Table 3. Study Outcomes.

Abbreviations: ASIA, American Spinal Injury Association; FES-RT, functional electrical stimulation resistance training; T, testosterone; TT, testosterone therapy; SCI, spinal cord injury; LTM, lean tissue mass; REE, resting energy expenditure; HO, heterotopic ossification; CSA, cross-sectional area; FIM, functional independence measure; PSA, prostate-specific antigen; GLUT4, glucose transporter type 4; Akt, protein kinase B; PGC-1α, peroxisome proliferator-activated receptor gamma coactivator 1-alpha; FAK, focal adhesion kinase; lbs., pounds; TBI, traumatic brain injury; QTaVI, QT apex interval variability.

Study	Primary Outcome	Secondary Outcomes
Holman et al., 2019 [21]	TT + FES-RT improved knee isometric torque by 48.4%, knee extensor CSA by 30.8%, rise time by 17.7% with no significant changes seen in the TT alone group.	TT + FES-RT did not change the half-time to relaxation & increased calcium reuptake by 7%.
Gorgey et al., 2020 [22]	TT + FES-RT for 16 weeks significantly increased the total gluteus maximus & medius muscle CSA area by 14% & 10%, respectively, compared to TT alone.	No significant change in the CSA of trunk & lower-leg muscles between groups.
Gorgey et al., 2020 [23]	TT + FES-RT increased the expression of GLUT4, total Akt, phosphorylated Akt, & mitochondrial activity of succinate dehydrogenase & citrate synthase compared to TT alone. TT + FES-RT increased muscle CSA by 27.5% & TT decreased muscle CSA by 9%.	There was a 27% non-significant increase in serum T in the TT + FES-RT group. TT + FES-RT & TT alone increased PGC-1α & FAK.
Bauman et al., 2011 [24]	TT for 12 months significantly increased total body, trunk, arm, & leg LTM by 7-10% as well as REE by 9%.	No significant change in weight, fat tissue mass, or oxygen consumption.
Bauman et al., 2015 [25]	The significant increase in total body LTM & REE at the end of 12 months of TT in the hypogonadal group was retained after the 6 months of TT discontinuation despite a decrease in serum T levels back to baseline levels.	No significant change in fat tissue mass in both groups. Significantly increased HDL-C levels were maintained in the hypogonadal group. The hepatic panel, hemoglobin, hematocrit, & PSA values were within normal range & did not change significantly in either group over the course of the study.
Gorgey et al., 2021 [26]	Low dose TT + weekly FES-RT for 16 weeks maintained muscle mass & basal metabolic rate compared to the no TT group. Both groups increased visceral adipose tissue without changes in cardiovascular, metabolism, or inflammatory biomarkers.	Low dose TT + weekly FES-RT maintained knee peak isometric & isokinetic torques. The decrease & cessation of TT increased the endogenous T levels.
Clark et al., 2008 [27]	ASIA discharge motor scores for ASIA C & D patients were significantly greater in the TT group compared to the control.	No significant difference in discharge FIM score for men with incomplete or complete SCI. No significant difference in ASIA discharge motor score in complete SCI.
Ripley et al., 2020 [28]	No significant difference between groups in the rate of improvement on the FIM. TT group improved its FIM score by 30 while the placebo group & eugonadal group improved FIM by 19.5 & 17.5, respectively. TT group improved grip strength by 19.5 lbs. while the placebo & eugonadal group improved grip strength by 14.8 lbs. & 5.5 lbs., respectively.	TT did not result in worsening agitation. The percentage of time with agitation or aggression was highest in the placebo group with agitation inversely correlated with T levels. No difference in adverse events between groups.
Holman et al., 2021 [29]	TT + FES-RT for 16 weeks slightly decreased yellow marrow, slightly increased red marrow, & improved trabecular measures at the knee joint. TT alone increased yellow marrow.	TT + FES-RT displayed greater increases in intermuscular fascia length than the TT alone group.
Moore et al., 2016 [30]	TT + FES-RT for 16 weeks increased whole thigh skeletal muscle CSA by 10% & knee extensor CSA by 17% without stimulating the growth of pre-existing HO.	TT alone increased whole thigh skeletal muscle CSA by 13% & knee extensor CSA by 7% without stimulating the growth of pre-existing HO.
Gorgey et al., 2019 [31]	TT + FES-RT for 16 weeks significantly increased total body LTM, whole muscle, & whole muscle knee extensor CSA with no changes in the TT alone group.	Glucose effectiveness improved by 28.5-31.5% in both groups. BMR increased 14-17% in the TT + FES-RT group.
La Fountaine et al., 2013 [32]	QTaVI is significantly elevated in the hypogonadal group at baseline compared to the eugonadal group. TT for 12 months improved QTaVI in hypogonadal men with chronic SCI.	No significant group differences in most of the resting ECG data at baseline or at 12 months. No group difference or intervention effects on lipids.