatory cytokines levels in radial and ulnar bones, and first row of carpal bones, tested using ELISA in week 0 (immediately following the training period) or after performing either a LRLF, HRLF, LRHF and HRHF task for 12 weeks. (A & D) Bone TNFalpha in week 0 and 12. (B & E) Bone IL-1beta in week 0 and 12. (C & F) Bone IL-1alpha in week 0 and 12. Symbols: a and aa: p < 0.05 and p < 0.01, compared to LRLF rats; b and bb: p < 0.05 and p < 0.01, compared to HRLF rats; * and **: p < 0.05 and p < 0.01, compared to food restricted controls (FRC) rats (indicated by dashed line). Mean and SEM are shown.
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Figure 3: Inflammatory cytokines levels in radial and ulnar bones, and first row of carpal bones, tested using ELISA in week 0 (immediately following the training period) or after performing either a LRLF, HRLF, LRHF and HRHF task for 12 weeks. (A & D) Bone TNFalpha in week 0 and 12. (B & E) Bone IL-1beta in week 0 and 12. (C & F) Bone IL-1alpha in week 0 and 12. Symbols: a and aa: p < 0.05 and p < 0.01, compared to LRLF rats; b and bb: p < 0.05 and p < 0.01, compared to HRLF rats; * and **: p < 0.05 and p < 0.01, compared to food restricted controls (FRC) rats (indicated by dashed line). Mean and SEM are shown.

Mentions: Since tissue injury increases production of inflammatory cytokines (as reviewed in [35,41,42]), we examined forelimb tissues for levels of TNF-alpha, IL-1alpha and IL-1beta. Flexor digitorum muscles and tendons, and forelimb bones (radius and ulna, and first row of carpal bones), had significantly increased inflammatory cytokines at the end of training (week 0) and at 12 weeks of task performance. They were particularly increased HRHF rat tissues, although HRLF rats had increased muscle TNF-alpha and tendon IL-1beta, and LRHF rats had increases in bones (Figures 1, 2 and 3). As described in detail below, force x repetition interaction effects were observed for 0- and 12-week muscles (IL-1alpha), 0-week tendons (trends only for IL-1beta and IL-1alpha), and 0-week bones (IL-1beta) (Figures 1C,F; 3B,C and 4B). Several individual effects from repetition and force were also observed, with the greatest increases in HRHF rat tissues.


The interaction of force and repetition on musculoskeletal and neural tissue responses and sensorimotor behavior in a rat model of work-related musculoskeletal disorders.

Barbe MF, Gallagher S, Massicotte VS, Tytell M, Popoff SN, Barr-Gillespie AE - BMC Musculoskelet Disord (2013)

Inflammatory cytokines levels in radial and ulnar bones, and first row of carpal bones, tested using ELISA in week 0 (immediately following the training period) or after performing either a LRLF, HRLF, LRHF and HRHF task for 12 weeks. (A & D) Bone TNFalpha in week 0 and 12. (B & E) Bone IL-1beta in week 0 and 12. (C & F) Bone IL-1alpha in week 0 and 12. Symbols: a and aa: p < 0.05 and p < 0.01, compared to LRLF rats; b and bb: p < 0.05 and p < 0.01, compared to HRLF rats; * and **: p < 0.05 and p < 0.01, compared to food restricted controls (FRC) rats (indicated by dashed line). Mean and SEM are shown.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3924406&req=5

