## 4 Discussion  
This prospective study monitored dance injuries in relation to strength, aerobic fitness, hip mobility, injury history, and training hours, and followed the effects of the pandemic on dancers. To the best of our knowledge, this is the first study following objective measures in pre-professional modern dancers, before and after the COVID-19 outbreak. Our main findings demonstrate that participation in strength training and higher baseline aerobic fitness differentiated non-injured from injured dancers. In other words, dancers who practiced strength training independently and in addition to dance during the pandemic were not injured pre- or post-COVID-19. In addition, dancers who showed higher aerobic performance in the pre-COVID-19 Chester Step Test reported no injuries pre-COVID-19, with a similar trend post-COVID-19. The dancers who practiced cardiovascular training independently apart from dance were less injured. These findings are in agreement with a systematic review examining elite female ballet dancers [30]. Reduced strength in the lower limbs and poor aerobic fitness were found to be risk factors for lower limb injury. Other studies in pre-professional and professional contemporary dancers conducted strength and aerobic exercise programs ranging from 1.5 to 6 months, with 2-3 sessions of 1-1.5 h/week [31; 32; 33]. These programs demonstrated a positive response to the training in the measures of aerobic fitness and improved lower body muscular power and strength [31; 32; 33]. Two studies were controlled [31; 33], and neither investigated injuries [31; 32; 33]. In contrast, [PERSON] et al. 's [16] randomized controlled trial did not find a positive effect of a four-month aerobic and strength intervention program for \begin{table}
\begin{tabular}{l c} \hline
**Self-Perceived Causes of Injury** & **No. of Reports** \\ \hline
**Incorrect body work and investing more power than necessary** & **12/24** \\ \hline
**High and intensive workload** & **8/24** \\ \hline Lack of strength as a result of inadequate independent training & 6/24 \\ \hline Previous injury leading to weakness, overcompensation from other body parts, & 5/24 \\ and decreased confidence in their body & 4/24 \\ \hline Specific repertoire & \\ \hline \end{tabular} Note: Responses given by more than a third of all dancers are bolded.  
\end{table} 
Table 4: Self-reported perceived causes of injury. pre-professional dancers on injuries, apart from a reduction in pain and lower-back injuries, when compared to educational sessions [16]. Aerobic training for dancers has some evidence to support its benefits. Aerobic exercise accelerates recovery [34], decreases pain perception, and improves mood [35]. Dance is heterogenic in its aerobic demands. In modern and ballet classes, HR was mainly below the aerobic training zone [36]. During center-class work, HR and oxygen uptake were higher than in the warm-up [37]. Performances demanded the highest HR levels. Professional modern dancers who often engaged in performances demonstrated lower HR in recovery, lower peak HR, and better aerobic fitness when compared to pre-professional modern dancers [38]. Therefore, there is a functional and physiological need for performing dancers to acquire aerobic fitness. Dance classes do not seem sufficient to improve dancers' aerobic fitness and strength [36; 39], let alone prepare them for the high demands of performances [2; 38]. Physical and mental fatigue may play a role in injury propensity [10; 29]. Current results suggest that better strength and aerobic capacity potentially elevates the threshold for fatigue in dancers [10]. Further research, including high-quality randomized controlled trials, is needed to specify aerobic and strength training recommendations in relation to injuries [36; 38]. The decrease in dancing time during the COVID-19 pandemic enabled dancers to add aerobic and strength training, but not all utilized this opportunity.