TABLE 1.
Studies describing the effects of loading and unloading on the surface area of the MTJ with a description of species used, muscles and muscle fiber types and the method used for measurements.
| Studies describing the effect of increased load on the MTJ | |||||
| Author, year, species | Sample Size pr Group | Muscles/dominant fiber type | Intervention | Method of measurement | Results |
| Kojima,2008,rat | 5 | Gastrocnemius/I Tibialis Ant./II | Running | Branching of fingers Angle of branching | ↑ |
| Curzi. 2012,rat | 6 | Gastrocnemius/I EDL/II | Running | Branching of fingers | ↑ |
| Curzi. 2016. rat | 3 | EDL/II | Running | Interface length/baseline(IL/B ratio) | ↑ |
| Sierra. 2018. rat | 3 | Soleus/I | Swimming | Length and thickness of invaginations and evaginations | ↑ |
| Jacob. 2019. rat | 5 | Sternomastoid/II | Swimming | IL/B | |
| Neto J, 2020 rat | 10 | Plantaris/II | Loaded ladder climb | Length and thickness of invaginations and evaginations | ↑ |
| Studies describing the effect of unloading the MTJ | |||||
| Author, year, species | Sample Size pr Group | Muscles/dominant fiber type | Intervention | Method of measurement | Results |
| Kannus, 1992. rat | 8 | Gastrocnemius/II Soleus/l | Immobilization 1 and 3 weeks | Length of surface area in relation to muscle fiber diameter | ↓ |
| Tidball 1992. rat | 6 | Plantaris/lI | Space flight -4 davs | Folding factor | ↓ |
| Zamora. 1995. rat | 2 5 | Soleus/I Plantaris/lI | Limb suspension for 8, 18 and 29 davs Space flight 14 days | No quantification | Only minor changes observed in Plantar is MTJ’s. thinning and lengthening of the foldings at MTJ of Soleus MTJ s |
| Roffino, 1998. rat | 8 | Soleus/I | Space flight 14 days | IL B ratio-named normalized interface values by the authors. | ↑ |
| Roffino, 2006.monkey | 2 | Soleus/I +II | Space flight 14 days | No qualification | - |
| de Palma, 2011,human | 12 Unloaded 3 controls | Gastrocnemius/I+II | Bed rest (mean 60 months) in chronic diseased patients | Length of surface area n relation to muscle fiber diameter | ↓ |
| Curzi,2013,rat | 4 | Plantaris/II | Unloading | IL/B ratio Length of primary digits Brancing of fingers | ↓ |
In most studies the assessments have not been performed blinded to study group. Most studies provide information about the number of foldings/invaginations measured per group and not per animal and have not provided information about the number of slides from each animal. Because of this, the results should be interpreted with some caution. Arrows indicate whether an increase (↑) or a decrease (↓) in the measures was reported. EDL, Extensor Digitorum Longus.