Figure 3: Inflammatory cytokines levels in radial and ulnar bones, and first row of carpal bones, tested using ELISA in week 0 (immediately following the training period) or after performing either a LRLF, HRLF, LRHF and HRHF task for 12 weeks. (A & D) Bone TNFalpha in week 0 and 12. (B & E) Bone IL-1beta in week 0 and 12. (C & F) Bone IL-1alpha in week 0 and 12. Symbols: a and aa: p < 0.05 and p < 0.01, compared to LRLF rats; b and bb: p < 0.05 and p < 0.01, compared to HRLF rats; * and **: p < 0.05 and p < 0.01, compared to food restricted controls (FRC) rats (indicated by dashed line). Mean and SEM are shown.
Mentions: Since tissue injury increases production of inflammatory cytokines (as reviewed in [35,41,42]), we examined forelimb tissues for levels of TNF-alpha, IL-1alpha and IL-1beta. Flexor digitorum muscles and tendons, and forelimb bones (radius and ulna, and first row of carpal bones), had significantly increased inflammatory cytokines at the end of training (week 0) and at 12 weeks of task performance. They were particularly increased HRHF rat tissues, although HRLF rats had increased muscle TNF-alpha and tendon IL-1beta, and LRHF rats had increases in bones (Figures 1, 2 and 3). As described in detail below, force x repetition interaction effects were observed for 0- and 12-week muscles (IL-1alpha), 0-week tendons (trends only for IL-1beta and IL-1alpha), and 0-week bones (IL-1beta) (Figures 1C,F; 3B,C and 4B). Several individual effects from repetition and force were also observed, with the greatest increases in HRHF rat tissues.

Bottom Line: In most cases, performance of the HRHF task induced the greatest tissue degenerative changes, while performance of moderate level tasks induced bone adaptation and a suggestion of muscle adaptation.Both high force tasks induced median nerve macrophage infiltration, spinal cord sensitization (increased substance P), grip strength declines and forepaw mechanical allodynia by task week 12.Prolonged performance of HRHF tasks exhibited significantly increased risk for musculoskeletal disorders, while performance of moderate level tasks exhibited adaptation to task demands.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Anatomy and Cell Biology, Temple University School of Medicine, 3500 North Broad St, Philadelphia 19140, PA, USA. mary.barbe@temple.edu.

ABSTRACT

Background: We examined the relationship of musculoskeletal risk factors underlying force and repetition on tissue responses in an operant rat model of repetitive reaching and pulling, and if force x repetition interactions were present, indicative of a fatigue failure process. We examined exposure-dependent changes in biochemical, morphological and sensorimotor responses occurring with repeated performance of a handle-pulling task for 12 weeks at one of four repetition and force levels: 1) low repetition with low force, 2) high repetition with low force, 3) low repetition with high force, and 4) high repetition with high force (HRHF).

Methods: Rats underwent initial training for 4-6 weeks, and then performed one of the tasks for 12 weeks, 2 hours/day, 3 days/week. Reflexive grip strength and sensitivity to touch were assayed as functional outcomes. Flexor digitorum muscles and tendons, forelimb bones, and serum were assayed using ELISA for indicators of inflammation, tissue stress and repair, and bone turnover. Histomorphometry was used to assay macrophage infiltration of tissues, spinal cord substance P changes, and tissue adaptative or degradative changes. MicroCT was used to assay bones for changes in bone quality.

Results: Several force x repetition interactions were observed for: muscle IL-1alpha and bone IL-1beta; serum TNFalpha, IL-1alpha, and IL-1beta; muscle HSP72, a tissue stress and repair protein; histomorphological evidence of tendon and cartilage degradation; serum biomarkers of bone degradation (CTXI) and bone formation (osteocalcin); and morphological evidence of bone adaptation versus resorption. In most cases, performance of the HRHF task induced the greatest tissue degenerative changes, while performance of moderate level tasks induced bone adaptation and a suggestion of muscle adaptation. Both high force tasks induced median nerve macrophage infiltration, spinal cord sensitization (increased substance P), grip strength declines and forepaw mechanical allodynia by task week 12.

Conclusions: Although not consistent in all tissues, we found several significant interactions between the critical musculoskeletal risk factors of force and repetition, consistent with a fatigue failure process in musculoskeletal tissues. Prolonged performance of HRHF tasks exhibited significantly increased risk for musculoskeletal disorders, while performance of moderate level tasks exhibited adaptation to task demands.

Show MeSH
Related in: MedlinePlus