## 3 Results
### SkM PCr Recovery Time  
Compared to healthy controls, the recovery time in the HF patients was consistently prolonged across the studies, as exhibited in Table 3. In four of the studies, this difference was of statistical significance. In the remaining two studies [29; 30], the difference was not statistically significant. In studies reporting T% recovery times, this was longer in HF patients compared to controls [29; 31]. Figure 3 displays the meta-analysis, which shows this difference between HF and controls to be statistically significant (SMD: \(-\)1.35, CI: \(-\)2.11, \(-\)0.59, \(p=0.0005\)). Mean recovery time was prolonged in the HF group than in healthy controls, and this was demonstrated across studies individually. There is considerable heterogeneity; the \(\mathrm{I}^{2}\) is 78%, and the \(\mathrm{T}^{2}\) is 0.64.  
Figure 3 shows a forest plot of the PCr recovery time from the included studies.  
Figure 3: Forest plot indicating the mean PCr/Pi recovery time between patients with HF and healthy controls. Horizontal lines represent 95% confidence intervals (CI). Pooled estimates and their 95% confidence intervals are represented by diamonds. RT: recovery time; HF: heart failure; HC: healthy controls [29; 30; 31; 32; 33; 34].  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Study**} & \multicolumn{4}{c}{**Controls**} & \multicolumn{4}{c}{**Heart Failure**} \\ \cline{2-9}  & \multicolumn{3}{c}{**Resting**} & \multicolumn{2}{c}{**Recovery**} & \multicolumn{2}{c}{**Resting**} & \multicolumn{2}{c}{**Recovery**} \\ \cline{2-9}  & \multicolumn{3}{c}{**PCr/Pi**} & \multicolumn{1}{c}{**PCr/ATP**} & \multicolumn{1}{c}{**Mean \(\pm\) SD**} & \multicolumn{1}{c}{**PCr Index**} & \multicolumn{1}{c}{**Recovery**} & \multicolumn{1}{c}{**Mean \(\pm\) SD**} & \multicolumn{1}{c}{**PCr/Pi**} & \multicolumn{1}{c}{**PCr/ATP**} & \multicolumn{1}{c}{**PCr Index**} & \multicolumn{1}{c}{**Recovery**} \\  & \multicolumn{1}{c}{**Mean \(\pm\) SD**} & \multicolumn{1}{c}{**Mean \(\pm\) SD**} & \multicolumn{1}{c}{**Mean \(\pm\) SD**} & \multicolumn{1}{c}{**Mean \(\pm\) SD**} & \multicolumn{1}{c}{**Mean \(\pm\) SD**} & \multicolumn{1}{c}{**PCr Index**} & \multicolumn{1}{c}{**Mean \(\pm\) SD**} \\ \hline [PERSON] 1987 [29] & 0.9 \(\pm\) 0.01 & 2.7 \(\pm\) 0.1 & T \% (s) & 0.86 \(\pm\) 0.4 & 0.87 \(\pm\) 0.03 & 2.8 \(\pm\) 0.4 & T \% & 1.72 \(\pm\) 1.5 \\ \hline [PERSON] 1988 [31] & 0.9 \(\pm\) 0.01 & NR & T \% (s) & 42 \(\pm\) 18 & 0.89 \(\pm\) 0.02 & NR & T \% & 75 \(\pm\) 52 \\ \hline [PERSON] 1988 [32] & 0.21 \(\pm\) 0.06 & NR & Recovery time (s) & 2.1 \(\pm\) 0.5 & 0.21 \(\pm\) 0.07 & NR & Recovery Time & 3.3 \(\pm\) 0.8 \\ \hline [PERSON] 1996 [30] & 0.098 \(\pm\) 0.01 & NR & Recovery Rate (s) & 0.27 \(\pm\) 0.026 & 0.159 \(\pm\) 0.03 & NR & Recovery Time & 0.273 \(\pm\) 0.028 \\ \hline [PERSON] 2000 [34] & 0.95 \(\pm\) 0.02 & NR & \(\hat{\mathrm{\circ}}\) PCr (s) & 36.5 \(\pm\) 5.8 & 0.91 \(\pm\) 0.05 & NR & \(\hat{\mathrm{\circ}}\) PCr & 76.3 \(\pm\) 30.2 \\ \hline Menon 2021 [33] & 0.1 \(\pm\) 0.02 & 7.93 \(\pm\) 1.7 & Recovery Rate (s) & 26.73 \(\pm\) 4.49 & 0.12 \(\pm\) 0.03 & 8.43 \(\pm\) 1.39 & Recovery Time & 50.1 \(\pm\) 8.51 \\ \hline \hline \end{tabular}
\end{table}
Table 3: PCr quantification at rest and recovery in HF patients and in healthy controls.